Hybrid Space Vector Modulation Strategy for Torque Ripple Minimization in Three-Phase Four-Switch Inverter-Fed PMSM Drives

Three-phase four-switch (TPFS) inverters are generally applied as cost-reduction topologies for permanent-magnet synchronous motor (PMSM) drives because of their reduced number of switching devices. However, undesirable torque ripples are produced by the inverter-fed PMSMs due to the application of nonsinusoidal voltages. Because the torque ripples are strongly influenced by the employed pulse width modulation (PWM) strategy, two commonly used switching sequences in TPFS inverter-fed PMSM drives are fully investigated based on the root mean square value of the torque ripples, in which the effects of the different equivalent zero vectors on the torque ripples are presented. Then, a hybrid space vector modulation (SVM) strategy is proposed to minimize the torque ripples by alternatively using the two equivalent zero vector synthesis approaches during a fundamental period. The sector division of the proposed hybrid SVM strategy is determined by the location of the stator current vector, which is quite different from the methods used in other SVM methods. Then, a simplified sector identification method is proposed to reduce the computational burden. The experimental results demonstrate that the proposed hybrid PWM strategy can effectively reduce torque ripples in TPFS inverter-fed PMSM drives.