Dissertations / Theses: 'Dc/ac Power Conversion'

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McClure, Morgan Taylor. "A Modular Architecture for DC-AC Conversion." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1340812711.

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Wang, Kunrong. "High-Frequency Quasi-Single-Stage (QSS) Isolated AC-DC and DC-AC Power Conversion." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/29394.

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The generic concept of quasi-single-stage (QSS) power conversion topology for ac-dc rectification and dc-ac inversion is proposed. The topology is reached by direct cascading and synchronized switching of two variety of buck or two variety of boost switching networks. The family of QSS power converters feature single-stage power processing without a dc-link low-pass filter, a unidirectional pulsating dc-link voltage, soft-switching capability with minimal extra commutation circuitry, simple PWM control, and high efficiency and reliability. A new soft-switched single-phase QSS bi-directional inverter/rectifier (charger) topology is derived based on the QSS power conversion concept. A simple active voltage clamp branch is used to clamp the otherwise high transient voltage on the current-fed ac side, and at the same time, to achieve zero-voltage-switching (ZVS) for the switches in the output side bridge. Seamless four-quadrant operation in the inverter mode, and rectifier operation with unity power factor in the charger (rectifier) mode are realized with the proposed uni-polar center-aligned PWM scheme. Single-stage power conversion, standard half-bridge connection of devices, soft-switching for all the power devices, low conduction loss, simple center-aligned PWM control, and high reliability and efficiency are among its salient features. Experimental results on a 3 kVA bi-directional inverter/rectifier prototype validate the reliable operation of the circuit. Other single-phase and three-phase QSS bi-directional inverters/rectifiers can be easily derived as topological extensions of the basic QSS bi-directional inverter/rectifier. A new QSS isolated three-phase zero-voltage/zero-current-switching (ZVZCS) buck PWM rectifier for high-power off-line applications is also proposed. It consists of a three-phase buck bridge switching under zero current and a phase-shift-controlled full-bridge with ZVZCS, while no intermediate dc-link is involved. Input power and displacement factor control, input current shaping, tight output voltage regulation, high-frequency transformer isolation, and soft-switching for all the power devices are realized in a unified single stage. Because of ZVZCS and single-stage power conversion, it can operate at high switching frequency while maintaining reliable operation and achieving higher efficiency than standard two-stage approaches. A family of isolated ZVZCS buck rectifiers are obtained by incorporating various ZVZCS schemes for full-bridge dc-dc converters into the basic QSS isolated buck rectifier topology. Experimental and simulation results substantiate the reliable operation and high efficiency of selected topologies. The concept of charge control (or instantaneous average current control) of three-phase buck PWM rectifiers is introduced. It controls precisely the average input phase currents to track the input phase voltages by sensing and integrating only the dc rail current, realizes six-step PWM, and features simple implementation, fast dynamic response, excellent noise immunity, and is easy to realize with analog circuitry or to integrate. One particular merit of the scheme is its capability to correct any duty-cycle distortion incurred on only one of the two active duty-cycles which often happens in the soft-switched buck rectifiers, another merit is the smooth transition of the input currents between the 60o sectors. Simulation and preliminary experimental results show that smooth operations and high quality sinusoidal input currents in the full line cycle are achieved with the control scheme.
Ph. D.

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Chen, Weilun Warren. "Bidirectional Three-Phase AC-DC Power Conversion Using DC-DC Converters and a Three-Phase Unfolder." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6905.

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Strategic use of energy storage systems alleviates imbalance between energy generation and consumption. Battery storage of various chemistries is favorable for its relatively high energy density and high charge and discharge rates. Battery voltage is in dc, while the distribution of electricity is still predominantly in ac. To effectively harness the battery energy, a dc-ac inverter is required. A conventional inverter contains two high-frequency switching stages. The battery-interfacing stage provides galvanic isolation and switches at high frequency to minimize the isolation transformer size. The grid-interfacing stage also operates at high frequency to obtain sinusoidal grid currents and the desired power. Negative consequences of high-frequency switching include increased switching loss and the generation of large voltage harmonics that require filtering. This dissertation proposes an alternative two-stage inverter topology aimed at reducing converter size and weight. This is achieved by reducing the number of high-frequency switching stages and associated filter requirements. The grid-interfacing stage is operated at the line frequency, while only the battery-interfacing stage operates at high frequency to shape the line currents and control power flow. The line-frequency operation generates negligible switching loss and minimal current harmonics in the grid-interfacing stage. As a result, the required filter is reduced in size. Hardware designs are performed and compared between the conventional and proposed converters to quantify expected size reduction. Control methods are developed and verified in simulation and experiment to obtain high-quality line currents at all power factors.

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Song, Yu Jin. "Analysis and design of high frequency link power conversion systems for fuel cell power conditioning." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2678.

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In this dissertation, new high frequency link power conversion systems for the fuel cell power conditioning are proposed to improve the performance and optimize the cost, size, and weight of the power conversion systems. The first study proposes a new soft switching technique for the phase-shift controlled bi-directional dc-dc converter. The described dc-dc converter employs a low profile high frequency transformer and two active full-bridge converters for bidirectional power flow capability. The proposed new soft switching technique guarantees soft switching over wide range from no load to full load without any additional circuit components. The load range for proposed soft switching technique is analyzed by mathematical approach with equivalent circuits and verified by experiments. The second study describes a boost converter cascaded high frequency link direct dc-ac converter suitable for fuel cell power sources. A new multi-loop control for a boost converter to reduce the low frequency input current harmonics drawn from the fuel cell is proposed, and a new PWM technique for the cycloconverter at the secondary to reject the low order harmonics in the output voltages is presented. The performance of the proposed scheme is verified by the various simulations and experiments, and their trade-offs are described in detail using mathematical evaluation approach. The third study proposes a current-fed high frequency link direct dc-ac converter suitable for residential fuel cell power systems. The high frequency full-bridge inverter at the primary generates sinusoidally PWM modulated current pulses with zero current switching (ZCS), and the cycloconverter at the secondary which consists of only two bidirectional switches and output filter capacitors produces sinusoidally modulated 60Hz split single phase output voltage waveforms with near zero current switching. The active harmonic filter connected to the input terminal compensates the low order input current harmonics drawn from the fuel cell without long-term energy storage devices such as batteries and super capacitors.

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Grant, David. "High power density AC to DC conversion with reduced input current harmonics." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/3906.

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This thesis investigates the bene ts and challenges arising from the use of minimal capacitance in AC to DC converters. The purpose of the research is to ultimately improve the power density and power factor of electrical systems connected to the grid. This is carried out in the con- text of a low cost brushless DC drive system operating from an o ine power supply. The work begins with a review of existing applications where it is prac- tical to use a limited amount of DC link capacitance. The vast majority of these have a load which is insensitive to supply power variations at twice the line frequency. Low performance motor drives are found to be the most prevalent, with the inertia of the rotor mitigating the e ect of torque ripple. Further research is carried out on active power factor cor- rection techniques suitable for this application, leading to the conclusion that no appropriate systems exist. A power supply is developed to enable a 24V, 200W brushless motor drive to operate from the mains. The system runs successfully using only 1μF of DC link capacitance, which causes the motor supply volt- age to have 100% ripple. It is noted that whilst this drastically reduces the low frequency input current harmonics, those occurring at the load switching frequency are greatly increased. To combat this, a novel active power factor correction system is proposed using a notch lter to detect the input current error. The common problem of voltage feedback ripple is avoided by eliminating the voltage control loop altogether. The main limitations are identi ed as a high sensitivity to load step changes and variations in line frequency. Despite this, a high power factor is maintained in all operating conditions, as well as compliance with the relevant harmonic standards.

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Zhao, Shishuo. "High Frequency Isolated Power Conversion from Medium Voltage AC to Low Voltage DC." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74969.

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Modern data center power architecture developing trend is analyzed, efficiency improvement method is also discussed. Literature survey of high frequency isolated power conversion system which is also called solid state transformer is given including application, topology, device and magnetic transformer. Then developing trend of this research area is clearly shown following by research target. State of art wide band gap device including silicon carbide (SiC) and gallium nitride (GaN) devices are characterized and compared, final selection is made based on comparison result. Mostly used high frequency high power DC/DC converter topology dual active bridge (DAB) is introduced and compared with novel CLLC resonant converter in terms of switching loss and conduction loss point of view. CLLC holds ZVS capability over all load range and smaller turn off current value. This is beneficial for high frequency operation and taken as our candidate. Device loss breakdown of CLLC converter is also given in the end. Medium voltage high frequency transformer is the key element in terms of insulation safety, power density and efficiency. Firstly, two mostly used transformer structures are compared. Then transformer insulation requirement is referred for 4160 V application according to IEEE standard. Solid insulation material are also compared and selected. Material thickness and insulation distance are also determined. Insulation capability is preliminary verified in FEA electric field simulation. Thirdly two transformer magnetic loss model are introduced including core loss model and litz wire winding loss model. Transformer turn number is determined based on core loss and winding loss trade-off. Different core loss density and working frequency impact is carefully analyzed. Different materials show their best performance among different frequency range. Transformer prototype is developed following designed parameter. We test the developed 15 kW 500 kHz transformer under 4160 V dry type transformer IEEE Std. C57.12.01 standard, including basic lightning test, applied voltage test, partial discharge test. 500 kHz 15 kW CLLC converter gate drive is our design challenge in terms of symmetry propagation delay, cross talk phenomenon elimination and shoot through protection. Gate drive IC is carefully selected to achieve symmetrical propagation delay and high common mode dv/dt immunity. Zero turn off resistor is achieved with minimized gate loop inductance to prevent cross talk phenomenon. Desaturation protection is also employed to provide shoot through protection. Finally 15 kW 500 kHz CLLC resonant converter is developed based on 4160V 500 kHz transformer and tested up to full power level with 98% peak efficiency.
Master of Science

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Rahim, Nasrudin Abd. "Closed-loop control of a current-mode AC/DC buck converter in 4 quadrant P-Q operation." Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/1342.

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Koran, Ahmed Mohammed. "Photovoltaic Source Simulators for Solar Power Conditioning Systems: Design Optimization, Modeling, and Control." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23681.

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This dissertation presents various systematic design techniques for photovoltaic (PV) source simulators to serve as a convenient tool for the dynamic performance evaluation of solar power conditioning systems and their maximum power point tracking algorithms. A well-designed PV source simulator should accurately emulate the static and the dynamic characteristic of actual PV generator. Four major design features should be adopted in any PV source simulator: (i) high power-stage efficiency, (ii) fast transient response-time, (iii) output impedance matching with actual PV generator, and (iv) precise reference generation technique. Throughout this research, two different PV source simulator systems are designed, modeled, and experimentally verified. The design of the first system focuses mainly on creating new reference generation techniques where the PV equivalent circuit is used to precisely generate the current-voltage reference curves. A novel technique is proposed and implemented with analog components to simplify the reference signal generator and to avoid computation time delays in digital controllers. A two-stage LC output filter is implemented with the switching power-stage to push the resonant frequency higher and thus allowing a higher control-loop bandwidth design while keeping the same switching ripple attenuation as in the conventional one-stage LC output filter. With typical control techniques, the output impedance of the proposed simulator did not
match the closed-loop output impedance of actual PV generator due to the double resonant peaks of the two-stage LC output filter. Design procedures for both control and power-stage circuits are explained. Experimental results verify the steady-state and transient performance of the proposed PV source simulator at around 2.7 kW output.
The design concept of the first simulator system is enhanced with a new type of PV source simulator that incorporates the advantages of both analog and digital based simulators. This simulator is characterized with high power-stage efficiency and fast transient response-time. The proposed system includes a novel three-phase ac-dc dual boost rectifier cascaded with a three-phase dc-dc interleaved buck converter. The selected power-stage topology is highly reliable and efficient. Moreover, the multi-phase dc-dc converter helps improve system transient response-time though producing low output ripple, which makes it adequate for PV source simulators.
The simulator circuitry emulates precisely the static and the dynamic characteristic of actual PV generator under different environmental conditions including different irradiance and temperature levels. Additionally, the system allows for the creation of the partial shading effect on PV characteristic. This dissertation investigates the dynamic performance of commercial and non-commercial solar power conditioning systems using the proposed simulator in steady-state and transient conditions. Closed-loop output impedance of the proposed simulator is verified at different operating conditions. The impedance profile --magnitude and phase- matches the output impedance of actual PV generator closely. Mathematical modeling and experimental validation of the proposed system is thoroughly presented based on a 2.0 kW hardware prototype. The proposed simulator efficiency including the active-front-end rectifier and the converter stages at the maximum power point is 96.4%.
Ph. D.

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Steckler, Pierre-Baptiste. "Contribution à la conversion AC/DC en Haute Tension." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI075.

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Le courant alternatif (AC) se prêtant bien à la majorité des problématiques de production, de transport et de distribution de l'électricité, on comprend qu'il soit massivement utilisé. Cependant, depuis plus d'un siècle, les bénéfices du courant continu haute tension (HVDC, pour High Voltage Direct Current) pour les longues distances sont bien connus. Aux interfaces, des convertisseurs AC/DC sont requis, leur composition évoluant au fil des avancées technologiques. Après avoir présenté les spécificités du HVDC et les contraintes qu'il introduit sur les convertisseurs AC/DC, ce manuscrit se focalise sur trois topologies : Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) et Series Bridge Converter (SBC). Elles sont présentées, dimensionnées et analysées en détail, puis comparées de façon quantitative en utilisant des indicateurs de performance originaux. Il en ressort que le MMC et le SBC sont particulièrement intéressants. La méthode de commande conventionnelle du MMC est ensuite présentée et ses propriétés structurelles sont mises en évidence. Une première loi de commande originale est présentée, avec des performances similaires mais une complexité inférieure à l'état de l'art. La seconde est non linéaire, basée sur la théorie de la platitude différentielle, et permet un suivi de puissance très rapide tout en assurant la stabilité exponentielle globale du système. Ces lois de commande sont évaluées en simulation, avec un modèle moyen et un modèle détaillé intégrant 180 sous-modules par bras. La dernière partie concerne le SBC. Après l'avoir modélisé, des résultats concernant une analyse structurelle de la topologie sont présentés ainsi qu'une loi de commande originale. Le rôle fondamental du transformateur pour les convertisseurs à structure série comme le SBC est souligné. Enfin, les performances de la loi de commande proposée sont testées en simulation
As Alternating Current (AC) is well suited for most of the production, transmission, and distribution applications, its massive use is easy to understand. However, for over a century, the benefits of High Voltage Direct Current (HVDC) for long-distance energy transmission are well known. To connect both, AC/DC converters are mandatory, whose nature evolves with technological progress. After the problematic induced by HVDC on AC/DC converters is presented, this manuscript is focused on three topologies: Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) and Series Bridge Converter (SBC). They are presented, sized, analyzed thoroughly, and compared in quantitative terms, using original key performance indicators. It appears that MMC and SBC are particularly promising. The conventional control method of the MMC is then presented, and its structural properties are highlighted. A first original control law is presented, with similar performances but less complexity than the state-of-the-art. A second control law, non-linear and based on differential flatness theory, is introduced. It allows a very fast power tracking response while ensuring the global exponential stability of the system. These control laws are tested in simulation, using an average model and a detailed model with 180 sub-modules per arm. The last part is dedicated to the SBC. After a modeling step, some results regarding its structural analysis are presented, and an original control law is introduced. The essential role of the transformer for series converters like the SBC is highlighted. Finally, the performance of the proposed control law is assessed in simulation

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Lu, Bing. "Investigation of High-density Integrated Solution for AC/DC Conversion of a Distributed Power System." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28128.

