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Gannett, Robert Ashley. "Control Strategies for High Power Four-Leg Voltage Source Inverters." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34251.
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In recent decades there has been a rapidly growing demand for high quality, uninterrupted power. In light of this fact, this study has addressed some of the causes of poor power quality and control strategies to ensure a high performance level in inverter-fed power systems. In particular, specific loading conditions present interesting challenges to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, realistic systems, with finite output impedances, encounter stability issues, unbalanced phase voltage, and harmonic distortion. Each of the loading conditions is presented in detail with a proposed control strategy in order to ensure superior inverter performance. Simulation results are presented for a 90 kVA, 400 Hz VSI under challenging loading conditions to demonstrate the merits of the proposed control strategies.
Unloaded or lightly loaded conditions can cause instabilities in inverter-fed power systems, because of the lightly damped characteristic of the output filter. An inner current loop is demonstrated to damp the filter poles at light load and therefore enable an increase in the control bandwidth by an order of magnitude. Unbalanced loading causes unequal phase currents, and consequently negative sequence and zero sequence (in four-wire systems) distortion. A proposed control strategy based on synchronous and stationary frame controllers is shown to reduce the phase voltage unbalance from 4.2% to 0.23% for a 100%-100%-85% load imbalance over fundamental positive sequence control alone. Non-linear loads draw harmonic currents, and likewise cause harmonic distortion in power systems. A proposed harmonic control scheme is demonstrated to achieve near steady state errors for the low order harmonics due to non-linear loads. In particular, the THD is reduced from 22.3% to 5.2% for full three-phase diode rectifier loading, and from 11.3% to 1.5% for full balanced single-phase diode rectifier loading, over fundamental control alone.Master of Science
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Alskran, Faleh A. "Dynamic modeling and analysis of the three-phase voltage source inverter under stand-alone and grid-tied modes." Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/18220.
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Master of ScienceDepartment of Electrical and Computer Engineering
Behrooz Mirafzal
Increasing energy demand, rising oil prices, and environmental concerns have forced attention to alternative energy sources that are environmentally friendly and independent of fossil fuels. Renewable energy sources (RES) have become an attractive alternative to the traditional energy sources for electric power generation. However, one of the main challenges of RES adaption arises when connecting RES to the electric grid. Voltage source inverters (VSIs), typically, connect RES to the electric grid. Similar to any engineering system, detailed dynamic models of the VSIs are needed for design and analysis purposes. However, due to the non-linearity of VSIs, development of dynamic models that can accurately describe their behavior is a complex task. In this thesis, a detailed averaged-state-space model of the two-level three-phase space vector pulse width modulation VSI and its companion LCL filter is derived. Because VSIs can operate under stand-alone and grid-tied modes, two models were derived for each case. In the derived models, the VSI modulation index m and phase angle ϕ are initially considered constant. In practice, however, these parameters are considered the main control parameters. To model these parameters as control inputs, small-signal models of the VSI under stand-alone and grid-tied modes were derived. To verify the accuracy of the developed large-signal and small-signal models, Matlab/Simulink simulations were carried out. The simulation results were compared against the models results. Moreover, the models were verified through lab experiments. The developed models can be used as design and analysis tools. In addition, the developed models can be used as fast and efficient simulation tools for system studies, when the modeling of switching transients is not needed. Nowadays, the number of VSIs connected to the electric grid is growing exponentially. The amount of time and computation needed to simulate VSIs using simulation software packages can be significantly decreased by the use of the developed models.
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Muhsen, Hani. "Three-Phase Voltage Source Inverter with Very High Efficiency Based on SiC Devices." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-199329.
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This dissertation aims at designing a three-phase voltage source inverter based on the SiC devices and mainly the SiC-MOSFET. The designed inverter offers a possibility to drive the power inverter with a very high efficiency, which can reach up to 99% for 16 kW rated power. The design is dedicated to the electric vehicle application, and it aims at
• Providing a comparative study on some of the current discrete SiC devices in terms of the total losses and the thermal conductivity. In addition, a behavioral study of the effective channel mobility with temperature variation in the SiC MOSFET will be investigated.
• Designing a gate driver which fits with the driving requirements of the SiC-MOSFET and provides a trade-off between the switching losses and the EMI behavior.
• Designing a three-phase voltage source inverter with 16 kW rated power; the design includes minimizing the inverter losses and extracts the EMI model of the power inverter by considering the effects of the parasitic parameters; moreover a short guideline for selecting the heat-sink based on the static network is introduced.
• Proposing a new and simplified carried-based PWM, this will reduce the harmonics in the output waveforms and enhance the utilization of the DC-link voltage.
• Proposing a new strategy for compensating the dead-time effect in carrier based-PWM and to find out the proper dead-time level in VSI based on SiC –MOSFET.
• Designing faults diagnosis and protection circuits in order to protect the power inverter from the common faults; overcurrent, short-circuit, overvoltage, and overtemperature faults.
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Lugo, Núñez David Rush. "High Power Density and Overcurrent Protection Challenges in the Design of a Three-Phase Voltage Source Inverter for Motor Drive Applications." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/30982.
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The voltage source inverter (VSI) is certainly the most popular topology used in dc
to ac power conversion. Virtually every commercial electric motor is driven by a VSI.
There is a need for smaller and more efficient drives in high performance applications
that is dictating unprecedented power density requirements on airborne motor drive
systems. In reply to this need, higher switching frequencies are being sought and new
switching devices like Silicon Carbide (SiC) JFETs have emerged. Although faster
switching rates favor a reduction in the size of passive components and alleviate the
current ripple in the inverter, a penalty is paid on switching losses. Owing to their low
switching energy profile, SiC JFETs stand as promising candidates in high switching
frequency environments. Their normally-on nature, however, raises a level of discomfort
among designers due to the added complexities in the gate drive circuitry and the
increased risk of dc bus shoot-through faults in voltage source inverters. Despite of these
challenges the use of SiC JFETs continues proliferating in high power density
applications. In an effort to study the new challenges introduced by this trend a 2 kW
IGBT-based three-phase voltage source inverter operating at 65 kHz was designed, built,
and tested. In addition a novel overcurrent protection residing in the inverter dc link is
proposed in response to the concern of using normally-on devices in voltage source
inverters. Successful hardware validation of both the VSI and the overcurrent protection
circuit is supported with experimental results.Master of Science
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Silva, Ivan da. "Modelagem e acionamento de uma máquina de indução de nove fases baseado em modulação espacial vetorial - SVPWM." Universidade Federal da Paraíba, 2015. http://tede.biblioteca.ufpb.br:8080/handle/tede/7558.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The interest for the study of multiphase (more than three phases) machines and variable speed drives has substantially increased in the last two decades. The advantages presented by the multiphase systems compared to their three-phase counterparts have being the the main effort to increase researches all over the world. Reduction in torque oscillation, lower current ratings, high drive reliability, better fault tolerance and harmonic content reduction in the DC bus are some of these advantages. The additional degrees of freedom due to extra phases make multiphase systems very flexible when it comes to control systems and modulation strategies. Although three-phase systems are predominant in industrial applications, the use of multiphase machines and drives has increased in very specific areas such as locomotive traction, electric ship propulsion, aerospace industry (more electric aircraft), electric and hybrid vehicles and industrial high power systems. Due to high coupling degree between electric variables in multiphase systems, modeling of multiphase machines has been and still is a challenge task in research centers. In this present work, analitic modeling of symmetric and asymmetric nine-phase machines using natural variables and space vector decomposition are presented. The principles used in the study are the same used for three-phase systems. However, multiphase systems are analised in multiple d-q planes. PWM modulation strategies based on space vectors theory (SVPWM) for a voltage source inverter (VSI) are presented. The multiphase drive system presented works in the linear operation region with sinusoidal voltage generation. Results for both machines and drive modeled are verified by simulation programs developed in C programming language an Matlab.
O interesse pelo estudo de máquinas de indução multifases (mais de três fases) e dos seus sistemas de acionamento cresceu substancialmente nas últimas duas décadas. As muitas vantagens apresentadas pelos sistemas multifases, em relação aos sistemas trifásicos convencionais, têm sido fatores motivadores para o aumento de pesquisas em todo o mundo. Redução das oscilações de torque, redução da corrente por fase, maior confiabilidade do acionamento, grande tolerância à faltas e redução no conteúdo harmônico da corrente no barramento CC são algumas destas vantagens. O maior grau de liberdade proporcionado pelas fases extras torna os sistemas multifases bastante flexíveis quanto às estratégias de modulação e de controle. Apesar da atual predominância da utilização das máquinas e acionamentos trifásicos na indústria, as máquinas multifases estão sendo cada vez mais utilizadas em áreas de aplicações específicas tais como tração de locomotivas, propulsão de navios elétricos de grande porte, indústria aeroespacial, tração de veículos híbridos e elétricos e sistemas industriais de alta potência. Devido ao alto grau de acoplamento entre as variáveis elétricas de um sistema multifases, a modelagem e análise desses sistemas tem representado uma tarefa desafiadora nos centros de pesquisa. No presente trabalho são apresentadas as modelagens analíticas de uma máquina de indução de nove fases simétrica e de uma máquina de nove fases assimétrica pelo método de variáveis naturais e pelo método de decomposição vetorial. Os princípios utilizados na modelagem são os mesmos utilizados nos sistemas trifásicos. No entanto, sistemas multifases são analisados em múltiplos planos d-q. Estratégias de modulação PWM baseadas na teoria de vetores espaciais (SVPWM) para um inversor de nove fases tipo VSI (Inversor Fonte de Tensão) são apresentadas para acionamento das máquinas. O sistema de acionamento apresentado trabalha na região linear de operação e gera tensão de saída senoidal. Dados de simulação obtidos a partir de programas desenvolvidos em linguagem C e Matlab são apresentados para ambas as máquinas de nove fases modeladas.
