Leakage Current Attenuation of a Three-Phase Cascaded Inverter for Transformerless Grid-Connected PV Systems

Three-phase cascaded inverter with leakage current reduction for the transformerless PV system is investigated in this paper. The common-mode loop model of the conventional three-phase cascaded H4 grid-connected inverter is established. The relationship among the leakage current, common-mode voltage, and differential mode voltage is analyzed. The inherent reason that the conventional cascaded H4 grid-connected inverter fails to reduce the leakage current is clarified. In order to solve the problem, a novel three-phase cascaded H5 grid-connected inverter and its modulation strategy are proposed. It can significantly reduce the leakage current. Finally, the performance tests of the cascaded H4 and H5 grid-connected inverters are carried out. The results verify the effectiveness of the proposed solution.