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Publication
Interligação de microrredes híbridas com um conversor multinível
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Abstract(s)
Nos tempos atuais a eficiência energética e a coordenação inteligente dos recursos
da rede são tópicos de maior importância. As microrredes híbridas apresentam-se como
uma solução interessante para a integração coordenada de fontes de geração e cargas DC
ou AC nos barramentos DC ou AC respetivamente. Isto permite eliminar algumas etapas
de conversão que tradicionalmente existem nas redes AC, aumentando assim a eficiência
energética.
Neste trabalho utilizou-se um conversor multinível para interligar uma microrrede AC a
uma microrrede DC. O conversor de interligação é capaz de realizar o controlo das correntes
AC, da tensão DC ou da tensão AC, dependendo dos cenários de funcionamento da microrrede
híbrida.
As correntes AC do conversor foram controladas através das técnicas de controlo por
modo de deslizamento (MD) e modulação por largura de impulsos (PWM), partindo dos
modelos das variáveis de estado do conversor. As tensões das microrredes AC e DC foram
controladas utilizando malhas externas com controladores PI (Proporcional-Integral).
O conversor de interligação foi simulado na plataforma MATLAB/Simulink nos três
cenários de funcionamento. Os resultados de simulação foram posteriormente confirmados em
laboratório através de um protótipo de baixa potência.
Os resultados obtidos demonstraram uma resposta dinâmica rápida das correntes AC em
ambos os métodos de controlo, com a técnica PWM a apresentar harmónicas mais reduzidas.
O controlo de tensão da microrrede DC foi bem efetuado e permitiu reagir adequadamente a
mudanças de referência e ao aumento do consumo da microrrede DC. No caso em que existe
geração local o conversor foi capaz de realizar o equilíbrio entre a potência produzida e a
potência consumida, transferindo o excesso de potência para a microrrede AC. O controlo de
tensão da microrrede AC, permitiu regular de forma adequada as tensões trifásicas e
reagir a mudanças de referência e variações do consumo.
Energy efficiency and smart coordination of grid resources are issues of utmost importance nowadays. Hybrid microgrids are an interesting solution for the integration of AC and DC loads and generation sources in their respective AC or DC buses. This allows for a reduction of voltage conversion stages that are prevalent in the more traditional AC grid, leading to a higher efficiency. In the scope of this work a multilevel converter was used to interconnect an AC microgrid to a DC microgrid. The interlinking converter can control either the AC currents, the DC bus voltage, or the AC bus voltage, depending on the hybrid microgrid operation mode. The converter AC currents were controlled using sliding mode and pulse width modulation (PWM) techniques starting from the converter state variable representation. The AC and DC microgrid voltages were controlled by outer loop PI (Proportional Integral) controllers. The three operation modes of the interlinking converter were simulated using MATLAB/Simulink. A low power laboratory prototype was later used to further confirm the simulations results. The results showed a fast dynamic response of the AC currents, using both control techniques. PWM however resulted in reduced harmonics. The DC microgrid voltage control was successfully implemented and resulted in a good response following changes in voltage reference and DC microgrid consumption. When local power production was available, the converter was able to transfer the excess power to the AC microgrid, thus balancing the produced and consumed local power. The AC microgrid voltage control was capable of adequately regulate the three phase AC voltages and react to changes in voltage reference and local power consumption.
Energy efficiency and smart coordination of grid resources are issues of utmost importance nowadays. Hybrid microgrids are an interesting solution for the integration of AC and DC loads and generation sources in their respective AC or DC buses. This allows for a reduction of voltage conversion stages that are prevalent in the more traditional AC grid, leading to a higher efficiency. In the scope of this work a multilevel converter was used to interconnect an AC microgrid to a DC microgrid. The interlinking converter can control either the AC currents, the DC bus voltage, or the AC bus voltage, depending on the hybrid microgrid operation mode. The converter AC currents were controlled using sliding mode and pulse width modulation (PWM) techniques starting from the converter state variable representation. The AC and DC microgrid voltages were controlled by outer loop PI (Proportional Integral) controllers. The three operation modes of the interlinking converter were simulated using MATLAB/Simulink. A low power laboratory prototype was later used to further confirm the simulations results. The results showed a fast dynamic response of the AC currents, using both control techniques. PWM however resulted in reduced harmonics. The DC microgrid voltage control was successfully implemented and resulted in a good response following changes in voltage reference and DC microgrid consumption. When local power production was available, the converter was able to transfer the excess power to the AC microgrid, thus balancing the produced and consumed local power. The AC microgrid voltage control was capable of adequately regulate the three phase AC voltages and react to changes in voltage reference and local power consumption.
Description
Keywords
Microrredes híbridas Conversor multinível NPC Controlo por modo de deslizamento Modulação por largura de impulso Controlador proporcional-integral Hybrid microgrids NPC multilevel converter Sliding mode controller Pulse width modulation Proportional-integral controller Engenharia Eletrotécnica - Telecomunicações . Faculdade de Ciências Exatas e da Engenharia