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1
Xiao, Shangyang. "PLANAR MAGNETICS DESIGN FOR LOW-VOLTAGE DC-DC CONVERTERS". Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4486.
Testo completoAbstract (sommario):
The objectives of this thesis are to design planar magnetic devices based on accurate electromagnetic analysis and miniaturize magnetics within desired low profile as well as small footprint. A novel methodology based on FEM simulation is proposed. By introducing Maxwell 2D simulator, optimal interleaving structures can be found to reduce AC losses that cannot otherwise be accounted for by conventional method. And 3D simulator is employed to make the results more realistic. Thus, high-efficiency high-power density magnetics is achieved.M.S.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical and Computer Engineering
2
Zhou, Yao. "High voltage DC/DC converter for offshore wind application". Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/18749.
Testo completoAbstract (sommario):
With the increasing interest in offshore wind power, the related technologies, including HVDC networks, are gaining similar levels of attention. For large scale wind farms far from shore, high voltage DC transmission can provide several advantages over traditional high voltage AC transmission. This thesis focuses on DC/DC converters, a core part of the HVDC network, especially for use in the high voltage, high power and offshore wind environment. The thesis examines a wide range of possible DC/DC converter topologies for the application. Different topologies are compared and evaluated in detail for use in a high power situation. Based on these results, three DC/DC converter topologies are selected for more detailed modelling. The simulation processes and results are presented in the thesis, which reveals the limitations and behaviour of the topologies when they are used at the MW level. In addition, the high power semiconductor switching devices are discussed and evaluated for each topology. To assess the suitability of the DC/DC converter topologies in the offshore wind application, the selected converter topologies are also analysed and modelled combined with a PMSG wind turbine. Finally, a down-scaled DC/DC converter prototype is built to verify the analysis and simulation results.
3
Luth, Thomas. "DC/DC converters for high voltage direct current transmission". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24466.
Testo completoAbstract (sommario):
High Voltage Direct Current (HVDC) transmission has to date mostly been used for point-to-point projects, with only a few select projects being designed from the outset to incorporate multiple terminals. Any future HVDC network is therefore likely to evolve out of this pool of HVDC connections. As technology improves, the voltage rating, at the point of commission, of the these connections increases. Interconnection therefore requires the DC equivalent of the transformer, to bridge the voltage levels and create a multi-terminal network. This thesis investigates new potential DC/DC converter topologies, which may be used for a range of HVDC applications. Simple interconnections of new and legacy HVDC links is unlikely to require a large voltage-step, but will be required to transfer a large amount of power. As the HVDC network develops it may become feasible for wind-farms and load-centres to directly connect to the DC network, rather than requiring new and dedicated links. Such a connection is called an HVDC tap and is typically rated at only a small fraction of the link's peak capacity (around 10\%). Such taps would connect a distribution voltage level to the HVDC network. DC/DC converters suitable for large-step ratios (>5:1) may find their application here. In this work DC/DC converters for both small and large step-ratios are investigated. Two approaches are taken to design such converters: first, an approach utilising existing converter topologies is investigated. As each project comes with a huge price-tag, their reliability is paramount. Naturally, technology that has already proven itself in the field can be modified more readily and quickly for deployment. Using two modular multilevel converters in a front-to-front arrangement has been found to work efficiently for large power transfers and low step-ratios. Such a system can be operated at higher than 50 Hz frequencies to reduce the volume of a number of passive components, making the set-up suitable for compact off-shore applications. This does however incur a significant penalty in losses reducing the overall converter efficiency. In the second approach DC/DC converter designs are presented, that are more experimental and would require significantly more development work before deployment. Such designs do not look to adapt existing converter topologies but rather are designed from scratch, purely for DC/DC applications. An evolution of the front-to-front arrangement is investigated in further detail. This circuit utilises medium frequency (>50 Hz) square current and voltage waveforms. The DC/DC step-ratio is achieved through a combination of the stacks of cells and a transformer. This split approach allows for high-step ratios to be achieved at similar system efficiencies as for the front-to-front arrangement. The topology has been found to be much more suitable for higher than 50 Hz operation from a losses perspective, allowing for a compact and efficient design.
4
Thomas, Stephan [Verfasser]. "A Medium-Voltage Multi-Level DC/DC Converter with High Voltage Transformation Ratio / Stephan Thomas". Aachen : Shaker, 2014. http://d-nb.info/1049383176/34.
Testo completo
5
Mwaniki, Fredrick Mukundi. "High voltage boost DC-Dc converter suitable for variable voltage sources and high power photovoltaic application". Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/37320.
Testo completoAbstract (sommario):
Important considerations of a photovoltaic (PV) source are achieving a high voltage and drawing currents with very little ripple component from it. Furthermore, the output from such a source is variable depending on irradiation and temperature. In this research, literature review of prior methods employed to boost the output voltage of a PV source is examined and their limitations identified. This research then proposes a multi-phase tapped-coupled inductor boost DC-DC converter that can achieve high voltage boost ratios, without adversely compromising performance, to be used as an interface to a PV source. The proposed converter achieves minimal current and voltage ripple both at the input and output. The suitability of the proposed converter topology for variable input voltage and variable power operation is demonstrated in this dissertation. The proposed converter is also shown to have good performance at high power levels, making it very suitable for high power applications.
Detailed analysis of the proposed converter is done. Advantages of the proposed converter are explained analytically and confirmed through simulations and experimentally. Regulation of the converter output voltage is also explained and implemented using a digital controller. The simulation and experimental results confirm that the proposed converter is suitable for high power as well as variable power, variable voltage applications where high voltage boost ratios are required.Dissertation (MEng)--University of Pretoria, 2013.
gm2014
Electrical, Electronic and Computer Engineering
Unrestricted
6
Wang, Xiangcheng. "HIGH SLEW RATE HIGH-EFFICIENCY DC-DC CONVERTER". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3196.
Testo completoAbstract (sommario):
Active transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive nonlinear control has been proposed to reduce delay times in the actual controller, which injects one nonlinear signal in transient periods and simplifies the linear controller design. Switching mode current compensator with nonlinear control in secondary side is proposed to eliminate the effect of opotocoupler, which reduces response times and simplifies the linear controller design in isolated DC-DC converters. A novel control method has been carried out in two-stage isolated DC-DC converter to simplify the control scheme and improve the transient response, allowing for high duty cycle operation and large step-down voltage ratio with high efficiency. A balancing winding network composed of small power rating components is used to mitigate the double pole-zero effect in complementary-controlled isolated DC-DC converter, which simplifies the linear control design and improves the transient response without delay time. A parallel post regulator (PPR) is proposed for wide range input isolated DC-DC converter with secondary side control, which provides small part of output power and most of them are handled by unregulated rectifier with high efficiency. PPR is easy to achieve ZVS in primary side both in wide range input and full load range due to 0.5 duty cycle. PPR has reduced conduction loss and reduced voltage rating in the secondary side due to high turn ratio transformer, resulting in up to 8 percent efficiency improvement in the prototype compared to conventional methods.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
7
Van, Rhyn P. D. "High voltage DC-DC converter using a series stacked topology". Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1269.
Testo completo
8
Gotti, Edoardo O. L. "A highly efficient low-output voltage DC to DC converter". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ39475.pdf.
Testo completo
9
zhou, hua. "MAGNETICS DESIGN FOR HIGH CURRENT LOW VOLTAGE DC/DC CONVERTER". Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3381.
