An improved direct-self control method for high-speed permanent magnet synchronous motor

Due to the limited switching frequency and precision constraints of speed sensor, high-speed permanent magnet synchronous motor(PMSM) cannot acquire excellent performance with conventional control algorithm as well as low-speed one. This paper proposes an improved direct-self control(DSC) for high-speed PMSM, which is introduced and improved from hexagon-DSC. In proposed algorithm, the air gap flux linkage is controlled to be a dodecagon with the insertion of two-phase-conduction voltage space vector. To further reduce the torque ripple, an air gap flux linkage reference compensator is proposed and introduced to regulate the current of turn-off phase to zero before commutation. The proposed algorithm can acquire excellent performance at low switching frequency and without speed sensor. Compared with the conventional hexagon-DSC, the flux linkage THD declines from 21.3% to 1.4%, and the torque ripple declines from approximately 20Nm to 1Nm. No more current or voltage sensor is needed, and the algorithm still keeps its simplicity. Simulation results proved the validity of the proposed algorithm and is showed in this paper.