Common-Mode Voltage Reduction of the Semi-Two-Stage Three-phase Inverter Base on Modified Modulation Scheme

Three phase semi-two-stage inverters have higher efficiency than that of the conventional two-stage three phase inverters, since part of the dc power can be fed to utility grid directly. However, these inverters have the issue of leakage current due to the high-frequency variation of CMV (common mode voltage). To solve this problem, a modified SVPWM modulation strategy is proposed which can reduce the CMV to different degrees with different input voltages. In addition, this method has few influences on the efficiency. Comparisons between the modified and the conventional modulations are also discussed. A 3 kW prototype is built to verify the effectiveness of the proposed modulation scheme.