A new PWM method with suppressed neutral point potential variation of three level inverter for AC servo motor drive

This paper presents a new PWM method with suppressed neutral point potential variation of a three level inverter for AC servo motor drive. The basic idea is that the vector output intervals corresponding to increase or decrease of neutral point potential during one sampling period are to be equal. The authors show the following simulation and experimental results: (1) in the case without suppression, the variation width of neutral point potential become large, and the deviation of neutral point potential produce the distortion of output current waveforms; and (2) in the case with suppression, the variation width of neutral point potential is reduced. Simulation and experimental results are presented to confirm the performance of the proposed method.