Testo completoAbstract (sommario):
With the increasing demand for small and cost efficient DC/DC converters, the power converters are expected to operate with high efficiency. Magnetics components design is one of the biggest challenges in achieving the higher power density and higher efficiency due to the significant portion of magnetics components volume in the whole power system. At the same time, most of the experimental phenomena are related to the magnetics components. So, good magnetics components design is one of the key issues to implement low voltage high current DC/DC converter. Planar technology has many advantages. It has low profile construction, low leakage inductance and inter-winding capacitance, excellent repeatability of parasitic properties, cost efficiency, great reliability, and excellent thermal characteristics. On the other side, however, planar technology also has some disadvantages. Although it improves thermal performance, the planar format increases footprint area. The fact that windings can be placed closer in planar technology to reduce leakage inductance also often has an unwanted effect of increasing parasitic capacitances. In this dissertation, the planar magnetics designs for high current low voltage applications are thoroughly investigated and one CAD design methodology based on FEA numerical analysis is proposed. Because the frequency dependant parasitic parameters of magnetics components are included in the circuit model, the whole circuit analysis is more accurate. When it is implemented correctly, integrated magnetics technique can produce a significant reduction in the magnetic core content number and it can also result in cost efficient designs with less weight and smaller volume. These will increase the whole converter's power density and power efficiency. For high output current and low output voltage applications, half bridge in primary and current doublers in secondary are proved to be a very good solution. Based on this topology, four different integrated magnetics structures are analyzed and compared with each other. One unified model is introduced and implemented in the circuit analysis. A new integrated magnetics component core shape is proposed. All simulation and experimental results verify the integrated magnetics design. There are several new magnetics components applications shown in the dissertation. Active transient voltage compensator is a good solution to the challenging high slew rate load current transient requirement of VRM. The transformer works as an extra voltage source. During the transient periods, the transformer injects or absorbs the extra transient to or from the circuit. A peak current mode controlled integrated magnetics structure is proposed in the dissertation. Two transformers and two inductors are integrated in one core. It can force the two input capacitors of half bridge topology to have the same voltage potential and solve the voltage unbalance issue. The proposed integrated magnetics structure is simple compared with other methods implementing the current mode control to half bridge topology. Circuit analysis, simulation and experimental results verify the feasibility of these applications.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
10
Cui, Shenghui [Verfasser], Doncker Rik W. [Akademischer Betreuer] De e Rainer [Akademischer Betreuer] Marquardt. "Modular multilevel DC-DC converters interconnecting high-voltage and medium-voltage DC grids / Shenghui Cui ; Rik W. de Doncker, Rainer Marquardt". Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1195238002/34.
Testo completo
11
Farag, Bassem. "High Voltage DC Arc Detection Model". Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-358478.
Testo completoAbstract (sommario):
High voltage (HV) battery systems are widely used in many applications nowadays. And due to the safety concerns regarding lithium-ion cells, the safety of the lithium-ion based battery systems is vital. One crucial danger for lithium-ion cells is heat, And as arcs formation can lead to heat generation within the system, it is important to detect arcs that take place frequently within HV battery systems. This thesis is done in cooperation with Northvolt AB and it focuses on assessing the ability to detect the occurrence of arcs in the system, but it does not focus on preventing arcs.The goal is to build a detection system to identify the occurrence of arcs, both within the battery system and in the connection between the battery system and the load (vehicle). The detection circuit should not affect the ability of the isolation measurement unit inside the system, and the detection system should be protected at all times. The circuit was designed and tested using LTSPice software. This is due to the absence of a ready system to test the circuit against at Northvolt. The system was able to detect arcs both within the battery system and when connecting the battery system to the vehicle. Additionally, as required by Northvolt, the detection system is designed without affecting the isolation measurement unit and the detection system is kept safe at all times by using an isolation circuit. Future work is recommended to generalize the detection system so it can be used in different high voltage applications. This can be done by testing the system against other HV systems and updating the filter and amplifier’s values, as well as the software thresholds. Additionally, it is recommended that the software module is calibrated against the real system during hardware testing. This calibration will optimize the software module and, thus, result in better detection.
12
Zeljkovic, Sandra [Verfasser]. "IGBT-based High Voltage to Low Voltage DC/DC Converter for Electric and Hybrid Vehicles / Sandra Zeljkovic". Aachen : Shaker, 2015. http://d-nb.info/1074087283/34.
Testo completo
13
Mai, Yuan Yen. "Current-mode DC-DC buck converter with current-voltage feedforward control /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ECED%202006%20MAI.
Testo completo
14
Hu, Jingying Ph D. Massachusetts Institute of Technology. "Design of a low-voltage low-power dc-dc HF converter". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43037.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 230-234).
Many portable electronic applications could benefit from a power converter able to achieve high efficiency across wide input and output voltage ranges at a small size. However, it is difficult for many conventional power converter designs to provide wide operation range while maintaining high efficiency, especially if both up-and-down voltage conversion is to be achieved. Furthermore, the bulk energy storage required at contemporary switching frequencies of a few megahertz and below limits the degree of miniaturization that can be achieved and hampers fast transient response. Therefore, design methods that reduce energy storage requirements and expand efficient operation range are desirable. This thesis focuses on the development of a High Frequency (HF) dc-dc SEPIC converter exploiting resonant switching and gating with fixed frequency control techniques to achieve these goals. The proposed approach provides high efficiency over very wide input and output voltage ranges and power levels. It also provides up-and-down conversion, and requires little energy storage which allows for excellent transient response. The proposed design strategies are discussed in the context of a prototype converter operating over wide input voltage (3.6 - 7.2V), output voltage (3 - 9V) and power (0.3 - 3W) ranges. The 20MHz converter prototype, utilizing commercial vertical MOSFETs, takes advantage of a quasi-resonant SEPIC topology and resonant gating technique to provide good efficiency across the wide operating ranges required. The converter efficiency stays above 80% across the entire input voltage range at the nominal output voltage. The closed-loop performance is demonstrated via an implementation of a PWM on-off control scheme, illustrating the salient characteristics in terms of additional control circuitry power dissipation and transient response.
by Jingying Hu.
S.M.
15
Chaput, Simon. "Convertisseur DC-DC CMOS haut voltage pour actuateurs MEMS/MOEMS électrostatiques". Mémoire, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/8063.
Testo completoAbstract (sommario):
La demande pour des appareils portables multifonctionnels encourage les manufacturiers à intégrer des microsystèmes électromécaniques (MEMS) ou optoélectromécaniques (MOEMS) à leurs produits pour réaliser de nouvelles fonctions ; les pico projecteurs constituent un excellent exemple. Or, dans le but d'utiliser ce type de composants, des tensions de polarisation variant entre 100 V et 300 V sont parfois nécessaires. La génération de ces tensions à partir de la pile de l'appareil exige des convertisseurs continu-continu (DC-DC) miniatures procurant un gain de tension de l'ordre de 100. C'est dans ce contexte général que ce projet réalisé pour Teledyne DALSA, un manufacturier de MEMS et concepteur de circuits intégrés haut voltage, a été réalisé. En intégrant ce circuit à ses circuits de contrôle de MEMS, Teledyne DALSA sera ainsi en mesure de proposer des systèmes plus complets à ses clients. Ce mémoire présente la conception d'un convertisseur DC-DC dans la technologie CO8G CMOS/DMOS haut voltage de Teledyne DALSA. Pour que la solution développée soit assez flexible, le circuit permet un ajustement de la tension de sortie entre 100 V et 300 V pour une puissance de sortie inférieure ou égale à 210 mW à partir d'une tension de batterie entre 2,7 V et 5,5 V. Afin de permettre une longue autonomie des appareils portables, ce projet vise une efficacité de transfert d'énergie de 70 % à la puissance de sortie typique de 75 mW à 220 V. De plus, la solution développée doit être la plus petite possible. À partir de l'état de l'art des circuits de gestion de l'alimentation, ce mémoire présente une conception haut niveau du circuit basée sur des raisonnements et calculs mathématiques simples. Bâtissant sur ces concepts, ce travail détaille la conception des composants de puissance, du circuit de puissance et du contrôleur nécessaire à la réalisation de ce projet. Bien que certaines difficultés, notamment le niveau moyen de l'oscillation de la tension de sortie de 1,6 V, ne permettent pas d'utiliser dès maintenant le circuit développé dans une application commerciale, la solution proposée démontre une amélioration entre 15 % et 43 % de l'efficacité de conversion par rapport au circuit flyback actuel de Teledyne DALSA. De plus, la solution proposée intègre un transistor de puissance 78 % plus petit que les transistors standards disponibles dans la technologie CO8G. Étant donnée l'innovation du circuit présenté au niveau des composants de puissance, du circuit de puissance et du contrôleur, ces résultats de l'implémentation initiale laissent envisager un bon potentiel pour cette architecture après une révision.
16
Yao, Liangbin. "HIGH CURRENT DENSITY LOW VOLTAGE ISOLATED DC-DC CONVERTERSWITH FAST TRANSIENT RESPONSE". Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3205.
