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

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Este trabalho tem como principal objetivo apresentar uma investigação e uma metodologia de projeto, até o presente momento inédita, de uma topologia de um conversor ca-cc trifásico de comutação forçada. Através da análise desenvolvida neste trabalho, determina-se um modelo matemático do conversor ca-cc para os quatro modos que determinam o processo da comutação nesse circuito. Esse modelo resulta em sistemas de equações fundamentais na forma de equações diferenciais, que são resolvidos com a finalidade de determinar o comportamento do circuito do conversor durante o processo de comutação e de obter uma metodologia de projeto. Com o objetivo de validar a investigação e o método de projeto foi implementada simulação computacional, no programa Simmon, dos intervalos de comutação do conversor ca-cc de comutação forçada. Essa estrutura, que durante a sua operação emprega tanto a comutação forçada como a natural, quando comparada com os conversores de comutação natural apresenta várias vantagens, como um alto fator de potência e a eliminação dos harmônicos de baixa ordem na linha ca (utilização da comutação forçada com a técnica de modulação por largura de pulso PWM), como mostra vátios trabalhos publicados, que estão desctitos na parte de referências bibliográficas deste texto. / The main objective of this work is to present an investigation and a design method, which up to now is not available in the literature, of a three-phase force commutated ac-dc convetier. From the analysis developed in this work one obtains the mathematical model of the ac-dc converter for its four modes of commutation, which determine the commutation process in the converter circuit. The fundamental equations, which have been written in the form of differential equations, are solved to determine the behaviour of the converter circuit during commutation, and also to obtain a design method. To validate the analysis and the design procedure, computer simulation of the commutation intervals of the ac-dc converter was implemented using the program Simnon. The three-phase ac-dc converter, which uses both forced and line commutation, when compared with the conventional line commutated converter, presents several advantages as a high power factor and the elimination of lower harmonics of the ac line (utilization of the forced commutation and the pulse width modulation strategy), as it is shown in several published works, which can be found in the references of this work.

This thesis mainly presents the design and implementation of a flyback converter with single-stage power factor correction. In the beginning, we propose different power factor collection (PFC) techniques referring to the inductor current of converter under three kinds of operation modes. In the continuous mode, we adopt the nonlinear-carrier control (NLC). Then, in the discontinuous mode and boundary mode, voltage-follower control (VFC) and transition mode technique control (TM) are adopted respectively. As to the converter analysis, we derive and verify the results of a small-signal model and perform equivalent circuit analysis by state-space averaging method, loss-free resistor (LFR) model, averaging method for two-time-scale system (AM), and current injected equivalent circuit approach (CIECA). Results derived from the above-mentioned models are compared and verified to be accurate of the system model. Furthermore, the control function and element design are implemented by simulation. We perform a PI controller to achieve better power factor based on results of analysis of the time and frequency domains analysis. Finally, three sets of different hardware are fabricated and verified depending on measured result and theoretical simulation.

The traditional AC/DC rectifier usually results in low power factor and serious harmonic distortion and it will bring about the serious pollution to power system. This thesis proposes boost power factor correction technique to solve these problems. First, we aim at power factor correction circuit which need input voltage sensing, to study its operating principle and design consideration, then design applicable voltage compensator by the frequency analysis and perform the simulation and implementation using the developed criterion. In order to prevent the shortcoming that power factor correction circuits with input voltage sensing and complexity is raised for a multiplier must be added to controller, we develop the power factor correction circuit without input voltage sensing. We perform the operating principle and control function by simulation, develop hardware scheme by analog components and place load variation to measure power factor and total harmonic distortion. According to experimental results and simulation, we confirm the new power factor correction circuit. When the full load is placed, the power factor can achieve 0.99 and the total harmonic distortion is lower than 8%.

