Carrier-based PWM strategy for post-fault reconfigured 3-level NPC inverter under imbalanced dc-link voltages

This paper presents an investigation on carrier-based PWM method of post-fault reconfigured topology for the three-level neutral-point-clamp (3-level NPC) inverter. The operation of 3-level NPC under device failure conditions is analyzed and the proposed fault-tolerant PWM strategy is able to continuously the operation of the inverter. The proposed carrier-based method is simple without complexity calculation, the duty cycles are defined based on the comparison between the modulation signals and high frequency carrier signal. Furthermore, the balanced output currents are obtained under the imbalanced dc-link voltage condition because the modulation signals are determined based on the feedback dc-link voltage. The proposed carrier-based PWM is verified by numerical simulation and it is validated by hardware experimentation on a laboratory prototype.