A New Modulation for Leakage Current Reduction of Modular Multilevel Converter

Leakage current is an important problem in non-isolated inverters, especially implemented in a medium- and high-voltage system. First, several analyses had carried out to reduce the high-frequency component of common-mode voltage (CMV) and the leakage current of a three-phase modular multilevel converter (MMC). Then, a new modulation method is proposed to keep CMV as the half of dc voltage and suppress the leakage current effectively. The peak value of leakage current can be suppressed under 5 mA, which complies with the VDE-0126-1-1 standard. Meanwhile, the parasitic capacitor voltage can be balanced automatically without the additional capacitor voltage control. Finally, the proposed scheme is verified in MATLAB/Simulink and tested on the hardware-in-loop platform. The effectiveness of the proposed scheme is verified by the experiment results.