Voltage Control Based on Energy Regulation for Electrolytic Capacitorless PMSM Drives

The energy buffering ability of the DC-link capacitor is weak in the electrolytic capacitorless system, so that the control of antiovervoltage and the voltage sag ride-through is difficult. In this paper, a DC-link voltage control strategy based on energy regulation is proposed. In the case of overvoltage, the DC-link voltage is stably controlled by regulating the q-axis current to prevent energy flow on the DC-link capacitor, and the braking rate is accelerated by the loss controller. When the grid voltage sags, the q-axis current is regulated to recover the kinetic energy of the motor to extend the time of the DC-link voltage at the preset value. The effectiveness of the proposed method in the grid voltage sag and different load conditions is verified in the simulation model of the electrolytic capacitorless system.