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With the development of information technology, power management for telecom and computer applications become a large market for power supply industries. To meet the performance and reliability requirement, distributed power system (DPS) is widely adopted for telecom and computer systems, because of its modularity, maintainability and high reliability. Due to limited space and increasing power consumption, power supplies for telecom and server systems are required to deliver more power with smaller volume. As the key component of DPS system, front-end AC/DC converter is under the pressure of continuously increasing power density. For conventional industry practices, some limitations prevents front-end converter meeting the power density requirement. In this dissertation, different techniques have been investigated to improve power density of front-end AC/DC converters. For PFC stage, at low switching frequency, PFC inductor size is large and limits the power density. Although increasing switching frequency can dramatically reduce PFC inductor size, EMI filter size might be larger at higher switching frequency because of the change of noise spectrum. Since the relationship between EMI filter size and PFC switching frequency is unclear for industry, PFC circuits always operate with switching frequency lower than 150 kHz. Based on the EMI filter design method, together with a simple EMI noise prediction model, relationship between EMI filter corner frequency and PFC switching frequency was revealed. The analysis shows that switching frequency of PFC circuit should be higher than 400 kHz, so that both PFC inductor and EMI filter size can be reduced. Although theoretical analysis and experimental results verify the benefits of high switching frequency PFC, it is essential to find a suitable topology that allows high switching frequency operation while maintains high efficiency. Three PFC topologies, single switch PFC, three-level PFC with range switch and dual Boost PFC, were evaluated with analysis and experiments. By using advanced semiconductor devices, together with proposed control methods, these topologies could achieve high efficiency at high switching frequency. Thus, the benefits of high frequency PFC can be realized. In front-end converter, large holdup time capacitor size is another barrier for power density improvement. To meet the holdup time requirement, bulky holdup time capacitor is normally used to provide energy during holdup time. Holdup time capacitor requirement can be reduced by using wider input voltage range DC/DC converte. Because LLC resonant converter can realized with input voltage range without sacrificing its normal operation efficiency, it becomes an attractive solution for DC/DC stage of front-end converters. Moreover, its small switching loss allows it operating at MHz switching frequency and achieves smaller passive component size. However, lack of design methodology makes the topology difficult to be implemented. An optimal design methodology for LLC resonant converter has been developed based on the analysis on the circuit during normal operation condition and holdup time. The design method is verified by a 1 MHz switching frequency LLC resonant converter with 76W/in3 power density. When front-end converter operates at high switching frequency, negative effects of circuit parasitics become more pronounced. By integrating active devices together with their gate drivers, Active Integrated power electronics module (IPEM) can largely reduce circuit parasitics. Therefore, switching loss and voltage stress on switching devices can be reduced. Moreover, IPEM concept can be extended into passive integration and EMI filter integration By using this power integration technology, power density and circuit performance of front-end converter can be improved, which is verified by theoretical analysis and experimental results.
Ph. D.

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Karamat, Asghar. "High frequency inverter-transformer-cycloconverter system for DC to AC (3-phase) power conversion." Thesis, Brunel University, 1991. http://bura.brunel.ac.uk/handle/2438/5195.

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This thesis is concerned with a 3-phase multistage high frequency link DC to AC power conversion with a novel inverter-cycloconverter circuitry. The conversion system is composed of a high frequency PWM inverter, step-up high frequency transformer and cycloconverter with bidirectional switching devices. In first stage the DC voltage of the power source , say a submarine battery, is inverted to a system of 3-phase sinusoidally modulated I kHz alternative wave forms. For this purpose a suggested optimized PWM technique for 3-phase inverter operation is adopted, in which harmonic components up to 17 th ( 17 kHz) are eliminated from the inverter output voltages. In the second stage, for DC input isolation from AC output and also for a voltage transformation ( here stepping-up )a high frequency ( size reduced ) transformer is employed. Generalized high frequency operation, influence and side effects of the transformer on overall system design & performance is investigated. In the final stage the 1 kHz -to- 50 Hz conversion process is accomplished by a 3-phase cycloconverter. The proposed "nonlinear modulation strategy" for cycloconverter output voltage and associated harmonic analysis is demonstrated, in which the harmonic components up to 38th (1.9 kHz ) are eliminated from the conversion system output voltage. To assess the suggested functioning principles for the inverter & cycloconverter , the prototype conversion system was developed. Some design criteria and switching device selection are presented, together with different voltage & current wave forms of the prototype system under resistive & inductive load (induction motor) and their respective spectra.

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Lopez, Santos Oswaldo. "Contribution to the DC-AC conversion in photovoltaic systems : Module oriented converters." Thesis, Toulouse, INSA, 2015. http://www.theses.fr/2015ISAT0001/document.

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Ces dernières années, un intérêt croissant pour les systèmes électroniques de puissance a été motivé par l'émergence de sources d'énergie distribuées et renouvelables raccordées aux réseaux électriques. Dans ce contexte, la nécessité de topologies de faibles puissances alimentées par quelques modules photovoltaïques, en évitant l'utilisation de transformateurs, a ouvert l'étude de convertisseurs spéciaux et l’étude des stratégies de commande associées afin d’assurer la stabilité, la fiabilité et un rendement élevé du dispositif. Une possible solution est d’utiliser un dispositif générique connu dans la littérature scientifique et commerciale comme « micro-onduleur » ou «convertisseur intégré au module » qui avec le module photovoltaïque définit un produit « plug and play » appelé "module AC".Ce travail est consacré à l'étude d'un micro-onduleur monophasé avec deux étapes sans transformateur raccordée au réseau. La topologie proposée est composé d’un convertisseur DC-DC non isolé élévateur avec un gain quadratique et un onduleur réducteur lié au réseau connectés en cascade. Le convertisseur DC-DC extrait en permanence la puissance maximale du module photovoltaïque malgré les changements dans les conditions environnementales. L'étape DC-AC injecte la puissance extraite par l'étape DC-DC dans le réseau et assure un niveau élevé de qualité de l’énergie. Les efforts de recherche de ce travail sont concentrés sur la mise au point de commandes utilisant comment base, la théorie de contrôle par mode de glissement, qui conduit à une mise en œuvre simple avec une description théorique complète validée á partir de simulations et expérimentations.Après avoir décrit l'état de l’art dans le premier chapitre, le manuscrit est divisé en quatre chapitres, qui sont dédiés respectivement à l’algorithme de recherche du point de puissance maximale (MPPT), á l’étape de conversion DC-DC, á l'étape de conversion DC-AC et finalement au micro-onduleur complet. Un nouvel algorithme de recherche extrémal du point de puissance maximale est développé (SM-ESC). Pour la étape DC-DC, le convertisseur élévateur quadratique avec seulement un interrupteur contrôlé est étudié utilisant le concept de résistance sans perte par mode de glissement (de l’acronyme anglais : Sliding-Mode Loss-Free-Resistor – SM-LFR) afin d’obtenir un gain de tension élevé avec un fonctionnement sûr et compatible avec l’algorithme MPPT. Pour la étape DC-AC, le convertisseur de pont complet est contrôlé comme un onduleur de source de puissance (de l’acronyme anglais : Power Source Inverter - PSI) en utilisant une commande par mode de glissement qui poursuit une référence sinusoïdale de courant de sortie. Cette commande est complétée par une boucle de régulation de la tension du bus DC qui assure une haute qualité d’énergie injectée dans le réseau. Enfin, les trois étapes constitutives sont fusionnées pour obtenir un micro-onduleur complètement contrôlé par la technique de mode de glissement, ce qui constitue le principal résultat et contribution de cette thèse
These last years, a growing interest in power electronic systems has been motivated by the emergence of distributed renewable energy resources and their interconnection with the grid. In this context, the need of low power topologies fed by a few photovoltaic modules avoiding the use of transformers opens the study of special converters and the associated control strategies ensuring stability, reliability and high efficiency. A resulted generic device known in the commercial and scientific literature as “microinverter” or “module integrated converter” performs a plug and play product together with the PV module called an “AC module”.This work is devoted to the study of a transformer-less single-phase double-stage grid-connected microinverter. The proposed topology has a non-isolated high-gain boost type DC-DC converter and a non-isolated buck type DC-AC converter connected in cascade through a DC bus. The DC-DC converter permanently extracts the maximum power of the PV module ensuring at the same time a good performance coping with power changes introduced by the change in the environmental conditions. The DC-AC stage injects the power extracted by the DC-DC stage into the grid ensuring a high level of power quality. The research efforts focus on the involved control functions based on the sliding mode control theory, which leads to a simple implementation with a comprehensive theoretical description validated through simulation and experimental results.After giving the state-of-the-art in the first chapter, the manuscript is divided into four chapters, which are dedicated to the Maximum Power Point Tracking (MPPT), the DC-DC stage and its control, the DC-AC stage and its control and the complete microinverter. A new Extremum Seeking Control (ESC) MPPT algorithm is proposed. The single-switch quadratic boost converter is studied operating as a Loss-Free-Resistor (LFR) obtaining a high DC output voltage level with a safe operation. The full-bridge converter is controlled as a Power Source Inverter (PSI) using a simple sliding-mode based tracking law, regulating the voltage of the DC bus and then ensuring a high power quality level in the grid connection. Finally, the three building blocks are merged to obtain a sliding mode controlled microinverter constituting the main result and contribution of the work

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Noon, John Patrick. "Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/101498.

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This work demonstrates the capability of a power electronic based power hardware-inthe- loop (PHIL) platform to emulate electric machines for the purpose of a motor drive testbench with a particular focus on induction machine emulation. PHIL presents advantages over full-hardware testing of motor drives as the PHIL platform can save space and cost that comes from the physical construction of multiple electric machine test configurations. This thesis presents real-time models that were developed for the purpose of PHIL emulation. Additionally, real-time modeling considerations are presented as well as the modeling considerations that stem from implementing the model in a PHIL testbench. Next, the design and implementation of the PHIL testbench is detailed. This thesis describes the design of the interface inductor between the motor drive and the emulation platform. Additionally, practical implementation challenges such as common mode and ground loop noise are discussed and solutions are presented. Finally, experimental validation of the modeling and emulation of the induction machine is presented and the performance of the machine emulation testbench is discussed.
Master of Science
According to the International Energy Agency (IEA), electric power usage is increasing across all sectors, and particularly in the transportation sector [1]. This increase is apparent in one's daily life through the increase of electric vehicles on the road. Power electronics convert electricity in one form to electricity in another form. This conversion of power is playing an increasingly important role in society because examples of this conversion include converting the dc voltage of a battery to ac voltage in an electric car or the conversion of the ac power grid to dc to power a laptop. Additionally, even within an electric car, power converters transform the battery's electric power from a higher dc voltage into lower voltage dc power to supply the entertainment system and into ac power to drive the car's motor. The electrification of the transportation sector is leading to an increase in the amount of electric energy that is being consumed and processed through power electronics. As was illustrated in the previous examples of electric cars, the application of power electronics is very wide and thus requires different testbenches for the many different applications. While some industries are used to power electronics and testing converters, transportation electrification is increasing the number of companies and industries that are using power electronics and electric machines. As industry is shifting towards these new technologies, it is a prime opportunity to change the way that high power testing is done for electric machines and power converters. Traditional testing methods are potentially dangerous and lack the flexibility that is required to test a wide variety of machines and drives. Power hardware-in-the-loop (PHIL) testing presents a safe and adaptable solution to high power testing of electric machines. Traditionally, electric machines were primarily used in heavy industry such as milling, processing, and pumping applications. These applications, and other applications such as an electric motor in a car or plane are called motor drive systems. Regardless of the particular application of the motor drive system, there are generally three parts: a dc source, an inverter, and the electric machine. In most applications, other than cars which have a dc battery, the dc source is a power electronic converter called a rectifier which converts ac electricity from the grid to dc for the motor drive. Next, the motor drive converts the dc electricity from the first stage to a controlled ac output to drive the electric machine. Finally, the electric machine itself is the final piece of the electrical system and converts the electrical energy to mechanical energy which can drive a fan, belt, or axle. The fact that this motor drive system can be generalized and applied to a wide range of applications makes its study particularly interesting. PHIL simplifies testing of these motor drive systems by allowing the inverter to connect directly to a machine emulator which is able to replicate a variety of loads. Furthermore, this work demonstrates the capability of PHIL to emulate both the induction machine load as well as the dc source by considering several rectifier topologies without any significant adjustments from the machine emulation platform. This thesis demonstrates the capabilities of the EGSTON Power Electronics GmbH COMPISO System Unit to emulate motor drive systems to allow for safer, more flexible motor drive system testing. The main goal of this thesis is to demonstrate an accurate PHIL emulation of a induction machine and to provide validation of the emulation results through comparison with an induction machine.

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Nathan, Kumaran Saenthan. "A novel DC-DC converter for photovoltaic applications." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288881.

