Development of three-phase line-interactive dynamic voltage restorer with new sag detection algorithm

This paper describes the development of a three-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 detector-1 is selected to calculate the RMS variation. The RMS variation detector-2 is selected when the instantaneous sag occurs under the operation of the RMS variation detector-1. The feasibility of proposed algorithm was verified through computer simulations and experimental works with reference to 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.