Common-Mode Circuit Analysis of Current-Source Photovoltaic Inverter for Leakage Current and EMI

Leakage current and electromagnetic interference (EMI) are closely related to the common-mode (CM) circuit in transformerless photovoltaic inverter systems. However, the correlation between them is elusive, as they are always studied independently because of the different frequency bands involved. This article establishes the CM circuit models of the current-source inverter, and the inherent relationship and the affecting factors between leakage current and CM EMI are revealed. Based on the established models, the leakage current and conducted EMI are accurately predicted with a reduced computational burden. In addition, some suppression measures for leakage current and CM EMI are derived, including the effectiveness of connecting a neutral wire. Finally, through simulations and experiments, the correctness of the theoretical analysis is verified.