Testo completoAbstract (sommario):
With the rapid development of microprocessor and semiconductor technology, industry continues to update the requirements for power supplies. For telecommunication and computing system applications, power supplies require increasing current level while the supply voltage keeps decreasing. For example, the Intel's CPU core voltage decreased from 2 volt in 1999 to 1 volt in 2005 while the supply current increased from 20A in 1999 to up to 100A in 2005. As a result, low-voltage high-current high efficiency dc-dc converters with high power-density are demanded for state-of-the-art applications and also the future applications. Half-bridge dc-dc converter with current-doubler rectification is regarded as a good topology that is suitable for high-current low-voltage applications. There are three control schemes for half-bridge dc-dc converters and in order to provide a valid unified analog model for optimal compensator design, the analog state-space modeling and small signal modeling are studied in the dissertation and unified state-space and analog small signal model are derived. In addition, the digital control gains a lot of attentions due to its flexibility and re-programmability. In this dissertation, a unified digital small signal model for half-bridge dc-dc converter with current doubler rectifier is also developed and the digital compensator based on the derived model is implemented and verified by the experiments with the TI DSP chip. In addition, although current doubler rectifier is widely used in industry, the key issue is the current sharing between two inductors. The current imbalance is well studied and solved in non-isolated multi-phase buck converters, yet few discusse this issue in the current doubler rectification topology within academia and industry. This dissertation analyze the current sharing issue in comparison with multi-phase buck and one modified current doubler rectifier topology is proposed to achieve passive current sharing. The performance is evaluated with half bridge dc-dc converter; good current sharing is achieved without additional circuitry. Due to increasing demands for high-efficiency high-power-density low-voltage high current topologies for future applications, the thermal management is challenging. Since the secondary-side conduction loss dominates the overall power loss in low-voltage high-current isolated dc-dc converters, a novel current tripler rectification topology is proposed. Theoretical analysis, comparison and experimental results verify that the proposed rectification technique has good thermal management and well-distributed power dissipation, simplified magnetic design and low copper loss for inductors and transformer. That is due to the fact that the load current is better distributed in three inductors and the rms current in transformer windings is reduced. Another challenge in telecommunication and computing applications is fast transient response of the converter to the increasing slew-rate of load current change. For instance, from Intel's roadmap, it can be observed that the current slew rate of the age regulator has dramatically increased from 25A/uS in 1999 to 400A/us in 2005. One of the solutions to achieve fast transient response is secondary-side control technique to eliminate the delay of optocoupler to increase the system bandwidth. Active-clamp half bridge dc-dc converter with secondary-side control is presented and one industry standard 16th prototype is built and tested; good efficiency and transient response are shown in the experimental section. However, one key issue for implementation of secondary-side control is start-up. A new zero-voltage-switching buck-flyback isolated dc-dc converter with synchronous rectification is proposed, and it is only suitable for start-up circuit for secondary-side controlled converter, but also for house-keeping power supplies and standalone power supplies requiring multi-outputs.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
17
Ikhide, Monday Aideloje. "DC line protection for multi-terminal High Voltage DC (HVDC) transmission systems". Thesis, Staffordshire University, 2017. http://eprints.staffs.ac.uk/4601/.
Testo completoAbstract (sommario):
The projected global energy shortage and concerns about greenhouse emissions have led to the significant developments in offshore wind farm projects around the globe. It is also envisaged that in the near future, a number of existing onshore converter stations and offshore stations will be interconnected to form a Multi-terminal (MT) HVDC systems, whereas protection issues remains a major challenge. This is largely due to the low inductance in DC network compared to AC interconnection which usually results in a sudden collapse in the DC voltage and rapid rise in the fault current thus reaching damaging levels in few milliseconds. Therefore faults in MT-HVDC system must be detected and cleared quickly before it reaches a damaging level; typically 4 – 6ms (including circuit breaker opening time) following the inception of the fault. For this reason, transient based protection techniques are ideal candidates if the protection scheme must be reliable and dependable. Transient based protection algorithms utilises the higher frequency components of the fault generated signal to detect a fault, therefore making it possible to detect the fault while the fault current is still rising and well before the steady state. The traditional protection algorithms developed for conventional high voltage AC (HVAC) systems such as distance protection are steady state based and as such not suitable for the protection of MT-HVDC systems. Another major issue is selectivity as only the faulty section must be isolated in the event of a fault. This constitutes a major challenge considering the anticipated lengths of the cables. Traditional protection techniques developed for two-terminal HVDC systems are also not suitable for MT-HVDC since it will de-energise the entire network and other sub-grids connected to the main network. DC line protection devices which will operate at a sufficient speed and which will isolate only the faulty section in the event of a fault are therefore required to avoid a total system failure during short circuit. It is anticipated that it will be achieved by the use of HVDC breakers, whereas the implementation and realisation of such circuit breakers still remain a major issue considering speed, complexity, losses and cost. However, two major vendors have proposed prototypes and hopefully these will be commercially available in the near future. The key issue still remains the development of a fast DC line fault detection algorithm; and it is on these premise that this research was undertaken. The work reported in this thesis is a novel time domain protection technique for application to HVDC grids. The protection principle developed utilises the “power” and “energy” accompanying the associated travelling wave following the occurrence of a fault to distinguish between internal and external fault. Generally, either the “power” or “energy” can provide full discrimination between internal and external faults. For an internal fault, the associated forward and backward travelling wave power; or the forward and backward wave energy must exceed a pre-determined setting otherwise the fault is regarded as external. This characteristic differences is largely due to the DC inductor located at the boundaries which provides attenuation for the high frequency transient resulting from an external fault, hence making the power and energy for an internal fault to be significantly larger than that for external fault. The ratio between the forward and backward travelling wave power; or between the forward and backward travelling wave energy provides directional discrimination. For a forward directional fault (FDF) with respect to a local relay, this ratio must be less than unity. However, the ratio is greater than unity for reverse directional faults (RDF). The resulting wave shape of the “travelling wave power” (TWP) components also led to the formulation of a novel protection algorithm utilising the wave shape concavity. For an internal fault, the second derivative of the resulting polynomial formed by the TWP must be negative, thereby indicating a “concave-upwards” parabola. However, for an external fault, the second derivative of the resulting polynomial formed by the TWP components must be positive indicating a “concave-downwards” parabola. The developed and proposed protection techniques and principles were validated against a full scale Modular Multi-level Converter (MMC) – based HVDC grid, and thereafter the protection algorithm was implemented in MATLAB. Wider cases of fault scenarios were considered including long distance remote internal fault and a 500Ω high resistance remote internal fault. In all cases, both the pole-pole (P-P) and pole-ground (P-G) faults were investigated. The simulation results presented shows the suitability of the protection technique as the discrimination between internal and external faults was made within 1ms following the application of the fault. Following this, the protection algorithm was implemented on both a low-cost experimental platform utilising an Arduino UNO ATmega328 Microcontroller and on a Compact RIO FPGA-based experimental platform utilising LAB-View. The experimental results obtained were consistent with those obtained by simulations. An advantage of the proposed technique is that it is non-unit based and as such no communication delays are incurred. Furthermore, as it is time domain - based, it does not require complex mathematical computation and burden / DSP techniques; hence can easily be implemented since it will require less hardware resources which ultimately will result in minimal cost.
18
Gowaid, Islam Azmy. "DC-DC converter designs for medium and high voltage direct current systems". Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27933.
Testo completoAbstract (sommario):
DC fault protection is one challenge impeding the development of multi-terminal dc grids. The absence of manufacturing and operational standards has led to many point-to-point HVDC links built at different voltage levels, which creates another challenge. Therefore, the issues of voltage matching and dc fault isolation in high voltage dc systems are undergoing extensive research and are the focus of this thesis. The modular multilevel design of dual active bridge (DAB) converters is analysed in light of state-of-the-art research in the field. The multilevel DAB structure is meant to serve medium and high voltage applications. The modular design facilitates scalability in terms of manufacturing and installation, and permits the generation of an output voltage with controllable dv/dt. The modular design is realized by connecting an auxiliary soft voltage clamping circuit across each semiconductor switch (for instance insulated gate bipolar transistor – IGBT) of the series switch arrays in the conventional two-level DAB design. With auxiliary active circuits, series connected IGBTs effectively become series connection of half-bridge submodules (cells) in each arm, resembling the modular multilevel converter (MMC) structure. For each half-bridge cell, capacitance for quasi-square wave (quasi two- level) operation is significantly smaller than typical capacitance used in MMCs. Also, no bulky arm inductors are needed. Consequently, the footprint, volume, weight and cost of cells are lower. Four switching sequences are proposed and analysed in terms of switching losses and operation aspects. A design method to size converter components is proposed and validated. Soft-switching characteristics of the analysed DAB are found comparable to the case of a two-level DAB at the same ratings and conditions. A family of designs derived from the proposed DAB design are studied in depth. Depending on the individual structure, they may offer further advantages in term of installed semiconductor power, energy storage, conduction losses, or footprint. A non-isolated dc-dc converter topology which offers more compact and efficient station design with respect to isolated DAB – yet without galvanic isolation – is studied for quasi two-level (trapezoidal) operation and compared to the isolated versions. In all the proposed isolated designs, active control of the dc-dc converter facilitates dc voltage regulation and near instant isolation of pole-to-pole and pole-to-ground dc faults within its protection zone. The same can be achieved for the considered non-isolated dc-dc converter topology with additional installed semiconductors. Simulation and experimental results are presented to substantiate the proposed concepts.
