A new discontinuous PWM strategy of neutral-point clamped inverter

In-this paper, a new carrier-based discontinuous PWM strategy for neutral-point-clamped (NPC) PWM inverter is proposed. The proposed discontinuous PWM scheme takes advantage of the special properties available in NPC inverter to minimize switching loss of the inverter simultaneously with neutral-point voltage control. This switching loss minimization is derived from the following two factors: less switching frequency ratio and the absence of switching in the vicinity of peak load current. The proposed PWM strategy differs from the conventional carrier-based PWMs in that the proposed one distributes nonswitching regions variably according to switching energy loss and variation of neutral-point voltage estimated from sampled phase current. In addition, it can produce the highest available output voltage because it is based on the concept of offset (zero sequence) voltage. The effectiveness of the proposed PWM strategy is verified by experiments