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Growing concerns about climate change have led to the world experiencing an unprecedented push towards renewable energy. Economic drivers and government policies mean that small, distributed forms of generation, like solar photovoltaics, will play a large role in our transition to a clean energy future. In this thesis, a novel DC-DC converter known as the Coupled Inductors Combined Cuk-SEPIC' (CI-CCS) converter is explored, which is particularly attractive for these photovoltaic applications. A topological modification is investigated which provides several benefits, including increased power density, efficiency, and operational advantages for solar energy conversion. The converter, which is based on the combination of the Cuk and SEPIC converters, provides a bipolar output (i.e. both positive and negative voltages). This converter also offers both step-up and step-down capabilities with a continuous input current, and uses only a single, ground-referenced switching device. A significant enhancement to this converter is proposed: magnetic coupling of the converter's three inductors. This can substantially reduce the CI-CCS converter's input current ripple - an important benefit for maximum power point tracking (MPPT) in photovoltaic applications. The effect of this coupling is examined theoretically, and optimisations are performed - both analytically and in simulations - to inform the design of a 4 kW prototype CI-CCS converter, switched at a high frequency (100 kHz) with a silicon carbide (SiC) MOSFET. Simulation and experimental results are then presented to demonstrate the CI-CCS converter's operation and highlight the benefits of coupling its inductors. An efficiency analysis is also undertaken and its sources of losses are quantified. The converter is subsequently integrated into a domestic photovoltaic system to provide a practical demonstration of its suitability for such applications. MPPT is integrated into the CI-CCS DC-DC converter, and a combined half bridge/T-type converter is developed and paired with the CI-CCS converter to form an entirely transformerless single-phase solar energy conversion system. The combination of the CI-CCS converter's bipolar DC output with the combined half bridge/T-type converter's bipolar DC input allows grounding at both the photovoltaic panels and the AC grid's neutral point. This eliminates high frequency common mode voltages from the PV array, which in turn prevents leakage currents. The entire system can be operated in grid-connected mode - where the objective is to maximise power extracted from the photovoltaic system, and is demonstrated in stand-alone mode - where the objective is to match solar generation with the load's power demands.

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Bulhosa, João Paulo Rodrigues. "Controlo de um conversor AC-DC-AC para turbinas eólicas baseadas no PMSG." Master's thesis, Instituto Politécnico de Bragança, Escola Superior de Tecnologia e de Gestão, 2009. http://hdl.handle.net/10198/2062.

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A dissertação teve como objectivo o estudo e implementação do controlo de um conversor AC-DC-AC, constituído por um conversor DC/DC elevador e um inversor de tensão monofásico, para efectuar a ligação à rede de turbinas eólicas baseadas no gerador síncrono de ímanes permanentes. O controlo global do conversor AC-DC-AC seguiu uma estratégia na qual o controlo do conversor elevador e do inversor de tensão monofásico é implementado de modo independente. O primeiro visa maximizar a potência extraída da turbina através da implementação de um algoritmo de seguimento do ponto de potência máxima (MPPT), enquanto o segundo tem a função de extrair toda a energia proveniente do primeiro fornecendo-a à rede eléctrica com factor de potência unitário. Isto é conseguido com controlo em corrente através do qual se procura garantir que a corrente gerada pelo inversor está em fase com a tensão da rede. O desenvolvimento do controlo foi realizado no programa Simulink. Os controladores foram dimensionados, implementados, testados e validados progressivamente, de modo a minimizar o número de parâmetros a ajustar ao mesmo tempo. Foi desenvolvida uma interface gráfica, utilizando o programa ControlDesk, para permitir os ajustes necessários dos controladores e visualização de diversas variáveis do sistema. Esta fase do trabalho foi desenvolvida no Instituto Politécnico de Bragança, com vista à implementação prática. Os trabalhos continuaram com a realização de um estágio, no âmbito do programa Erasmus, no CIEMAT – Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas e posteriormente no CEDEX - Centro de Estudios y Experimentación de Obras Públicas, em Madrid. No CIEMAT foi apresentado o estado de desenvolvimento dos realizados no IPB, tendo em vista a implementação laboratorial. Os primeiros resultados experimentais foram obtidos no CEDEX com o controlo do conversor elevador. The goal of this dissertation was the analysis, implementation and control of an AC-DC-AC power converter built with a DC/DC step-up converter and a single phase inverter for grid-tied wind turbines based on permanent magnet synchronous generator. The overall control of the converter AC-DC-AC followed a strategy in which the control of the step-up converter and the single phase inverter was implemented independently. The first is used to maximize the power available in the wind turbine through the implementation of an algorithm for the maximum power point tracking (MPPT), while the second is used to capture all the energy provided by the first and send it to the grid with unit power factor. This is achieved with current control of the inverter in order to ensure that the current generated by the inverter is in phase with the mains voltage. The development of the monitoring program was carried out with the software Simulink. The PI controllers were designed, implemented, tested and validated step-by-step to minimize the number of parameters to adjust the same time. A graphical interface was developed using the software ControlDesk to allow suitable adjustments of the control, and display several variables of the system. This stage of work was developed at the Instituto Politécnico de Bragança, in view of the practical implementation. The work continued during an internship within the framework of Erasmus in CIEMAT - Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas and later in CEDEX - Centro de Estudios y Experimentación de Obras Públicas, in Madrid. In CIEMAT, the state of development of the work developed in IPB was presented, and continued in view of the implementation in laboratory. The first experimental results were obtained in CEDEX with the control of the step-up converter.

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Ghita, Ion. "Commande avancée de convertisseurs de puissance : application aux réseaux électriques embarqués." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC061.

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Dans les dernières années, le respect de l’environnement est devenu une des grandes préoccupations des clients du secteur automobile. Les constructeurs cherchent à réduire les émissions carbones de ses produits et les véhicules hybrides ou purement électriques apparaissent comme une alternative viable aux véhicules thermiques. Un des éléments importants de la réussite de la commercialisation des véhicules électriques est la recharge de la batterie qui peut être effectuée par différents moyens, avec des chargeurs embarqués/débarqués, à domicile ou sur la voie-publique. Dans ce domaine un système de charge performant doit notamment être robuste vis-à-vis des contraintes extérieures( perturbations réseaux, impédances de ligne, charges de plusieurs véhicules en même temps), avoir un bon rendement entre la puissance puisée à la prise et celle délivrée à la batterie, maitriser les courants harmoniques rejetés sur le réseau électrique (respect des différentes contraintes réglementaires liées aux perturbations émises). Pour répondre à ces exigences les travaux de cette thèse proposent des commandes innovantes des convertisseurs de puissance contenus dans les chargeurs électriques. Dans un premier temps, la modélisation des convertisseurs de puissance est réalisée en moyenne à la période de commutation et en moyenne généralisée pour d´écrire le processus de génération des harmoniques des courants et tensions des convertisseurs. Des lois de commande non-linéaire fondées sur la théorie de stabilité au sens de Lyapunov sont proposées de fac¸on à induire un comportement en boucle fermée satisfaisant les exigences souhaitées pour les convertisseurs de puissance. La partie commande est complétée par une partie d’observation nécessaire pour l’estimation des signaux non-mesurés et pour l’extraction harmonique. Enfin dans la dernière partie de la thèse, les différentes stratégies de commande sont validées par rapport aux exigences via une co-simulation en reproduisant l’architecture de logiciel model in the loop utilisée dans l’industrie
In the last few years the question of respecting the environment became a central concern of car users. The electric cars respond to the public trend of reducing the toxic emissions of conventional cars. The success of electric cars depends on the charging of the batteries, charging done either at home or on the public domain.The charging system has to respond to the following performance criteria:-robustness to exterior constraints: network perturbations, line impedance, multiple simultaneous charging of vehicles.-a good efficiency for the power transfer between the received power and the power delivered to the battery.-respecting the power distributer constrains for network harmonic pollution.These three points impose the need for efficient control laws for the battery charger. In this context, the power converters (AC / DC - DC / DC) are key components in electrical chargers , an improved control law of these elements can provide a better level of performance for the charger.This work is a continuation of previous work that resulted in several theses with CIFRE funding, in collaboration with Renault in the context of the electric car (but not only):- From an industrial viewpoint, the doctoral student will draw on the expertise, experience and Renault's test facilities in the field of electric traction in the automotive transport.- From an academic point of view the work will benefit from the skills of the working group 'System control’ within the L2S laboratory, in the field of multi-physics modelling, design of control laws and optimization.Supervision will be provided by:- Emmanuel Godoy (Professor, HDR, advisor) and Dominique Beauvois (professor, co-director) of the academic point of view.- Pedro Kvieska (Engineer, Doctor, Ecole Centrale de Nantes) for industrial management within Renault.Objectives of the thesisThe first two years of thesis work will focus on methodological studies of dedicated control laws. During the third year the work will be focused on the implementation of the proposed architectures and control strategies by: implementing of the new control strategies as prototypes on test bench and on the transferability of the proposed control approaches.A big part of the last year will naturally be devoted to the writing of the doctoral thesis and the preparation of the defence

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Wu, Wei. "MICRO-CIRCUIT DIODE FOR ULTRA-LOW-POWER ENERGY HARVESTING." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1415.

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Harvesting energy from ultra-low-power vibration energy sources typically employs a rectifier circuit as the first power conditioning stage. The Schottky diode has a 0.15 V - 0.2 V threshold voltage and can not extract energy efficiently at low voltage. Other technologies such as MOSFET bridge or active diode are designed to minimize the voltage drop to reduce the conduction loss. However, these designs require either additional power supplies to operate comparators or have a larger threshold turn-on voltage than Schottky. Therefore, most rectifiers have an unresponsive or significant low-efficiency zone when the input power is low. This dissertation will elaborate on a backward diode based self-powered micro-circuit diode that will operate in the extremely weak or low alternating source applications, where the existing approaches offer poor outcomes. This proposed micro-circuit diode was compared to a Schottky diode in several experiment setup. The micro-circuit based half-wave rectifier circuit harvested 3.1 mV DC at a 239.5 Ohm load when the input magnitude is 50 mV while the Schottky diode was unable to convert this ultra-low AC power. This dissertation also provides the analysis of two alternating sources, the oscillatory electromagnetic generator and the piezoelectric energy harvester, to conduct experiments in a more realistic context. The micro-circuit diode shows excellent advantages in electromagnetic generator experiment, the micro-circuit based half-wave rectifier circuit harvested 5.16 mV DC at a 0.5 kOhm load when the input magnitude is 40 mV. However, due to the large leakage current in negative resistance region, this micro-circuit is unable to show advantages in piezoelectric energy harvester applications.

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18

LaBella, Thomas Matthew. "A High-Efficiency Hybrid Resonant Microconverter for Photovoltaic Generation Systems." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50526.

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The demand for increased renewable energy production has led to increased photovoltaic (PV) installations worldwide. As this demand continues to grow, it is important that the costs of PV installations decrease while the power output capability increases. One of the components in PV installations that has lots of room for improvement is the power conditioning system. The power conditioning system is responsible for converting the power output of PV modules into power useable by the utility grid while insuring the PV array is outputting the maximum available power. Modular power conditioning systems, where each PV module has its own power converter, have been proven to yield higher output power due to their superior maximum power point tracking capabilities. However, this comes with the disadvantages of higher costs and lower power conversion efficiencies due to the increased number of power electronics converters. The primary objective of this dissertation is to develop a high-efficiency, low cost microconverter in an effort to increase the output power capability and decrease the cost of modular power conditioning systems. First, existing isolated dc-dc converter topologies are explored and a new topology is proposed based on the highly-efficient series resonant converter operating near the series resonant frequency. Two different hybrid modes of operation are introduced in order to add wide input-voltage regulation capability to the series resonant converter while achieving high efficiency through low circulating currents, zero-current switching (ZCS) of the output diodes, zero-voltage switching (ZVS) and/or ZCS of the primary side active switches, and direct power transfer from the source to the load for the majority of the switching cycle. Each operating mode is analyzed in detail using state-plane trajectory plots. A systematic design approach that is unique to the newly proposed converter is presented along with a detailed loss analysis and loss model. A 300-W microconverter prototype is designed to experimentally validate the analysis and loss model. The converter featured a 97.7% weighted California Energy Commission (CEC) efficiency with a nominal input voltage of 30 V. This is higher than any other reported CEC efficiency for PV microconverters in literature to date. Each operating mode of the proposed converter can be controlled using simple fixed-frequency pulse-width modulation (PWM) based techniques, which makes implementation of control straightforward. Simplified models of each operating mode are derived as well as control-to-input voltage transfer functions. A smooth transition method is then introduced using a two-carrier PWM modulator, which allows the converter to transition between operating modes quickly and smoothly. The performance of the voltage controllers and transition method were verified experimentally. To ensure the proposed converter is compatible with different types of modular power conditioning system architectures, system-level interaction issues associated with different modular applications are explored. The first issue is soft start, which is necessary when the converter is beginning operation with a large capacitive load. A novel soft start method is introduced that allows the converter to start up safely and quickly, even with a short-circuited output. Maximum power point tracking and double line frequency ripple rejection are also explored, both of which are very important to ensuring the PV module is outputting the maximum amount of available power. Lastly, this work deals with efficiency optimization of the proposed converter. It is possible to use magnetic integration so that the resonant inductor can be incorporated into the isolation transformer by way of the transformer leakage inductance in order to reduce parts count and associated costs. This chapter, however, analyzes the disadvantages to this technique, which are increased proximity effect losses resulting in higher conduction losses. A new prototype is designed and tested that utilizes an external resonant inductor and the CEC efficiency was increased from 97.7% to 98.0% with a marginal 1.8% total cost increase. Additionally, a variable frequency efficiency optimization algorithm is proposed which increases the system efficiency under the high-line and low-line input voltage conditions. This algorithm is used for efficiency optimization only and not control, so the previously presented simple fixed-frequency modeling and control techniques can still be utilized.
Ph. D.

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Alves, Montanari Allan. "Enhanced instantaneous power theory for control of grid connected voltage sourced converters under unbalanced conditions." IEEE Transactions on Power Electronics, 2017. http://hdl.handle.net/1993/32184.