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Thacker, Timothy Neil. "Control of Power Conversion Systems for the Intentional Islanding of Distributed Generation Units." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/30814.
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Within the past decade, talk has arisen of shifting the utility grid from centralized, radial sources to a distributed network of sources, also known as distributed generation (DG); in the wake of deregulation, the California energy crisis, and northeastern blackouts.
Existing control techniques for DG systems are designed to operate a system either in the connected or disconnected (islanding) mode to the utility; thus not allowing for both modes to be implemented and transitioned between. Existing detection and re-closure algorithms can also be improved upon. Dependent upon the method implemented, detection algorithms can either cause distortions in the output or completely miss a disturbance. The present re-closure process to reconnect to the utility is to completely shutdown and wait five minutes. The proposed methods of this study improve upon existing methods, via simulation and hardware experimentation, for DG systems that can intentionally islanding themselves.
The proposed, â switched-modeâ , control allows for continuous operation of the system during disturbances by transitioning the mode of control to reflect the change in the system mode (grid-connected or islanding). This allows for zero downtimes without detrimental transients.
The proposed detection method can sense disturbances that other methods cannot; and within 25 ms (approximately 1.5 line-cycles at 60 Hz). This method is an improvement over other methods because it eliminates the need to purposely distort the outputs to sense a disturbance.
The proposed re-closure method is an improvement over the existing method due to the fact that it does not require the system to de-energize before re-synchronizing and reconnecting to the utility. This allows for DGs to continuously supply power to the system without having to shut down. Results show that the system is generally ready to reconnect after 2 to 5 line cycles.Master of Science
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Tazay, Ahmad F. "Smart Inverter Control and Operation for Distributed Energy Resources." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7097.
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The motivation of this research is to carry out the control and operation of smart inverters and voltage source converters (VSC) for distributed energy resources (DERs) such as photovoltaic (PV), battery, and plug-in hybrid electric vehicles (PHEV). The main contribution of the research includes solving a couple of issues for smart grids by controlling and implementing multifunctions of VSC and smart inverter as well as improving the operational scheme of the microgrid. The work is mainly focused on controlling and operating of smart inverter since it promises a new technology for the future microgrid. Two major applications of the smart inverter will be investigated in this work based on the connection modes: microgrid at grid-tied mode and autonomous mode.
\indent In grid-tied connection, the smart inverter and VSC are used to integrate DER such as Photovoltaic (PV) and battery to provide suitable power to the system by controlling the supplied real and reactive power. The role of a smart inverter at autonomous mode includes supplying a sufficient voltage and frequency, mitigate abnormal condition of the load as well as equally sharing the total load's power. However, the operational control of the microgrid still has a major issue on the operation of the microgrid. The dissertation is divided into two main sections which are:
1- Low-level control of a single smart Inverter.
2- High-level control of the microgrid.
The first part investigates a comprehensive research for a smart inverter and VSC technology at the two major connections of the microgrid. This involves controlling and modeling single smart inverter and VSC to solve specific issues of microgrid as well as improve the operation of the system. The research provides developed features for smart inverter comparing with a conventional voltage sourced converter (VSC). The two main connections for a microgrid have been deeply investigated to analyze a better way to develop and improve the operational procedure of the microgrid as well as solve specific issues of connecting the microgrid to the system.
A detailed procedure for controlling VSC and designing an optimal operation of the controller is also covered in the first part of the dissertation. This section provides an optimal operation for controlling motor drive and demonstrates issues when motor load exists at an autonomous microgrid. It also provides a solution for specific issues at operating a microgrid at autonomous mode as well as improving the structural design for the grid-tied microgrid. The solution for autonomous microgrid includes changing the operational state of the switching pattern of the smart inverter to solve the issue of a common mode voltage (CMV) that appears across the motor load. It also solves the issue of power supplying to large loads, such as induction motors. The last section of the low-level section involves an improvement of the performance and operation of the PV charging station for a plug-in hybrid electric vehicle (PHEV) at grid-tied mode. This section provides a novel structure and smart controller for PV charging station using three-phase hybrid boost converter topology. It also provides a form of applications of a multifunction smart inverter using PV charging station.
The second part of the research is focusing on improving the performance of the microgrid by integrating several smart inverters to form a microgrid. It investigates the issue of connecting DER units with the microgrid at real applications. One of the common issues of the microgrid is the circulating current which is caused by poor reactive power sharing accuracy. When more than two DER units are connected in parallel, a microgrid is forming be generating required power for the load. When the microgrid is operated at autonomous mode, all DER units participate in generating voltage and frequency as well as share the load's power. This section provides a smart and novel controlling technique to solve the issue of unequal power sharing. The feature of the smart inverter is realized by the communication link between smart inverters and the main operator. The analysis and derivation of the problem are presented in this section.
The dissertation has led to two accepted conference papers, one accepted transaction IEEE manuscript, and one submitted IET transaction manuscript. The future work aims to improve the current work by investigating the performance of the smart inverter at real applications.
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Venugopal, S. "Study On Overmodulation Methods For PWM Inverter Fed AC Drives." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/278.
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A voltage source inverter is commonly used to supply a variable frequency variable voltage to a three phase induction motor in a variable speed application. A suitable pulse width modulation (PWM) technique is employed to obtain the required output voltage in the line side of the inverter. Real-time methods for PWM generation can be broadly classified into triangle comparison based PWM (TCPWM) and space vector based PWM (SVPWM).
In TCPWM methods such as sine-triangle PWM, three phase reference modulating signals are compared against a common triangular carrier to generate the PWM signals for the three phases.
In SVPWM methods, a revolving reference voltage vector is provided as voltage reference instead of three phase modulating waves. The magnitude and frequency of the fundamental component in the line side are controlled by the magnitude and frequency, respectively, of the reference vector.
The fundamental line side voltage is proportional to the reference magnitude during linear modulation. With sine-triangle PWM, the highest possible peak phase fundamental voltage is 0.5Vdc, where Vdc is the DC bus voltage, in the linear modulation zone. With techniques such as third harmonic injection PWM and space vector based PWM, the peak phase fundamental voltage can be as high as (formula) (i.e., 0:577Vdc)during linear modulation. To increase the line side voltage further, the operation of the VSI must be extended into the overmodulation region. The overmodulation region extends upto the six-step mode, which gives the highest possible ac voltage for a given (formula).
In TCPWM based methods, increasing the reference magnitude beyond a certain level leads to pulse dropping, and gradually leads to six-step operation. However, in SVPWM methods, an overmodulation algorithm is required for controlling the line-side voltage during overmodulation and to achieve a smooth transition from PWM to six-step mode.
Numerous overmodulation algorithms have been proposed in the literature for space vector modulated inverter. A well known algorithm among these divides the overmodulation zone into two zones, namely zone-I and zone-II. This is termed as the 'existing overmodulation algorithm' here. This algorithm is modified in the present work to reduce computational burden without much increase in the line current distortion.
During overmodulation, the fundamental line side voltage and the reference magnitude are not proportional, which is undesirable from the control point of view. The present work ensures a linear relationship between the two.
Apart from the fundamental component, the inverter output voltage mainly consists of harmonic components at high frequencies (around switching frequency and the integral multiples) during linear modulation. However, during overmodulation, low order harmonic components such as 5th, 7th, 11th, 13th etc., are also present in the output voltage. These low order harmonic voltages lead to low order harmonic currents in the motor. The sum of the lower order harmonic currents is termed as 'lower order current ripple'. The present thesis proposes a method for estimation of lower order current ripple in real-time.
In closed loop current control, the motor current is fed back to the current controller. During overmodulation, the motor current contains low order harmonics, which appear in the current error fed to the controller. These harmonic currents are amplified by the current error amplifier deteriorating the performance of the drive.
It is possible to filter the lower order harmonic currents before being fed back. However, filtering introduces delay in the current loop, and reduces the bandwidth even during linear modulation. In the present work, the estimated lower order current ripple is subtracted from the measured current before the latter is fed back to the controller.
The estimation of lower order current ripple and the proposed current control are verified through simulation using MATLAB/SIMULINK and also experimentally on a laboratory prototype. The experimental setup comprises of a field programmable gate arrays (FPGA) based digital controller, an IGBT based inverter and a four-pole squirrel cage induction motor.
(Pl refer the original document for formula)
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Voldoire, Adrien. "Outil de développement et d'optimisation dédié aux onduleurs SiC de forte puissance." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT037.
