A simple space vector PWM scheme to operate a three-level NPC inverter at high modulation index including over-modulation region, with neutral point balancing

Multilevel inverters are being increasingly used for high-power medium-voltage applications. Three-level neutral point clamped (NPC) topology is most widely used topology of multilevel inverters. However, at higher modulation index, particularly in over-modulation region, the neutral point fluctuation deteriorates the performance of the inverter. Furthermore, operating the inverter at lower modulation index implies that it is operated at lower voltages only, and the installed DC link capacity is not fully utilized. This paper proposes a simple space vector PWM scheme for operating a three-level NPC inverter at higher modulation indices including over-modulation region, with neutral point balancing. Experimental results are provided.