Design and Simulation of L and LCL Filters for the Interconnection of a Three Phase NPC Inverter to the Grid

Este trabalho apresenta o estudo de um inversor NPC de 6 kW e 380 V, trifÃsico, para interconexÃo de sistemas de geraÃÃo distribuÃda à rede elÃtrica. O inversor à estudado nas frequÃncias de chaveamento de 3, 4 e 6 kHz, sendo interligado à rede elÃtrica atravÃs dos filtros L e LCL. Para identificar qual filtro passivo, L ou LCL, se adequa melhor ao inversor em estudo foram realizadas simulaÃÃes numÃricas para diferentes situaÃÃes, validando o projeto do inversor e a modelagem vetorial desenvolvida. A resposta do controle à satisfatÃria, pois o inversor à capaz de controlar o fluxo de potÃncia ativa e reativa entregues à rede elÃtrica. Diante dos resultados obtidos percebeu-se que o filtro LCL apresentou um menor conteÃdo harmÃnico para as trÃs frequÃncias estudadas em relaÃÃo ao filtro L. Ambos os filtros atenderam aos requisitos da norma Std IEEE 1543, no entanto o filtro L à o mais indicado para o inversor em estudo, pois alÃm de atender a norma, o mesmo apresenta um menor custo quando comparado ao filtro LCL.This paper presents the study of a 6 kW, 380 V, three phase NPC inverter for interconnecting distributed generation unit to the grid. The inverter is studied with switching frequency of 3, 4 and 6 kHz, and it is interconnected to the grid through L and LCL filters. To identify which passive filter, L or LCL, is best suited to the inverter under study, a mathematical model has been proposed and several numerical simulations have been carried out to validate the design of the inverter and vector model developed. The control response is satisfactory, since the inverter is able to control the flow of active and reactive power delivered to the grid. Based on these results it was noticed that the LCL filter showed a lower harmonic content for the three frequencies studied in relation to the filter L. Both filters met the requirements of the standard IEEE Std 1543, however the filter L is the most suitable for the inverter under study, because the filter L not only meet the standard but also it presents a lower cost when compared to the LCL filter