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La volonté de diminuer la consommation en carburant en aéronautique amène à repenser les architectures de distribution et de conversion de puissance embarquées. L’utilisation d’un outil d’optimisation déterministe apparait comme une solution prometteuse pour prendre en compte les compromis intrinsèques aux convertisseurs statiques en pré-dimensionnement, avec pour objectif de minimiser leur masse. Un outil d’optimisation est donc proposé pour apporter des éléments de comparaison entre différentes topologies d’onduleur et entre différentes solutions technologiques.Le développement de l’outil passe par l’élaboration de modèles analytiques pour être compatible avec l’utilisation d’un algorithme à base de gradients. Une analyse harmonique reposant sur des transformées de Fourier permet de reconstituer les ondulations de chaque signal, en regard des normes aéronautiques. La modélisation s’intéresse également à la construction de modèles pour les composants passifs et actifs, permettant en particulier d’évaluer les pertes et donc le rendement du convertisseur. L’intégralité des modèles développés fait l’objet d’une validation expérimentale sur un prototype à 10 kW.L’utilisation d’un algorithme à base de gradient n’étant pas classique en électronique de puissance, des études sont menées pour valider la méthodologie proposée. Ces études montrent l’adéquation du choix d’un tel algorithme avec le besoin de pré-dimensionnement, tout en indiquant ses limites et les perspectives. Enfin, l’outil d’optimisation est utilisé pour comparer différentes solutions architecturales et technologiques sur des cas d’application aéronautiques. Les résultats obtenus sont discutés en regard des méthodes de dimensionnement classiquesThe exponential development of aircraft transportation is a threat in the context of global warming. One of the solutions investigated consists in increasing the amount of embedded electrical power systems and actuators. Using a deterministic optimization tool appear as a promising solution to take into account the multiple compromises in a power converter design during the pre-design step, with the goal to minimize the weight. An optimization tool is proposed to bring comparative elements between different inverter topologies and technological solutions.The development of the tool requires elaborating analytical models to be compliant with the gradient-based algorithm. Harmonic analyses with Fourier transform enable calculating the signal ripples, to respect aircraft standards. Components are also designed precisely with appropriate loss models to estimate the converter efficiency. All the developed models are experimentally validated with a 10 kW prototype.As the use a gradient-based algorithm is not common in power electronics, studies are carried out to validate this proposed methodology. These studies show the effectiveness of the algorithm choice in the pre-design step, and indicates some limits and forecasts. Finally, the algorithm is used to compare different architectural and technological solutions on aircraft cases. The results are discussed regarding classical sizing methodologies
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Oberdorf, Michael Craig. "Power losses and thermal modeling of a voltage source inverter." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FOberdorf.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2006.Thesis Advisor(s): Alexander Julian. "March 2006." Includes bibliographical references (p. 103-104). Also available online.
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Blevins, Stephen T. "Operating standby redundant controller to improve voltage source inverter reliability." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FBlevins.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2007.Thesis Advisor(s): Julian, Alexander L. "December 2007." Description based on title screen as viewed on January 18, 2008. Includes bibliographical references (p. 123). Also available in print.
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Barnes, Lemuel Gregory III. "Voltage-source inverter output waveform compensation using adaptive intelligent control." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/39997.
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A single-layer neural network-based voltage compensation technique which generates minimum-distortion sinusoidal output voltages from a three-phase PWM inverter used for uninterruptible power supplies (UPS) is described. The proposed compensation technique is implemented in a microprocessor-based controller constructed in the stationary d-q frame where the controller sampling rate is twice the inverter switching frequency. The structure of a feed-forward artificial neural network connects network inputs and outputs through multiple linear or nonlinear
neuron models, and processes these input/output data associations in a
parallel distributed manner. Network inputs in the form of UPS load voltage commands and load current feedback are propagated forward in the network each controller sampling period generating the inverter output voltage commands, the network outputs, which are converted to three phase inverter switching Signals using the space vector PWM waveform generation process.Ph. D.
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Barnes, Lemuel Gregory. "Voltage-source inverter output waveform compensation using adaptive intelligent control /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10192006-115605/.
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Adabi, Firouzjaee Jafar. "Remediation strategies of shaft and common mode voltages in adjustable speed drive systems." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/39293/1/Jafar_Adabi_Firouzjaeel_Thesis.pdf.
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AC motors are largely used in a wide range of modern systems, from household appliances to automated industry applications such as: ventilations systems, fans, pumps, conveyors and machine tool drives. Inverters are widely used in industrial and commercial applications due to the growing need for speed control in ASD systems. Fast switching transients and the common mode voltage, in interaction with parasitic capacitive couplings, may cause many unwanted problems in the ASD applications. These include shaft voltage and leakage currents.
One of the inherent characteristics of Pulse Width Modulation (PWM) techniques is the generation of the common mode voltage, which is defined as the voltage between the electrical neutral of the inverter output and the ground. Shaft voltage can cause bearing currents when it exceeds the amount of breakdown voltage level of the thin lubricant film between the inner and outer rings of the bearing. This phenomenon is the main reason for early bearing failures.
A rapid development in power switches technology has lead to a drastic decrement of switching rise and fall times. Because there is considerable capacitance between the stator windings and the frame, there can be a significant capacitive current (ground current escaping to earth through stray capacitors inside a motor) if the common mode voltage has high frequency components. This current leads to noises and Electromagnetic Interferences (EMI) issues in motor drive systems.
These problems have been dealt with using a variety of methods which have been reported in the literature. However, cost and maintenance issues have prevented these methods from being widely accepted. Extra cost or rating of the inverter switches is usually the price to pay for such approaches. Thus, the determination of cost-effective techniques for shaft and common mode voltage reduction in ASD systems, with the focus on the first step of the design process, is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1.
Electrical power generation from renewable energy sources, such as wind energy systems, has become a crucial issue because of environmental problems and a predicted future shortage of traditional energy sources. Thus, Chapter 2 focuses on the shaft voltage analysis of stator-fed induction generators (IG) and Doubly Fed Induction Generators DFIGs in wind turbine applications. This shaft voltage analysis includes: topologies, high frequency modelling, calculation and mitigation techniques. A back-to-back AC-DC-AC converter is investigated in terms of shaft voltage generation in a DFIG. Different topologies of LC filter placement are analysed in an effort to eliminate the shaft voltage.
Different capacitive couplings exist in the motor/generator structure and any change in design parameters affects the capacitive couplings. Thus, an appropriate design for AC motors should lead to the smallest possible shaft voltage. Calculation of the shaft voltage based on different capacitive couplings, and an investigation of the effects of different design parameters are discussed in Chapter 3. This is achieved through 2-D and 3-D finite element simulation and experimental analysis.
End-winding parameters of the motor are also effective factors in the calculation of the shaft voltage and have not been taken into account in previous reported studies. Calculation of the end-winding capacitances is rather complex because of the diversity of end winding shapes and the complexity of their geometry. A comprehensive analysis of these capacitances has been carried out with 3-D finite element simulations and experimental studies to determine their effective design parameters. These are documented in Chapter 4. Results of this analysis show that, by choosing appropriate design parameters, it is possible to decrease the shaft voltage and resultant bearing current in the primary stage of generator/motor design without using any additional active and passive filter-based techniques.
The common mode voltage is defined by a switching pattern and, by using the appropriate pattern; the common mode voltage level can be controlled. Therefore, any PWM pattern which eliminates or minimizes the common mode voltage will be an effective shaft voltage reduction technique. Thus, common mode voltage reduction of a three-phase AC motor supplied with a single-phase diode rectifier is the focus of Chapter 5. The proposed strategy is mainly based on proper utilization of the zero vectors.
Multilevel inverters are also used in ASD systems which have more voltage levels and switching states, and can provide more possibilities to reduce common mode voltage. A description of common mode voltage of multilevel inverters is investigated in Chapter 6.
Chapter 7 investigates the elimination techniques of the shaft voltage in a DFIG based on the methods presented in the literature by the use of simulation results. However, it could be shown that every solution to reduce the shaft voltage in DFIG systems has its own characteristics, and these have to be taken into account in determining the most effective strategy.
Calculation of the capacitive coupling and electric fields between the outer and inner races and the balls at different motor speeds in symmetrical and asymmetrical shaft and balls positions is discussed in Chapter 8. The analysis is carried out using finite element simulations to determine the conditions which will increase the probability of high rates of bearing failure due to current discharges through the balls and races.
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Un, Emre. "Common Mode Voltage And Current Reduction In Voltage Source Inverter Driven Three Phase Ac Motors." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609062/index.pdf.
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In this thesis various reduced common mode voltage (RCMV) pulse width modulation (PWM) techniques and active/passive common mode voltage (CMV) reduction methods for voltage source inverter driven three-phase AC motors are theoretically and practically investigated. A novel RCMV-PWM method, the near state PWM (NSPWM) method is proposed for operation at high modulation index. At low modulation index, a modified version of an existing RCMV-PWM method, AZSPWM1, termed as MAZSPWM, is proposed to mitigate the voltage reflection problem of the method. An optimum modulation algorithm combining NSPWM and MAZSPWM with seamless transition is proposed. The proposed RCMV-PWM methods significantly reduce CMV but they suppress common mode current (CMC) partially. Utilization of a common mode inductor together with RCMV-PWM methods is effective in suppressing the CMC. In the study, in addition to the CMV characteristics, various practical performance characteristics such as voltage linearity, inverter output current ripple, inverter DC-link current ripple, and output line-to-line voltage pulse pattern are also analyzed. The study involves analysis, computer simulations, and detailed laboratory experiments.
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Moghadam, Mansour Salehi. "Current-source-based low frequency inverter topology." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/12750.