19
Aboushady, Ahmed Adel. "Design, analysis, and modelling of modular medium-voltage DC/DC converter based systems". Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18685.
Testo completoAbstract (sommario):
This thesis investigates the design and analysis of modular medium-voltage dc/dc converter based systems. An emerging converter application is feeding offshore oil and gas production systems located in deep waters, on the sea bed, distant from the onshore terminal. The phase-controlled series-parallel resonant converter (SPRC) is selected as the dc/dc converter unit, for a 10kV dc transmission system. The converter has a high efficiency in addition to favourable soft switching characteristics offered by resonant converters which enable high frequency operation, hence designs with reduced footprints. The phase-controlled SPRC is studied in the steady-state and a new analysis is presented for the converter operational modes, voltage gain sensitivity, and analytically derived operational efficiency. The maximum efficiency criterion is used as the basis for selection of converter full load operational conditions. The detailed design of the output LC filter involves new mathem atical expressions for interleaved multi-module operation. A novel large signal dynamic model is proposed for the phase-controlled SPRC with state feedback linearization. The model preserves converter large signal characteristics while providing a tool for faster simulation and simplified closed loop design and stability analysis. Using this model, a Kalman filter based estimator is proposed and applied for sensorless multi-loop output voltage control. The objective is to enhance the single-loop PI control dynamic response and closed loop stability with no additional sensors required for the inner loop state variables. Dynamic performance and robustness of the converter to operational circuit parameter variations are achieved with three new robust controllers; namely, Lyapunov, sliding mode, and predictive controllers. Finally, converter multi-module operation is studied, catering for voltage and current sharing of the subsea load-side step-down converter. To achieve a step- down voltage, the phase-controlled SPRC modules are connected in an input-series connection to share the medium level transmission voltage. Output-series and output-parallel connections are used to reach higher power levels. A new sensorless load voltage estimator is developed for converters remotely controlled. Matlab/Simulink simulations and experimental prototype results are used to substantiate all the proposed analysis techniques and control algorithms.
20
Mao, Hong. "Topology and control investigation for low-voltage high-current isolated DC-DC converters". Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/4405.
Testo completoAbstract (sommario):
University of Central Florida College of Engineering ThesisHigh conversion efficiency and fast transient response at high switching frequency are the two main challenges for low-voltage high-current DC-DC converters, which are the motivations of the dissertation work. To reduce the switching power loss, soft switching is a desirable technique to keep power loss under control at high switching frequencies. A Duty-Cycle-Shift (DCS) concept is proposed for half-bridge DC-DC converters to reduce switching loss. The concept of this new control scheme is shifting one of the two symmetric PWM driving signals close to the other, such that ZVS can be achieved for the lagging switch due to the shortened resonant interval.
Ph.D.
Doctorate;
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical and Computer Engineering
216 p.
xviii, 216 leaves, bound : ill. ; 28 cm.
21
Yao, Liangbin. "High current density low voltage isolated DC-DC converters with fast transient response". Orlando, Fla. : University of Central Florida, 2007. http://purl.fcla.edu/fcla/etd/CFE0001814.
Testo completo
22
Moon, Seung-Ryul. "Multiphase Isolated DC-DC Converters for Low-Voltage High-Power Fuel Cell Applications". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/32442.
Testo completoAbstract (sommario):
Fuel cells provide a clean and highly efficient energy source for power generation; however, in order to efficiently utilize the energy from fuel cells, a power conditioning system is required. Typical fuel cell systems for stand-alone and utility grid-tied stationary power applications are found mostly with low nominal output voltages around 24 V and 48 V, and power levels are found to be 3 to 10 kW [1][2]. A power conditioning system for such applications generally consists of a dc-dc converter and a dc-ac inverter, and the dc-dc converter for low-voltage, high-power fuel cells must deal with a high voltage step-up conversion ratio and high input currents. Although many dc-dc converters have been proposed, most deal with high input voltage systems that focus on step-down applications, and such dc-dc converters are not suitable for low-voltage, high-power fuel cell applications.
Multiphase isolated dc-dc converters offer several advantages that are very desirable in low-voltage, high-power fuel cell applications. First, a multiphase is constructed with paralleled phases, which increase power rating and current handling capability for high input current. Second, an interleaving control scheme produces a high operating frequency with a low switching frequency, and the high operating frequency reduces size of passive components. Thirdly, use of a transformer provides electrical isolation and a high conversion ratio. Lastly, several multiphase converters are capable of soft-switching operation, which increases converter efficiency.
This thesis examines two highly efficient, soft-switching dc-dc converters that are targeted for fuel cell applications. The thesis also describes the convertersâ basic operating principles and analyzes performance for low-voltage, high-power fuel cell applications. 5-kW prototypes for each converter are built and tested with a fuel cell simulator. Experimental switching waveforms and efficiency profiles are shown to support the described basic principles and the analysis. Major features and differences between these two converters are also discussed.Master of Science
23
Gebreab, Ermias K. "Interfacing of battery with a medium voltage DC-DC converter using MATLAB/Simulink". Kansas State University, 2013. http://hdl.handle.net/2097/15759.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Electrical and Computer Engineering
Sanjoy Das
Noel Schulz
Electrical power, although convenient form of energy to distribute and use, cannot easily be stored in large quantities economically. Most electrical power generated by utility plants is consumed simultaneously in real time. However, in some cases, energy storage systems become crucial when power generated from sources does not fulfill peak power load demand in a power system or energy storage systems are needed as backup. Due to these reasons, various technologies such as batteries, ultracapacitors (UC), superconducting magnetic energy storage (SEMS) and flywheels are beneficial options for energy storage systems. Shipboard power systems must use one or more energy storage systems in order to backup the existing power system if locally generated power is unavailable. This will lessen the effect of voltage sags on power quality, and improve system reliability. This report mainly focuses on the design of a Boost DC-DC converter and the integration of that converter with a previously designed battery storage model, as well as the effect of varying loads at the end of the converter.
24
Dixon, Juan W. (Juan Walterio). "A DC voltage regulated, controlled current PWM rectifier /". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65923.
Testo completo
25
Laberge, Sebastien. "DC voltage generation using periodic bit-stream modulation". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33976.
Testo completoAbstract (sommario):
In recent years, the trend for continuous down-scaling of CMOS device dimension has made analog design much more challenging. This trend has been a major driving force in trying to find new approaches for designing common analog building blocks. One such block is the bandgap voltage reference. This common circuit serves the purpose of generating a fixed DC voltage reference and has uses in a wide variety of applications.This thesis introduces a new way of generating a programmable DC voltage reference with similar performance to the traditional means. This voltage reference generator is based on periodic bit-stream modulation and relies on simple digital logic combined with a low pass filter (LPF) to demodulate the DC reference level. The advantage of the proposed DC voltage reference lies in its immunity to technology scaling as it is mostly digital. The programmability of the proposed circuit also makes it usable as a digital to analog converter (DAC).
Through simulation and experimental results obtained using a set of integrated circuits implemented in 0.35 mum, 0.25 mum and 0.18 mum CMOS technologies a number of conclusions are reached. The tradeoffs between the two different bit-stream modulation scheme, pulse width modulation (PWM) and pulse density modulation (PDM), are compared yielding PDM as the best approach. The analysis and simulation of a new synthesis method will demonstrate that high-order passive RC filters yield the most attractive realization of the LPF. Experimental results will also demonstrate that performance due to temperature variations comparable to bandgap references can be achieved. A set of experiments will also demonstrate the excellent performance of this voltage reference when used as a DAC. Lastly, the use of asynchronous logic for generating periodic bit-streams will be shown to yield promising results.
