Order-Domain-Based Harmonic Injection Method for Multiple Speed Harmonics Suppression of PMSM

Torque ripple degrades the performance of a permanent magnet synchronous motor (PMSM). Harmonic injection method can minimize torque ripple well by suppressing the speed harmonic. But its performance under transient conditions is not satisfactory. Moreover, too much computation and complex parameter adjustment limit its application in multiharmonic suppression of speed. Therefore, this article proposes an order-domain-based harmonic injection (OHI) method for multiple speed harmonics suppression under both steady-state and transient conditions. In the OHI method, speed harmonics are extracted as feedback signals and suppressed by a speed harmonic controller. The speed harmonic controller is designed based on real and imaginary parts. The relations among the voltage, current, and speed harmonics are derived. According to these relations, speed harmonics are adjusted directly by voltage harmonics. For faster harmonic extraction, the real-time angular-domain Fourier transform (AFT) is proposed by improving an AFT algorithm. The OHI method has less calculation and simpler parameter adjustment compared with existing methods. So, it is more suitable for multiharmonic suppression of speed. Due to the extremely fast respond of speed harmonic control loop, the OHI method is effective even under transient conditions. The OHI method is simulated and experimentally evaluated in PMSM servosystem.