Comprehensive Comparative Assessment of Multiphase Overmodulation Techniques and Three-Phase Discontinuous PWM Methods Applied to Symmetrical Six-Phase Induction Motor Drives Under Overmodulation

Among six-phase motors, those featuring symmetrical six-phase motor with a single neutral point (S6N1) offer enhanced fault tolerance. However, a single neutral point lowers the dc-link utilization in the linear pulsewidth modulation (PWM) range. Most previous multiphase overmodulation (OVM) methods address this limitation by injecting just nontorque current-producing harmonics. However, although some OVM methods have been compared regarding current distortion for S6N1, some others have not, and a comparison concerning complexity and inverter and copper loss remains lacking. Moreover, it is unclear if any attain the minimum voltage distortion (MVD), effective in reducing current distortion. Additionally, although three-phase discontinuous PWM (DPWM) approaches have been extended to multiphase drives for the linear PWM region, their behavior in the S6N1 OVM range has not been reported nor compared yet. This article assesses and compares, as its main contribution, the multiphase OVM approaches and three-phase DPWM methods in the S6N1 OVM range concerning voltage and current distortion, inverter and copper loss, and complexity. For comparative purposes, a simple MVD implementation is also devised. Considering the aforesaid figures of merit and certain relevant scenarios, this comparative study establishes the most suitable techniques. The experiments are performed by using an S6N1 induction motor.