A Harmonic Injection Method Equivalent to the Resonant Controller for Speed Ripple Reduction of PMSM

This paper proposes a straightforward and effective control strategy to reduce the periodic speed ripple of the permanent-magnet synchronous motor (PMSM). The control strategy can be described as injecting current harmonics whose amplitude and phase can be adjusted automatically to compensate for periodic speed ripple. Compared with the resonant controller with the Tustin transform, the method proposed in the paper can track speed ripple frequency without frequency displacement, realizing no steady-state error. Besides, the system stability is analyzed, and the phase compensation scheme is proposed to increase the phase stability. Moreover, the equivalence between the harmonic injection module and the resonant controller has been analyzed, which provides a simple way to understand the phase compensation of the resonant controller. The theoretical analysis and experimental results are presented to verify the feasibility of the proposed harmonic injection method.