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This thesis introduces a new method especially designed to control the instantaneous power in voltage sourced converters operating under unbalanced conditions, including positive, negative and zero sequence content. A transformation technique, labelled mno transformation, was developed to enable the decomposition of the total instantaneous power flowing on three-phase transmission topologies into constant and oscillating terms. It is applied to three-wire and four-wire schemes, especially accommodating zero sequence unlike previous approaches. Classical and modern electric power theories are presented, particularly focusing on their definitions for adverse AC scenarios. The main mathematical transformations conceived to analyze such situations are summarized, showing their respective advantages and disadvantages. An enhanced instantaneous power theory is introduced. The novel proposed power equations, named mno instantaneous power components, expands the application of the p-q theory, which is attached to the αβ0 transformation. The mno instantaneous power theory is applied to develop an innovative power control method for grid connected voltage sourced converters in order to minimize power oscillations during adverse AC scenarios, particularly with zero sequence content. The method permits to sustain constant instantaneous three-phase power during unbalanced conditions by controlling independently the constant and the oscillating terms related to the instantaneous power. The effectiveness of the proposed control approach and the proposed power conditioning scheme was demonstrated using electromagnetic transient simulation of a VSC connected to an AC system.
May 2017

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JÃnior, JosÃ Ailton LeÃo Barboza. "A Double boost converter with PFC and series/parallel input connection for uninterrupted power system." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16257.

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fator de potÃncia e recurso para operar com dois valores de tensÃo de entrada. O mesmo Ã aplicÃvel a sistemas ininterruptos de energia do tipo dupla conversÃo ou on-line com caracterÃsticas de tensÃo de entrada bivolt (110 Vca e 220 Vca) e desta maneira Ã descartada a utilizaÃÃo de um autotransformador com seletor de tensÃo. O conversor em estudo Ã composto por dois conversores CA-CC boost clÃssicos, em que, para uma tensÃo de entrada de 110 Vca as entradas sÃo conectadas em paralelo e para uma tensÃo de entrada de 220 Vca as entradas sÃo conectadas em sÃrie. A ideia Ã fazer com que se tenha uma divisÃo equilibrada na entrada de cada conversor quando a tensÃo da rede elÃtrica for 220 Vca. Assim cada conversor boost clÃssico recebe metade da tensÃo total de alimentaÃÃo do conversor proposto. A estratÃgia de controle Ã baseada no controle por modo corrente mÃdia aplicada a ambos os conversores para proporcionar a correÃÃo do fator de potÃncia e a regulaÃÃo da tensÃo de saÃda. Para verificar o estudo teÃrico foi desenvolvido o projeto do circuito de potÃncia e controle validando atravÃs de resultados de simulaÃÃo e experimentais para um protÃtipo de 2,4 kW. Para a conexÃo paralelo e sÃrie das entradas, os resultados obtidos foram satisfatÃrios e o conversor operou adequadamente.
This work presents a study of a Double Boost AC-DC Converter with power factor correction and dual input voltage operation capability via a selector switch. Such converter can be applied to on-line uninterruptible power supplies with dual voltage input characteristics, this way avoiding the usage of a low frequency autotransformer. The studied structure is composed by two AC-DC classical boost converters, in which for input voltage of 110 Vac both its inputs are connected in parallel, and, for 220 Vac, they are connected in series. The control strategy is based in the average current mode control applied to both converters, in order to provide the power factor correction and output voltage regulation. Simulation and experimental results for 2.4 kW are presented, and so are validate the theoretical study and design. Connecting the inputs in parallel and series, the results were satisfactory and the converter operated properly.

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Caballero, Diaz Luis. "Contributions to the design and operation of a multilevel-active-clamped Dc-Ac grid- connected power converter for wind energy conversion systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/454979.

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The demand of wind energy has considerably increased during the last decades. In order to fulfil this great energy demand, wind energy conversion systems (WECS) are designed to manage higher power ratings. Currently, the most attractive power converter topology in commercial WECS is the conventional two-level back-to-back voltage-source converter (2L-B2B). However, the 2L-B2B topology could have difficulties to achieve an acceptable performance with the available switching devices for the largest WECS, even though having the cost advantage. Instead, multilevel converters increase the power without increasing neither current nor blocking voltage of the power semiconductors, enabling a cost-effective design for the largest WECS using the available switching devices. Within the multilevel converters, the 3L-NPC topology offers high penetration in the market of large WECS. However, one of its major drawbacks is that the power loss is unevenly distributed among the switching devices. Therefore, the 3L-NPC output power capability is limited by the thermal performance of the most stressed switching device, which depends on the operating point. The 3L-ANPC topology was proposed in order to improve the power loss distribution among the power semiconductors. The 3L-ANPC provides a controllable path for the neutral current. Hence, the 3L-ANPC is able to offer certain freedom to distribute the power loss among the power semiconductors. As a consequence, and compared to the 3L-NPC, the thermal performance is more uniform and the output power capability increases. However, there is still room for improvement. In light of the previous discussion, the proposed thesis defines enhanced design guidelines for the dc-ac grid-connected 3L-ANPC power converter, focused on improving its reliability and electrical performance, and following the trend of the current state of the art to define a feasible solution for the next generation of WECS. The thesis contributions are based on defining an enhanced power device configuration and a novel commutation sequence, avoiding concentrating both significant conduction and switching losses on a single power semiconductor device. This allows then selecting the most appropriate device for each converter position, which leads to a better converter efficiency and to a more uniform power loss distribution and thermal performance. This also leads to a higher converter power rating, and it is expected to improve the converter reliability.
La demanda de energía eólica ha incrementado considerablemente durante las últimas décadas. Con el objetivo de satisfacer esta gran demanda, los sistemas de conversión de energía eólica (WECS) son diseñados para operar con mayores niveles de potencia. Actualmente, la topología de convertidor de potencia más atractiva en los WECS comerciales es el convertidor de dos niveles operando en fuente de tensión y configuración back to back (2L-B2B). Sin embargo, esta topología podría tener dificultades para ofrecer un comportamiento aceptable en los WECS de mayor potencia con los dispositivos actuales, incluso aunque su coste sea reducido. En cambio, los convertidores multinivel pueden incrementar la potencia sin necesidad de incrementar la corriente ni el voltaje de bloqueo de los dispositivos, permitiendo conseguir un diseño adecuado para los WECS de mayor potencia usando los dispositivos actuales. Dentro de los convertidores multinivel, la topología 3L-NPC tiene una gran aceptación en el mercado eólico, siendo una solución común en los WECS de mayor potencia. Sin embargo, su gran inconveniente es que la potencia pérdida es distribuida de una manera desequilibrada entre los dispositivos. De este modo, la potencia de salida se ve limitada por el comportamiento térmico del dispositivo más estresado a nivel térmico, el cual depende del punto de operación. De esta manera, la topología 3L-ANPC fue propuesta con el objetivo de mejorar la distribución de las pérdidas del convertidor entre los dispositivos. El convertidor 3L-ANPC proporciona un camino totalmente controlable para la conexión del punto neutro. Por lo tanto, el convertidor 3LANPC es capaz de ofrecer cierto grado de libertad para distribuir la potencia pérdida entre los dispositivos. Como consecuencia, y comparado con el convertidor 3L-NPC, el comportamiento térmico es mucho más equilibrado y la potencia de salida puede ser incrementada. Sin embargo, todavía hay margen de mejora para alcanzar mejores prestaciones en el comportamiento del convertidor 3L-ANPC. A raíz de la argumentación anterior, la tesis propuesta define nuevas guías de diseño para el convertidor 3L-ANPC cc-ca conectado a la red. Las guías de diseño están focalizadas en mejorar la fiabilidad y el comportamiento eléctrico del convertidor, respetando la tendencia del estado del arte actual para definir una solución factible para la próxima generación de WECS. Las contribuciones de la tesis están basadas en definir una configuración de dispositivos mejorada y una secuencia de conmutación novedosa, evitando concentrar grandes pérdidas de conducción y de conmutación en un mismo dispositivo. Las contribuciones permiten seleccionar el dispositivo más adecuado para cada posición del convertidor, consiguiendo una mejor eficiencia y una distribución de pérdidas y comportamiento térmico más equilibrado. Además, también permiten operar con potencias más elevadas, y mejorar la fiabilidad del convertidor.

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Gonçalves, Amilcar Flamarion Querubini. "Sistema de geração distribuída controlado em tensão e potência e utilizado de forma isolada ou conectada à rede de distribuição." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-28012016-080537/.

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Esta tese apresenta uma estratégia de controle para gerenciar a potência entregue ou absorvida da rede, independente de características das cargas locais. Para atingir este objetivo é utilizado um inversor fonte de tensão (VSI) que funcionará semelhante a um sistema de geração distribuída (GD) ou como um filtro ativo. O VSI é controlado por meio de controladores clássicos em cascata, nos quais a malha interna é utilizado para estabilizar a corrente e a malha externa controla a tensão nos terminais de saída da GD. Para melhorar a resposta do VSI são colocados filtros ressonantes em paralelo ao controlador de tensão (P+RES). Além disso, as respostas dos filtros ressonantes são melhoradas através da utilização de um método adequado de discretização, no qual os coeficientes são alterados dinamicamente mediante a frequência de sincronismo produzido pelo algoritmo de sincronismo (PLL). O controle de potência apresenta duas estruturas de controle em malha fechada: uma para controlar a potência reativa através da rede pelo ajuste da amplitude da tensão da GD, e o outra para controlar a potência ativa, modificando o ângulo de defasagem entre as tensões da rede e as tensões GD. Por fim, um conjunto de simulações e resultados experimentais é apresentado para validar todas as propostas deste trabalho.
This thesis presents a control strategy to manage the power delivered to or absorbed from the grid, independently of the local load characteristics. To achieve this goal, a voltage source inverter (VSI) will work as a distributed generation system (DG) or according to active filter. The VSI will be controlled by means of a double cascade classical controller, in which the inner loop is used to stabilize the VSI output current and the outer loop controls the DG terminal voltage. To improve the response of the VSI, resonant filters are placed in parallel. Additionally, resonant filter dynamic responses are enhanced through the use of a proper discretization method, in which the coefficients are changed dynamically by means of the synchronism frequency produced by the phase-locked loop (PLL) algorithm. This study also exhibits two closed-loop structures: one to control the reactive power through the grid by adjusting the DG voltage amplitude, and the other to control the active power by modifying the angle of displacement between the grid and the DG voltages. Both power control structures operate adequately in decoupled operation mode, so that one has a faster dynamic response than the other. To verify all statements proposed in this thesis, a set of simulations and experimental results are presented.

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Silva, Luciano de Souza da Costa e. [UNESP]. "Retificador boost entrelaçado com elevado fator de potência e sem ponte de diodos." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/87091.

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Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-15Bitstream added on 2014-06-13T18:49:30Z : No. of bitstreams: 1 silva_lsc_me_ilha.pdf: 2144752 bytes, checksum: 39f1f729cd628eedd60a6b582fefd576 (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Este trabalho propõe um conversor CA-CC, modulado por largura de pulso (PWM), de elevado fator de potência, dotado de um controle variável da razão cíclica. O estágio de potência do conversor pré-regulador do fator de potência (PFP) proposto é composto por múltiplas células entrelaçadas. A integração das técnicas de entrelaçamento (interleaving) à técnica de eliminação da ponte retificadora da entrada (bridgeless) busca diminuir as perdas de energia e distribuir os esforços de corrente nos semicondutores da estrutura conversora de potência. O levantamento bibliográfico foi realizado com intuito de analisar resultados e características de conversores CA-CC baseados em estruturas PFP boost modificadas. Comparações foram realizadas levando em consideração as características de distorção harmônica, fator de potência, complexidade do circuito de controle, eficiência energética, esforços nos semicondutores de potência e emissão de interferência eletromagnética (IEM). O conversor proposto é então equacionado e os valores dos componentes acumuladores de energia determinados são escritos como função das especificações de projeto. Análises gráficas indicam o comportamento da distorção harmônica e do fator de potência da estrutura atuando em diferentes níveis de tensão. Simulações são realizadas como forma de comprovar a eficácia do sistema conversor no que se refere à correção do fator de potência e à distribuição dos esforços nos semicondutores de potência. Os principais resultados estão dispostos em tabelas comparativas, que indicam um fator de potência praticamente unitário. O sistema de regulação da tensão saída, testado via simulação computacional, apresenta resultados que demonstram boa dinâmica na resposta transitória e erro nulo a regime frente às variações de carga e afundamentos na...
This paper proposes an AC-DC converter, pulse width modulated (PWM) with high power factor and a variable duty cycle control. The power factor preregulator (PFP) converter proposed is composed of multiple bridgeless boost interleaved cells. The integration of these techniques allows a reduction in the energy losses and sharing the stress in power semiconductors. The literature review was performed in order to analyze the results and characteristics of AC-DC converters based on modified PFC boost structures. Comparisons were made taking into account the characteristics of harmonic distortion, power factor, complexity of control circuitry, energy efficiency, current stress in power semiconductors, and emission of electromagnetic interference (EMI). The proposed converter is mathematically equated and the values of the reactive components are written as a function of design specifications. Graphical analysis indicates the behavior of harmonic distortion and power factor of the structure at different voltage levels. Simulations are performed in order to demonstrate compliance of the converter system with respect to the power factor correction and distribution efforts in the power semiconductors. The main results are arranged in comparative tables which indicate power factor very closed to unity. The control system applied to the converter was evaluated through the computer simulations which showed good dynamics at transient response and null steady-state error faced to load variations and sags in the voltage supply. The prototype for the power stage implemented in the laboratory operated according... (Complete abstract click electronic access below)

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de, Groot Martijn. "Development of a Plug and Play Solution for Commercial Off-grid Solar Refrigeration : Presenting a Battery Supported System Providing the AC Power Required to run a Coolfinity 300L Commercial Refrigerator." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302991.

