Selective Harmonic Elimination PWM Switching Principle in Multi-Mode Modulation for Five-Phase Permanent Magnet Synchronous Motors

Multi-phase permanent magnet synchronous motors (PMSM) are potentially used in the field of rail transit and due to theirs high power density and high reliability. For high power applications, Multi-mode modulation strategy based on selective harmonic elimination pulse width modulation (SHEPWM) are often used to achieve excellent current performance at very low switching frequency. However, the current impact caused by transition process of SHEPWM with different carrier ratios is a terrible issue in engineering application. To address this problem, this paper investigates the generation mechanism of current impact in the transition process according to the equivalent circuit model of five-phase PMSM firstly. Furthermore, theoretical analysis results proved that each phase independent switching scheme can achieve different carrier ratio SHEPWM smooth transition. Finally, the simulation results have verified the correctness and effectiveness of the theoretical analysis.