A Study on the Neutral Point Voltage Control Limitation Area in Three-Level Inverter

3레벨 인버터의 중성점 전압 제어 제한 영역에 관한 연구

A three-level inverter is widely used thanks to its excellent performances, but the voltage may fluctuate at the neutral point of the split DC-Link. Neutral point voltage fluctuations cause inverter performance degradation and switching element damage, so the neutral point voltage control is essential. However, the neutral point control can be also limited by modulation index and power factor. This paper analyzes the limitation of the neutral point voltage control due to the limitation of zero-sequence voltage, and suggests a method to determine the region where the PWM has to be changed for a better neutral point control.