Fault-tolerant operating analysis of a quad-inverter multiphase multilevel AC motor drive

This paper investigates a new fault-tolerant strategy of a multi-phase multi-level ac motor drive. The proposed approach is based on four conventional 2-level threephase voltage source inverters (VSIs) supplying the open-end windings of a dual three-phase motor (asymmetric six-phase machine), quadrupling the power capability of a single VSI with given voltage and current ratings. The developed faulttolerant control algorithm is able to generate multi-level voltage waveforms, equivalent to the ones of a 3-level inverter, and to share the total motor power among the four dc sources within each switching period. The investigated ac motor drive has been numerically implemented and a complete set of simulation results, under healthy and for three degraded modes of the system, are given to prove the effectiveness of the whole strategy.