Capacitor Voltage Balancing for Five-Level Neutral-Point Clamped Inverter using Modified Carrier Waves for Carrier-Based PWM Technique

Multilevel inverter (MLI) are now mostly preferred topology for high-power medium-voltage induction motor drives. From various available topology of multi-level inverter neutralpoint clamped (NPC) is widely preferred due to its simplicity and inherent advantages. NPC mainly have a problem of fluctuating neutral-point potential (NPP), which leads to severe problem like increase in total harmonics distortion (THD) and increase in voltage stress of the power semiconductor switches. This paper focused towards the capacitor voltage balancing in five-level NPC with use of phase-disposed pulse width modulation technique (PD-PWM). An analysis of effects of various offset in carrier waves on capacitor voltages is analyzed, by use of band detector close-loop control is done and based on band detection various offset value is added in carrier waves to reduce the discrepancy in capacitor voltages.