Mitigation of voltage sags in a distribution system due to three phase to ground fault using DVR

Abstract

Voltage sags defined as short-duration reductions in the rms voltage on one or more electrical phases are becoming the most important power quality concern to electric utility customers with sensitive loads. They are characterized by their magnitude and duration (which is typically 0.5 to 30 cycles). Sags are predominantly caused by faults that are unavoidable on the distribution systems due to the interconnectivity of the utility systems. The distribution-class dynamic voltage restorer (DVR) is a series connected power electronics device which can compensate for distribution system sags and swells. By enhancing the voltage, the DVR can increase the availability of sensitive loads. For a successful compensation, the DVR must be able to detect the voltage sag and control the inverter to restore the voltage. The sliding mode control is used for the DVR. Using sliding mode control to the DVR, additional sag detection method is eliminated. This improves the dynamic response of the DVR and also DVR is able to compensate for any variation in source voltage. In this paper, a DVR with sliding mode control strategy is used to alleviate the voltage sags caused due to faults occurring on the parallel feeders in a single-phase distribution system. The DVR along with the other parts of the distribution system are simulated using MATLAB/SIMULINK.