O presente trabalho realiza o estudo e implementação de um filtro ativo de potência paralelo (FAPP) aplicado em sistemas trifásicos a quatro fios utilizando a topologia de um inversor de tensão four-legs, visando a redução do conteúdo harmônico gerado por cargas não lineares e a compensação de reativos. A geração das correntes de referência de compensação é obtida através da estratégia de compensação baseada no sistema de eixos de referência síncrona (SRF) a qual utiliza conceitos de controle vetorial. O sincronismo do sistema SRF é realizado através de um circuito q-PLL (q-Phase Locked Loop) o qual é baseado no conceito da teoria da potência instantânea imaginária (teoria pq). A análise matemática da topologia four-legs é desenvolvida a fim de se obter um modelo linear em espaço de estados que represente o sistema físico para os sistemas de coordenadas abc, αβ0 e dq0. O método de controle proposto é implementado em eixos dq0, através de três controladores do tipo PI (Proporcional-Integral), os quais são projetados utilizando os conceitos de margem de estabilidade. Um estudo detalhado da modulação Space Vector aplicada a sistemas trifásicos four-legs é apresentado. Resultados de simulações são apresentados para validar o modelo do filtro proposto bem como a técnica de controle aplicada. Por fim, os resultados experimentais obtidos são avaliados considerando a a recomendação IEEE 519-1992 para mostrar a capacidade do FAPP na supressão de correntes harmônicas e compensação de potência reativa. / This work deals with the study and analysis of a parallel active power filter (APF) applied to three-phase four-wire systems using a four-leg inverter, aiming the suppresion of the harmonic content of non-linear loads and reactive power compensation. The generation of the compensation current references is obtained by means of the strategy based on the synchronous reference frame (SRF) system, which utilizes the concepts of vector control. The timing of the SRF system is performed through a q-PLL (q-Phase Locked Loop) circuit that is based on the imaginary instantaneous power theory. Mathematical analysis is developed in order to obtain a linear model in state space that represents the physical system in the coordinate systems abc, αβ0 and dq0. The proposed control method is implemented in dq0 axes through three Proportional-Integral (PI) controllers, which are designed using the concepts of stability margin. A detailed study of Space Vector modulation applied to three-phase four-leg inverter is presented. Simulation results are presented to validate the model of the APF and the control technique adopted. Finally, experimental results are obtained and evaluated considering the recommendation IEEE 519-1992 to show the capability of the parallel APF of current harmonic suppression and reactive power comensation.

Thesis (MTech (Electrical, Electronic and Computer Engineering))--Cape Peninsula University of Technology, 2015. / The growing interest in the use of solar energy to mitigate climate change, reduction in the cost of PV system and other favourable factors have increased the penetration of the PV(Photovoltaic) systems in the market and increase in the worldwide energy supply. The main component in a DG is a smart inverter connected in a grid-tied mode which serves as a direct interface between the grid and the RES (Renewable Energy System). This research work presents a three phase grid-tied inverter with active and reactive power control capabilities for renewable energy sources (RES) and distributed generators (DG). The type of the inverter to be designed is a Voltage Source Inverter (VSI). The VSI is capable of supplying energy to the utility grid with a well regulated DC link at its input. The solution this project proposes is an implementation of the designed filter to effectively reduce the harmonics injected into the grid to an acceptable value according to standards and also an approach to control the real and reactive power output of the inverters to help solve the problems of instability and power quality of the distribution system. The design, modelling and simulation of the smart inverter system is performed in MATLAB/SIMULINK software environment. A 10 kW three-phase voltage source inverter system connected to the utility grid was considered for this research. Series of simulations for the grid-connected inverter (GCI) model was carried out using different step changes in active and reactive power references which was used to obtain the tracking response of the set power references. The effectiveness of the control system which was designed to track the set references and supply improved power quality with reduced current ripples has been verified from the simulation results obtained.

