A Beat Phenomenon Suppression Method in the Reduced DC-link Capacitance IPMSM Drives

Beat phenomenon is an important concern in the application of the reduced DC-link capacitance IPMSM drives, which leads to the low-frequency oscillation of the motor speed and current. In the previous literature, the beat phenomenon could be divided into two types: one is the interaction of DC-link voltage and inverter output voltage, and the other one is caused by the negative impedance of the voltage control loop. In this paper, another type of the beat phenomenon caused by the fluctuated DC-link voltage and the load torque is analyzed from the view of the interaction between two different frequency sinusoidal current signals. In order to mitigate the low-frequency oscillation of the motor speed and current, the motor harmonic current corresponding to the fluctuated load torque is suppressed by the resonant controller applied in parallel to the current controller. The effectiveness of the proposed method is verified by experimental results.