A new detection method of voltage sag based on period phase concept

A new definition of period phase of voltage is put forward, which resets the phase of voltage to zero when the waveform crosses zero with rising edge, after that it will count the phase of voltage by accumulating mode at each sampling point. With detection method based on the definition above, the phase and amplitude of voltage can be easily deduced, and the voltage sag can also be judged exactly in most cases. For the detection of phase and amplitude of voltage after sag, two-point approach is proposed. The detection methods introduced in this paper have the advantages such as easy to realize and calculate, and quick dynamic response. The methods apply to the voltage detection of three-phase and single phase DVR. Simulation and experimental results verify the validity of the methods.