Beatless Control Strategy Based on Impedance Reshaping for PMSM Drives With Small DC-Link Capacitors

This article investigates the beat phenomenon in permanent magnet synchronous motor (PMSM) drives with small direct current link (dc-link) capacitors caused by the interactions of the fundamental current and the dc-link inspired harmonics. The proposed impedance reshaping based beatless method not only reduces the low-frequency envelop in motor currents, but also improves the quality of grid currents. The harmonics in the beat current are analyzed in an impedance perspective, and a beatless control strategy is proposed by reshaping the impedance of the PMSM drive system at dominated harmonics. By generating the adjusting currents at the dominated harmonics on motor current vector, the small-signal model of the system is immune to the variation of the steady-state values, which ensures the validity of the beat suppression over a wider operating range. Experimental results show the effectiveness of the proposed method in a prototype of PMSM drive with small dc-link capacitors.