Improvement of a PWM controlled NPC GTO inverter for AC motor drives

This paper describes the application of the vector control technique to a three level or NPC (neutral point clamped) inverter using a DSP (digital signal processor) TMS320C25. A newly developed PWM technique for this kind of inverter is applied. As a result the switching losses as well as the current distortions are reduced. A smaller fluctuation of the neutral point voltage was also obtained. The proposed method was applied to a 20 kW motor using an NPC converter and inverter. Theoretical and practical aspects as well as the experimental results are presented in this report.