This paper emphasizes voltage sag as one of a power quality concern and Dynamic Voltage Restorer (DVR) is using for mitigation of voltage sag. DVR is a custom power devices that most operative and efficient. Consequently, the determination of this project is to study how the DVR functions during compensating of voltage sag. The distribution network has been a selection of as a sample to study the DVR system. This network consists of two feeders, and each feeder connected to the balanced load. A fault has been applied to one of the feeders. Then, voltage sags occurred at another feeder. Matlab Simulink was chosen as the software to simulate the system. Mathematics model for calculation of voltage sag, and voltage injection by DVR System also labelled.The effect of power devices, different circuit topologies, and constraints of components was discussed. The result of the simulation was recorded and discussed while the conclusions and recommendations of this project were done.

Keywords : Dynamic Voltage Restorer, Voltage Sag, Power Quality (PQ), Voltage Sag Compensation, Voltage Source Inverter (VSI).