Adaptive Beat Suppression Strategy Based on Voltage Angle Harmonics Regulation for Electrolytic Capacitorless PMSM Drives

The beat phenomenon in electrolytic capacitorless permanent magnet synchronous motor (PMSM) drives is serious within field-weakening (FW) region. This paper proposes an adaptive beat suppression strategy through regulating the voltage angle harmonics. By dividing the admittance in FW region into voltage sampling time-delay admittance and FW characteristic admittance, the relationship between beat envelope and the admittances is quantitatively analyzed. It is revealed that the conventional method can only reduce the influence of voltage sampling time-delay admittance. The proposed strategy constructs a closed-loop harmonic control of the DC-link voltage and the voltage angle to minimize the amplitude of beat envelope. By reshaping the impedance relationships between DC-link voltage and motor currents at inherent frequency, the FW characteristic admittance is reduced and the beat phenomenon in this region is suppressed effectively. Based on the reshaped impedance model, the control parameters are adaptively regulated with the motor speed and dq-axis currents. Experimental results show the effectiveness of the proposed method in a PMSM system with small DC-link capacitors.