26
Alsseid, Aleisawee M. "Dynamics and control of high voltage DC grids". Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=189675.
Testo completoAbstract (sommario):
Recently, HVDC based on VSC technology has become an area of growing interest because of its suitability in forming a transmission link for transmitting large amounts of power. M-VSC-HVDC has the possibility of being an attractive alternative to AC transmission in city centres, where underground cable transmission is preferred for safety and environmental reasons. Multi-terminal DC grids based on VSC-HVDC could be a competitive and attractive option, for many applications such as the integration of renewable energy and oil/gas platforms into the onshore grid system for supplying power to large metropolitan areas. Therefore, this thesis focuses on the control of M-VSC-HVDC and DC grids based on VSC. Firstly, a detailed non-linear model on a Power System Computer Aided Design/ElectroMagnetic Transients including Direct Current (PSCAD/EMTDC) simulation software for a 2-terminal HVDC based on VSC is presented in chapter 3. In the context of what is a complicated controller analysis and design task, the detailed analytical linear small signal state-space VSC-HVDC test system is modelled in MATLAB and is presented in chapter 3. The model should have good accuracy within the frequency range for the main HVDC control loop i.e. below 100Hz. Secondly, an eigenvalue stability study for control gains optimization is presented in chapter 4, with the use of the root locus technique. Very good matching accuracy is established in chapter 4 for the linear analytical model when compared with the detailed non-linear PSCAD test system models. A detailed comparison of the outer-loop control performance at the receiving end is presented in chapter 5. PID control (inner-loop) with d-axis current control and the DC voltage droop control (outer-loop) is confirmed to be adequate for advanced control design for an M-VSC-HVDC system and DC grid network. A 121st order MIMO small signal linearized dynamic model of a 5-terminal DC network is presented in chapter 6. The model accuracy is verified using detailed non-linear PSCAD simulation. The model has been used to study the effects of the DC voltage droop control on the dynamic and transient behaviour of the DC network. The work presented in this thesis therefore seeks to make a novel contribution by; presenting a detailed non-linear and linearized dynamic model of a DC grid based on a VSC test system. This model has significantly increased our confidence in the feasibility of DC grid networks. A higher order MIMO small signal linearized dynamic model of a 5-terminal DC network and an M-VSC-HVDC has been developed. They are the most detailed analytical models currently available. These models can be used for larger DC grids of any complexity. This thesis applies modeling knowledge boundaries to the automated building of an analytical model of a DC system and could be adapted for a very complex DC system. Two main issues regarding the implementation of the droop scheme have been investigated systematically by using the developed small signal model. Namely, the impacts and the selections of the DC droop gain and the cutoff frequency of the DC voltage droop filter. A systematic design of DC droop gains for DC grids has been presented. This thesis resolves a number of issues with developing DC grids and increases our confidence in building future complex DC transmission systems.
27
Cavanagh, Kathleen Alison. "Stability-constrained design for low voltage DC microgrids". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120235.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-93).
Microgrids are a promising solution to reducing the energy access gap. However, microgrids are inherently fragile systems as they are not globally stable. This thesis considers two voltage instabilities that can arise in DC microgrids as a result of tightly controlled loads in the presence of inductive delays. First, we examine the instability that arises when a constant power load is added to or removed from a network where the topology is unknown. While removing the dependence of the stability certificate on the interconnection structure creates a major technical challenge, it is beneficial as it allows for ease in network modification as the needs of a community vary. We thus develop conditions on individual power sources and loads such that a network comprised of many arbitrarily-connected units will be stable. We use Brayton-Moser potential theory to develop design constraints on individual microgrid components that certify transient stability-guaranteeing that the system will return to a suitable equilibrium after a change to the overall network loading. We find that stability can be guaranteed by installing a parallel capacitor at each constant power load, and we derive an expression for the required capacitance. Second, we analyze the small-signal instabilities in microgrids containing arbitrary, rather than constant power, loads. This network representation allows for a more accurate representation of DC loads controlled by power converters which have a destabilizing negative incremental impedance over a finite frequency band in contrast to constant power loads which have a negative incremental impedance over all frequencies. While there are many established methods for the small-signal stability certification of DC networks, these methods do not explicitly account for the influence of network. In contrast, we develop a method for stability assessment of arbitrary DC grids by introducing the Augmented Power Dissipation and showing that it's positive definiteness is a sufficient condition for stability. We present an explicit expression for this quantity through load and network impedances and show how it could be directly used for stability certification of complex networks.
by Kathleen Alison Cavanagh.
S.M.
28
Lorentz, Vincent. "Bidirectional DC voltage conversion for low power applications". Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/LORENTZ_Vincent_2008.pdf.
Testo completoAbstract (sommario):
Cette thèse se focalise sur la conversion de tension utilisée dans l’équipement mobile. Le concept présenté combine le convertisseur de tension avec l’unité de gestion de l’énergie en constituant un convertisseur de puissance intelligent (IPC) intégré dans la batterie et capable de fournir une tension régulée et ajustable, adaptable à tout équipement mobile. L’IPC doit permettre un flux d’énergie bidirectionnel car la batterie doit être rechargée. L’IPC a été conçu, simulé, tracé dans le layout et fabriqué avec une finesse de gravure de 0. 18μm dans une technologie mixed-signal CMOS de UMC. L’IPC possède une tension de fonctionnement de 1. 2V-3. 6V, un courant continu maximum de 2000mA, et une fréquence de fonctionnement de 100kHz-10MHz. Des solutions nouvelles ont été développées pour l’IPC. Premièrement, une méthode pour détecter automatiquement le chargeur de batterie a été développée. Deuxièmement, une boucle de régulation continue a été développée. Elle permet d’augmenter ou de diminuer la tension à convertir dans les deux directions et à des fréquences élevées. Troisièmement, le dimensionnement dynamique de MOSFET a été développé pour maximiser l’efficacité de conversion à faible charge. Quatrièmement, une méthode d’estimation du courant moyen à travers l’inductance a été développée pour des fréquences jusqu’à 10MHz. Cinquièmement, une interface I2C a été implémentée pour permettre la configuration de l’unité de gestion de l’énergie. Comme la batterie intelligente contient un système de management de batterie et offre une tension ajustable, elle peut être facilement remplacée. L’upgrade des batteries devient possible, et l’autonomie des équipements mobiles est allongéeThis thesis focuses on the voltage conversion used in mobile equipment. The novel concept exposed consists in combining the voltage conversion unit with the battery management unit, thus building an intelligent power converter (IPC), that is integrated into the battery and is able to provide a regulated and adjustable voltage directly to the mobile equipment, thus making it adaptable to every mobile equipment. Because the battery must also be recharged, the IPC must allow a bidirectional energy flow. The IPC has been designed, simulated, laid-out and manufactured in a 0. 18 μm mixed-signal CMOS technology from UMC. The IPC requires an operating voltage between 1. 2V-3. 6V, an average load current up to 2000mA, and an operating frequency in the range of 100kHz-10MHz. Novel solutions were developed for the IPC. First, a method was developed for detecting automatically the connection of a battery charger in parallel to the load. Second, a continuous regulation loop was developed, which enables highly efficient step-up and step-down conversion in both directions and at high switching frequencies. Third, dynamic MOSFET sizing was developed, to maximize the conver-sion efficiency at light load. Fourth, a current sensing method has been developed for estimating the average inductor current at switching frequencies up to 10MHz. Fifth, an I2C interface was imple-mented, to enable digital programming of the battery management. Since the intelligent battery contains a battery management and provides an adjustable voltage, it can be easily replaced. This enables battery upgrading, so that the operating time of the mobile equipment is extended
