Control of dynamic voltage restorer under voltage sag and nonlinear load

Abstract

In this paper, a nonlinear control scheme for dynamic voltage restorer (DVR) is proposed to reduce the voltage disturbances for loads under grid voltage sags and nonlinear loads. First, the nonlinear model of the system consisting of LC filter is obtained in the dqO synchronous reference frame. Then, the controller design is performed by using the sliding mode control, where the load voltages are kept almost sinusoidal by controlling the dqO axis components of the DVR output voltages. With this scheme, the power quality is significantly improved, compared with the conventional proportional-integral (PI) controller under grid voltage sags and nonlinear Ioads. Simulation studies are performed to verify the validity of the proposed method.