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A DC to AC inverter can be classified in different topologies; some of these topologies are three level and multilevel inverter. Both types have some advantages and disadvantages. Three level inverters can be applied for low power applications because it is cheaper and has less semiconductor losses at high switching frequencies with poor total harmonic distortion (THD). Multilevel inverters (MLI) can be applied for higher power applications with less THD. However, the MLI has more cost and conductive power losses in comparison with three level inverters. In order to overcome the limitations of three and multilevel topologies, this thesis presents a new controlling topology of multilevel DC/AC inverters. The proposed multilevel inverter topology is based on a current source inverter, which consists of a buck/boost, boost and flyback converters, and an H-bridge inverter. The output voltage of the inverter is shaped through the control of just one main semiconductor switch. This new topology offers almost step-less output voltage without the need for multi DC source or several capacitor banks as in the case of other multilevel inverter topologies. The efficiency of the proposed topology is higher than other inverter topologies for medium power applications (2-10 kW). The proposed topology also generates smaller Total Harmonic Distortion (THD) compared to other inverter topologies. The two main key aspects of the proposed circuit is to keep the switching losses as low as possible and this is achieved through the control of a single switch at relatively low frequency and also to generate an improved AC Voltage waveform without the need for any filtering devices. The output frequency and voltage of the proposed circuit can be easily controlled according to the load requirements. The proposed inverter topology is ideal for the connection of renewable energy; this is due to its flexibility in varying its output voltage without the need of fixed turns-ratio transformers used in existing DC/AC inverter topologies. The harmonic contents of the output of this proposed topology can be controlled without the need of any filter. The simulation and practical implementation of the proposed circuits are presented. The practical and simulation results show excellent correlation.
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Butcher, Nicholas David. "Active Paralleling of High Power Voltage Source Inverters." Thesis, University of Canterbury. Electrical and Computer, 2007. http://hdl.handle.net/10092/3430.
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Power electronics are becoming established in ever broadening areas of industry. The transition from previous generation technology is driven by the oportunity for improvements in controllability, efficiency, and longevity. A wide variety of power semiconductors are available, however power handling capacity is still a significant limitation for many applications. An increase in the capacity of a single device is usually accompanied by a drop in switching frequency, and hence achievable system bandwidth. Increased capacity can be attained without this loss in bandwidth by using multiple lower power devices in parallel. Products based on parallel device topologies are already present in the marketplace, however there are many associated complications. The nature of these complications depends on the control method and topology used, but no system combines high performance and high power with high reliability and easy maintainability. This research aims to identify and develop a method that would provide a system of voltage source inverters with a total capacity in excess of 10MVA, with effective control bandwidth comparable to a 100kVA system. Additionally, the method should be equally applicable at still higher power levels in the future with the anticipated development of higher capacity power semiconductors. The primary goal when using paralleled devices is to achieve an even distribution of system load between them, as unbalanced load leads to poor system utilisation. Devices can be paralleled either passively, in which devices are controlled in common and characteristics inherent to the device are relied upon to balance load; or actively, in which devices are individually controlled and monitored to improve load balance. A key component of the thesis is the identification and analysis of the inadequacies inherent to passively paralleled systems. It is the limitations of passive paralleling that provide the motivation to develop an active parallel control mechanism. Following the analysis, an active control algorithm is developed and implemented on a paralleled system. The proposed system topology consists of an array of medium power Voltage Source Inverter (VSI) modules operating in parallel. Each module is controlled semi-independently at a local level, with an inter-module communications network to enable active equalisation of module load, and redundant fault management. An innovative load equalisatiion algorithm is developed and proven, the key feature of which is this inclusion of a synthetic differential resistance between modules within the system. The result is a modular expandable structure offering the potential for very high power capacity combined with quality of response usually only found in low power systems. The system as a whole is extremely reliable as any module can be isolated in the event of a fault without significantly affecting the remainder of the network. Performance results from both simulation and experimentation on a two module small scale prototype are given. Using the developed topology and control method extremely accurate load balancing can be achieved without degradation of the response characteristics. The system is tested up to only 2.4kW in the course of this research, but the correlation with simulation is high and gives confidence that the developed mechanism will allow the 10MV A goal to be achieved. Following the developmental stage of this research the technology has been applied to a commercial system comprising parallel structures of up to 8 modules with a total power handling capacity of 1MVA with no deterioration in performance. 2MVA systems are deliverable with the current technology without any changes, and higher power levels are expected to be easily achieved.
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Shokrollah-Timorabadi, Hamid. "Voltage source inverter for voltage and frequency control of a stand-alone self-excited induction generator." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/MQ34139.pdf.
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Norman, Rosemary Anne. "High-performance current regulation for voltage-source-inverter-fed induction motor drives." Thesis, University of Bradford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.514187.
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Han, Qiang. "Average-value modeling of brushless dc motors with 120-degree voltage source inverter." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31625.
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Average-value modeling is indispensable for large and small-signal analysis of electromechanical systems with power electronic drives. Analytical development of accurate average-value models for the brushless dc motor with 120-degree inverter systems is particularly challenging due to the complicated commutation-conduction patterns of the stator currents.
This thesis is comprised of several manuscripts that present the research results in this area. First manuscript compares the brushless dc motors with 180 and 120-degree inverters, and the average-value modeling of these systems. In 180-degree inverters, each phase is always connected to the dc source and the average voltages are readily known. In 120-degree inverters, each phase is open-circuited for a fraction of a revolution resulting in discontinuous phase current and different commutation-conduction patterns, which makes it challenging to obtain an accurate average-value model. The second manuscript extends a recently proposed parametric approach to numerical averaging of power electronic converters to construct an average-value model for a brushless dc motor with a 120-degree inverter system. In the proposed model, a proper qd model of the permanent magnet synchronous machine is used, and the inverter dynamics are represented by nonlinear algebraic functions that relate the averaged terminal voltages and currents of the inverter switching-cell. These parametric functions are obtained numerically using the detailed model. The third manuscript presents a different parametric approach to construct a new average-value model that possesses greater accuracy. This new model also uses proper qd model of the permanent magnet synchronous machine but is based on appropriately averaging the transformed stator voltages in both commutation and conduction subintervals. In this approach, the required commutation angle is represented as a nonlinear algebraic function, which is obtained from the detailed simulation.
The conducted case studies are based on two typical industrial motors with different electrical time constants, and include hardware measurements, detailed simulation, and comparison with the best-known-to-day published average-value model. The proposed models are shown to be more accurate in a large- and small-signal sense than the previous published model and applicable to motors with a large range of parameters including electrical time constant.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Samoylenko, Nikolay. "Analysis of voltage-source-inverter-driven brushless dc motors with unbalanced Hall sensors." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32450.
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Brushless dc motors with Hall sensors are widely used in various industrial and electromechanical applications. These machines have often been considered in the literature, under one common assumption - ideal placement of the sensors, which is often not the case, especially for low-precision motors. This thesis is composed of three manuscripts which investigate the unbalance of Hall sensors and propose methods to eliminate its adverse effects. The studies presented here show that misalignment of Hall sensors leads to unbalanced operation of the inverter and motor phases, which in turn results in increased low-frequency harmonics in torque ripple, possible acoustic noise, and degradation of the overall drive performance. Thus, the first manuscript introduces the problem of the misaligned Hall sensors by using a detailed model of a sample brushless dc motor and proposes a simple yet practical averaging technique to significantly decrease the effects of the misplaced sensors in steady state. The second manuscript extends the discussion to the dynamic performance of a low-precision brushless dc motor by introducing extrapolating filters which specifically target the transient operation. The third manuscript generalizes the concepts presented in the first two papers by taking into account both steady-state and transient performances and provides extensive hardware studies. The presented research considers a typical industrial brushless dc motor and includes measurements, detailed models and hardware experiments to validate the analysis. The proposed averaging approach is shown to achieve performance characteristics very close to those of a motor with perfectly balanced Hall sensors.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Andrews, Darin M. "Direct torque control of a three-phase voltage source inverter-fed induction machine." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/38872.
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Approved for public release; distribution is unlimited.The scope of this thesis involves various techniques to control the torque of a voltage source inverter-fed induction motor. The three methods investigated here are voltage by frequency, known as scalar control, field-oriented control with and without space vector modulation, and direct torque control. Although all three techniques have been proven effective, each technique possesses its own advantages and disadvantages. In todays engineering world, time and money are saved by utilizing software developed to accurately model a physical system and to compare with hardware previously implemented in a lab. Comparisons can be made to determine how each of these torque control methods perform under static and dynamic modes of operation. The United States military can benefit from this study by modifying or adding onto the software models developed here with little cost and use these models to do trade studies without the cost of lab demonstrations.
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Wang, Xiaodan. "The EMI Filter Design for GaN HEMT Based Two-Level Voltage Source Inverter." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu152424286628544.
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Li, He. "High Switching Frequency High Switching Speed Inverter Design." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524240971896427.
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Alamri, Basem Rashid. "Losses and cost optimisation of PV multilevel voltage source inverter with integrated passive power filters." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/14537.