Batteriebetriebene Mobilgeräte sind ein wichtiger Tragpfeiler des heutigen Markts, besonders seit Mobiltelefone und Digitalkameras eingeführt wurden. Allerdings haben Mobilgeräte einen Nachteil: die Batterie verfügt über eine begrenzte Kapazität, die nur auf zwei Wege erweitert werden kann. Der erste Weg besteht in der Entwicklung von neuen Batteriechemien, um die Energiedichte zu erhöhen. Der zweite Weg besteht in einer effizienteren Nutzung dieser Energie durch ein intelligenteres Ener-giemanagement. Diese Dissertation befasst sich mit dem zweiten Ansatz, und zwar mit der Span-nungswandlung, die üblicherweise in Mobilgeräten benutzt wird. Ziel des vorgestellten Konzeptes ist es, den Spannungswandler mit dem Energiemanagement zu kombinieren, um damit einen intelligen-ten Leistungswandler (IPC) zu realisieren, der in die Batterie integriert wird. Diese intelligente Batterie liefert eine geregelte und einstellbare Spannung. Damit ist sie in jedem Mobilgerät einsetzbar. Der IPC muss einen bidirektionalen Energiefluss erlauben, um die Batterie aufladen zu können. Der IPC wurde entwickelt und simuliert. Ein Layout wurde erstellt und in einer 0. 18 μm-Mixed-signal CMOS-Technologie von UMC gefertigt. Ein auf Cadence- Software basierender Full-custom-Designfluss wurde erstellt. Zusätzlich zu den Modellen von UMC wurden Monte-Carlo-Modelle entwi-ckelt, um die Variationen des Herstellungsprozesses bei den Simulationen berücksichtigen zu können. Um Elektromigration zu verhindern, wurden Designregeln geschrieben, damit eine Stromüberlastung der Metallverbindungen im Leistungsteil vermieden wird. Die technischen Daten des IPCs sind ein Betriebsspannungsbereich von 1,2 V-3,6 V, ein konstanter Laststrom bis zu 2000mA und eine Be-triebsfrequenz im Bereich von 100 kHz bis 10 MHz. Mehrere neue Lösungen wurden für den IPC entwickelt. Erstens wurde eine Methode entwickelt, um ein Batterieladegerät zu erkennen, da die Richtung des Energieflusses durch die Anwesenheit dieses Ladegerät parallel zur Last bestimmt wird. Zweitens wurde eine kontinuierliche Regelungsschleife entwickelt, die es ermöglicht, bei hohen Frequenzen die gewandelte Spannung in beide Richtungen hoch- und herunterzusetzen. Drittens wurde eine dynamische Einstellung der Weite des MOSFETs entwickelt, um den Wirkungsgrad im Schwachlastbereich zu erhöhen. Bei Frequenzen über 1MHz wurde eine absolute Wirkungsgraderhöhung von 25% erreicht. Viertens wurde für Betriebsfrequenzen bis 10MHz eine Methode zur Abschätzung des Stromes durch die Induktivität entwickelt. Fünftens wurde eine digitale I2C-Schnittstelle implementiert, um das Konfigurieren des Energiemanagement-systems zu ermöglichen. Da die intelligente Batterie ein Batteriemanagementsystem enthält und eine einstellbare Spannung ausgibt, kann sie einfach ausgetauscht werden. Das Upgraden von Batterien wird möglich (z. B. Ande-re Chemie, höhere Energiedichte), so dass die Betriebsdauer erweitert wird. Die Integration der Elekt-ronik erlaubt es, zusätzlich Schutzfunktionen gegen Kurzschlüsse, Überladung oder Fälschungen unterzubringen
29
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.
Testo completoAbstract (sommario):
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
30
Faktor, Richard. "Kvalita napětí v DC sítích". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316940.
Testo completoAbstract (sommario):
This diploma thesis deals with elektrical power quality in DC grids. Electrical power is commodity and therefore it must be represented not just with quantitative, but also with qualitative parameters. Nowadays, there is an increasing demand for bigger implementation of renewable energy sources and more efficient power systems, which motivates installation of DC grids. However, development of DC grids is decelerated by lack of standardization alson in power quality. The work includes definition of power quality parameters and their measurement methodology.
31
Deng, Na. "DC-DC converters for current flow control, voltage conversion and integration of energy storage systems in DC grids". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6326/.
Testo completoAbstract (sommario):
The advantages of DC transmission over the traditional AC transmission, particularly under medium and high voltage level, are widely recognised in recent years. In order to utilise DC power transmission in a more efficient manner, a construction of multi-terminal DC grids is put forward in previous literature. However, the development of large-scale DC grids faces various technical challenges, such as the power flow management, the voltage conversion and regulation, and the fault current management. One substantial and promising solution against these technical challenges whilst enhancing the controllability and flexibility of DC grids is by the inclusion and control of DC-DC converters. In this thesis, three potential applications of the DC-DC converter in future DC grids are investigated: 1) acting as a DC current/power flow controller for current/power flow management in meshed DC grids; 2) acting as a DC transformer for the interconnection of DC grids; 3) acting as a DC interface for integrating energy storage systems into DC grids.
32
Hadzimusic, Rasid. "Design of Low Voltage Low Power and Highly Efficient DC-DC Converters, Theoretical Guidelines". Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2225.
Testo completoAbstract (sommario):
In this thesis a predefined design parameters are used to present theoretical guidelines for design of low voltage, and low power DC-DC converter with high power efficiency and low levels of EMI (Electro-Magnetic Interference). This converter is used to alter the DC voltage supplied by the power source. Several DC-DC converters of different types and topologies are described and analyzed. Switched converter of buck topology is found to satisfy the design criteria most adequately and therefore is chosen as the solution for the task of the thesis. Three control schemes are analysed PWM (Pulse-Width Modulation), PFM (Phase-Frequency Modulation), and Sliding control. PWM is found to be most appropriate for implementation with this type of converter. Further, basic operation of the buck converter which includes two modes of operation CCM (Continuous-Conduction Mode) and DCM (Discontinuous-Conduction Mode) is described. Power losses associated with it are analysed as well. Finally several techniques for power conversion improvement are presented.
33
Kang, Wen. "A line and load independent zero voltage switching dc/dc full bridge converter topology". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ59307.pdf.
Testo completo
34
Hsu, Ting-Chuan, e 許丁泉. "Zero-Voltage-Switching Interleaved DC/DC Converter". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/32964201312058939292.
Testo completoAbstract (sommario):
碩士雲林科技大學
電機工程系碩士班
97
An interleaved DC/DC converter with less power switches is presented in this thesis. Two forward converter cells are connected in parallel and unite common power switches without using extra switching devices to achieve the features of interleaving and zero-voltage-switching (ZVS). Active-clamping circuit is adopted at the primary side of transformers to circulate the energy stored in magnetizing inductor and leakage inductor of transformers and reduce the switching losses and noises on power switches. In addition, the paralleling manner with interleaving technique has shared the output current and diminished its ripple effectively. Principles of operation, steady state analyses and design procedure are explained. Finally, experimental results with a 75W prototype circuit are provided to verify the analysis.
35
Chung, Shu-Ting, e 鐘淑婷. "Design of DC-DC voltage boosted regulator". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/99715493263364512385.
Testo completoAbstract (sommario):
碩士國立中興大學
電機工程學系所
94
This content of this thesis is to present a charge pump circuit which applied to non-volatile memories with a new proposed regulator. The complete circuit includes a voltage-controlled oscillator, a four-phase generator, a high-amplitude generator, a charge pumping circuit and the new proposed voltage regulator circuit. According to prior literatures, we know that it is required a voltage regulator to control the voltage produced by charge pumping circuit for applications in non-volatile memory. In this thesis, unlike the most popular regulator using comparator to switch the oscillator on or off to regulate the charge pumping circuit, the proposed regulator circuit dynamically adjusts the frequency of oscillator circuit so that the charge pumping circuit can generate the desired constant voltage. This new simple circuit reduces ripples at the output. The DC-DC voltage boosted regulator circuit can generate the output voltages of 7V~9V according to the different reference voltages with the oscillation frequency up to 16MHz, while the output ripple of this circuit is less than 260mV.
36
Huang, Wei-Lin, e 黃威霖. "A High Efficiency CMOS DC-DC Switching Voltage Regulator for Low Voltage Applications". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/59522187804192606403.
