Control system design for energy optimized Dynamic Voltage Restorer

Voltage deviations, often in the form of voltage sags, can cause severe process disruptions and result in substantial economic loss. The Dynamic Voltage Restorer (DVR) has been proposed to protect sensitive loads from the effects of voltage sags on the distribution feeder. The compensation capability of a DVR depends primarily on the maximum voltage injection ability and the amount of stored energy available within the restorer. In this paper a new phase advance compensation (PAC) strategy for the DVR is proposed in order to enhance the voltage restoration property of the device. The scheme requires only an optimum amount of energy injection from the DVR to correct a given voltage sag. Using the proposed method it can be shown that a particular disturbance can be corrected with less amount of storage energy compared to that of existing in-phase boosting method. In the end a closed-loop controller that consists of an inner current loop and an outer voltage loop is also incorporated into the DVR system.