Compensation Voltage Injection Based Neutral Point Voltage Fluctuation Suppression for NPC Converter

Three-level neutral point clamped (NPC) inverter is widely used in new energy power generation, motor drive and many other occasions. However, the neutral point voltage imbalance of NPC inverter will affect the output of the inverter system, and the control of neutral point voltage has become a research hotspot. In this paper, a compensation voltage injection based neutral point voltage balancing method is proposed, which controls the neutral point current in the switching cycle to realize neutral point voltage self-balance. MATLAB/Simulink simulation model is established to verify the effectiveness of the method, and the simulation results show that the low-frequency fluctuation of the neutral point voltage caused by the modulation wave is eliminated by injecting compensation voltage, the magnitude of high-frequency fluctuation is less than 5% of the low-frequency fluctuation.