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Nowadays, the need for more contributions from renewable energy sources is rapidly growing. This is forced by many factors including the requirements to meet the targeted reductions of greenhouse gas emissions as well as improving the security of energy supply. According to the International Renewable Energy Agency (IRENA) report 2016, the total installed capacity of solar energy was at least 227 GWs worldwide by the end of 2015 with an annual addition of about 50 GWs in 2015, making solar power the world’s fastest growing energy source. The majority of these are grid-connected photo voltaic (PV) solar power plants, which are required be integrated efficiently into the power grids to meet the requirements of power quality standards at the minimum total investment cost. For this, multilevel voltage source inverters (VSI) have been applied extensively in recent years. In practice, there is a trade-off between the inverter’s number of levels and the required size of output filter, which is a key optimisation area. The aim of this research is to propose a generic model to optimise the design number of levels for the Cascaded H-Bridge Multilevel Inverter (CHB-MLI) and the size of output filter for medium voltage – high power applications. The model is based on key measures, including inverter power loss minimisation, efficient control for minimum total harmonic distortion (THD), minimisation of total system cost and proposing the optimum size of output filter. This research has made a contribution to knowledge in the optimisation of CHB-MLI for medium-voltage high-power applications, in particular, the trade-off optimisation of the inverter’s number of levels and the size of the output filter. The main contribution is the establishment and demonstration of a sound methodology and model based on multi-objective optimisation for the considered key measures of the trade-off model. Furthermore, this study has developed a generic precise model for conduction and switching loss calculation in multilevel inverters. Moreover, it applied Genetic Algorithm (GA) optimisation to provide a complete optimum solution for the problem of selective harmonic elimination (SHE) and suggests the optimum size of output passive power filter (PPF) for different levels CHB-MLIs. The proposed trade-off optimisation model presents an efficient tool for finding the optimum number of the inverter’s levels and the size of output filter, in which the integration system is at its lowest cost, based on optimisation dimensions and applied system constraints. The trade-off optimisation model is generic and can be applied to any multilevel inverter topologies and different power applications.
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Kitson, Joanne. "Shunt regulation of a three-phase voltage bus by means of a bi-directional voltage-fed quasi Z-source inverter." Thesis, University of Bristol, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761205.
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Chai, Elaina T. "Design, implementation, and verification of a multipurpose, flexible, three-phase back-to-back voltage-source inverter." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91449.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.16
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 87-88).
In this thesis, I designed, implemented, and verified a multi-purpose,three-phase back-to- back voltage source inverter for grid connected applications. This inverter features extensive hardware protection, opto-isolation between the power stage and the controller, and reconfigurable I/O routing. The converter is designed for both research and teaching to enable rapid prototyping and verification of advanced control algorithms for grid-connected converters, motor drives etc. I also demonstrate the utility of the power electronics converter as a vector controlled PMSM motor drive. Finally, I use the inverter to perform frequency domain validation of a hardware-in-the-loop simulator. I then design and implement a virtual spectrum analyzer, whose implementation required the creation of a DFT algorithm in python based on the Goertzel algorithm.
by Elaina T. Chai.
M. Eng.
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Mamat-Ibrahim, Mohd Rosailan bin. "A wavelet-fuzzy based algorithm for condition monitoring and fault detection of a voltage source inverter." Thesis, Swansea University, 2003. https://cronfa.swan.ac.uk/Record/cronfa42668.
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The popularity of the variable-speed induction machine as a drive mechanism has increased rapidly. This has led to the voltage source inverter induction machine being used to drive numerous applications such as electric vehicles and trains. Unfortunately, the condition monitoring and fault detection of these types of drives is an area, which has been left largely untouched by the research community. This is due to the high harmonic contents of the machine supply making the rigorous mathematical analysis of the drive complex. Fortunately, the interesting development in signal processing theory, especially wavelet transform, has sparked a new interest in condition monitoring of voltage source inverter induction machine. The wavelet transform have two important features, which, are important for the condition monitoring and fault detection purpose; time localization ability and multi-resolution analysis. Furthermore, the wavelet can be combined with an artificial intelligent system to provide an acceptable system with high accuracy and reliability. The work herein presented is a contribution to voltage source inverter induction machine condition monitoring and fault detection using the combination of wavelet transform and fuzzy logic. The research was concentrated on some typical fault events of voltage source inverter that allow reduced operating conditions of the drive system without triggering the short circuit protection.
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John, Malte [Verfasser]. "Frequency-domain modeling of harmonic interactions in pulse-width modulated voltage-source inverter drives / Malte John." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1183907060/34.
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Bennett, Nicholas. "A vector controlled AC drive incorporating an ultrasonic voltage source inverter and a permanent magnet synchronous machine." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240472.
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Titiz, Furkan Kaan [Verfasser], Doncker Rik W. [Akademischer Betreuer] De, and Sibylle [Akademischer Betreuer] Dieckerhoff. "A three-phase low-voltage grid-connected current source inverter / Furkan Kaan Titiz ; Rik W. de Doncker, Sibylle Dieckerhoff." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1216040907/34.
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Titiz, Furkan Kaan Verfasser], Doncker Rik W. [Akademischer Betreuer] [De, and Sibylle [Akademischer Betreuer] Dieckerhoff. "A three-phase low-voltage grid-connected current source inverter / Furkan Kaan Titiz ; Rik W. de Doncker, Sibylle Dieckerhoff." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1216040907/34.
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Cornwell, William Lincoln. "Switching Frequency Effects on Traction Drive System Efficiency." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34983.
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Energy demands are steadily increasing as the world's population continues to grow. Automobiles are primary transportation means in a large portion of the world. The combination of fuel consumption by automobiles along with the shrinking fossil fuel reserves makes the development of new more energy efficient technologies crucial. Electric vehicle technologies have been studied and are still being studied today as a means of improving fuel efficiency. To that end, this work studies the effect of switching frequency on the efficiency of a hybrid electric vehicle traction drive, which contains both an internal combustion engine as well as electric motor. Therefore improving the efficiency of the electric motor and its drive will help improve the viability of alternative vehicle technologies. Automobiles spend the majority of their operational time in the lower speed, lower torque region. This work focuses on efficiency improvements in that region. To estimate the efficiency trend, the system is modeled and then tested both electrically and thermally. The efficiency is shown to increase at lower switching frequencies. The experimental results show that there are some exceptions, but the basic trend is the same.Master of Science
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Cetin, Nebi Onur. "Design And Implementation Of Advanced Pulse Width Modulation Techniques And Passive Filters For Voltage Source Inverter Driven Three-phase Ac Motors." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612236/index.pdf.
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Advanced pulse width modulation (PWM) techniques such as space vector PWM, active zero state PWM, discontinuous PWM, and near state PWM methods are used in three-phase AC motor drives for the purpose of obtaining low PWM current ripple, wide voltage linearity range, and reduced common mode voltage (CMV). In some applications, a filter is inserted between the inverter and the motor for the purpose of reducing the stresses in the motor. The motor current PWM ripple components, terminal voltage overshoots, shaft voltage, and bearing currents, etc. can all be reduced by means of PWM techniques and passive filters. Various PWM techniques and passive filter types exist. This thesis studies the combinations of PWM techniques and filters and evaluates the performance of the motor drive in terms of the discussed stresses in the motor. PWM techniques are reviewed, a generalized algorithm for the implementation of PWM techniques is developed, and implementation on a 4 kW rated drive is demonstrated. Filter types are studied, among them the common mode inductor and the pure sine filter (PSF) configurations are investigated in detail. Filters are designed and their laboratory performance is evaluated. In the final stage the advanced PWM techniques and filters are combined, the incompatibility problem of discontinuous PWM methods with the PSF is illustrated. A cure based on rate of change limiter is proposed and its feasibility proven in the laboratory experiments. With the use of the proposed PWM algorithm and PSF, a motor drive with ideal DC to AC conversion stage (DC to pure sine) is achieved and its performance is demonstrated in the laboratory.
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Muhsen, Hani [Verfasser], Josef [Akademischer Betreuer] Lutz, and Mario [Gutachter] Pacas. "Three-Phase Voltage Source Inverter with Very High Efficiency Based on SiC Devices / Hani Muhsen ; Gutachter: Mario Pacas ; Betreuer: Josef Lutz." Chemnitz : Universitätsbibliothek Chemnitz, 2016. http://d-nb.info/1213814960/34.
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Superczynski, Matthew J. "Analysis of the Power Conditioning System for a Superconducting Magnetic Energy Storage Unit." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34860.
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Superconducting Magnetic Energy Storage (SMES) has branched out from its application origins of load leveling, in the early 1970s, to include power quality for utility, industrial, commercial and military applications. It has also shown promise as a power supply for pulsed loads such as electric guns and electromagnetic aircraft launchers (EMAL) as well as for vital loads when power distribution systems are temporarily down. These new applications demand more efficient and compact high performance power electronics.
A 250 kW Power Conditioning System (PCS), consisting of a voltage source converter (VSC) and bi-directional two-quadrant DC/DC converter (chopper), was developed at the Center for Power Electronics Systems (CPES) under an ONR funded program. The project was to develop advanced power electronic techniques for SMES Naval applications. This thesis focuses on system analysis and development of a demonstration test plan to illustrate the SMES systems' ability to be multitasked for implementation on naval ships. The demonstration focuses on three applications; power quality, pulsed power and vital loads.
An integrated system controller, based on an Altera programmable logic device, was developed to coordinate charge/discharge transitions. The system controller integrated the chopper and VSC controller, configured applicable loads, and dictated sequencing of events during mode transitions.
Initial tests with a SMES coil resulted in problems during mode transitions. These problems caused uncontrollable transients and caused protection to trigger and processors to shut down. Accurate models of both the Chopper and VSC were developed and an analysis of these mode transition transients was conducted. Solutions were proposed, simulated and implemented in hardware. Successful operation of the system was achieved and verified with both a low temperature superconductor here at CPES and a high temperature superconductor at The Naval Research Lab.Master of Science
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Ekström, Rickard. "Offshore Marine Substation for Grid-Connection of Wave Power Farms : An Experimental Approach." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229191.