Este trabalho apresenta um estudo comparativo, o projeto e a implementação de técnicas de controle lineares e não-lineares aplicadas em conversores estáticos de energia elétrica. O principal objetivo deste estudo é controlar, tanto a tensão de saída como o equilíbrio das tensões dos capacitores do barramento CC (Corrente Contínua) de um inversor NPC (Neutral Point Campled) três níveis monofásico. As técnicas de controle utilizadas são o PID (Proporcional-Integral-Derivativo), o ANLPID-GGF (Adaptive Non Linear PID – Gaussian Like Gain Functions), o LQR (Linear Quadratic Regulator) e o SDRE (State Dependent Riccati Equation). O ANLPID-GGF é uma proposta de otimização do controlador PID convencional utilizando funções de ganhos variáveis. Todos os controladores são projetados para manter os mesmos pólos dominantes (autovalores) do sistema em malha fechada de acordo com o modelo do conversor. Desta forma é possível realizar uma comparação mais coerente entre as quatro técnicas de controles estudadas. Com a determinação dos pólos dominantes do sistema é realizado o projeto dos controladores LQR e SDRE por alocação de pólos. Com o projeto por alocação de pólos pode-se evitar os sobre sinais comuns nas aplicações que utilizam controladores LQR e SDRE. Através da análise comparativa entre os quatro controladores, pode-se identificar as características distintas de cada método. Desta forma, também é proposta uma implementação paralela de controladores onde é feita uma associação ponderada entre as leis de controle, dando origem a uma estratégia de controle adaptativo ponderado que melhora o desempenho do sistema, tanto em tempo de resposta quanto na redução dos overshoots. As quatro técnicas de controle utilizadas e a estratégia proposta do controle adaptativo são implementadas em FPGA (Field Programmable Gate Array), utilizando a ferramenta DSP Builder para desenvolvimento e compilação do código HDL (Linguagem de Descrição de Hardware). Resultados de simulações e experimentais são apresentados com o objetivo de validar o desenvolvimento teórico proposto. / This work presents a comparative study, design and implementation of linear and nonlinear control techniques applied on power electronics converters. The main objective of this study is to control the output voltage and the voltage balance between the DC bus voltage capacitors balance of a three level NPC inverter. The control techniques used are the classic PID, the ANLPID-GGF, LQR and SDRE. The Non-Linear PID – Gaussian Gain Functions is considered a new nonlinear control technique used for optimization of the classic linear PID control. Taken the converter transfer function, the designs of the four controllers are set so the operating point of the closed loop system presents the same natural frequency. Thus, the comparative analysis of the performance of each control can be performed more precisely. The pole placement technique is used to design the LQR and SDRE controllers. By means of a comparative analysis of the controllers, it a parallel combination of the designed controllers is also proposed, yielding a weighted adaptive control system. The weighted adaptive controller improves the system performance, both in response time and in controlled magnitudes overshoots reduction. The four control techniques and the strategy an adaptive control proposed are implemented on FPGA, using the DSP Builder tool for the development and compilation the VHDL code. Simulation results are presented in order to validate the proposed theoretical development.

Este trabalho apresenta um estudo comparativo, o projeto e a implementação de técnicas de controle lineares e não-lineares aplicadas em conversores estáticos de energia elétrica. O principal objetivo deste estudo é controlar, tanto a tensão de saída como o equilíbrio das tensões dos capacitores do barramento CC (Corrente Contínua) de um inversor NPC (Neutral Point Campled) três níveis monofásico. As técnicas de controle utilizadas são o PID (Proporcional-Integral-Derivativo), o ANLPID-GGF (Adaptive Non Linear PID – Gaussian Like Gain Functions), o LQR (Linear Quadratic Regulator) e o SDRE (State Dependent Riccati Equation). O ANLPID-GGF é uma proposta de otimização do controlador PID convencional utilizando funções de ganhos variáveis. Todos os controladores são projetados para manter os mesmos pólos dominantes (autovalores) do sistema em malha fechada de acordo com o modelo do conversor. Desta forma é possível realizar uma comparação mais coerente entre as quatro técnicas de controles estudadas. Com a determinação dos pólos dominantes do sistema é realizado o projeto dos controladores LQR e SDRE por alocação de pólos. Com o projeto por alocação de pólos pode-se evitar os sobre sinais comuns nas aplicações que utilizam controladores LQR e SDRE. Através da análise comparativa entre os quatro controladores, pode-se identificar as características distintas de cada método. Desta forma, também é proposta uma implementação paralela de controladores onde é feita uma associação ponderada entre as leis de controle, dando origem a uma estratégia de controle adaptativo ponderado que melhora o desempenho do sistema, tanto em tempo de resposta quanto na redução dos overshoots. As quatro técnicas de controle utilizadas e a estratégia proposta do controle adaptativo são implementadas em FPGA (Field Programmable Gate Array), utilizando a ferramenta DSP Builder para desenvolvimento e compilação do código HDL (Linguagem de Descrição de Hardware). Resultados de simulações e experimentais são apresentados com o objetivo de validar o desenvolvimento teórico proposto. / This work presents a comparative study, design and implementation of linear and nonlinear control techniques applied on power electronics converters. The main objective of this study is to control the output voltage and the voltage balance between the DC bus voltage capacitors balance of a three level NPC inverter. The control techniques used are the classic PID, the ANLPID-GGF, LQR and SDRE. The Non-Linear PID – Gaussian Gain Functions is considered a new nonlinear control technique used for optimization of the classic linear PID control. Taken the converter transfer function, the designs of the four controllers are set so the operating point of the closed loop system presents the same natural frequency. Thus, the comparative analysis of the performance of each control can be performed more precisely. The pole placement technique is used to design the LQR and SDRE controllers. By means of a comparative analysis of the controllers, it a parallel combination of the designed controllers is also proposed, yielding a weighted adaptive control system. The weighted adaptive controller improves the system performance, both in response time and in controlled magnitudes overshoots reduction. The four control techniques and the strategy an adaptive control proposed are implemented on FPGA, using the DSP Builder tool for the development and compilation the VHDL code. Simulation results are presented in order to validate the proposed theoretical development.

