NONLINEAR CONTROL OF THREE-PHASE FOUR-WIRE DYNAMIC VOLTAGE RESTORER UNDER GRID VOLTAGE SAG CONDITIONS

Tóm tắt

In this paper, a nonlinear control scheme based on backstepping theory for dynamic voltage restorer (DVR) is proposed to mitigate the voltage disturbances for loads under grid voltage sags. A nonlinear model of system with pulse-width modulation (PWM) voltagesource inverter (VSI) including the output inductor-capacitor (LC) filters in the dq0 synchronous reference frames is derived. The controllers of three-phase line-to-neutral load voltages in dq0 components are designed by nonlinear control theory. With the proposed scheme, the load voltage is regulated to reach the rated value and its waveform becomes almost sinusoidal, in comparison with the proportional-integral (PI) controller under grid voltage sags. Simulations are implemented to verify the validity of the proposed method.