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In this report the design and testing of a plug and play system to run Coolfinity’s Icevolt 300 refrigerator on solar panels is discussed. Such a system will be able to provide adequate cooling for food & beverages in area’s with unreliable or no electricity available. Currently such systems are only available for small chest refrigerators, while the Icevolt 300 is a large standing commercial refrigerator with a glass door. This is ideal for shops, cafés restaurants and smaller distribution centres. The system contains a solar charge controller, a battery and an inverter. First the component specifications and required solar panels are calculated. From those calculations system components are evaluated. A custom casing is designed to fit the components. An OEM is chosen and the chosen Inverter is tested extensively. The tests show that the inverter does not have any problems starting the Icevolt 300 compressor at a reduced voltage. Many battery manufacturers are evaluated and samples from three different manufacturers are obtained and tested. Samples of one of the manufacturers match specifications and have no issues with the high start up power of the compressor. A full system test proofs that the system works, but also indicates that the original refrigerator consumption estimate was too low. This means more PV panels are needed than originally estimated. With the information from the tests a new model is build that estimates the performance more accurate. A program is written to estimate the performance and decide the PV panels required. The pilot series of the case showed a lot of improvements are needed in the case design, especially on cost. A test is prepared in Mali but no test data is obtained yet. Based on the work done it would be recommend to investigate DC direct refrigerators instead of continuing the path of PV to AC systems.
I denna rapport diskuteras design och testning av ett plug and play - system för att köra Coolfinity’s Icevolt 300 -kylskåp på solpaneler. Ett sådant system kommer att kunna tillhandahålla tillräcklig kylning för mat och dryck i områden med opålitlig eller ingen tillgänglig el. För närvarande är sådana system endast tillgängliga för små kylboxar, medan Icevolt 300 är ett stort stående kommersiellt kylskåp med en glasdörr. Detta är idealiskt för butiker, kaféer och mindre distributionscentra. Systemet innehåller en laddningsregulator för solpaneler, ett batteri och en växelriktare. Först beräknas komponentspecifikationerna och nödvändiga solpaneler. Utifrån dessa beräkningar utvärderas systemkomponenter. Ett anpassat hölje är utformat för att passa komponenterna. En OEM väljs och den valda växelriktaren testas utförligt. Testerna visar att växelriktaren inte har några problem att starta Icevolt 300 -kompressorn med reducerad spänning. Många batteritillverkare utvärderas och prover från tre olika tillverkare erhålls och testas. Prover från en av tillverkarna matchar specifikationerna och har inga problem med kompressorns höga starteffekt. Ett fullständigt systemtest bevisar att systemet fungerar, men indikerar också att den ursprungliga uppskattningen av kylförbrukningen var för låg. Det betyder att fler PV -paneler behövs än vad som ursprungligen beräknades. Med informationen från testerna byggs en ny modell som uppskattar prestandan mer exakt. Ett program skrivs för att uppskatta prestanda och bestämma vilka PV -paneler som krävs. Pilotserien för höljet visade att många förbättringar behöver göras vad beträffar höljets design, särskilt vad gäller kostnaden. Ett test förbereds i Mali men inga testdata har erhållits ännu. Baserat på det utförda arbetet skulle det rekommenderas att undersöka direkta DC -kylskåp istället för att fortsätta vägen för PV till AC-system.

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Alves, rodrigues Luis Gabriel. "Design and characterization of a three-phase current source inverter using 1.7kV SiC power devices for photovoltaic applications." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT030.

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Classiquement, la chaîne de conversion de l’énergie électrique des centrales photovoltaïques comporte un champ photovoltaïque (PV) délivrant une tension maximale de 1kV suivi d’un hacheur élévateur connecté à un onduleur de tension triphasé. Cette chaîne de conversion à deux étages (DC/DC + DC/AC) est ensuite raccordée sur le réseau moyenne tension au travers d’un transformateur BT/HTA. Dans l’objectif de simplifier les systèmes de conversion PV, ce travail de recherche s’intéresse à l’étude et la mise en œuvre d’une topologie DC/AC n’employant qu’un seul étage de conversion : l’Onduleur de Courant triphasé. Bien que relativement simple, l’Onduleur de Courant présente comme inconvénient majeur les pertes par conduction. Pour pallier ce problème, des interrupteurs à grand-gap au Carbure de Silicium (SiC) sont employés, ce qui permet de convertir de l’énergie de façon performante (η>98.5%) tout en gardant une fréquence de commutation élevée (plusieurs dizaines de kHz). Les modules à semi-conducteurs de puissance du marché n’étant pas compatibles avec ce type de convertisseur, des modules particuliers en SiC ont été développés dans le cadre de la thèse. La caractérisation dynamique de ces nouveaux modules est réalisée dans le but de servir de base à la conception d’un démonstrateur de l’Onduleur de Courant d’une puissance nominale de 60kW. Enfin, le rendement de la partie semi-conducteur de puissance est évalué par une méthode calorimétrique confirmant l’aptitude de la topologie à fonctionner à des fréquences de commutation supérieures. L’originalité de ces travaux réside principalement dans la conception, caractérisation et mise en œuvre de ce nouveau module de puissance adapté à cette topologie connue, mais peu étudiée à l’heure actuelle avec des interrupteurs au SiC
Classically, the energy conversion architecture found in photovoltaic (PV) power plants comprises a multitude of solar arrays delivering a maximum voltage of 1kV followed by a step-up chopper connected to a three-phase voltage source inverter. This two-stage conversion system (DC/DC + DC/AC) is then connected to the MV grid through a LV/MV transformer. In order to simplify the PV systems, this research work focuses on the study and implementation of a DC/AC topology employing a single conversion stage: the three-phase current source inverter (CSI). Although relatively simple, the CSI presents as major drawback the conduction losses. To deal with this problem, wide-bandgap silicon carbide (SiC) semiconductors are used, which allows to efficiently convert energy (η> 98.5%) while keeping a relatively high switching frequency (several tens of kHz). Nonetheless, since the available power semiconductor modules on the market are not compatible with the CSI, a novel 1.7kV SiC-based module is developed in the context of the thesis. Thus, the dynamic characterization of the new SiC device is carried out and serves as a basis for the design of a 60kW Current Source Inverter prototype. Finally, the inverter’s semiconductor efficiency is evaluated through a calorimetric method, confirming the ability of the topology to operate at higher switching frequencies. At the present time, little research has been conducted on the CSI implementation with SiC devices. The originality of this work lies mainly in the design, characterization and implementation of the new SiC power module adapted to this well-known inverter topology

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Dbeiss, Mouhannad. "Mission Profile-Based Accelerated Ageing Tests of SiC MOSFET and Si IGBT Power Modules in DC/AC Photovoltaic Inverters." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT020/document.

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Dans le cas des installations photovoltaïques, l’onduleur est le premier élément défaillant dont il est difficile d’anticiper la panne, et peu d’études ont été faites sur la fiabilité de ce type de convertisseur. L'objectif de cette thèse est de proposer des outils et méthodes en vue d'étudier le vieillissement des modules de puissance dans ce type d'application en se focalisant sur les phénomènes de dégradation liés à des aspects thermomécaniques. En règle générale, le vieillissement accéléré des modules de puissance est effectué dans des conditions aggravées de courant (Cyclage Actif) ou de température (Cyclage Passif) pour accélérer les processus de vieillissement. Malheureusement, en appliquant ce type de vieillissement accéléré, des mécanismes de défaillances qui ne se produisent pas dans la vraie application peuvent être observés et, inversement, d'autres mécanismes qui se produisent habituellement peuvent ne pas apparaître. La première partie de la thèse se focalise donc sur la mise en place d'une méthode de vieillissement accéléré des composants semi-conducteurs des onduleurs photovoltaïques. Cela est fait en s’appuyant sur l’analyse des profils de mission du courant efficace de sortie des onduleurs et de la température ambiante, extraits des centrales photovoltaïques situées au sud de la France sur plusieurs années. Ces profils sont utilisés pour étudier les dynamiques du courant photovoltaïque, et sont introduites dans des modèles numériques pour estimer les pertes et les variations de la température de jonction des semi-conducteurs utilisés dans les onduleurs, en utilisant l’algorithme de comptage de cycles "Rainflow". Cette méthode est ensuite mise en œuvre dans deux bancs expérimentaux. Dans le premier, les composants sous test sont des modules IGBT. Les composants sont mis en œuvre dans un banc de cyclage utilisant la méthode d'opposition et mettant en œuvre le profil de vieillissement défini précédemment. Un dispositif in-situ de suivi d'indicateurs de vieillissement (impédance thermique et résistance dynamique) est également proposé et évalué. Le deuxième banc est consacré à l'étude de modules de puissance à base de MOSFET SiC. Le vieillissement est effectué dans les mêmes conditions que pour les modules IGBT et de nombreux indicateurs électriques sont monitorés mais, cette fois ci, en extrayant les composants de l'onduleur de cyclage. Les résultats obtenus ont permis de déterminer des indicateurs de vieillissement d’IGBT et de MOSFET SiC utilisés dans un onduleur photovoltaïque
In the case of photovoltaic installations, the DC/AC inverter has the highest failure rate, and the anticipation of its breakdowns is still difficult, while few studies have been done on the reliability of this type of inverter. The aim of this PhD is to propose tools and methods to study the ageing of power modules in this type of application, by focusing on ageing phenomena related to thermo-mechanical aspects. As a general rule, the accelerated ageing of power modules is carried out under aggravated conditions of current (Active Cycling) or temperature (Passive Cycling) in order to accelerate the ageing process. Unfortunately, when applying this type of accelerated ageing tests, some failure mechanisms that do not occur in the real application could be observed, while inversely, other mechanisms that usually occur could not be recreated. The first part of the PhD focuses on the implementation of an accelerated ageing method of the semiconductor devices inside photovoltaic inverters. This is accomplished by analyzing the mission profiles of the inverter’s output current and ambient temperature, extracted over several years from photovoltaic power plants located in the south of France. These profiles are used to study photovoltaic current dynamics, and are introduced into numerical models to estimate losses and junction temperature variations of semiconductors used in inverters, using the cycle counting algorithm “Rainflow”. This method is then performed in two experimental test benches. In the first one, the devices under test are IGBT modules, where the accelerated ageing profile designed is implemented using the opposition method. Moreover, an in-situ setup for monitoring ageing indicators (thermal impedance and dynamic resistance) is also proposed and evaluated. The second bench is devoted to study the ageing of SiC MOSFET power modules. The accelerated ageing test is carried out under the same conditions as for the IGBT modules with more monitored electrical indicators, but this time by disconnecting the semiconductor devices from the inverter. The results obtained allowed to determine several potential ageing indicators of IGBTs and SiC MOSFETs used in a photovoltaic inverter

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Silva, Luciano de Souza da Costa e. "Retificador boost entrelaçado com elevado fator de potência e sem ponte de diodos /." Ilha Solteira : [s.n.], 2011. http://hdl.handle.net/11449/87091.

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Orientador: Falcondes Jose Mendes de Seixas
Banca: Guilherme de Azevedo e Melo
Banca: Jurandir de Oliveira Soares
Resumo: Este trabalho propõe um conversor CA-CC, modulado por largura de pulso (PWM), de elevado fator de potência, dotado de um controle variável da razão cíclica. O estágio de potência do conversor pré-regulador do fator de potência (PFP) proposto é composto por múltiplas células entrelaçadas. A integração das técnicas de entrelaçamento (interleaving) à técnica de eliminação da ponte retificadora da entrada (bridgeless) busca diminuir as perdas de energia e distribuir os esforços de corrente nos semicondutores da estrutura conversora de potência. O levantamento bibliográfico foi realizado com intuito de analisar resultados e características de conversores CA-CC baseados em estruturas PFP boost modificadas. Comparações foram realizadas levando em consideração as características de distorção harmônica, fator de potência, complexidade do circuito de controle, eficiência energética, esforços nos semicondutores de potência e emissão de interferência eletromagnética (IEM). O conversor proposto é então equacionado e os valores dos componentes acumuladores de energia determinados são escritos como função das especificações de projeto. Análises gráficas indicam o comportamento da distorção harmônica e do fator de potência da estrutura atuando em diferentes níveis de tensão. Simulações são realizadas como forma de comprovar a eficácia do sistema conversor no que se refere à correção do fator de potência e à distribuição dos esforços nos semicondutores de potência. Os principais resultados estão dispostos em tabelas comparativas, que indicam um fator de potência praticamente unitário. O sistema de regulação da tensão saída, testado via simulação computacional, apresenta resultados que demonstram boa dinâmica na resposta transitória e erro nulo a regime frente às variações de carga e afundamentos na... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This paper proposes an AC-DC converter, pulse width modulated (PWM) with high power factor and a variable duty cycle control. The power factor preregulator (PFP) converter proposed is composed of multiple bridgeless boost interleaved cells. The integration of these techniques allows a reduction in the energy losses and sharing the stress in power semiconductors. The literature review was performed in order to analyze the results and characteristics of AC-DC converters based on modified PFC boost structures. Comparisons were made taking into account the characteristics of harmonic distortion, power factor, complexity of control circuitry, energy efficiency, current stress in power semiconductors, and emission of electromagnetic interference (EMI). The proposed converter is mathematically equated and the values of the reactive components are written as a function of design specifications. Graphical analysis indicates the behavior of harmonic distortion and power factor of the structure at different voltage levels. Simulations are performed in order to demonstrate compliance of the converter system with respect to the power factor correction and distribution efforts in the power semiconductors. The main results are arranged in comparative tables which indicate power factor very closed to unity. The control system applied to the converter was evaluated through the computer simulations which showed good dynamics at transient response and null steady-state error faced to load variations and sags in the voltage supply. The prototype for the power stage implemented in the laboratory operated according... (Complete abstract click electronic access below)
Mestre

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Shah, Vatsal Sonikbhai. "Optimization and Up-Gradation of 3-Phase Half-Bridge Inverter Board." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-173664.

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Solar Bora AB is a Linköping based company that provides end to end solution for clean and reliable energy. System developed by them generates high power 230V AC to run electrical appliances. The system consist of string of batteries which are charged by rooftop solar cells and the energy stored in the batteries is converted to AC to provide a grid voltage like experience even though the system is not connected to a grid. Energy stored in the batteries need to be converted from DC to AC efficiently. Inverter used for conversion should be efficient enough to reduce losses. This master thesis deals with optimization and Up-gradation of Half-Bridge inverter board so that switching loss can be minimized to increase efficiency. Initial part of the thesis involves investigation of different parameters which contribute to losses in inverter. Based on that some improvements were suggested in existing design of half-bridge board. Another task involved in the thesis was complete re-design of half-bridge. More efficient and robust components were selected for complete re-design. Based on new components and its specifications a new circuit and PCB was designed in Altium Designer. Lab testing was performed to verify the functionality of new Half-bridge.

