Desenvolvimento de um solid state transformer para aplicações residenciais em smart grids

Dissertação de mestrado em Engenharia Eletrónica e de ComputadoresO consumo de energia elétrica é essencial para o quotidiano das pessoas e empresas, sendo por isso necessário um fornecimento de energia elétrica com ótima qualidade. Posto isto, torna-se fundamental o desenvolvimento de equipamentos que assegurem uma ótima qualidade de energia elétrica. Durante os últimos 20 anos, o solid-state transformer (SST) tem sido alvo de investigação científica no sentido de substituir o transformador convencional. Face aos transformadores convencionais, o SST apresenta inúmeras vantagens, tais como, a redução do volume e peso e o facto de permitir um elevado grau de controlabilidade. Este controlo permite elevados padrões de qualidade de energia elétrica, pois controla a corrente de entrada para que tenha reduzida distorção harmónica e para que o fator de potência seja unitário. Os SSTs podem também permitir uma melhor integração das energias renováveis e de sistemas de armazenamento de energia, tal como gestão de energia nas micro-grids, sendo assim um bloco chave no desenvolvimento das smart grids. Além disso, com a introdução desta tecnologia, será possível a comunicação com os fornecedores de energia e os clientes visando estabelecer modos de operação específicos. Apesar das diversas vantagens, um SST apresenta algumas desvantagens. Atualmente, um SST não é tão eficiente como um transformador convencional, sendo também mais caro devido a utilização de diversos dispositivos eletrónicos. Em parte, o problema da eficiência é o resultado das perdas dos semicondutores utilizados (MOSFET, IGBT), sendo que com o surgimento de novos semicondutores como os SiCs (silicom carbide), verifica-se uma diminuição das perdas e um incremento da frequência de operação. Esta dissertação apresenta o desenvolvimento de um SST monofásico que permite o controlo da corrente de entrada e da tensão e frequência de saída. Consequentemente, com esta controlabilidade, é possível atingir elevados padrões de qualidade de energia elétrica. Após o estudo do estado da arte sobre conversores de eletrónica de potência e sobre estratégias de controlo, foi desenvolvido um modelo de simulação para verificar o funcionamento do SST. Posteriormente, foi desenvolvido um protótipo laboratorial e foram obtidos resultados experimentais.The consumption of electric energy is essential for the daily life of people and companies, therefore a supply of electric energy with excellent quality is required. Thereby, it is fundamental to develop equipment that ensures excellent quality of electrical energy. During the last 20 years, the solid-state transformer (SST) has been the subject of scientific research to replace the conventional transformer. Compared to conventional transformers, the SST has many advantages, such as reduction of volume and weight and a high degree of controllability. This control allows high standards of electric power quality because it controls the input current so that it has reduced harmonic distortion and allows a unity power factor. SSTs enable better integration of renewable energy and energy storage systems, such as micro-grids power management, and are a key block in the development of smart grids. In addition, the introduction of this technology will enable communication with energy suppliers and customers to establish specific modes of operation. Despite the several advantages, an SST has some disadvantages. Currently, an SST is not as efficient as a conventional transformer and is also more expensive due to the use of various electronic devices. In part, the efficiency problem is the result of the losses of the used semiconductors (MOSFET, IGBTs), and with the emergence of new semiconductors such as SiCs (silicon carbides), there is a decrease in losses and an increase in the frequency of operation. This dissertation presents the development of a single-phase SST that allows the control of the input current and the output voltage and the output frequency. Consequently, with this controllability, it is possible to achieve high standards of electrical power quality. After a state-of-the-art study on power electronics converters and control strategies, a simulation model was developed to verify the functioning of the SST. Subsequently, a laboratory prototype was developed, and experimental results were obtained.Este trabalho de dissertação está enquadrado no projeto de IC&DT “ESGRIDS – Enhancing Smart GRIDs for Sustainability”, financiado pela Fundação para a Ciência e Tecnologia, com a referência POCI-01-0145-FEDER-016434 (Projetos I&D em Co-Promoção). Este trabalho de dissertação está enquadrado no projeto de IC&DT “DAIPESEV – Development of Advanced Integrated Power Electronic Systems for Electric Vehicles”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEI EEE/30382/2017

A novel three-phase multilevel AC-DC converter operating as a shunt active power filter: Validation considering an industrial environment

Power quality problems are an issue that requires, each more, particular attention, among others, to prevent equipment failure and improve efficiency. In this context, this paper presents a novel three-phase four-wire multilevel AC-DC converter operating as a shunt active power filter aiming to reduce the current harmonic distortion, low power factor, and current unbalances, which are introduced by the non-linear loads. The proposed topology comprises a total of six full bridges, where every two full bridges are arranged in a cascade structure and connected to one of the phases of the power grid. Both the proposed topology, as well as the applied control algorithm, are validated using computer simulations considering the most relevant conditions of operation in an industrial environment. The obtained results validate the proposed three-phase multilevel converter when operating as a shunt active power filter, showing that the power quality problems presented in the currents are compensated and the converter operates with the multilevel characteristic for all the conditions of operation

Computer studies of the operation of a Three Phase Four Wire Shunt Active Power Filter applied to the Industry

EAI SESC 2021 - 3rd EAI International Conference on Sustainable Energy for Smart Cities (online event), November 24 – 26, 2021 - Portugal.As the industry progresses, power quality problems become more and more rele-vant. The increase of non linear loads in industries, leads to higher current har-monic distortion and low power factor. In order to mitigate these problems, this paper validates a shunt active power filter (SAPF). The adopted topolo-gy and its control algorithm are analyzed through computer simulations consider-ing real industrial load models, which were elaborated from data collected in power quality analyzers that were connected to different points of an industry. The results achieved validate the correct operation of the applied SAPF, as well as it presents the improvements obtained of the total current distortion and neutral current.This work is supported by: European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Pro-gramme (COMPETE 2020) [Project nº 39479; Funding Reference: POCI-01-0247-FEDER-39479]