Synchronized Six-Step Voltage Generation in High-Speed PMSM Drive

Synchronized voltage generation has already been considered in the context of pulse width modulation (PWM). References prove that synchronized PWM substantially decreases subharmonics in inverter output voltage when operating with low switching-to-fundamental frequency ratio. This paper identifies problems of unsynchronized voltage generation in electric drives under six-step inverter operation. Guidelines for the synchronization scheme were formulated, considering both minimization of voltage subharmonics and drive control properties. A comprehensive algorithm for adjusting the voltage update rate in six-step permanent magnet synchronous motor (PMSM) drive was presented. Superior properties of the synchronized six-step voltage generation were demonstrated by simulation and experiment for an exemplary 5-kW PMSM drive.