Minimum Torque Ripple Control of Permanent Magnet Synchronous Motor in the Stationary Reference Frame

To suppress torque ripple caused by non-sinusoidal back electromotive force (EMF), non-sinusoidal currents should be injected into the PMSM. Direct torque control (DTC) has been proposed to achieve this aim. Nevertheless it has many unavoidable drawbacks, especially the large torque ripples produced at low speed. The multiple reference frame theory can be applied to track the desired currents with a number of harmonics, while the control scheme is too complex and requires too many computations. In this paper, we propose a novel approach to suppress the torque ripple of PMSM in the stationary reference frame. A closed form solution is suggested in order to design the optimal excitation current waveforms, with which the torque ripple caused by the back-EMF harmonics up to an arbitrary degree can be completely eliminated. By using the self-tuning multiple-frequency resonant controllers, the regulated currents can perfectly track proposed optimal excitation current waveforms, and the undesired torque ripple is efficiently suppressed. The simulated and experimental results confirm the validity and effectiveness of the proposed approach