Testo completoAbstract (sommario):
碩士國立成功大學
電機工程學系碩博士班
92
Abstract The design and implementation of a DC-DC buck switching regulator for low supply voltage electronic system is presented in this thesis. This switching regulator has low output ripple in steady state and fast transient response when the load is suddenly changed. It also has high power conversion efficiency that is suitable for portable electronic applications that are powered by batteries such as mobile phone, digital camera, PDA, etc. The switching regulator IC is designed with high operation frequency for reducing the output voltage ripple and the transient response recovery time. In addition, the feedback loop bandwidth is designed as wide as possible to achieve fast transient response. For making power conversion more efficient, the regulator is enhanced with two operation modes, PWM and PFM, for heavy and light load conditions. Another technique for increasing the power conversion efficiency is to design the buffer for driving the power MOSFET with the characteristics of anti-shoot through current and adaptive dead time control. This technique can prevent the occurrences of the shoot through current and reduce the body diode conduction time during switching transitions. To eliminate the excess large current at the start up of the regulator that may damage the devices of the power stage, the soft start operation is designed. This regulator IC is fabricated with TSMC 0.35um 2P4M 3.3V/5V Mixed Signal CMOS technology through CIC. The chip size is about 1.5×1.5 mm2. Other detailed performances will be described in the following chapters.
37
Lee, Ming-Shiun, e 李明勳. "A Low Voltage Step-Up DC-DC Converter with Negative Voltage Control Technique". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/88440015833354730058.
Testo completoAbstract (sommario):
碩士國立中興大學
電機工程學系所
101
In recent years, energy harvesting technologies have become a very popular field of study. With these technologies, we can transform environmental energy, such as solar energy, heat, and vibration energy, into electric energy. The harvesting energy can be used for electronic devices without external battery, such as wireless sensor networks or wearable biomedical devices. A critical part of the whole system is the interface circuit that lies between the energy source and the load circuit to provide proper voltage and current level to the load circuit. In wearable electronics products, the biggest problem of the application of thermal energy transfer is the low voltage output. For the load circuit to use this power, an interface circuit for boosting is the design to focus. Thus, a low-voltage startup DC-to-DC boost converter is designed and the negative voltage control technology (NVCT) is utilized to enhance efficiency by minimizing the leakage current when the Native NMOS is off. The converter is composed of low voltage clock generator, negative voltage generator, pulse generator, voltage detector, buffer, power transistor, and passive element. First, voltage source provides a voltage to the low voltage clock generator, which outputs clock signal to drive the Native NMOS power switch. When the output capacitor is charged to a predetermined voltage value, the voltage detector sends a signal to change operation. The negative voltage generator generates a negative voltage to turn off the Native NMOS power transistor. Finally, the normal VTH power switch is responsible for the second phase of the step-up. The circuit was designed by using TSMC 0.18um 1P6M CMOS process. The startup voltage is 300mV and the output voltage can reach 2V with no load. The maximum voltage conversion efficiency is 63% with 1.5mA of output current, and the maximum load current is 3.2mA with 1V output voltage.
38
Liu, Yi-Ting, e 劉怡婷. "Voltage Scalable Switched Capacitor DC-DC Converter for Near-Threshold Voltage Integrated Circuit". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/cn5c3d.
Testo completoAbstract (sommario):
碩士國立交通大學
電機工程學系
102
This thesis proposes a DC-DC converter operation at 0.5 V. The circuit consists of four parts: a comparator, a digital control circuit, a switched capacitor and a digital circuit under test (DUT). The digital control circuit take the comparator output to control the switched capacitor operation to achieve the target voltage according to the reference voltage. It’s 2-phase interleaved converter can be configured into three topologies, which supports the output voltages of 0.25-0.45 V from the 0.5 V input supply, it has an efficiency between 59-79% for the load current of 100 µA. This converter is designed with all digital control without any static power consumption. At the load of 0.45 V and 100 µA, the switched capacitor consumes 57 µW. Among them, 45 µW is for the DUT with an efficiency of 79 %. The comparator and the digital control consume only 2 µW under lowest load power. It can be applied to implantable biomedical chip with low power consumption circuits. This chip is fabricated in TSMC GUTM 90 nm CMOS process, with high efficiency. The chip area is 1mm × 1mm.
39
Chen, Chin-Lin, e 陳契霖. "Programmable Switching Type DC-DC Voltage Down Converter". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/13462720562386543462.
Testo completoAbstract (sommario):
碩士國立中央大學
電機工程學系
86
For application in a low voltage and low power digitalcircuit design, a programmable switching type DC-DCVoltage Down Converter (VDC) circuit is proposed in thisthesis. The analysis of switching type VDC are described and some formulae are derived. Techniques to improve the power efficiency of VDC circuit are introduced and discussed. We develop a new structure of PWM used in the VDC. For our PWM circuit, the frequency and duty cycle of the pulse width modulation wavecan be chosen by 5 control bits. Combining a digitally controlled oscillator based tapped delay line into the PWM, the PWM is more stable and robust delay linewhen process variation occurs. The power efficiency of the VDC when operating in 1MHz can reach 93%. Finally, we layout the programmable switching type VDC circuit by using the TSMC 0.6um 1P3M process technology. The core area is about 650um*350um and can supply current up to 120mA.
40
Chen, Yi-Hao, e 陳奕豪. "High-Accuracy Energy Modulation DC-DC Voltage Converter". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/55498855955482748351.
Testo completo
41
Lin, Li-Min, e 林立敏. "Study on Fundamental Characteristics and Switching Voltage Surge Suppression of DC/DC Voltage Converters". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/17361303154423938852.
Testo completoAbstract (sommario):
碩士國立聯合大學
電機工程學系碩士班
99
The main purpose of this thesis is to study the basic characteristics of DC converters, power components within the parasitic elements of the estimated value and applications, switching surge voltage generation and improvement, and zero current switching technology. First, explore the basic characteristics of DC converters for comparative analysis in theory, simulation, and measurement data. Secondly, explore switch voltage oscillation waveform of the generated and improvement , and through the oscillation waveform to estimate the switching elements of the parasitic capacitance. In isolated converter, the voltage oscillation and parasitic capacitance can be used to estimate the power transformer of the leakage inductance value. Then, use the leakage inductance and parasitic capacitance can be design a good buffer to reduce the surge voltage of switch. Finally, explore principle of zero current switching and design-related circuits to reduce switching losses
42
PAN, GUANG-HUA, e 潘光華. "Resonant high voltage DC converter". Thesis, 1988. http://ndltd.ncl.edu.tw/handle/86954567194956024001.
Testo completo
43
Guo, Yu Jie, e 郭宇傑. "A Low Voltage Startup DC-DC Boost Converter with Two Stage and Negative Voltage Control Technique". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/26909756201096278435.
Testo completoAbstract (sommario):
碩士國立中興大學
電機工程學系所
103
According to the increasing demands for energy sources and losses of natural resources, green technology has become more and more important. In daily life, there are solar energy, thermal energy and vibration energy surrounding us, which can be stored into a battery as a supply source, by using an energy harvester and a converter. The main problem for thermal energy conversion is that the converted voltage is too low for usual circuit to operate. Therefore, we have designed a low startup, two-stage DC-DC boost converter with negative voltage control which can improve the leakage problem of the native transistor. The two-stage design can improve the compatibility between the external capacitors and the whole circuit. The boost converter is composed of a low-voltage clock generator, a negative voltage generator, a duty-cycle generator, a voltage detector, power MOS and some passive components. In the first stage, the low-voltage clock generator generates a signal to turn on the native transistor for boosting. Then, in the second stage, the negative voltage generator will shut the first stage down and the output signal of the voltage detector will switch on the threshold voltage control circuit for the second stage boosting operation. This circuit is implemented with the TSMC 0.18um 1P6M process, with 300mV startup voltage and 1.5V output voltage with zero-load current; its peak conversion efficiency can reach 73% with 1mA load current. Furthermore, the minimum voltage for the circuit to start up is 180mV, which can boost to 1.2V with zero-load current.
44
Wu, Bo-lin, e 吳柏霖. "A Study of Low Voltage DC - DC Step-up Converter". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/42739426392569211565.
Testo completoAbstract (sommario):
碩士國立聯合大學
電子工程學系碩士班
96
In order to lengthen the employ time and saving power in the consumer electronic products, low operation voltage and low dissipate energy are the important developed issues. In this thesis, a low-voltage DC to DC step-up converter circuit will be investigated, which will enable a lower power voltage step-up to a target voltage by this converter circuit. The chief architectures are the Pulse Frequency Modulation ( PFM ) and the Pulse Width Modulation ( PWM ), they are operated in the light loading and heavy loading to decrease the power dissipation, respectively. Eventually, this PFM module will work under 0.77V, the PWM can work under 0.75V. Meanwhile, the whole chip were established by the UMC 0.5μm 1P3M CMOS model.
