Research on voltage sags detection method based on delay small angle dq transform

Voltage sag is one of the most serious problems of power quality. For its compensation, the detection speed and accuracy of the characteristic values of amplitude, phase jump, duration is crucial. A new characteristic values calculation method is proposed in this paper. Firstly, two-phase orthogonal voltage vector is obtained through variable angle single phase voltage. Secondly, virtual three-phase voltage is constructed by the orthogonal voltage vector, and then the characteristic values are calculated through abc to dq transformation. At the same time, the mathematical morphology filter is utilized with better real-time in the link of low-pass filter. Compared with Butterworth low pass filter, the mathematical morphology filter has the advantage in voltage sag detection. Finally, a detection model is built using PSCAD, it is found that the proposed method has better performances of faster response property and higher accuracy in sag detection compared to other detection methods, which can meet the requirements of real-time compensation of DVR.