Development of line-interactive dynamic voltage restorer with hybrid sag detection

This paper describes the development of a 3-phase line-interactive DVR with a new sag detection algorithm. The developed detection algorithm has a hybrid structure composed of an instantaneous detector and the RMS-variation detectors. The source voltage passes through the sliding-window DFT and RMS calculator, and the instantaneous sag detection part. If instantaneous sag is detected, the RMS variation detectors confirm whether the sag is real or not. The feasibility of proposed algorithm was verified through computer simulations and experimental works using a prototype of line-interactive DVR with 3 kVA rating. The line-interactive DVR with proposed algorithm can compensate the input voltage sag and interruption within 2 ms delay. The developed DVR can effectively compensate the voltage sag or interruption for the sensitive load, such as computer, communication equipment, and automation equipment.