A Novel Soft-start Method for SVG Based on D-axis Orientation

摘要

In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,and reliable.When the uncontrolled rectification stage ends,a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation,then the signal is transmitted to the three-phase inverter bridge.The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid.The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value,then the soft-start resistor is removed,which means the shock-free soft-start process is completed.Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper.