Revista Eletrônica de Potência (Brazilian Journal of Power Electronics)

Palavras Chaves: Capacitor chaveado, Conexão com a Rede Elétrica, Controle, Inversor boost, Linearização, Modelagem

Resumo

Neste artigo propõe-se o emprego do inversor boost diferencial a capacitor chaveado (SCDBI) em aplicações que requerem conexão com a rede elétrica. O SCDBI é um inversor elevador, cujo ganho pode ser aumentado a partir da adição de células a capacitor chaveado, e possui saída em tensão, o que permite injetar correntes na rede com baixa ondulação usando apenas um filtro L. Esses atributos favorecem o emprego da topologia em sistemas de estágio único, onde a tensão de entrada é menor que o valor de pico da tensão de saída. Alguns dos desafios atrelados ao uso do SCDBI estão relacionados à característica de ganho não linear e aos modelos dinâmicos de ordem elevada. Neste artigo, é proposta uma modelagem simplificada e uma técnica de linearização estática, que possibilitam a utilização de um controlador proporcional-integral e uma malha de feedforward para controlar a corrente injetada na rede elétrica. O trabalho também aborda a análise estática do conversor com modulação unipolar e apresenta os procedimentos de dimensionamento. A validação do estudo é feita através dos resultados obtidos a partir de um protótipo de 250 W, conectado à rede de 220 V eficaz, com tensão de entrada de 60 V, frequência de comutação de 50 kHz, rendimento de 90% e corrente de saída com THD menor que 5%.

Title: Switched capacitor boost inverter connected to the grid

Keywords: Boost inverter, Connecting to the electrical grid, Control, Linearization, Modelling, Switched capacitor

Abstract

This paper proposes the employment of the switched-capacitor differential boost inverter (SCDBI) for applications that require grid-connection. The SCDBI is a step-up converter, which allows the increasing of the gain adding more switched capacitor cells. Furthermore, its output voltage characteristic enables injecting currents with low ripple even using just an L filter. Those attributes support the employment of the topology in single-stage systems connected to the grid, in which the input voltage is lower than the output voltage. Some of the challenges of using SCDBI connected to the grid are related to the nonlinear static gain characteristic and high order dynamic models. In this paper, a simplified modelling and a static linearization technique are proposed, which allow the use of a proportional integral controller with a feedforward loop for regulating the current injected into the grid. Furthermore, the static analysis of the converter with unipolar modulation and design methodology are also presented. The validation of the theoretical analysis is achieved through a 250 W prototype connected to 220 V RMS voltage grid, with input voltage of 60 V, switching frequency of 50 kHz, efficiency of 90%, and grid current THD less than 5%.

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