Metodologia de projeto para um filtro LCL modificado com adição de um indutor de modo-comum para aplicações fotovoltaicas sem transformador conectadas à rede
Keywords: MLCL filter, common-mode inductor, common-mode voltage, transformerless photovoltaic system
AbstractGrid-connected transformerless photovoltaic (PV) systems have become very popu- lar, due to their smaller size/weight, greater efficiency and lower cost. However, the common- mode voltage (CM) generated in power inverters causes leakage current, which according to PV standards, must be limited. Among different methods to limit leakage current, the modified LCL (MLCL) filter with passive damping is an efficient and simple solution. However, it is necessary to oversize the components of the MLCL filter to keep the leakage current below 300 mA rms, established by PV standards, increasing the size of the differential inductors. On the other hand, a CM inductor can be added to limit the leakage current. These inductors process less energy, and therefore considerably reduce the total volume of magnetic devices in the power stage. This paper presents a methodology to size the elements of an MLCL filter with a CM inductor that complies with the PV standards, in a transformerless three-phase two-level grid-connected inverter. Simulation results are presented to confirm the theoretical analyses.