A new minimal energy control of the DC link energy in four-wire dynamic voltage restorer

The quality of electrical energy supply such as voltage sag is becoming more important for sensitive loads. This paper deals with four-wire dynamic voltage restorer (DVR), which is a series device that generates an AC voltage and injects it in series with the supply voltage through an injection transformer to compensate the voltage sag. In this paper the techniques of correcting the supply voltage sag in a distribution feeder is presented. In addition, a new concept of restoration techniques is proposed to inject minimum energy based on given apparent power for DVR during compensation. Simulation results carried out by PSCAD/EMTDC, show that the proposed method could be minimizing the injection real power of DVR with given apparent power.