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Rahimi, Arian. "Design And Implementation Of Low Power Interface Electronics For Vibration-based Electromagnetic Energy Harvesters." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613820/index.pdf.

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For many years batteries have been used as the main power sources for portable electronic devices. However, the rate of scaling in integrated circuits and micro-electro-mechanical systems (MEMS) has been much higher than that of the batteries technology. Therefore, a need to replace these temporary energy reservoirs with small sized continuously charged energy supply units has emerged. These units, named as energy harvesters, use several types of ambient energy sources such as heat, light, and vibration to provide energy to intelligent systems such as sensor nodes. Among the available types, vibration based electromagnetic (EM) energy harvesters are particularly interesting because of their simple structure and suitability for operation at low frequency values (<
10 Hz), where most vibrations exits. However, since the generated EM power and voltage is relatively low at low frequencies, high performance interface electronics is required for efficiently transferring the generated power from the harvester to the load to be supplied. The aim of this study is to design low power and efficient interface electronics to convert the low voltage and low power generated signals of the EM energy harvesters to DC to be usable by a real application. The most critical part of such interface electronics is the AC/DC converter, since all the other blocks such as DC/DC converters, power managements units, etc. rely on the rectified voltage generated by this block. Due to this, several state-of-the-art rectifier structures suitable for energy harvesting applications have been studied. Most of the previously proposed rectifiers have low conversion efficiency due to the high voltage drop across the utilized diodes. In this study, two rectifier structures are proposed: one is a new passive rectifier using the Boot Strapping technique for reducing the diode turn-on voltage values
the other structure is a comparator-based ultra low power active rectifier. The proposed structures and some of the previously reported designs have been implemented in X-FAB 0.35 µ
m standard CMOS process. The autonomous energy harvesting systems are then realized by integrating the developed ASICs and the previously proposed EM energy harvester modules developed in our research group, and these systems have been characterized under different electromechanical excitation conditions. In this thesis, five different systems utilizing different circuits and energy harvesting modules have been presented. Among these, the system utilizing the novel Boot Strap Rectifier is implemented within a volume of 21 cm3, and delivers 1.6 V, 80 µ
A (128 µ
W) DC power to a load at a vibration frequency of only 2 Hz and 72 mg peak acceleration. The maximum overall power density of the system operating at 2 Hz is 6.1 µ
W/cm3, which is the highest reported value in the literature at this operation frequency. Also, the operation of a commercially available temperature sensor using the provided power of the energy harvester has been shown. Another system utilizing the comparator-based active rectifier implemented with a volume of 16 cm3, has a dual rail output and is able to drive a 1.46 V, 37 µ
A load with a maximum power density of 6.03 µ
W/cm3, operating at 8 Hz. Furthermore, a signal conditioning system for EM energy harvesting has also been designed and simulated in TSMC 90 nm CMOS process. The proposed ASIC includes a highly efficient AC-DC converter as well as a power processing unit which steps up and regulates the converted DC voltages using an on-chip DC/DC converter and a sub-threshold voltage regulator with an ultra low power management unit. The total power consumption on the totally passive IC is less than 5 µ
W, which makes it suitable for next generation MEMS-based EM energy harvesters. In the frame of this study, high efficiency CMOS rectifier ICs have been designed and tested together with several vibration based EM energy harvester modules. The results show that the best efficiency and power density values have been achieved with the proposed energy harvesting systems, within the low frequency range, to the best of our knowledge. It is also shown that further improvement of the results is possible with the utilization of a more advanced CMOS technology.

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Fernandes, Rodolfo Castanho [UNESP]. "Retificador trifásico de 18 pulsos com estágio CC controlado por histerese constante." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/87117.

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Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-03Bitstream added on 2014-06-13T20:29:04Z : No. of bitstreams: 1 fernandes_rc_me_ilha.pdf: 1607084 bytes, checksum: d60bd1d35a36564730a6c9f6b43790ab (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho propõe um novo conversor CA-CC trifásico de múltiplos pulsos com estágios CC-CC elevadores de tensão controlados pela técnica de histerese constante. Nesta proposta não são empregados indutores de interfase. A finalidade deste conversor é a de possibilitar um barramento CC regulado para aplicações embarcadas, acionamentos elétricos e afins, sempre com preocupações relacionadas aos aspectos de Qualidade de Energia Elétrica. Assim, a proposta deve apresentar elevado fator de potência, baixa distorção harmônica total de corrente drenada da rede elétrica. Ampla revisão bibliográfica, reunindo as propostas mais recentes da literatura para conversores com mesma finalidade, é feita para que sejam estudadas as estruturas de potência, técnicas de controle, versatilidade, possibilidade de isolamento galvânico e robustez. Em seguida, é detalhada a proposta principal deste trabalho por meio da apresentação do equacionamento do autotransformador, dos estágios elevadores de tensão e da técnica de controle. Esta análise permite que sejam feitas simulações com todos os elementos do conversor CA-CC e então, se desenvolva o projeto físico dos elementos magnéticos e se escolham os componentes eletrônicos do protótipo. O número reduzido de componentes de controle e a simplicidade dos circuitos de potência são grandes atrativos da proposta discutida. Todas as informações relevantes são descritas detalhadamente e, sempre que possível, meios alternativos de solucionar problemas são também apresentados, de forma que fiquem claras as possibilidades de melhoria da técnica empregada. A operação conjunta de todos os elementos mais a técnica de controle foi validada, de maneira que se comprovou, por meio de ensaios, todos os princípios de funcionamento da proposta de conversor CA-CC. Pelos resultados experimentais, obteve-se corrente drenada...
This work proposes a new AC-DC three-phase multipulse converter with DC-DC boost stages and constant hysteresis control. The objective of this converter is to provide a reliable DC bus for on-board applications, electric motor drives and similars, always considering power quality issues. Thus, the proposal presents high power factor and low harmonic distortions in the currents from the mains. A wide revision is made on other recent proposals found in the scientific literature. Different topologies are compared considering power circuits, control techniques, isolation possibility and robustness. The second chapter presents the details on the main proposal of this work and also the mathematical equations that describe the autotransformer, boost converters and control strategy. Later, simulation results are commented and discussed and the physical design is detailed. The output filter elements, power components and control elements are specified. Experimental results including main waveforms, efficiency, voltage regulation and temperature rise are presented for the autotransformer. The boost stages are also tested and its results are discussed. Finally, the proposed AC-DC converter is tested and the control technique applied to the power stage is validated

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TENÓRIO, JÚNIOR Gilberto Alves. "Inversores Fonte Z monofásicos e conversor de dois estágios para sistemas fotovoltaicos sem Transformador." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/19498.

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Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-11T12:39:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado M276 - Gilberto.pdf: 3559945 bytes, checksum: e0e92cec09c72c5a7b8b98260c3b9a8e (MD5)
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Este trabalho apresenta um estudo comparativo de conversores monofásicos aplicados a sistemas fotovoltaicos sem transformador. Topologias de inversores sem transformador têm menores custos, tamanho e peso. Contudo, a não utilização do transformador pode ser responsável por consideráveis valores de correntes de fuga. A associação em série de vários módulos fotovoltaicos se faz necessária para alcançar o nível de tensão desejado no barramento c.c.. Com o intuito de reduzir o número de módulos fotovoltaicos em série, topologias com característica de elevação de tensão (boost) podem ser utilizadas. Portanto, topologias que possuem estas características e que possam apresentar baixos valores de correntes de fuga devem ser escolhidas para o estudo. As topologias presentes neste trabalho são: o conversor de dois estágios, o inversor fonte Z monofásico com diodo adicional, e o inversor fonte Z de três estados.
This work presents a comparative study of single-phase converters applied to transformerless photovoltaic systems. Topologies of transformerless inverters have lower costs, size and weight. However, not using it may cause considerable amounts of leakage currents. The association in series of several PV modules is needed to achieve the voltage level desired in d.c. bus. In order to reduce the number of photovoltaic modules in series, topologies with voltage boost characteristic can be used. Therefore, topologies that have voltage boost characteristic and can have low leakage current values are chosen for the study. Topologies present in this work are: the two stages single-phase converter, the single-phase Z-source inverter with additional diode, and the single-phase three switch three state Z-source inverter.

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32

Rivas, Juan 1976. "Radio frequency dc-dc power conversion." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38691.

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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2007.
Includes bibliographical references (p. 197-204).
THIS THESIS addresses the development of system architectures and circuit topologies for dc-dc power conversion at very high frequencies. The systems architectures that are developed are structured to overcome limitations associated with conventional designs. In particular, the new architectures described here structure the energy processing and control functions of the system in such a manner that high efficiency can be achieved across wide load range while regulating the output. Moreover, these architectures are amenable to circuit designs operating at fixed frequency and duty ratio, considerable easing the circuit design. The thesis also develops new circuit designs that are well suited to these new architectures. As part of this, two new gate drives and control methods are introduced that greatly reduce gating loss at VHF frequencies for fixed frequency, fixed duty ratio operation. One of these gating schemes provides near theoretical minimum loss by resonantly wave shaping the gate voltage to have a trapezoidal drive voltage. This waveshaping approach is then taken a step further, yielding a new class of dc-dc converter that archives a significant reduction in peak switch voltage stress, requires small passive components with low energy storage, and provides the capability for extremely rapid startup and shutdown. This new class of converter is well adapted to the architectures and gate drive methods proposed in the thesis. It is expected that the new architectures and circuit designs introduced here will contribute to the development of power converter having greatly reduced size and improved transient performance.
by Juan Rivas.
Sc.D.

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33

Alepuz, Menéndez Salvador Simón. "Aportació al control del convertidor CC/CA de tres nivells." Doctoral thesis, Universitat Politècnica de Catalunya, 2004. http://hdl.handle.net/10803/6330.

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La presente tesis estudia, propone y realiza sus principales aportaciones en el campo del control para el convertidor CC/CA de tres niveles, sobre la topología denominada Neutral-Point-Clamped, aunque se puede extender a otras topologías y/o número de niveles. Se presenta una metodología de modelado que emplea funciones de conmutación de fase, el operador de promediado y la transformación D-Q, tal que los modelos obtenidos en el dominio D-Q contienen una información completa sobre la dinámica del sistema. La estrategia de conmutación se puede entender como una extensión de la estrategia PWM senoidal de dos a tres niveles. Esta estrategia es simple y no realiza el control de ninguna de las variables del sistema. En esta tesis, el controlador se encarga de regular todas las variables del sistema, incluido el equilibrio del bus de continua. Este es un enfoque diferente del convencional, donde el equilibrio del bus de continua se consigue mediante la elección adecuada de los estados redundantes del convertidor en la estrategia de conmutación, mientras que el resto de variables se regulan a través del controlador. Para la realización del controlador, se propone la técnica de control lineal multivariable LQR (Linear Quadratic Regulator), complementada con la técnica de control no lineal adaptativo denominada programación de ganancia (Gain Scheduling). Se presenta, además, una metodología de cálculo del controlador. Este control es versátil, abierto y adaptable. En cualquier caso, el controlador se puede adaptar a las necesidades concretas de cada aplicación. El cálculo del controlador se realiza mediante simulación con MatLab-Simulink. Los modelos matemáticos que emplean las funciones de conmutación del convertidor son aquellos que ofrecen un mejor compromiso entre velocidad de simulación y precisión. Para validar el control propuesto, se ha diseñado y construido un equipo experimental donde el controlador se ha mostrado aplicable, útil y eficaz en la regulación de las distintas cargas y aplicaciones experimentadas, incluso con carga no lineal, bajo diferentes condiciones de trabajo y variables a controlar, tanto en régimen permanente como en procesos transitorios. La rapidez y calidad de la respuesta transitoria es comparable a la de otros sistemas de control publicados. Es especialmente interesante el excelente control conseguido del equilibrio del bus de continua. Además, la robustez del control permite cancelar el error estacionario aunque diferentes parámetros del sistema presenten desviaciones significativas respecto los valores esperados. El uso de la programación de ganancia junto con la técnica LQR se ha mostrado muy efectivo, puesto que permite realizar diferentes tipos de control. Se ha comprobado la congruencia entre simulaciones y resultados experimentales obtenidos, lo que valida los modelos de simulación empleados y el proceso de diseño del controlador mediante simulación.
This dissertation study, propose and carry out the main contributions in the field of three-level inverter control, using the topology Neutral-Point-Clamped, although results can be extended to other topologies and/or number of levels. A procedure for modelling is presented, based on line-switching functions, moving average operator and D-Q transformation. Then, the obtained models in D-Q frame contain complete information about system dynamics. Switching strategy is simple and can be considered as an extension of two-level sinusoidal PWM to three level. The system variables are not controlled by the switching strategy. In this work, all the system variables are controlled by the regulator, including DC-link balance. This control approach is different than the conventional one, where DC-link balance is achieved by means of a proper selection of redundant states in the switching strategy, and the other variables are controlled by the regulator. The regulator is based on the multivariable linear control technique LQR (Linear Quadratic Regulator), in combination with the non-linear adaptive control technique Gain Scheduling. Moreover, a methodology for the calculation of the controller is presented. This controller is versatile, open and adaptable. However, the controller can be built depending on the concrete specifications of each application. The controller is calculated by means of simulation using MatLab-Simulink. The mathematical models based on the switching functions of the converter give the best trade-off between simulation speed and precision. In order to validate the proposed controller, an experimental prototype has been designed and implemented. Experimental results show that the controller is useful and effective for the regulation of different loads and applications, even with non-linear loads, different operation points and variables to control, in steady-state and transitory operation. Dynamic response speed and quality are similar to other control systems in the literature. The DC-link balance control achieved is specially interesting. Furthermore, steady-state error is cancelled due to the robustness of the controller, even though significant deviation of different system parameters are present. The use of Gain-Scheduling in combination with LQR is effective, allowing the calculation of regulators with different control strategies. Good agreement between simulations and experimental results has been found. This result validates simulation models and the design method for the controller, based on simulations.

