Research And Development Of DC Dynamic Voltage Restorer

The production lines equipped with variable frequency drives(VFD) require increasing high quality of electric power supply.When voltage sag occurs in power systems,VFD may be tripped off thus may affect the reliability of production lines.This thesis systematically studies the impact of voltage sags on VFD,and analyzes the working principles and existing measures for the voltage sags mitigation.An ultra-capacitor based DC dynamic voltage restorer is proposed,and the corresponding main circuits and the control circuits are designed. An ultra-capacitor array capacity optimization method and the ultra-capacitor charging-discharging control method are proposed.When the motor is in the constant proportion of voltage to frequency control,simulation and experimental on DC dynamic voltage restorer are carried out.Experiment results show that the proposed method can support the inverter DC bus voltage,and reduce the impact of voltage sags on VFD effectively.