Cascaded iH6 multilevel inverter with leakage current reduction for transformerless grid-connected photovoltaic system

The reduction of common mode leakage current in centralized inverter for grid-connected PV (photovoltaic) system has been well studied. However, the research in cascaded multilevel inverter PV system is not far enough. This paper focuses on analyzing the generation mechanism of common mode leakage current and building equivalent circuit model of cascaded PV system. By clarifying the reason why the conventional cascaded H4 (full-bridge inverter) PV system fails to reduce the common mode leakage current, a new cascaded iH6 inverter PV system is proposed. The related theoretical analysis and simulation results are given, and it is verified that the common mode leakage current can be greatly reduced compared with the conventional cascaded H4 system. Meanwhile, the cascaded iH6 inverter PV system does not need an EMI filter to suppress the high frequency noise.