Advanced Control Strategy of Dynamic Voltage Restorers for Distribution System Using Sliding Mode Control Input-Output Feedback Linearization

Abstract

In this paper, a nonlinear control scheme for dynamic voltage restorer (DVR) under grid voltage sags and nonlinear loads is proposed to mitigate the voltage disturbances for loads. First, the nonlinear model of the system consisting of LC filter based on a feedback linearization technique is obtained in the d-q synchronous reference frame. Then, the controller design of the linearized model is performed by employing the sliding mode control, where the load voltages are kept constant by controlling the d-q axis components of the DVR output voltages. With this scheme, the power quality is significantly improved, compared with the traditional methods with the PI controller under grid voltage sags and nonlinear loads. Also, the system cost and power loss of the proposed DVR is significantly minimized thanks to the use of a smaller number of power switches (four-switch three-phase inverter) with a lower rating voltage without degrading the compensation performance of the DVR. Simulation studies are performed to verify the validity of the proposed method.