Esta dissertação de mestrado propõe desenvolver a modulação vetorial (space vector – SV) para um inversor trifásico multinível híbrido assimétrico de nove níveis por fase com ponte-H em cascata (cascaded H-bridge – CHB). A verificação do desempenho ocorre através de simulações em software de simulação matemática, e posterior comparações entre duas simulações realizadas, como também a comparação da simulação de melhor desempenho com simulações obtidas com a modulação por síntese de formas de onda quase-quadradas e a modulação híbrida. Para tanto, inicialmente são revisadas as topologias de inversores de frequência mais tradicionais na literatura, identificando as suas características para justificar a escolha da topologia híbrida assimétrica. Posteriomente são revisados os métodos de modulação para inversores de frequência, identificando na modulação vetorial vantagens para sintetização das tensões de linha. Após, são relacioanados trabalhos envolvendo a modulação space vector aplicada em inversores multiníveis. Em seguida, a modulação SV é desenvolvida para o inversor trifásico multinível híbrido assimétrico de nove níveis por fase com ponte-H em cascata, sendo realizadas as seguintes etapas: definição dos possíveis vetores de comutação (estados de chaveamento) do inversor proposto no espaço tridimensional e no plano α-β; identificação dos planos limites e dos planos de separação dos setores no plano α-β; obtenção das matrizes de decomposição e; definição da sequência de comutação. Os resultados, obtidos por meio de software de simulação matemática, dos gráficos das tensões de fase e tensões de linha, assim como os valores de distorção harmônica total (total harmonic distortion – THD), fator de distorção de primeira ordem (first order distortion factor – DF1), tensão de modo comum, espectro harmônico dos sinais das tensões (de fase e de linha) são analisados, sendo os índices de THD, DF1 e tensão de modo comum comparados entre duas sequências de comutação diferentes para o inversor proposto. Também, os valores desses índices são comparados com outras técnicas de modulação (modulação por síntese de formas de onda quase-quadradas (QQ) e a modulação híbrida). O desenvolvimento e os resultados das simulações da modulação SV na topologia híbrida assimétrica de nove níveis proposta, assim como as análises das comparações, apontam resultados satisfatórios, identificando um potencial grandioso da modulação SV desenvolvida. / This dissertation proposes to develop the space vector (SV) modulation for a three phase hybrid asymmetric multilevel inverter of nine levels per phase with cascaded H-bridge (CHB). Performance verification occurs through software simulations, and subsequent comparisons between two simulations performed, as well as the comparison of the best performance simulation with simulations obtained with the step wave modulation and hybrid modulation. To do this, the topologies of more traditional frequency inverters are reviewed in the literature, identifying their characteristics to justify the choice of hybrid asymmetric topology. Subsequently, the modulation methods for frequency inverters are reviewed, identifying the advantages of vector modulation for the synthesis of line voltages. Afterwards, works involving the space vector modulation applied in multilevel inverters are related. Then, the SV modulation is developed for a three phase hybrid asymmetric multilevel inverter of nine levels per phase with cascaded H-bridge (CHB). The following steps are performed: definition of the possible switching vectors (switching states) of the proposed inverter in three-dimensional space and in the plane α-β; identification of boundary planes and separation plans of sectors in the α-β plane; obtaining the decomposition matrices e; definition of the switching sequence. The results, obtained through mathematical simulation software, of the phase voltages and line voltages graphs, as well as the values of total harmonic distortion (THD), first order distortion factor (DF1), common mode voltage, harmonic spectrum of the voltage signals (phase and line) are analyzed, with THD, DF1 and common mode voltage indices being compared between two different switching sequences for the proposed inverter. In addition, the values of these indices are compared with other modulation techniques (step wave modulation and hybrid modulation). The development and results of the SV modulation simulations in the nine-level hybrid asymmetric topology proposed, as well as the comparative analyzes, indicate satisfactory results, identifying a great potential for SV modulation developed.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis deals with three phase inverters and the different control strategies that can be associated with an inverter being used together. The first part of this thesis discusses the present research in the fields of PV panels, motor drive systems and three phase inverters along with their control. This control includes various strategies like MPPT, Volts-Hertz and modulation index compensation. Incorporating these techniques together is the goal of this thesis. A new topology for operating an open end motor drive system has also been discusses, where a boost converter and a flyback converter have been used in cascade to run a three phase motor. The main advantage of this is increasing the number of levels and improving the quality of the output voltage, not to mention a few other benefits of having the proposed circuit. A new algorithm has also been designed for starting and stopping the motor, which controls the current drawn from the power source during starting.

