Optimization of Torque Ripple for Low-Carrier-Ratio Dual Three-Phase PMSM With Pulse Pattern Control

Aiming at mitigating the torque ripple at low-carrier-ratio operating conditions, an optimal pulsewidth modulation (PWM) scheme is proposed for the dual three-phase permanent-magnet synchronous motor (DTP-PMSM). The current trajectory induced by inverter harmonic voltages on the torque subspace is derived and the model of torque ripple is established. Then, the switching angles are optimized offline to mitigate the torque ripple directly while limiting the current harmonics simultaneously. It is revealed that the torque ripple is influenced by torque angle in addition to the voltage harmonics. Moreover, the differences between the optimal switching angles for torque ripple and those for current harmonics in DTP-PMSM are analyzed. To achieve the closed-loop control performance, the proposed optimal PWM strategy is applied to the model predictive pulse pattern control (MP
³
C) scheme. The experimental results are given to verify the validity of the proposed optimal PWM-based MP
³
C scheme.