45
Yang, Chih-Neng, e 楊智能. "Class E Resonant DC/DC Converter with Controlled Output Voltage". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/25899885786766706415.
Testo completoAbstract (sommario):
碩士國立海洋大學
電機工程學系
85
In this thesis, we make a high-frequency high-efficiency resonant DC/DC converter,Which is composed of a classical Class E inverter and a Class Erectifier.The converter operates with load resistance ranging from a full loadto infinity,while maintaining Zero-Voltage switching for the transistor in the inverter and the diode in the rectifier. The output voltage is varied from 3Vto 30V at an input voltage of 12V.We take simulation for two different switching frequencies which are under thecases of 25 kHz and 100 kHz,respectively. In the precondition to satisfy theresult, we can raise the switching frequency for our achivement due to reducethe size of the elements in advance.At last,we varify the theorem from the simulating result of PSpice and the experimenal data.
46
Hung, LingWei, e 黃翎維. "The designs and applications of DC to DC voltage converterH". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/99101654236801403687.
Testo completoAbstract (sommario):
碩士高苑科技大學
電機工程研究所
100
The purpose of this thesis in the design and application DC to DC boost converter of an applied electric bicycle, electric power systems, solar hydrogen power station. Mainly discusses adjustable output voltage of the converter and double input converter. To regulate the output voltage of the power converter, analog circuit as a control signal, and with a feedback circuit to complete the closed-loop control, in order to achieve the stability of the load changes, the output voltage. Power conversion efficiency can be achieved effectively enhance the efficiency of the electric bike and solar hydrogen power station in more than 90%. This thesis is on the investigation a transformative electric bike (E-Bike) which is capable to perform triple operation modes, including traveling, exercise and electricity generation. The structure of the transformative E-Bike is based on extension of a usual E-Bike with operation modes of electric power assistance and regenerative braking. The proposed transformative E-Bike is featured by a DC-DC converter with tunable duty ratio so that the voltage input/output ratio of the converter can be suitably adjusted to obtain a desired electric energy recharging voltage level with corresponding vehicle's deceleration force or exercise resistance.Under traveling operation, battery provides assistance power via motor for vehicle driving force other than human force and also accumulates electric energy when the motor is functioning as generator driven by the vehicle. Under the operations of exercise operation or electricity generation, the rear wheel equipped with motor/generator is lifted from ground and fixed properly. By adjusting the recharging voltage level via the tunable DC-DC converter, a suitable exercise resistance can be attained with electric energy recharged to battery in an exercise operation. While in the operation of electricity generation, the human force is transferred to electric power output with adjusted voltage level. The team members attended the 2011 Taipei International Invention Show & Technomart from Sep. 29 to Oct.2 and were awarded a bronze medal in the invention contest . The devised transformative E-Bike has also later been sent for the 2011 International Innovation and Invention Competition and won a gold medal on this event, Nov. 28. Also, this thesis is on the study of renewable energy system with proton exchange membrane fuel cell and electrolyzer using the photovoltaic energy for producing hydrogen. The input energy of this system is based on the transformation of photovoltaic cell from solar radiation and the output energy is sent to user based on instantaneous requirement. The energy system mainly consists of the charging battery for storing electric energy in a short-term manner and the electrolyzer/fuel cell devices for energy storage in hydrogen formation for mid-term usage. The investigated issues mainly include the optimal specification for the principal components in the energy system, and the design of an exemplary energy system for demonstration.
47
Chen, Kuan-cheng, e 陳冠丞. "High-efficiency high-voltage DC/DC step-down chip design". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/36796732916723368848.
Testo completoAbstract (sommario):
碩士國立雲林科技大學
電子與光電工程研究所碩士班
101
In this thesis, it uses the process of TSMC 0.25 um CMOS HIGH VOLTAGE MIXED SIGNAL to complete a total of three wafers and be off the assembly line of TSMC through CIC. The wafers are as the following respectively: (a) low-dropout linear regulator. Measurement results show that the feature of low voltage drop allows the conversion efficiency is up to 98.5% when the input voltage and the output voltage of circuit are similar; (b) simple-switching buck converter. It uses relatively simple feedback circuit to complete PWM control, and measurement results show that the PWM frequency will be decreased as the load increases, which can be applied to the load sensing in the future; (c) digital control switching buck converter. It uses all-digital way to control and generate PWM. It can fix PWM to obtain the best output voltage. The circuit can provide different voltage levels conversion according to the different functional needs. Additionally, digital control switching buck converter uses FPGA to achieve LED driver circuit and then apply to LED driving. According to different applications, it uses different LED serial number, so LED is also changed as the driving voltage. This paper presents self-adaptive voltage regulation LED driving system. The input voltage is fixed at 40V, and the output voltage can follow different LED serial number to adjust to optimal driving automatically. The maximum output current can be driven to 1A. It can adjust LED brightness in accordance with user requirements. The circuit test results show the adjustable output voltage range is 0V ~ 38V, and it can drive 10 1W white LED (300mA), or 10 3W White LED (500mA), or 5 5W white LED (600mA) with maximum efficiency 84.69%.
48
Shiau, Jung-yi, e 蕭仲義. "Sliding mode voltage control of DC/DC buck-boost converter". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/99441053412284159291.
Testo completoAbstract (sommario):
碩士正修科技大學
機電工程研究所
97
Comparing with the conventional power converters, switching power converters possess the advantages of high efficiency, small size and wide range of voltage operation, so that they are widely applied in the application of portable electronic products and equipment in recent years. This thesis mainly focuses on the development and implementation of Buck/Boost converter with a sliding mode voltage controller, to achieve the stable desired controlled voltage output. Firstly, the stable sliding surface function is designed due to the control system. It can be observed that the entire controlled region can be divided into three subspaces. Based on Lyapunov stable theory, the controller is proposed to enforce the system trajectory from the arbitrary point toward the sliding surface in the finite time, remain on the surface and slides along to equilibrium point exponentially. In addition, based on a fixed frequency pulse width modulation technology, the proposed controller is realized by controlling the duty cycle of switch device to achieve desired stable voltage output under the influence of loading variation. The hardware system includes the integrated design of converters, controller, sawtooth signal generation circuit and drive circuit. According to the simulation software of PSpice, the, the encouraged system performance is validated by the testing of different loadings. Finally, the hardware system is implemented by analogic circuit to verify feasibility of the proposed control structure according to the different voltage inputs and loading uncertainties.
49
Wiegman, Herman L. N. "A DC/DC converter for a dual voltage automotive system". 1991. http://catalog.hathitrust.org/api/volumes/oclc/24158184.html.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Wisconsin--Madison, 1991.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 104).
50
LIAO, LIEN-HSI, e 廖連喜. "Implementation of DC-DC Converter with Wide-Range Input Voltage". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/yt38j9.
Testo completoAbstract (sommario):
碩士國立雲林科技大學
電機工程系
106
This thesis studies four kinds of DC-DC converters with a wide range of input voltages. The first converter is the Flyback S21 converter, the second converter is the Flyback S22 converter, the third converter is the Forward S21 converter, and the fourth converter is the Forward S22 converter. The first two are based on the conventional flyback converters, with an S2 power switching element added to the primary and secondary sides, respectively. The latter two are based on the conventional forward converters, one S2 power switching element is added to the primary and secondary sides, similarly. The role of the S2 switch is to change the turns ratio of the transformer, with the uA 741 operational amplifier as the control IC. When the input voltage is less than the set value, the S2 switch is ON; conversely, when the input voltage is greater than the set value, the S2 switch is OFF. By changing the turns ratio between the primary side and the secondary side with the ON/OFF of the S2 power switch, the converter input voltage range can be increased. In addition, the S1 power switching element is controlled by the PWM IC TL494 to maintain the stability of the output voltage and the output current. Firstly, this study introduces the application and types of converters. Secondly, it discusses the basic operating principles of flyback and forward converters, designs the main components of the circuit, and finally verifies their feasibility through simulation and implementation. The implemented circuits were characterized by a DC input voltage between 10 and 160V, a DC 5V output voltage, 2A load current, and 10W rated power.