A Novel Detection Method for Voltage Sags

Determining the start and end of the voltage sag event is very important for sag analysis and mitigation. There are several detection methods for voltage sags in which sag voltages are usually expressed in the terms of RMS. The RMS method represents one cycle historical average value, not instantaneous value which may lead to long detection time when voltage sag has occurred. This paper will proposed a novel voltage sag detection method based on miss voltage technique. Proper dead-band and hysteresis are used in the method. The actual instantaneous voltage is compared with certain percentage of desired grid voltage and certain percentage of the amplitude of the grid voltage. Through instantaneous value comparison, low instantaneous value of the grid is shielded which overcome the mishandling turnover of voltage sags. The approach is fully described, and the results are compared with other methods for marking the beginning and end of sag, such as RMS value evaluation method and Peak-value method and simulation result provides that the method is efficient and fast and can be used to determine the initiation and recovery of voltage sags accompanied by missing voltage technique.