Modern switch-mode power supplies (SMPS) used for point-of-load (PoL) applications need to meet increasingly stringent requirements on voltage regulation, while minimizing physical volume and optimizing conversion efficiency. The focus of this thesis is the voltage regulation capability of low-power PoL converters during load transients. The main objective is to investigate converter topologies and control techniques that can achieve fast and smooth transient performance without significant penalty in volume and efficiency. The digital control method is used due to its ability to implement sophisticated control algorithms. The first part of this thesis investigates a dual output stages converter, with a small auxiliary output stage connected in parallel with the main output stage. While the main output stage is responsible for steady-state operation and designed to achieve optimum efficiency, the auxiliary stage is activated when a load transient occurs, to help suppress voltage deviation. Experimental results on a 6 V-to-1 V, 3W buck converter shows 35% improvement in peak transient voltage deviation while maintaining the same efficiency profile, compared to an equivalent buck converter. The second part of this thesis introduces a flyback-transformer based buck (FTBB) converter. In this topology, the conventional buck inductor is replaced with the primary winding of the flyback transformer, an extra switch, and a set of small auxiliary switches on the secondary side. During heavy-to-light load transients the inductor current is steered away from the output capacitor to the input port, achieving both energy recycling and savings due to reduced voltage overshoots. The light-to-heavy transient response is improved by reducing the equivalent inductance of the primary transformer winding to its leakage value. Compared to an equivalent buck converter, experiment results on a 6 V-to-1 V, 3 W prototype show three times smaller maximum output voltage deviation during load transients and, for frequently changing loads, about 7% decrease in power losses.

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.

abstract: The development of a Solid State Transformer (SST) that incorporates a DC-DC multiport converter to integrate both photovoltaic (PV) power generation and battery energy storage is presented in this dissertation. The DC-DC stage is based on a quad-active-bridge (QAB) converter which not only provides isolation for the load, but also for the PV and storage. The AC-DC stage is implemented with a pulse-width-modulated (PWM) single phase rectifier. A unified gyrator-based average model is developed for a general multi-active-bridge (MAB) converter controlled through phase-shift modulation (PSM). Expressions to determine the power rating of the MAB ports are also derived. The developed gyrator-based average model is applied to the QAB converter for faster simulations of the proposed SST during the control design process as well for deriving the state-space representation of the plant. Both linear quadratic regulator (LQR) and single-input-single-output (SISO) types of controllers are designed for the DC-DC stage. A novel technique that complements the SISO controller by taking into account the cross-coupling characteristics of the QAB converter is also presented herein. Cascaded SISO controllers are designed for the AC-DC stage. The QAB demanded power is calculated at the QAB controls and then fed into the rectifier controls in order to minimize the effect of the interaction between the two SST stages. The dynamic performance of the designed control loops based on the proposed control strategies are verified through extensive simulation of the SST average and switching models. The experimental results presented herein show that the transient responses for each control strategy match those from the simulations results thus validating them. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

Recently, photovoltaic (PV) generation is becoming increasingly popular in industrial applications. As a renewable and alternative source of energy they feature superior characteristics such as being clean and silent along with less maintenance problems compared to other sources of the energy. In PV generation, employing a Maximum Power Point Tracking (MPPT) method is essential to obtain the maximum available solar energy. Among several proposed MPPT techniques, the Perturbation and Observation (P&O) and Model Predictive Control (MPC) methods are adopted in this work. The components of the MPPT control system which are P&O and MPC algorithms, PV module and high gain DC-DC boost converter are simulated in MATLAB Simulink. They are evaluated theoretically under rapidly and slowly changing of solar irradiation and temperature and their performance is shown by the simulation results, finally a comprehensive comparison is presented.

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.

Este trabalho apresenta um conversor CC - CC baseado em Capacitores Chaveados de 6 fases e tempos intercalados com o objetivo de coletar energia fotovoltaica projetado em tecnologia CMOS de 130 nm para ser usado em aplicações em Internet das Coisas e Nós Sensores. Ele rastreia o máximo ponto de entrega de energia de um painel fotovoltaico policristalino de 3 cm x 3 cm através de modulação da frequência de chaveamento com o objetivo de carregar baterias. A razão da tensão de circuito aberto foi a estratégia de rastreio escolhida. O conversor foi projetado em uma tecnologia CMOS de 130 nm e alcança uma eficiência de 90 % para potencias de entrada maiores do que 30 mW e pode operar com tensões que vão de 1.25 até 1.8 V, resultando em saídas que vão de 2.5 até 3.6, respectivamente. Os circuitos periféricos também incluem uma proteção contra sobre tensão na saída de 3.6 V e circuitos para controle, que consomem um total máximo de potência estática de 850 A em 3.3 V de alimentação. O layout completo ocupa uma área de 300 x 700 m2 de silício. Os únicos componentes não integrados são 6x100 nF capacitores.

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

Este trabalho apresenta um conversor CC - CC baseado em Capacitores Chaveados de 6 fases e tempos intercalados com o objetivo de coletar energia fotovoltaica projetado em tecnologia CMOS de 130 nm para ser usado em aplicações em Internet das Coisas e Nós Sensores. Ele rastreia o máximo ponto de entrega de energia de um painel fotovoltaico policristalino de 3 cm x 3 cm através de modulação da frequência de chaveamento com o objetivo de carregar baterias. A razão da tensão de circuito aberto foi a estratégia de rastreio escolhida. O conversor foi projetado em uma tecnologia CMOS de 130 nm e alcança uma eficiência de 90 % para potencias de entrada maiores do que 30 mW e pode operar com tensões que vão de 1.25 até 1.8 V, resultando em saídas que vão de 2.5 até 3.6, respectivamente. Os circuitos periféricos também incluem uma proteção contra sobre tensão na saída de 3.6 V e circuitos para controle, que consomem um total máximo de potência estática de 850 A em 3.3 V de alimentação. O layout completo ocupa uma área de 300 x 700 m2 de silício. Os únicos componentes não integrados são 6x100 nF capacitores.

abstract: The most important metrics considered for electric vehicles are power density, efficiency, and reliability of the powertrain modules. The powertrain comprises of an Electric Machine (EM), power electronic converters, an Energy Management System (EMS), and an Energy Storage System (ESS). The power electronic converters are used to couple the motor with the battery stack. Including a DC/DC converter in the powertrain module is favored as it adds an additional degree of freedom to achieve flexibility in optimizing the battery module and inverter independently. However, it is essential that the converter is rated for high peak power and can maintain high efficiency while operating over a wide range of load conditions to not compromise on system efficiency. Additionally, the converter must strictly adhere to all automotive standards. Currently, several hard-switching topologies have been employed such as conventional boost DC/DC, interleaved step-up DC/DC, and full-bridge DC/DC converter. These converters face respective limitations in achieving high step-up conversion ratio, size and weight issues, or high component count. In this work, a bi-directional synchronous boost DC/DC converter with easy interleaving capability is proposed with a novel ZVT mechanism. This converter steps up the EV battery voltage of 200V-300V to a wide range of variable output voltages ranging from 310V-800V. High power density and efficiency are achieved through high switching frequency of 250kHz for each phase with effective frequency doubling through interleaving. Also, use of wide bandgap high voltage SiC switches allows high efficiency operation even at high temperatures. Comprehensive analysis, design details and extensive simulation results are presented. Incorporating ZVT branch with adaptive time delay results in converter efficiency close to 98%. Experimental results from a 2.5kW hardware prototype validate the performance of the proposed approach. A peak efficiency of 98.17% has been observed in hardware in the boost or motoring mode. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

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.