Abstract: The Dynamic Voltage Restorer (DVR), which is the most efficient and effective modern custom power device used in power distribution networks to protect customers with an uninterrupted flow of energy at smooth sinusoidal voltage at contracted magnitude &frequency have large nonlinear loads, purity of the waveform of supplies is lost .this ends are producing many power quality problems from various disturbances of the power supply. this paper presents the study &analysis enhancement of power quality problems ,voltage sag& swells with the applications its by using proposed control DVR techniques used. At present, most of DVR use feed-forward control because of the compensation response time requirement, this kind of control may introduce steady state error and on-site calibration problems. discrete PWM-based control scheme is implemented, with reference to DVR. The aim of the control scheme is to maintain a constant voltage magnitude at the sensitive load point, under the system disturbance .simulation results show the capability of the DVR to control conditions.

Keywords: Dynamic Voltage Restorer (DVR), discrete pwm based control scheme, voltage sag, voltage swell, MATLAB.