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Wave power is a renewable energy source with great potential, which is why there are more than a hundred ongoing wave power projects around the world. At the Division of Electricity, Uppsala University, a point-absorber type wave energy converter (WEC) has been proposed and developed. The WEC consists of a linear synchronous generator placed on the seabed, connected to a buoy floating on the surface. Power is absorbed by heave motion of the buoy, and converted into electric energy by the generator. The point-absorber WEC must be physically much smaller than the wavelength of the incoming waves, and can therefore not be scaled to very high power levels. Instead, the total power output is boosted by increasing the number of WECs, connecting them in wave power farms. To transfer the electric energy to the grid, an intermediate marine substation is proposed, where an AC/DC/AC conversion step is performed. Within this PhD-work, a full-scale offshore marine substation has been designed, constructed and experimentally evaluated. The substation is rated for grid-connection of seven WECs to the local 1kV-grid, and is placed on the seabed 3km off the coast at a depth of 25m. Various aspects of the substation design have been considered, including the mechanical and electrical systems, the WEC electrical interface, offshore operations and the automatic grid connection control system. A tap change circuit and different multilevel topologies have also been proposed. This dissertation has an experimental approach, validating a major part of the work with lab results. The final substation electrical circuit has been tested at rated grid voltage with a fluctuating input power source. The efficiency has been measured and the implemented functions are verified. Offshore operations have been successfully carried out and offshore wave farm data is expected in the nearby future.
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Haji, Miragha Amirhossein. "Generation Control in Small IsolatedPower Systems." Thesis, KTH, Elektroteknisk teori och konstruktion, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118921.
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This thesis is concerned with the generation control in small isolated power systems consisting of inverter interfaced generation systems. First the components of an individual distributed generation system (DGS) as well as the corresponding control schemes for active and reactive power flow are discussed and implemented. Then the contribution of multiple DGS to meet the requirement of the loads in both gridconnected and island operations are discussed. Having evaluated the performance of each developed model such as voltage source inverter, PQ and PV controlled as well as reference DGS, the impact of voltage degradation on power load control in isolated systems is analyzed. Finally a new method for generation control in a small power system based on power sharing between multiple DGS with voltage degradation consideration as the last alternative for sustaining the system is proposed and implemented.-11D
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Senturk, Osman Selcuk. "Series Active Filter Design, Control, And Implementation With A Novel Load Voltage Harmonic Extraction Method." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608819/index.pdf.
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Series Active Filters (SAF) are designed for harmonic isolation and load voltage regulation of single-phase and three-phase voltage harmonic source type nonlinear loads. The novel Absolute Value Method (AVM) for load voltage harmonic extraction is proposed and applied in the control algorithm of SAF. The SAF compensated systems are represented by simplified linear models such that SAF controller gains can be easily determined. Harmonic isolation and load voltage regulation performances of 2.5 kW single-phase and 10 kW three-phase SAF compensated systems are evaluated by detailed simulations. Laboratory prototype single-phase and three-phase SAFs and loads are designed and manufactured. Digital signal processor based control platform is employed. Exclusive laboratory tests are conducted. Via laboratory experiments and simulations it is shown that AVM yields superior harmonic isolation and load voltage regulation performance compared to the conventional low/high pass filtering method. Theory, simulations, and experiments are well correlated and illustrate the feasibility of the proposed method.
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Sahoo, Smrutirekha. "Impact Study: Photo-voltaic Distributed Generation on Power System." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-32369.
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The grid-connected photo-voltaic (PV) system is one of the most promising renewable energy solutions which offers many benefits to both the end user and the utility network and thus it has gained the popularity over the last few decades. However, due to the very nature of its invariability and weather dependencies, the large scale integration of this type of distributed generation has created challenges for the network operator while maintaining the quality of the power supply and also for reliable and safe operations of the grids. In this study, the behavioral impact of large scale PV system integration which are both steady and dynamic in nature was studied. An aggregate PV model suited to study the impacts was built using MATLAB/Simulink. The integration impacts of PV power to existing grids were studied with focus on the low voltage residential distribution grids of Mälarenergi Elnät AB (10/0.4 kV). The steady state impacts were related to voltage profile, network loss. It was found that the PV generation at the load end undisputedly improves the voltage profile of the grid especially for the load buses which are situated at farther end of the grid. Further, with regard to the overvoltage issue, which is generally a concern during the low load demand period it was concluded that, at a 50% PV penetration level, the voltage level for the load buses is within the limit of 103% as prescribed by the regulator excepting for few load buses. The voltage level for load buses which deviate from the regulatory requirement are located at distance of 1200 meter or further away from the substation. The dynamic impact studied were for voltage unbalancing in the grid, which was found to have greater impact at the load buses which is located farther compared to a bus located nearer to the substation. With respect to impact study related to introduction of harmonics to the grid due to PV system integration, it was found that amount of harmonic content which was measured as total harmonic distortion (THD) multiplies with integration of more number of PV system. For a 50 % penetration level of PV, the introduced harmonics into the representative network is very minimal. Also, it was observed from the simulation study that THD content are be less when the grid operates at low load condition with high solar irradiance compared to lower irradiance and high load condition.
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Winkler, Stefan, and Ralf Werner. "Verluste in synchronen Reluktanzmaschinen am Spannungszwischenkreis-Umrichter." TU Bergakademie Freiberg, 2019. https://tubaf.qucosa.de/id/qucosa%3A38458.
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In diesem Beitrag wird gezeigt, welche Auswirkung die Rotorform einer Reluktanzmaschine und die Ansteuerung mittels Umrichter auf den Verlusthaushalt der Maschine hat. Darüber hinaus werden die Möglichkeiten zur Verluststeuerung, welche sich durch den Betrieb von Reluktanzmaschinen ergeben, vorgestellt.This paper shows the effect of the rotor shape of a reluctance machine and the converter control on the losses of the machine. In addition, it will be shown which possibilities for loss control will result from the operation of reluctance machines.
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Celanovic, Ivan. "A Distributed Digital Control Architecture for Power Electronics Systems." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34998.
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This thesis proposes a novel approach to power electronics system design that is based on the open-architecture distributed digital controller and modular power electronics building blocks (PEBBs). The proposed distributed digital controller partitions the controller in three levels of control authority. The power stage controller, designated as hardware manager, is responsible for low-level hardware oriented tasks; the high level controller, designated as applications manager, performs higher-level application-oriented tasks; and the system level controller handles system control and monitoring functions.
Communications between the hardware-oriented controller and the higher-level controller are implemented with the previously proposed 125 Mbits/sec daisy-chained fiber optic communication protocol. Real-time control and status data are communicated by means of communication protocol. The distributed controller on the power converter level makes the system open, flexible and simple to use. Furthermore, this work gives an overview and comparison of current state-of-the-art communication protocols for real-time control applications with emphasis on industrial automation and motion control. All of the studied protocols have been considered as local area networks (LAN) for system-level control in power converter systems. The most promising solution has been chosen for the system level communication protocol.
This thesis also provides the details of design and implementation of the distributed controller. The design of both the hardware and software components are explained. A 100 kVA three-phase voltage source inverter (VSI) prototype was built and tested using the distributed controller approach to demonstrate the feasibility of the proposed concept.Master of Science
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Kruger, Gert Lodewikus. "Implementation and evaluation of V/f and vector control in high–speed PMSM drives / Kruger G.L." Thesis, North-West University, 2011. http://hdl.handle.net/10394/7609.
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The McTronX research group, at the Potchefstroom campus of the North–West University, has
been researching Active Magnetic Bearings (AMBs). A fully suspended, flywheel energy storage
system (FESS) has been developed. Due to excessive unbalance on the rotor, the motor drive
could not be tested up to its rated speed. In the interim, until the rotor can be balanced and
other rotor dynamic effects have been investigated, the group decided that the existing drive
control should be improved and tested on a high–speed permanent magnet synchronous motor
(PMSM), using normal roller element bearings.
In order to test the motor control a second (identical) PMSM, mechanically coupled to the
former, operates in generator mode which serves as the torque load. Two different control algorithms,
namely V/f and vector control, are designed and implemented on a rapid control
prototyping system, i.e. dSPACE®. The V/f control is an open–loop, position sensorless technique,
whilst the vector controller makes use of a position sensor.
From the design and implementation it became clear that the vector control is more robust,
in the sense that it is less sensitive on parameter variations and disturbances. It can start up
reliably even under full load conditions.
The V/f control is an attractive alternative to the vector control, especially in AMB systems,
where it may be difficult to mount the position sensor, has to operate in a hazardous environment
not suited to the sensor or could degrade the reliability of the AMB system. The cost of the
position sensor is not really a concern compared to the cost of an AMB system. The V/f control
is more suited to fan and pump applications, which has a low dynamic requirement. The V/f
control has high startup currents and is not recommended for applications requiring a high
starting torque or fast acceleration during operation.
The inverter, which drives the PMSM, also had to be developed. With regard to the motor
control, the effects of inverter non–idealities had to be accounted, especially for the V/f control.
The implemented control algorithms were tested up to 20 krpm. Discrepancies between the expected
and actual results are discussed. Overall, the controllers performed as desired. Generally,
the project goals have been reached satisfactorily.Thesis (M.Ing. (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.
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Wahid, Ferdus. "Analysis Of A Wave Power System With Passive And Active Rectification." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-425722.
