Common Mode Voltage and Neutral Point Potential Optimization Control for a Three-Level NPC Inverter

In this paper, a common mode voltage (CMV) and neutral point (NP) potential optimization control method for a three-level NPC inverter is introduced. In this method, an optimal zero-sequence voltage injection method is adopted to balance the NP potential. Based on this, the range of reference voltages is limited to suppress the CMV which is increased by zero-sequence voltage injection. At the same time, the impact of modulation ratio on CMV is considered for the range of reference voltages limitation. Experiment is carried out to verify the correctness of the theoretical analysis and the effectiveness of the improved method for the three-level NPC inverter in this paper.