A single-phase, buck-boost based, dual-output AC-DC converter is studied in this thesis. The converter has two DC outputs with opposite polarities, which share the same ground with the input power line. The power stage performance, including the input filter, is studied and procedure to select power components is given. The circuit model is analyzed to develop appropriate control. Zerocrossing distortion of the source input current is addressed and a solution is proposed. Experimental results are satisfactory in that a high power factor line current results for steady-state operation.

This thesis comprises modeling and simulation of an AC-DC converter (Battery charger). An AC-DC converter may cause a high frequency distortion in the electrical power network or augment the existing distortion caused by other devices connected to the network. The goal is to design a controller for suppressing this noise at a reasonable level. We hope the thesis can be considered as a step forward to solve the original problem. One needs an accurate model of the AC-DC converter, to design such a controller. This study tries to clarify the effects of theline inductance on the performance of the converter by modeling and simulating the converter during the commutation time. The idea is to model and simulate the converter for two different conditions; first in the Normal condition by neglecting the effect of line impedance, second in the Commutation condition by considering the effect of the line impedance on commutation of the diodes. One can perform a complete simulation of the converter with combining these two models. The thesis deals with AC-DC converters, Hamiltonian-port modeling, simulation and MATLAB programming using the functionality of the S-function and SIMULINK.

Les Alimentations Sans Interruption (ASI) ont pour rôle de protéger les charges sensibles. Leur utilisation nécessite l’usage de convertisseur de puissance AC/DC triphasé abaisseur et/ou élévateur de tension. Les ASI utilisent généralement une chaîne de conversion DC/DC+DC/AC ayant un rendement aux alentours de et sont souvent employées de façon continue. L’objectif de cette thèse est donc d’étudier un convertisseur DC/AC triphasé réversible en puissance susceptible de fonctionner en abaisseur et en élévateur de tension pour atteindre un rendement souhaité de 98% avec un minimum de 97,5%. L’étude s’oriente vers des architectures de convertisseurs peu conventionnelles, l’utilisation de semi-conducteurs grand gap (SiC) et de composants passifs à faible pertes. Une méthode de comparaison rapide qui est à la fois analytique et numérique est présentée pour dimensionner ces architectures en se basant sur les caractéristiques fournies par les constructeurs. La solution ‘Gradateur Onduleur Différentiel’ a été jugée comme la plus adaptée à nos besoins. Les choix techniques pour ce convertisseur sont détaillés, puis une étude de faisabilité présentée. Le convertisseur retenu est non linéaire et sa commande utilise des principes de fonctionnement atypiques, différentes stratégies de régulation sont donc présentées. Des tests sont effectués pour valider la commande mise en place et réaliser les essais fonctionnels et mesures de rendement. Enfin les résultats sont comparés aux prévisions et la solution proposée est finalement globalement comparée à la chaîne de conversion AC/DC+DC/DC classique. / Uninterruptible Power Supply (UPS) aim at quasi-instantaneous protection of critical loads. A DC to 3-phase AC stepup/stepdown converter is needed. For UPS, energy transfer using battery generally uses a 2-stage DC/DC+DC/AC conversion with an efficiency close to 96%. UPS are generally running permanently. The goal of this PhD is to optimize this conversion chain to aim at a target efficiency of 98% with a minimum requirement of 97%. To achieve this, our study will start with a survey of reversible architectures with both stepup and stepdown capability. Using wide bandgap semi-conductors and low-loss passive components are also part of this study. The power converter topologies are compared with a quick dimensioning method wich use both analytic analyse and simulation to realised an element selection based on characteristic given by the constructors. Eligible power converters are evaluated and compared and the “AC chopper+Inverter” architecture is found to best match our requirements. Then the technical choices of the power converter are detailed and a feasibility study is presented for the worst-case scenario. The selected power converter topology is non-linear and its control includes specific states, different strategies for the network and DC line electric parameter regulation are presented. To allow the verification of the proposed regulation, functional tests and efficiency measurement at different points are realised on the prototype. As a conclusion, the results gathered with the prototype are compared to those of a more conventional AC/DC+DC/DC power chain.

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