The design of a high-frequency transformer at levels above 1 kVA is limited by the winding and core materials which are available. This res~arch presents methods for the design and modeling of a 10 kVA transformer operating at a frequency of 20 kHz using readily available materials. A special winding technique is employed to increase both energy density and transformation efficiency by reducing leakage inductance and eddy current losses in the windings. The procedures for calculating the equivalent circuit parameters applicable to this design are outlined, and the calculated values compared with the measured quantities. A thermal analysis of the design is also explored using the equivalent circuit model as a basis for the calculation. Some of the calculations are specific to this particular design, whereas others are quite generic, however the overall concepts employed in the design and analysis of this device have widespread application within the area of high-frequency, high-power transformer design. / Master of Science

No description available.

It is customary to obtain ac power from batteries through a power converter, where mains ac power is not readily available. Such a power converter is also needed in several mobile/ airborne/ space applications. Till recently this application is served by a H bridge inverter followed by a low frequency transformer and a passive low pass filter. The H bridge inverter employs high frequency pulse width modulation. The transformer is made of standard silicon steel. The filter is made of L and C elements. In such a converter the magnetics account for about 30% of cost and 50% of weight. Moreover the dc input current in such converters is discontinuous, leading to poor efficiency. There is need for an input filter as well. This thesis presents the development of an inverter with high frequency (hf) link. The power converter employs a boost front end resulting in continuous input current. The H bridge inverter employs phase modulation technique with soft switching features. The boost converter and the H bridge share power devices. The isolation transformer handles high frequency ac power and is compact. It is shown that the transformer size can be reduced by more than one order of magnitude. There is a rear end cycloconverter to reconvert the high frequency ac power into 50 Hz output power. Innovative pulse sequencing in the cycloconverter ensures loss-less switching. The pulse width modulation shifts the dominant harmonic frequency to double the switching frequency. The output LC filter is light. The converter can handle bidirectional power. The controller is digital. The overall concept was demonstrated through the 500 W prototype design. The proposed topology offers small size, low losses and continous input current. The controller is digital and offers totally software based compensation and settings. It is expected that on account of the small size and cost, this topology is likely to become more popular in the near future. The applications of such power converters will bring down the size and cost of UPS, solar inverters, wind mill inverters etc.

This research addresses some of the difficulties faced when operating voltage controlled inverters with synchronous generators in microgrids. First, an overview of microgrid value propositions is provided, and the problems faced when attempting to use microgrids to provide improved power quality are discussed. Design considerations for different types of microgrids are provided to enable microgrids to deliver the desired functionality without adding unnecessary cost. The main body of this research investigates the poor transient load sharing encountered between voltage controlled inverters and synchronous generators in islanded operation. Poor transient load sharing results in high peak inverter rating requirements and high cost. The tradeoff between power quality and power sharing is highlighted, and methods to improve transient load sharing are proposed. The use of current limiting to protect inverters during faults and overloads is also investigated. Stability problems are identified when using simple inverter current limiting methods when operating in parallel with synchronous generators. Virtual impedance current limiting is proposed to improve transient stability during current limiting. The methods proposed in this thesis for mitigating inverter overloads and faults will allow for more reliable and cost effective application of inverter based distributed energy resources with synchronous generators in microgrids.