Overvoltage Suppression Strategy for Permanent Magnet Synchronous Motor System without Electrolytic Capacitor Based on Maximum Current Limitation

The lifetime of the traditional motor drive system is directly affected by the DC side electrolytic capacitors. However, the system without electrolytic capacitor is prone to overvoltage under the condition of motor deceleration or sudden load shedding due to the serious decrease in energy storage capacity of the DC side capacitor. The traditional overvoltage suppression strategy is difficult to achieve the maximum copper loss during the rapid braking process for the system without electrolytic capacitor due to the slow change of the d-axis current given, and the overvoltage suppression performance is poor. In this paper, an overvoltage suppression strategy for permanent magnet synchronous motor system without electrolytic capacitor is proposed based on maximum current limitation. First, the d-axis current is calculated in real time using the maximum current limitation condition of the system operation. Once overvoltage phenomenon occurs, the d-axis current is immediately maximized to increase the copper loss of the motor. In addition, the control variables of the q-axis voltage controller are changed, which further improves the effect of overvoltage suppression. Finally, the correctness and effectiveness of the proposed method are verified by simulation.