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 three-phase 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 fault-tolerant 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, under healthy and for three degraded modes of the system, are given to prove the effectiveness of the whole strategy.