An Improvement of a Fast Single-Phase Voltage Sag Detection Method under Distorted Grid Voltages

A fast single-phase voltage sag detection method under distorted grid voltages is presented in this paper. The synchronously rotating reference frame (SRRF) is applied to the proposed single-phase voltage sag detection to gain fast and proper operation. In the park transformation, the set of 2 AC voltages are needed to generate the DC voltages that are varied with the grid voltages. These 2 AC voltages are the reference AC voltage and its perpendicular AC voltage. To accomplish this requirement, the differentiator is employed in the fast single-phase voltage sag detection to form the perpendicular AC voltage from acquired grid voltage. The original fast single-phase voltage detection can work well in the ideal grid voltages that without harmonic, however, it is unable to work in the distorted grid voltages. This paper proposed an improvement of a fast single-phase voltage sag detection which is able to use in the distorted grid voltages with fast and proper operation.