This master thesis presents the development of an auxiliary power supply to provide energy to sensors, gate drivers, instrumentation circuits and control of a three-stage Solid State Transformer (SST). These devices require an insulated power supply of ±15V and 5V. For reason of reliability and modularity, a distributed auxiliary source is proposed. Thus, it is necessary a power supply to provide energy to the low voltage (LV) side and another to the medium voltage (MV) side. With this proposal, the auxiliary power supply does not need to have the same galvanic insulation of the SST, 25kV. However, a local power supply must operate at high voltage levels and, consequently, contain a high step-down voltage gain. Relative to LV side, the most generally used topologies as an auxiliary power supply are discussed. However, these topologies cannot be used at the MV converters, due to the high voltage stress levels involved. A study of topologies used on medium and high voltage and which enable to reach a high step-down voltage gain is realized, and two interesting topologies for this application were found. One of them uses a Flying capacitor converter connected in cascade with a Double-Ended Flyback converter. The Flying capacitor converter lowers the DC bus voltage in a controlled manner to low voltage levels. So the Double-ended Flyback converter operates in LV and provides the insulated outputs to command circuits of SST. The other topology is a unidirectional four-level NPC converter operating as Double-ended Flyback converter. For this case, a modulation strategy that allows the converter to reach a high step-down voltage gain was also proposed. These topologies were evaluated and the one which showed the best result was the four-level Double-ended Flyback converter. This converter was implemented and the experimental results prove to be effective. For the LV side, a Half-bridge LLC resonant converter as auxiliary power supply was used. This converter operates in ZVS and performs the output voltage regulation through the operating frequency variation. The experimental results of this converter are also presented. / Este trabalho de mestrado apresenta o desenvolvimento de fontes auxiliares para alimentar sensores, circuitos de comando, instrumentação e o controle de um Transformador de Estado Sólido (SST) de três estágios. Estes dispositivos necessitam de alimentação isolada com tensões de ±15V e 5V e por questões de confiabilidade e modularidade, propõe-se a utilização de fontes auxiliares distribuídas. Assim, emprega-se uma fonte auxiliar para alimentar o lado de média tensão (MT) e outra para alimentar o lado de baixa tensão (BT). Com essa proposta, as fontes auxiliares não necessitam ter a mesma isolação galvânica do SST, 25kV. Entretanto, uma das fontes locais deve operar em níveis de tensão elevados e, por consequência, apresentar baixo ganho estático. No lado de BT, as principais topologias normalmente utilizadas como fonte auxiliar são discutidas. No entanto, devido aos altos níveis de tensão envolvidos, estas topologias não podem ser aplicadas ao conversor que opera em MT. Um estudo sobre topologias aplicadas a média tensão e que possibilitam alcançar um baixo ganho estático é realizado, sendo que duas topologias se mostram interessantes para esta aplicação. Uma consiste na utilização de um conversor de capacitores flutuantes conectado em cascata com um conversor Double-Ended Flyback. O conversor de capacitores flutuantes rebaixa a tensão do barramento CC, de forma controlada, para baixa tensão. Assim o Double-Ended Flyback opera em BT e fornece as saídas isoladas para alimentar os circuitos de comando do SST. A outra topologia trata-se de um conversor NPC de quatro níveis unidirecional operando como conversor Double-Ended Flyback. Para este caso, também foi proposta uma estratégia de modulação que permite o conversor alcançar o baixo ganho estático. Essas topologias foram avaliadas, apresentando melhor resultado a esta aplicação o conversor Double-ended Flyback de quatro níveis, conforme será demonstrado neste trabalho. Esse conversor foi implementado e os resultados experimentais comprovam o seu funcionamento. Para a fonte do lado de BT utilizou-se um conversor Half-Bridge LLC ressonante que opera em ZVS e realiza a regulação da tensão de saída pela variação da frequência de operação. Os resultados experimentais deste conversor também são apresentados.