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34

Alepuz, Menéndez Salvador Simón. "Aportación al control del convertidor CC/CA de tres niveles." Doctoral thesis, Universitat Politècnica de Catalunya, 2004. http://hdl.handle.net/10803/6330.

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Abstract:

La presente tesis estudia, propone y realiza sus principales aportaciones en el campo del control para el convertidor CC/CA de tres niveles, sobre la topología denominada Neutral-Point-Clamped, aunque se puede extender a otras topologías y/o número de niveles. Se presenta una metodología de modelado que emplea funciones de conmutación de fase, el operador de promediado y la transformación D-Q, tal que los modelos obtenidos en el dominio D-Q contienen una información completa sobre la dinámica del sistema. La estrategia de conmutación se puede entender como una extensión de la estrategia PWM senoidal de dos a tres niveles. Esta estrategia es simple y no realiza el control de ninguna de las variables del sistema. En esta tesis, el controlador se encarga de regular todas las variables del sistema, incluido el equilibrio del bus de continua. Este es un enfoque diferente del convencional, donde el equilibrio del bus de continua se consigue mediante la elección adecuada de los estados redundantes del convertidor en la estrategia de conmutación, mientras que el resto de variables se regulan a través del controlador. Para la realización del controlador, se propone la técnica de control lineal multivariable LQR (Linear Quadratic Regulator), complementada con la técnica de control no lineal adaptativo denominada programación de ganancia (Gain Scheduling). Se presenta, además, una metodología de cálculo del controlador. Este control es versátil, abierto y adaptable. En cualquier caso, el controlador se puede adaptar a las necesidades concretas de cada aplicación. El cálculo del controlador se realiza mediante simulación con MatLab-Simulink. Los modelos matemáticos que emplean las funciones de conmutación del convertidor son aquellos que ofrecen un mejor compromiso entre velocidad de simulación y precisión. Para validar el control propuesto, se ha diseñado y construido un equipo experimental donde el controlador se ha mostrado aplicable, útil y eficaz en la regulación de las distintas cargas y aplicaciones experimentadas, incluso con carga no lineal, bajo diferentes condiciones de trabajo y variables a controlar, tanto en régimen permanente como en procesos transitorios. La rapidez y calidad de la respuesta transitoria es comparable a la de otros sistemas de control publicados. Es especialmente interesante el excelente control conseguido del equilibrio del bus de continua. Además, la robustez del control permite cancelar el error estacionario aunque diferentes parámetros del sistema presenten desviaciones significativas respecto los valores esperados. El uso de la programación de ganancia junto con la técnica LQR se ha mostrado muy efectivo, puesto que permite realizar diferentes tipos de control. Se ha comprobado la congruencia entre simulaciones y resultados experimentales obtenidos, lo que valida los modelos de simulación empleados y el proceso de diseño del controlador mediante simulación.
This dissertation study, propose and carry out the main contributions in the field of three-level inverter control, using the topology Neutral-Point-Clamped, although results can be extended to other topologies and/or number of levels. A procedure for modelling is presented, based on line-switching functions, moving average operator and D-Q transformation. Then, the obtained models in D-Q frame contain complete information about system dynamics. Switching strategy is simple and can be considered as an extension of two-level sinusoidal PWM to three level. The system variables are not controlled by the switching strategy. In this work, all the system variables are controlled by the regulator, including DC-link balance. This control approach is different than the conventional one, where DC-link balance is achieved by means of a proper selection of redundant states in the switching strategy, and the other variables are controlled by the regulator. The regulator is based on the multivariable linear control technique LQR (Linear Quadratic Regulator), in combination with the non-linear adaptive control technique Gain Scheduling. Moreover, a methodology for the calculation of the controller is presented. This controller is versatile, open and adaptable. However, the controller can be built depending on the concrete specifications of each application. The controller is calculated by means of simulation using MatLab-Simulink. The mathematical models based on the switching functions of the converter give the best trade-off between simulation speed and precision. In order to validate the proposed controller, an experimental prototype has been designed and implemented. Experimental results show that the controller is useful and effective for the regulation of different loads and applications, even with non-linear loads, different operation points and variables to control, in steady-state and transitory operation. Dynamic response speed and quality are similar to other control systems in the literature. The DC-link balance control achieved is specially interesting. Furthermore, steady-state error is cancelled due to the robustness of the controller, even though significant deviation of different system parameters are present. The use of Gain-Scheduling in combination with LQR is effective, allowing the calculation of regulators with different control strategies. Good agreement between simulations and experimental results has been found. This result validates simulation models and the design method for the controller, based on simulations.

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35

Zengel, Jason A. "DC-DC power conversion with galvanic isolation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FZengel.pdf.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2003.
Thesis advisor(s): Robert W. Ashton, Todd R. Weatherford. Includes bibliographical references (p. 83-84). Also available online.

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36

Lo, Franco Francesco. "Integrazione di sistemi di accumulo a batterie e impianti fotovoltaici di grande taglia per applicazioni grid-connected." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.

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In un impianto fotovoltaico connesso alla rete elettrica, l’ integrazione di un sistema di accumulo permette di raccogliere l’ energia dal solare nelle ore di minor richiesta di rete (di giorno), ed erogarla nei momenti di bassa produzione e di maggiore richiesta di rete (la sera). In collaborazione con ENGIE Eps, è sorta l’ esigenza di confrontare tre diverse tipologie di accoppiamento delle batterie in un impianto ibrido PV+Batteria connesso alla rete elettrica. La prima architettura è chiamata AC coupling poiché il BESS (Battery Energy Storage System) è connesso tramite opportuni convertitori, direttamente alla rete elettrica. La terza e la seconda architettura sono denominate DC Coupling poiché il BESS è collegato tramite un convertitore o senza, al lato DC dell’ impianto. Il confronto è stato realizzato analizzando i flussi di potenza dell’ impianto facendo riferimento a dati di produzione reali forniti da ENGIE Eps. Più in particolare, sono stati forniti i dati di produzione e di irraggiamento di un impianto reale di potenza massima pari a 285 MW, con storage di capacità pari a 275 MWh. La valutazione della potenza richiesta all’ impianto è stata ottenuta dall’analisi del segnale AGC relativo alla rete nella quale l’ impianto è inserito. Tale segnale `e stato generato a partire da dati di frequenza di rete forniti dall’ azienda. Dall’ analisi precedentemente descritta si è individuata l’ architettura migliore in termini di rendimento, che risulta essere la DC coupling con DC/DC sulla batteria. Nell’ ultima parte della tesi si è inoltre svolto su richiesta di ENGIE Eps, lo studio del controllo dei convertitori relativi all’ architettura in esame. La strategia di controllo individuata è descritta nel dettaglio in questo documento.

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37

Wahby, Riad Samir 1981. "Radio frequency rectifiers for DC-DC power conversion." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16690.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Includes bibliographical references (p. 75-78).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
A significant factor driving the development of power conversion technology is the need to increase performance while reducing size and improving efficiency. In addition, there is a desire to increase the level of integration of DC-DC converters in order to take advantage of the cost and other benefits of batch fabrication techniques. While advances in the power density and integration of DC-DC converters have been realized through development of better active device technologies, much room for improvement remains in the size and fabrication of passive components. To achieve these improvements, a substantial increase in operating frequency is needed, since intermediate energy storage requirements are inversely proportional to frequency. Unfortunately, traditional power conversion techniques are ill-suited to handle this dramatic escalation of switching frequency. New architectures have been proposed which promise to deliver radical performance improvements while potentially reaching microwave frequencies. These new architectures promise to enable substantial miniaturization of DC-DC converters and to permit much a higher degree of integration. The principal effort of this thesis is the development of design and characterization methods for rectifier topologies amenable to use in the new architectures. A computational design approach allowing fast and accurate circuit analysis and synthesis is developed and applied, along with traditional analysis, to two demonstrative rectifier topologies. In addition, the application of coupled magnetic structures for parasitic mitigation is considered. Experimental implementations are investigated to verify analytic and computational results.
by Riad Samir Wahby.
M.Eng.

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38

Liang, Chenchen. "Contribution à l'étude d'une chaîne de conversion d'énergie AC-DC / DC-DC tolérantes aux défauts." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4080/document.

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Pour répondre au contexte d’exploitation des énergies renouvelables marines où l’accès aux systèmes de production d’énergie électrique est délicat, cette thèse porte sur l’étude d’une chaîne de conversion d’énergie tolérante aux défauts. Trois volets sont investigués : l’analyse comportementale de la topologie, le contrôle de la puissance produite ainsi que la détection et la localisation des défauts. La chaîne est constituée d’une MSAP pentaphasée, d’un redresseur à diodes à 5 bras et de 3 convertisseurs DC-DC de type Boost entrelacés. Pour la stratégie de contrôle de la puissance de sortie, un double asservissement est appliqué au bloc DC-DC. Des modèles dynamiques petits signaux sont établis. La boucle interne est dédiée à l’asservissement du courant d'entrée de l’étage Boost et la boucle externe au contrôle de la puissance. Trois types de régulateurs en courant sont étudiés et comparés. Des approches de synchronisation des commandes des 3 Boosts sont proposées. Il ressort que le régulateur non linéaire, dit MRC, satisfait complètement aux performances désirées. Le contrôle de puissance, intégré ensuite dans la chaîne complète de production d’énergie et testé pour différents modes de fonctionnement sains et dégradés, est de très bon niveau. Des méthodes de détection et de localisation des défauts au niveau de l’entrée et de la sortie du redresseur ont été développées. En se basant sur la mesure des courants de phase ou sur la mesure de la tension en sortie du redresseur, les défauts côté AC sont détectés et localisés. La détection côté continu est de faible complexité. Cette méthode est ensuite étendue aux défauts de l’étage DC-DC en utilisant son courant d’entrée
To answer the context of marine renewable energy exploitation where the access of energy production system is difficult, this thesis deals with the study of a fault tolerant energy conversion chain. Three aspects are investigated: behavior analysis of the topology; output power control; detection and location of faults. The chain involves a five-phase PMSG, a five-leg diode rectifier and a three-interleaved DC-DC Boost converter. Concerning the output power control strategy, a double-loop control is applied on the DC-DC block. Small-signal dynamic models are established. The inner loop is used for controlling the input current of the Boost stage. The outer loop is for the output power. Three types of current controllers are studied and compared. Methods of synchronization for the three-interleaved Boost converter control are proposed. It results that the nonlinear controller, called in French version, the MRC, totally satisfies the desired performances. The control of power, which is then used for the full conversion chain, is tested under different operating modes (health and fault) and is of high performances. Several methods for detecting and locating rectifier’s AC and DC side faults have been developed. Based on the measurements of phase currents or the measurement of the output voltage of the rectifier, AC side faults can be detected and located. DC measurement based fault detection is of low complexity. This method is then extended to the faults of DC-DC block by using its input current

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39

Ficagna, Paulo Canuto dos Santos. "Modelagem, projeto e implementação de um conversor isolado com um único estágio e correção do fator de potência." Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/8450.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This Master Thesis presents a new analysis, modeling and design guideline for an Insulated Power Factor Corrected Single-Stage Converter. First, the operating principle is presented which provides a better understanding of the converter. So, based on this new analysis, the two operation modes description and the new steady-state gain of the converter are provided. A new control strategy for the input current control-loop is also proposed which provides an improvement of the total harmonic distortion (THD). The conditions to reset the magnetic flux for the high frequency transformer (HFT) into a switching period and the mitigation of the reactive energy are provided. At the sequence, the transfer functions that describe the dynamic behavior of the output voltage and the input current due to perturbations on duty-cycle and input voltage are derived. These dynamic models are derived based on the averaged equivalent circuit (AEC) obtained by modeling an equivalent DC-DC converter. Finally, the design guideline and experimental results for validation of the mathematical analysis and numerical simulation confirmation are provided.
Esta Dissertação de Mestrado apresenta uma nova análise, modelagem e metodologia de projeto de um conversor CA-CC isolado com um único estágio e correção do fator de potência. Inicialmente, é apresentado o princípio de operação do conversor em estudo propiciando um melhor entendimento do funcionamento do mesmo. Assim, baseada na nova análise, são apresentados os dois modos de operação do conversor e o novo ganho estático resultante. Também é proposta uma nova estratégia de controle para a corrente de entrada do conversor proporcionando uma redução na distorção harmônica total (DHT). Também serão estabelecidas as condições necessárias para a desmagnetização do núcleo do transformador de alta freqüência (TAF) em um período de chaveamento e a minimização de reativos circulantes. Posteriormente, são obtidas as funções de transferências que descrevem o comportamento dinâmico da tensão de saída e da corrente de entrada para perturbações na variável de controle ou na tensão de entrada. Esses modelos dinâmicos serão derivados do circuito médio equivalente (CME) obtido através da modelagem do conversor em estudo operando como um conversor CC-CC equivalente. Por fim, são apresentadas uma metodologia de projeto e os resultados experimentais para a validação da análise matemática e confirmação dos resultados obtidos através de simulações numéricas.

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Anderson, Glenn Warwick Jan. "Hybrid simulation of AC-DC power systems." Thesis, University of Canterbury. Electrical and Computer Engineering, 1995. http://hdl.handle.net/10092/1176.

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Transient stability studies are primarily concerned with the generator response of ac power systems and use only steady state type equations to model HVdc converter terminals. These equations are adequate for small disturbances at the converter terminals but cannot accurately represent a converters behaviour during, and through its recovery of, a significant transient disturbance. A detailed three phase electromagnetic analysis is necessary to describe the converters correct behaviour. This thesis describes an accurate and effective hybrid method combining these two types of studies, for analyzing dynamically fast devices such as HVdc converters within ac power systems. Firstly, conventional techniques are reviewed for both a transient stability analysis of power systems and for an electromagnetic transient analysis of HVdc converters. This review deals in particular with the two programs that constitute the hybrid developed in this thesis. Various techniques are then examined to efficiently and accurately pass the dynamic effects of an HVdc link to an ac system stability study, and the dynamic effects of an ac system to a detailed HVdc link study. An optimal solution is derived to maximise the inherent advantages of a hybrid. Finally, the hybrid is applied to a test system and its effectiveness in performing its task is shown.

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41

Mayes, Peter Richard. "A novel AC/DC bidirectional power converter." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239439.

