A five-level neutral-point-clamped H-bridge PWM inverter with superior harmonics suppression: a theoretical analysis

A new control strategy for a five-level neutral-point-clamped (NPC) H-bridge PWM inverter is proposed. It is shown that a three-level class BD PWM output can be obtained from one leg of the inverter if the phases of both the modulating signal and carrier are appropriately chosen. This new control strategy is called three-level NPC PWM and is very simple. By combining the three-level outputs from both legs of the NPC H-bridge PWM inverter, a five-level PWM output is achieved. A theoretical harmonic analysis of the proposed inverter has been carried out. It is shown that the inverter exhibits superior harmonics suppression property and only multiples of the fourth-order families of the cross-modulated harmonics are present.