A hybrid synchronously rotating reference frame-based voltage sag detection under distorted grid voltages

A hybrid synchronously rotating reference frame (HSRRF)-based voltage sag detection is proposed in this paper. The proposed method provides the fast and accurate voltage sag detection even in the distorted grid voltage environments. A hybrid algorithm is used to improve the performance by a combination of the instantaneous voltage sag detection part and the synchronously rotating reference frame (SRRF)-based voltage sag detection part. If any instantaneous voltage sag is detected and the voltages from SRRF-based voltage sag detection part decreases to the reference value, then the completed voltage sag condition is recognized. This proposed voltage sag detection provides a shorter detection time in every condition when comparing to the conventional methods. The validation of proposed algorithm is confirmed through the computer simulations which are operated in the distorted grid voltages with various conditions of the voltage sag.