Full textAbstract:
Wave energy converter (WEC) harnesses energy from the ocean to produce electrical power. The electrical power produced by the WEC is fluctuating and is not maximized as well, due to the varying ocean conditions. As a consequence, without any intermediate power conversion stage, the output power from the WEC can not be fed into the grid. To feed WEC output power into the grid, a two-stage power conversion topology is used, where the WEC output power is first converted into DCpower through rectification, and then a DC-AC converter (inverter) is used to supply AC power into the grid. The main motive of this research is to extract maximum electrical power from the WEC by active rectification and smoothing the power fluctuation of the wave energy converter through a hybrid energy storage system consisting of battery and flywheel. This research also illustrates active and reactive power injection to the grid according to load demand through a voltage source inverter.
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Buchta, Luděk. "Kompenzace nelinearit při řízení střídavých pohonů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-408028.
Full textAbstract:
Analysis of the dead-time effect and other nonlinearities of the voltage source inverter was carried out in the introduction of the doctoral thesis. Three compensation strategies for vector controlled PMSM were proposed based on the analysis. The voltage disturbance observer with cost function of current errors is based on the model of PMSM, known machine parameters and easily measurable quantities. The second observer which estimates the dq- axes currents and the value of the voltage error with one parameter only is designed based on the harmonic analysis and Kalman filter algorithm. The third method combines an adaptive approach with feedback and voltage disturbance observer that is based on the PMSM model. Furthermore, the two compensation methods for vector controlled induction motor were proposed. In the first case, the standard compensation strategy is extended by a harmonic compensator that suppresses the residual 6th harmonic component in dq- axes currents. The last strategy detects the polarity of the estimated phase currents that are obtained by the Kalman filter. All compensation strategies have been verified by MATLAB/Simulink simulations and by experiments on real drives.
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Dehghanikiadehi, Abbas. "Commande vectorielle innovante pour véhicules électriques ou hybrides." Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC012/document.
Full textAbstract:
Durant ces dernières années, l'intérêt pour les technologies des véhicules à faibles émissions de carbone a fait un bond important à travers l'Union européenne (UE) et au-delà, encouragé en cela par les gouvernements et les constructeurs automobiles. De grands espoirs ont été mis plus récemment dans les véhicules électriques (VE) et les véhicules électriques hybrides (VEH) en tant que technologies clés pour atténuer le changement climatique, améliorer la sécurité énergétique et favoriser une nouvelle branche de l'industrie dans le secteur automobile. Ainsi, l'électrification des transports a été considérée comme une stratégie clé pour réduire les émissions de CO2 dans le secteur des transports. Le principal défi est d’augmenter l’autonomie des véhicules (ce qui a toujours été au coeur de la concurrence des industries du transport), ainsi que la durée de vie des volumineuses et coûteuses batteries. Par conséquent, ceci indique que le rendement du convertisseur de puissance est un des points clés à développer pour les générations des véhicules électriques à venir. L’autre paramètre influant est la qualité de la tension et du courant (en particulier la suppression des harmoniques basses fréquences) qui permet de réduire la taille des filtres d'entrée et de sortie de ces convertisseurs. L'objectif de cette thèse est de parvenir à un meilleur rendement en proposant de nouvelles structures de convertisseur de puissance et des commandes vectorielles modifiées ; le choix de deux onduleurs alimentant un moteur ouvert aux deux extrémités. Après l'analyse étape par étape, modèle théorique, simulation et enfin une mise en oeuvre expérimentale, il a été constaté que les nouvelles méthodes proposées sont compétitives et peuvent s’appliquer aux cas des VEH et des VE afin d’apporter des caractéristiques supérieures en termes d’efficacité et de qualité de tension et de courantOver the last decade, the interest for low-carbon vehicle technologies has surged among both governments and automotive manufacturers across and beyond the European Union (EU). Great hopes have been put, first, on biofuel vehicles and more recently on electric vehicles (EVs) and hybrid electric vehicles (HEVs) as key technologies to mitigate climate change, enhance energy security and nurture new industry branches within the automotive sector. So electrification of vehicles has been seen as a key strategy to reduce CO2 emissions from the transport sector. The main challenge toward EVs and HEVs is to keep driving for longer distance (which has been always fields for competition among traction industries) as well as lifetime battery cells as storage system. As a result, these indicate importance of power converter efficiency as a key gate for next generations of these up-coming vehicles. The next parameter is the quality of output voltage/current (especially by suppressing low-order harmonics) to reduce the size of filtering. The aim of this thesis is to achieve better efficiency and output voltage/current Total Harmonic Distortion (THD) by proposing novel power converter and associated Pulse Width Modulation (PWM) methods while imposing modification on power converter topology. As a result, dual-inverter is proposed to supply open-end motor from both sides. To this aim, three PWM methods are suggested as: The first one, Modified Space Vector Modulation (MSVM) for dual-inverter supplied by single dc source, improves efficiency by 4-5% (while having lower switching losses), and reduces Common Mode Voltage (CMV) levels by 66%, as well. The voltage/current harmonics are analytically analyzed which shows mainly better performance. Effective switching frequency is also reduced by 66% due to the reduction of number of commutations. In the second one, Near State PWM (NSPWM) is adapted for dual-inverter supplied by single dc source in order to eliminate triplen harmonics (therefore Zero Sequence Voltage, ZSV) and improve efficiency (by 3-4%) compared to Space Vector Modulation (SVM). Additionally due to avoiding use of zero vectors, CMV is improved by 66%. While having 8 commutations instead of 12 in SVM, effective switching frequency is improved by 33%. And finally, the third proposed method deals with NSPWM for dual-inverter supplied by two isolated dc sources wherein efficiency and CMV levels show the same performance as previous one. However, in this method, voltage THD is highly reduced compared to SVM. Triplen harmonics of the output voltage are inherently suppressed by the structure. These 3 proposed methods are analytically studied and their performances are step by step simulated in Matlab/Simulink environment. Then the methods are implemented in dualinverter fed open-end motor in laboratory setup; and the results are compared with these of SVM. Finally, it is found that novel proposed methods are so competitive solutions to be applied in HEVs and EVs and bring superior efficiency and voltage/current harmonic features
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Gongora, Vicente de Lima. "Sistema de fornecimento de potência a partir de célula a combustível utilizando conversor estático com modulação delta modificada." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-13122018-134202/.
Full textAbstract:
Este trabalho, constitui-se em uma contribuição para o estudo das estratégias de mo-dulação direta baseadas em histerese e que funcionam em frequência fixa de comutação. Tem como objetivo principal propor a estratégia delta modificada, que diferencia-se na forma de ajuste da largura de banda de histerese, alterando-se seus limites e em como executa o comando de bloqueio das chaves de potência, para que a corrente de saída se mantenha em frequência fixa de operação e apresente rápida resposta dinâmica no sistema controlado. Para tanto, não necessita da utilização de derivadas, nem de uma corrente média de referência, tão pouco, se utiliza dos tempos de comutação. A estratégia proposta, comprova que é possível produzir os adequados pulsos de comando para o processamento da energia proveniente de célula combustível, através do conversor estático de potência, utilizando-se, principalmente, dos valores de ultrapassagem nos limites estabelecidos de histerese. Como objetivo secundário desta pesquisa, desenvolve-se um conversor CC/CC auxiliar para adaptar e estabilizar a energia proveniente da CAC, compondo-se um sistema útil que serve de base para fornecer energia, aos mais diversos tipos de cargas em CC. Além disso, apresenta-se uma revisão das estratégias de modulação em modo direto para o controle da corrente de saída no conversor estático, tendo como base a tensão nos terminais de um indutor. Contudo, outras estratégias são naturalmente citadas, no transcorrer deste trabalho, devido haver combinações entre as diferentes estratégias moduladoras e controladoras comentadas.This work, is a contribution to the study of direct modulation strategies based on hysteresis and that operate at fixed switching frequency. Its main objective is to propose the modified delta strategy, which differentiates from the others strategies in the form of adjustment of hysteresis bandwidth, changing its limits and in executing the locking command of the power keys, so that the output current is maintain at fixed frequency of operation and a rapid dynamic response in the controlled system. In order to do so, it does not require the use of derivatives or a reference average current and also the switching times are not used. This strategy shows that it is possible to produce the appropriate command pulses for the processing of fuel cell energy by the static power converter using mainly the exceedance limit values. As a secondary objective of this research, an auxiliary DC/DC converter is developed to adapt and stabilize the energy coming from the fuel cell, forming a useful system that serves as a base to supply power to the most diverse types of DC loads. In addition, we present a review of the direct-mode modulation strategies for the control of the output current in the static converter, updating data, and based on the voltage at the terminals of an inductor; how-ever, others strategies are naturally cited because there are combinations between the different modulating strategies and controllers commented on in the course of this work.
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Lee, Bong-ha. "Active power system compensator with fuzzy vector controller." Thesis, Queensland University of Technology, 2002. https://eprints.qut.edu.au/36152/1/36152_Lee_2002.pdf.