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Al-Mothafar, M. R. D. "High frequency inverter-cycloconverter system for DC to AC conversion." Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378135.

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43

Elshaer, Mohamed A. "AC/DC Smart Control and Power Sharing of DC Distribution Systems." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/556.

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The purpose of this research is to develop a grid connected DC distribution system to ensure efficient integration of different alternate sources to the power system. An investigation of different AC and DC converter topologies and their control is conducted. A new converter topology for sharing DC power was developed to enhance the efficiency and stability of the alternate sources connected to the DC Distribution System. Mathematical model and control system design of the developed converters were included in the thesis. A novel smart-PID controller for optimal control of DC-DC converter was used as voltage controller in PV systems. This controller maximizes the stable operating range by using genetic algorithm (GA) to tune the PID parameters ultimately at various loading conditions. A fuzzy logic approach was then used to add a factor of intelligence to the controller such that it can move among different values of proportional gain, derivative gain, and integral gain based on the system conditions. This controller allows optimal control of boost converter at any loading condition with no need to retune the parameters or possibility of failure. Moreover, a novel technique to move between the PI and PID configurations of the controller such that the minimum overshoot and ripple are achieved. This increases the controller applicability for utilization of PV systems in supplying sensitive loads. An effective algorithm for optimizing distribution system operation in a smart grid, from cost and system stability points of view, was developed. This algorithm mainly aims to control the power available from different sources so they satisfy the load demand with the least possible cost while giving the highest priority to renewable energy sources. Moreover, a smart battery charger was designed to control the batteries and allow them to discharge only when there is a small load predicted. During the period they become available, they act as a buffer for the predicted large load to increase the stability of the system and reduce voltage dips.

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Seixas, Mafalda Maria Morais. "Conversão eólica offshore ligada à rede elétrica: modelação e simulação." Doctoral thesis, Universidade de Évora, 2015. http://hdl.handle.net/10174/16084.

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A tese incide sobre a modelação e simulação de um sistema de conversão de energia eólica offshore com ligação à rede elétrica por transmissão de energia elétrica estudada quer em corrente alternada quer em corrente contínua, no contexto atual de reestruturação do setor elétrico, e integrando a dinâmica relevante. Além da transmissão de energia elétrica, o sistema é constituído por uma plataforma flutuante semissubmersível; uma turbina eólica de velocidade variável; um sistema de transmissão de energia mecânica cuja dinâmica é descrita respetivamente por uma, duas, três ou cinco massas girantes; um gerador síncrono com excitação assegurada por meio de ímanes permanentes; um conversor eletrónico de energia, descrito respetivamente por um conversor de dois níveis ou por um conversor multinível na configuração de díodos de ligação múltipla de três, de quatro, de cinco ou de p níveis. O controlo do sistema utiliza o modo de deslizamento associado com a modulação PWM por vetores espaciais e controladores PI, ditos de clássicos, ou controladores PI de ordem fracionária. Os comportamentos que advêm do facto da energia eólica ser uma fonte de energia variável, com intermitência, assim como, os de eventuais falhas de funcionamento dos dispositivos que controlam o sistema são estudados na tese, recorrendo a simulações computacionais. As contribuições fundamentais envolvem a modelação do conversor de p níveis, as correntes nos bancos de condensadores associadas aos níveis de tensão e a estratégia de controlo do conversor multinível para a selecção do vetor de tensão. As simulações computacionais permitem concluir sobre o desempenho favorável do sistema e simultaneamente fornecem informação quantificada sobre o comportamento das grandezas mecânicas e elétricas, permitindo quer em fase de projeto, quer em fase de utilização o estudo de comportamentos que necessitam de serem corrigidos devido a serem potencialmente indesejáveis; Offshore Wind Energy Conversion System Connected to the Electric Grid: Modeling and Simulation Abstract: The thesis focuses on the modeling and simulation of offshore wind energy conversion systems connected to the electric grid either by an alternated current link or by a direct current link in a view of timeliness developments on electricity sector restructuring and integrating the relevant dynamics. Besides the electricity transmission, the system consists of a semi-submersible floating platform; a variable speed wind turbine; a mechanical transmission system described respectively by one, two, three, or five masses; a synchronous generator with excitation provided by means of permanent magnets; an electronic power converter, respectively described by a two-level converter or by a multi-level converter in a multiple point clamped topology of three, four, five, or p levels. The control of the system uses PWM by space vector modulation associated with sliding mode and classic PI or fractional order PIcontrollers. The behaviors due to fact that wind energy is a variable, intermittently, source of energy, as well as, due to eventual malfunctions of devices controlling the systems are studied in the thesis, using computer simulations. The fundamental contributions involve the modeling of the p levels converter, the capacitor banks current associated with the voltage level, the control strategy of the multilevel converter for the voltage vector selection. The computer simulations allow to conclude on the favourable performance of the system and simultaneously allow data on mechanical and electric quantities, allowing either in design phase or in usage phase the study of behaviors that need to be corrected because of the potentially undesirability.

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Yang, Xiaoguang Miu Karen Nan. "Unbalanced power converter modeling for AC/DC power distribution systems /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1231.

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Baltierrez, Jason. "Multiple Input, Single Output DC-DC Conversion Stage for DC House." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2028.

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n this thesis project, a proposed architecture for the multiple input, single output conversion stage for the DC House was designed, simulated, and tested. This architecture allows for multiple different input sources to be used to create a single higher power output source. The design uses a DC-DC boost converter with a parallelable output which has been demonstrated to allow increased total output power as a function of the number of input sources available. The parallelable output has been shown to distribute load amongst the input sources relatively closely to optimize the system. This approach is also desirable since it allows for flexibility in multiple configurations it can be used in. The design was tested using hardware and data results show the performance met and exceeded the needs of the DC House project. Data was taken for configuration with 1, 2, 3, and 4 input sources providing greater than 600W of total output power at an efficiency of greater than 92%. This architecture demonstrates the possibility of expanding the total available power for a single output in proportion to the number of available input sources.

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Ahmad, Khan Naveed. "Power Loss Modeling of Isolated AC/DC Converter." Thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-109717.

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Several research activities at KTH are carried out related to Isolated AC/DC converters in order to improve the design and efficiency. Concerning the improvement in the mentioned constraints, losses of the elements in the prototype converter are modeled in this thesis work. The obtained loss model is capable of calculating the losses under different circumstances. The individual contribution of losses for each element at different conditions can be obtained, which is further useful in improving the design and therefore, efficiency. The losses in different elements of the converter, including power semiconductor devices, RC-snubbers, transformer and filter inductor at different operating points can be computed by using the obtained model. The loss model is then validated by comparing the analytical results with the measurements. The results based on developed loss model show consistency with the measured losses. The comparison at different conditions shows that, the difference between measured and analytical results ranges between 10% to 20 %. The difference is due to those losses which are disregarded because of their negligible contribution. On the other hand, it is also observed that if the neglected losses are counted, the difference reduces up to 10%.

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Haryani, Nidhi. "Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96397.

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One of the greatest technological challenges of the world today is reducing the size and weight of the existing products to make them portable. Specifically, in electric vehicles such as electric cars, UAVs and aero planes, the size of battery chargers and inverters needs to be reduced so as to make space for more parts in these vehicles. Electromagnetic Interference (EMI) filters take up a more than 80 % of these power converters, the size of these filters can be reduced by pushing the switching frequency higher. High frequency operation (> 300 kHz) leads to a size in reduction of EMI filters though it also leads to an increase in switching losses thus compromising on efficiency. Thus, soft switching becomes necessary to reduce the losses, adding more electrical components to the converter to achieve soft switching is a common method. However, it increases the physical complexity of the system. Hence, advanced control methods are adopted for today's power converters that enable soft switching for devices specifically ZVS turn-on as the turn-off losses of next generation WBG devices are negligible. Thus, the goal of this research is to discover novel switching algorithms for soft turn-on. The state-of the-art control methods namely CRM and TCM achieve soft turn-on by enabling bi-directional current such that the anti-parallel body diode starts conducting before the device is turned on. CRM and TCM result in variable switching frequency which leads to asynchronous operation in multi-phase and multi-converter systems. Hence, TCM is modified in this dissertation to achieve constant switching frequency, as the goal of this research is to be able to achieve ZVS turn-on for a three-phase converter. Further, Triangular Current Mode (TCM) to achieve soft switching and phase synchronization for three-phase two-level converters is proposed. It is shown how soft switching and sinusoidal currents can be achieved by operating the phases in a combination of discontinuous conduction mode (DCM), TCM and clamped mode. The proposed scheme can achieve soft switching ZVS turn-on for all the three phases. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kW with a density of 110 W/in3. The discussion of TCM in current literature is limited to unity power factor assumption, however this limits the algorithm's adoption in real world applications. It is shown how proposed TCM algorithm can be extended to accommodate phase shift with all the three phases operating in a combination of DCM+TCM+Clamped modes of operation. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kVA with a density of 110 W/in3. TCM operation results in 33 % higher rms current which leads to higher conduction losses, as WBG devices have lower on-resistance, these devices are the ideal candidates for TCM operation, hence to accurately obtain the device parameters, a detailed device characterization is performed. Further, proposed TCM+DCM+Clamped control algorithm is extended to three-level topologies, the control is modified to extract the advantage of reduced Common Mode Voltage (CMV) switching states of the three-level topology, the switching frequency can thus be pushed to 3 times higher as compared to state-of-the-art SVPWM control while maintaining close to 99 % efficiency. Two switching schemes are presented and both of them have a very small switching frequency variation (6%) as compared to state-of-the-art methods with >200% switching frequency variation.
Doctor of Philosophy
Power supplies are at the heart of today's advanced technological systems like aero planes, UAVs, electrical cars, uninterruptible power supplies (UPS), smart grids etc. These performance driven systems have high requirements for the power conversion stage in terms of efficiency, density and reliability. With the growing demand of reduction in size for electromechanical and electronic systems, it is highly desirable to reduce the size of the power supplies and power converters while maintaining high efficiency. High density is achieved by pushing the switching frequency higher to reduce the size of the magnetics. High switching frequency leads to higher losses if conventional hard switching methods are used, this drives the need for soft switching methods without adding to the physical complexity of the system. This dissertation proposes novel soft switching techniques to improve the performance and density of AC/DC and DC/AC converters at high switching frequency without increasing the component count. The concept and the features of this new proposed control scheme, along with the comparison of its benefits as compared to conventional control methodologies, have been presented in detail in different chapters of this dissertation.

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Gray, Weston L. "DC to DC power conversion module for the all-electric ship." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68166.

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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 91-92).
The MIT end to end electric ship model is being developed to study competing electric ship designs. This project produced a model of a Power Conversion Module (PCM)- 4, DC-to-DC converter which interfaces with the MIT model. The focus was on the Medium Voltage DC (MVDC) architecture, and therefore, the PCM-4 converts a MVDC bus voltage of 3.3, 6.5 or 10 kVDC to 1 kVDC. The design describes the transient and steady-state behavior, and investigates the naval architecture characteristics. A modular architecture, similar to SatCon Applied Technology's Modular Expandable Power Converters, was selected as the best balance for the wide variation in loads experienced. The model consists of a standard module that can be paralleled internally to provide for a wide range of system power requirements. Naval architecture parameters, such as weight, volume, efficiency, and heat load, were compiled into a parametric format allowing a reasonable approximation of actual weight and volume as a function of rating and efficiency and heat load as a function of loading. All of the parameters were evaluated for dependence on the MVDC bus voltage. Verification of the model was pursued through comparison to available simulations of similar power electronics to ensure that the model provided reasonable time response and shape. Finally, the model met all requirements with the exception of efficiency which was slightly lower than the requirement although several ideas were presented to improve efficiency.
by Weston L. Gray.
S.M.
Nav.E.

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Du, Sijun. "Energy-efficient interfaces for vibration energy harvesting." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270359.

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Ultra low power wireless sensors and sensor systems are of increasing interest in a variety of applications ranging from structural health monitoring to industrial process control. Electrochemical batteries have thus far remained the primary energy sources for such systems despite the finite associated lifetimes imposed due to limitations associated with energy density. However, certain applications (such as implantable biomedical electronic devices and tire pressure sensors) require the operation of sensors and sensor systems over significant periods of time, where battery usage may be impractical and add cost due to the requirement for periodic re-charging and/or replacement. In order to address this challenge and extend the operational lifetime of wireless sensors, there has been an emerging research interest on harvesting ambient vibration energy. Vibration energy harvesting is a technology that generates electrical energy from ambient kinetic energy. Despite numerous research publications in this field over the past decade, low power density and variable ambient conditions remain as the key limitations of vibration energy harvesting. In terms of the piezoelectric transducers, the open-circuit voltage is usually low, which limits its power while extracted by a full-bridge rectifier. In terms of the interface circuits, most reported circuits are limited by the power efficiency, suitability to real-world vibration conditions and system volume due to large off-chip components required. The research reported in this thesis is focused on increasing power output of piezoelectric transducers and power extraction efficiency of interface circuits. There are five main chapters describing two new design topologies of piezoelectric transducers and three novel active interface circuits implemented with CMOS technology. In order to improve the power output of a piezoelectric transducer, a series connection configuration scheme is proposed, which splits the electrode of a harvester into multiple equal regions connected in series to inherently increase the open-circuit voltage generated by the harvester. This topology passively increases the rectified power while using a full-bridge rectifier. While most of piezoelectric transducers are designed with piezoelectric layers fully covered by electrodes, this thesis proposes a new electrode design topology, which maximizes the raw AC output power of a piezoelectric harvester by finding an optimal electrode coverage. In order to extract power from a piezoelectric harvester, three active interface circuits are proposed in this thesis. The first one improves the conventional SSHI (synchronized switch harvesting on inductor) by employing a startup circuitry to enable the system to start operating under much lower vibration excitation levels. The second one dynamically configures the connection of the two regions of a piezoelectric transducer to increase the operational range and output power under a variety of excitation levels. The third one is a novel SSH architecture which employs capacitors instead of inductors to perform synchronous voltage flip. This new architecture is named as SSHC (synchronized switch harvesting on capacitors) to distinguish from SSHI rectifiers and indicate its inductorless architecture.

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