This master thesis presents the development of a 100 W LED driver, suitable for outdoor and street lighting. In order to match the driver and LED features, special functionalities are added to the electronic system. To obtain a long lifetime, electrolytic capacitor are exchanged by film capacitor, with longer useful lifetime. However, this practice outcome in higher bus voltage ripple, which have to be compensated in the LED current control stage, named as power control stage. To achieve special functionalities, the proposed driver is designed to operate with universal input voltage and dimming capability, being the entire driver control implement in a digital way, increasing significantly the LED driver flexibility. After the literature review, which aimed to evaluate the characteristics of the LED driver topology structure, the two independent stage topology is selected. The buckboost converter operating in discontinuous conduction mode is employed on the power factor correction stage. The power control stage is composed by the DC/DC LLC resonant converter. Once the LED driver topology is defined, each converter is designed, following by the small signal modeling and the control system design. Experimental results of the driver operating with a reduced bus voltage capacitance (25 μF), are presented for a universal input voltage (85 – 265 VRMS) and different dimming levels (100% − 30%). A high power factor (> 0,94) and a medium to high efficiency (> 82%) is noticed in whole operation points, as well as, a reduced flicker (< 10%), being in accordance with the recent released IEEE Std 1789-2015 and IEC61000-3-2 Class C. / Este trabalho apresenta o desenvolvimento de um driver para o acionamento de um módulo de LEDs de 100 W, destinado a iluminação de exteriores ou iluminação pública. De forma a compatibilizar as características do LED com o driver, diferentes funcionalidades e condições de operação são adicionadas ao sistema eletrônico desenvolvido. Para alcançar longa vida útil, o driver desenvolvido substituiu os capacitores eletrolíticos por capacitores de filme. No entanto, essa prática resulta em maiores ondulações da tensão de barramento, as quais são compensadas pelo estágio de controle da corrente dos LEDs. De modo a aumentar as funcionalidades do driver, o mesmo opera com tensão de entrada universal e controle da intensidade luminosa, sendo o sistema de controle do driver implementado de forma digital, aumentando consideravelmente sua flexibilidade. Após revisão da literatura, a qual objetivou avaliar as características das estruturas e topologias empregadas em drivers para LEDs, seleciona-se a estrutura de dois estágios independentes. O conversor buck-boost operando no modo de condução descontínuo de corrente é empregado no estágio de correção do fator de potência. Para o estágio de controle da corrente dos LEDs, utiliza-se o conversor CC/CC meia ponte ressonante LLC. Definida a estrutura topológica, bem como os conversores utilizados, o projeto dos elementos é desenvolvido, seguido da modelagem dinâmica e do projeto do sistema de controle de cada estágio. Resultados experimentais do driver com reduzida capacitância de barramento (25 μF) mostram a sua operação com tensão de entrada universal (85 – 265 VRMS) e controle de intensidade luminosa (100% − 30%). Verificou-se um alto fator de potência (> 0,94) em toda a faixa de operação, rendimento média-alto (> 82%), bem como reduzida modulação de intensidade luminosa (< 10%), estando em conformidade com a IEEE Std 1789-2015 e a IEC61000-3-2 Classe C.

<p dir="ltr">The short lifespan of capacitors in power electronics converters is a significant challenge. These capacitors, often electrolytic, are vital for voltage smoothing and frequency filtering. However, their susceptibility to heat, ripple current, and aging can lead to premature faults. This can cause issues like output voltage instability and short circuits, ultimately resulting in catastrophic failure and system shutdown. Capacitors are responsible for 30% of power electronics failures.</p><p dir="ltr">To tackle this challenge, scientists, researchers, and engineers are exploring various approaches detailed in technical literature. These include exploring alternative capacitor technologies, implementing active and passive cooling solutions, and developing advanced monitoring techniques to predict and prevent failures. However, these solutions often come with drawbacks such as increased complexity, reduced efficiency, or higher upfront costs. Additionally, research in material science is ongoing to develop corrosion-resistant capacitors, but such devices are not readily available.</p><p dir="ltr">This dissertation presents a capacitorless solution for dc-dc and dc-ac converters. The proposed solution involves harnessing parasitic elements and integrating them as intrinsic components in power converter technology. This approach holds the promise of enhancing power electronics reliability ratings, thereby facilitating breakthroughs in electric vehicles, compact power processing units, and renewable energy systems. The central scientific premise of this proposal is that the capacitance requirement in a power converter can be met by deliberately augmenting parasitic components.</p><p dir="ltr">Our research hypothesis that incorporating high dielectric material-based thin-films, fabricated using nanotechnology, into planar magnetics will enable the development of a family of capacitorless electronic converters that do not rely on discrete capacitors. This innovative approach represents a departure from the traditional power converter schemes employed in industry.</p><p dir="ltr">The first family of converters introduces a novel capacitorless solid-state power filter (SSPF) for single-phase dc-ac converters. The proposed configuration, comprising a planar transformer and an H-bridge converter operating at high frequency, generates sinusoidal ac voltage without relying on capacitors. Another innovative dc-ac inverter design is the twelve step six-level inverter, which does not incorporate capacitors in its structure.</p><p dir="ltr">The second family of capacitorless topologies consists of non-isolated dc-dc converters, namely the buck converter and the buck-boost converter. These converters utilize alternative materials with high dielectric constants, such as calcium copper titanate (CCTO), to intentionally enhance specific parasitic components, notably inter capacitance. This innovative approach reduces reliance on external discrete capacitors and facilitates the development of highly reliable converters.</p><p dir="ltr">The study also includes detailed discussions on the necessary design specifications for these parasitic capacitors. Furthermore, comprehensive finite element analysis solutions and detailed circuit models are provided. A design example is presented to demonstrate the practical application of the proposed concept in electric vehicle (EV) low voltage side dc-dc power converters used to supply EVs low voltage loads.</p>