Full textAbstract:
Active power compensation of reactive power and harmonic distortion caused by non-linear loads can be achieved by using a current controlled, voltage-source
inverter based compensator. The compensation technique used injected waveform control along with vector control based on instantaneous power theory allows a general purpose inverter based compensator to perform full
compensation of var, power factor and harmonic distortion and other non-linear components. Dr. Keith Hoffman has developed an instantaneous control algorithm capable of
eliminating harmonics and calculating the in-phase fundamental load current needed to supply the real power at the same time. The application of his technique to a new 'Switch State Coarse Fuzzy Vector Controller' is discussed in detail as well as the operation of the experimental system. The author has also
developed a compensator system that exhibits accurate control by using the instantaneously determined reference current compared with the supply current directly rather than using compensator current control as in previous methods. In microprocessor control applications, the power semiconductor switching speeds of a compensator is limited by the microprocessor calculation times. It is
demonstrated that simplifying the control circuit using a vector controller and reducing logic calculation times using coarse fuzzy logic control can be an effective and simple technique utilising both microprocessor and analogue based calculations. Two types of controller where investigated with one being a microprocessor-based fuzzification and the other an analogue comparator-based
fuzzification, are demonstrated and compared with each other. Results from the undertaken experiments show practical relevance of the developed instantaneous reference current vector calculator and 'Switch State
Coarse Fuzzy Vector Controller'. Useful techniques that integrate fuzzy control theory with conventional and modem control algorithms and switching strategies
are discussed in detail.
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Bakkar, Mostafa. "Sag effects on protection system in distributed generation grids." Doctoral thesis, Universitat Politècnica de Catalunya, 2022. http://hdl.handle.net/10803/673721.
Full textAbstract:
Distributed Generators (DGs) are sensible to voltage sags, so the protection devices must trip fast to disconnect the faulted part of the grid. The DG disconnection will not be desirable in the near future with a large penetration, so it will be necessary to lay down new requirements that should be based on avoiding unnecessary disconnections. Therefore, to prevent unnecessary tripping when inverter-based DGs are connected to the Medium Voltage (MV) grid, reliable and effective protection strategies need to be developed, considering the limited short-circuit current contribution of DG.
The initial goal of this study is to employ different possible control strategies for a grid-connected inverter according to the Spanish grid code and to analyze the output voltage behavior during symmetrical and unsymmetrical voltage sags. The analytical development of the proposed strategies shows the impacts of the sag on currents, voltages, active and reactive powers.
Another goal of this research is to propose a protection strategy based on Artificial Intelligence for a radial or ring distribution system with high DG penetration. The protection strategy is based on three different algorithms to develop a more secure, redundant, and reliable protection system to ensure supply continuity during disturbances in ring and radial grids without compromising system stability. In order to classify, locate and distinguish between permanent or transient faults, new protection algorithms based on artificial intelligence are proposed in this research, allowing network availability improvement disconnecting only the faulted part of the system. This research introduces the innovative use of directional relay based on a communication system and Artificial Neural Network (ANN). The first algorithm, Centralize algorithm (CE), collects the data from all the PDs in the grid in the centralized controller. This algorithm detects the power flow direction and calculates the positive-sequence current of all the PDs in the grid. Significant benefits of this system are that it consolidates the entire systems security into a single device, which can facilitate system security control. However, the CE will not pinpoint the exact location of the fault if there is any loss of information due to poor communication. Therefore, the systems redundancy can be improved by cooperating with a second algorithm, the Zone algorithm (ZO). ZO algorithm is based on zone control using peer-to-peer connectivity in the same line. The faulty line in that zone may be identified by combining the two PDs data on the same line. The most relevant advantage of this algorithm is its flexibility to adapt to any grid modification or disturbance, even if they are just temporary, unlike the CE, which is fixed to the existing grid configuration. The third protection algorithm, Local algorithm (LO), has been proposed without depending on the communication between the PDs; then, the protection system can work properly in case of a total loss of communication. Each PD should be able to detect if the fault is located in the protected line or another line by using only the local information of the PD. According to the type of fault and based on local measurements at each PD of abc voltages and currents, different algorithms will be applied depending on the calculation of the sequence components. The main advantage of this algorithm is the separate decision of each PD, and avoiding communication problems.
In case of radial grids, both mechanical breakers and Solid State Relays (SSRs) are used to verify the protection strategies, and in the case of ring grids, mechanical breakers are used, due to the limitations in required voltage difference of SSR.
The proposed protection algorithms are compared with conventional protections (Overcurrent and Differential) protections to validate the contribution of the proposed algorithms, especially in reconfigurable smart grids.El objetivo inicial de este estudio es emplear diferentes estrategias de control posibles para un inversor conectado a la red segun el código de red español y analizar el comportamiento de la tensión de salida durante caídas de tensión simétricas y asimétricas. El desarrollo analítico de las estrategias propuestas muestra los impactos de los huecos de tensión en las corrientes, tensiones, potencias activas y reactivas. Otro objetivo de esta investigación es proponer una estrategia de protecclón basada en lnteligencia Artificial para una red del Sistema de Distribución, radial o en anillo, con elevada penetración de Generación Distribuida. La estrategia de protección se basa en tres algoritmos diferentes para desarrollar un sistema de protección más seguro, redundante, y fiable, que asegure la continuidad de suministro durante perturbaciones en redes radiales o en anillo sin comprometer la estabilidad del sistema. Para clasificar, localizar y distinguir entre faltas permanentes o transitorias, se proponen en este trabajo nuevos algoritmos de protección basados en inteligencia artificial, permitiendo la mejora de la disponibilidad de la red, al desconectar sólo la parte del sistema en falta. Esta investigación introduce la innovación del uso del rele direccional basado en un sistema de comunicación y Redes Neuronales Artificiales (ANN). El primer algoritmo, Algoritmo Central (CE), recibe los datos de todos los PDs de la red en un control central. Este algoritmo detecta la dirección de flujo de cargas y calcula la corriente de secuencia positiva de todos los PDs de la red. El entrenamiento de ANNs incluye variaciones en la corriente de cortocircuito y la dirección del flujo de potencia en cada PD. Los beneficios mas significativos de este sistema son que concentra la seguridad total del sistema en un único dispositivo, lo que puede facilitar el control de la seguridad del sistema. Sin embargo, el CE no determinara con precisión la localización exacta de la falta si hay alguna perdida de información debida a una pobre comunicación. Por lo tanto, la redundancia del sistema se puede mejorar cooperando con un segundo algoritmo, el algoritmo de Zona (ZO). El algoritmo ZO se basa en un control de zona usando la conectividad entre dispositivos de protección de una misma línea. La línea en falta en esa zona puede identificarse combinando los datos de los dos PDs de la misma línea.. La ventaja mas relevante de este algoritmo es su flexibilidad para adaptarse a cualquier modificación de la red o perturbación, incluso si sólo son temporales, a diferencia del CE, que se ha adaptado para la configuración de la red existente. El tercer algoritmo de protección, algoritmo Local (LO), ha sido propuesto sin dependencia de la comunicación entre PDs; por lo tanto, el sistema de protección puede operar correctamente en el caso de una pérdida total de comunicación. Cada PD debe poder detectar si la falta esta ubicada en la línea protegida o en otra línea, utilizando sóIo la información local del PD. Según el tipo de falta, y en base a medidas locales en cada PD, de tensiones y corrientes abc, se aplican diferentes algoritmos en función del cálculo de las componentes simétricas. La principal ventaja de este algoritmo es la actuación por separado de cada PD, evitando los problemas de comunicación. En el caso de las redes radiales, se utilizan tanto interruptores mecánicos como réles de estado sóIido (SSR) para verificar las estrategias de protección, y en el caso de las redes en anillo se utilizan interruptores mecánicos, debido a las limitaciones de tensión para su conexión. Los algoritmos de protección propuestos se comparan con protecciones convencionales (Sobrecorriente y Diferencial) para validar la contribución de los algoritmos propuestos, especialmente en redes inteligentes reconfigurables.
Enginyeria Elèctrica
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Santos, Junior Francisco Antonio Ferreira dos. "Modelagem, análise e experimentação de sistema fotovoltaico isolado baseado em plataforma de simulação com diagrama de blocos." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/8444.
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This paper presents a block diagram modeling of a grid-independent photovoltaic power generation system, including the steps of DC regulation, voltage inversion, and control system based on dynamic simulations in Simulink / Matlab® exclusively using the built-in blocks available in its library. A well-known technique in literature called MPPT (maximum power point tracking) was used for tracking the maximum power of the photovoltaic generation. However, the control that was used to maintain a constant output voltage of the Push-Pull is based on a method that is similar to the MPPT, which configures a novelty of this research. The integration of modeling the entire PV system with these control systems is carried out in Simulink for investigaton and production of simulation results. An experimental platform that includes an emulator of photovoltaic panels, a 1 kW Push-Pull converter, a three-phase inverter with three arms and a hydraulic load constituided by a motor-pump was built in the laboratory. The experimental results corroborate the methodology that was used.
Este trabalho apresenta uma modelagem em diagramação de blocos de um sistema de geração de energia fotovoltaico isolado, incluindo as etapas de regulação CC, inversão de tensão e sistema de controle com base em simulações dinâmicas no ambiente Simulink/Matlab® utilizando, exclusivamente, os blocos built-in disponíveis em sua biblioteca. Uma técnica bem conhecida na literatura foi utilizada para o rastreio da máxima potência da geração fotovoltaica. No entanto, o controle utilizado para manter a tensão de saída constante do Push-Pull é baseado num método similar ao do rastreio da máxima potência, o que configura uma novidade deste trabalho. A integração da modelagem de todo o sistema fotovoltaico com estes sistemas de controle é realizada no ambiente Simulink para averiguação e produção dos resultados de simulação. Uma plataforma experimental que inclui um emulador de painéis fotovoltaicos, um Push-Pull de 1 kW de potência, um inversor trifásico de três braços e uma carga hidráulica constituída por um motobomba foi construída em laboratório. Os resultados experimentais corroboram a metodologia utilizada.