Amplitude-Phase Based Optimal Voltage Harmonic Injection for Speed Harmonic Minimization in SPMSM

Low torque ripple level is the prerequisite for surface-mounted permanent magnet synchronous machines to maintain control accuracy and speed stability. Since the speed harmonic's amplitude is proportional to the torque harmonic's amplitude, torque ripple can be reduced by speed harmonic minimization. Harmonic injection method is a practical speed harmonic minimization method. But current harmonic regulation and complex theoretical derivation are required in existing methods. What's more, the effectiveness of many methods will deteriorate when the parameters of permanentmagnet synchronous machine (PMSM) and proportional integral (PI) controllers vary. In order to avoid the influence of parameter variations and complex algorithms, an amplitude-phase-based optimal voltage harmonic injection method is proposed for speed harmonic minimization in this article. The influence of the injected voltage harmonic's amplitude and phase on the speed harmonic's amplitude is first analyzed. Then, a simple speed harmonic controller based on the optimization of injection voltage harmonic's amplitude and phase is designed. The proposed method does not rely on the motor parameters. Moreover, the proposed method is easy to implement. It does not need to regulate current harmonics. The proposed method is simulated and experimentally evaluated under both steady-state and transient conditions.