Abstract: The problems of voltage sag detection of the industrial park distribution network after a large number of DGs were analyzed.The detailed design research based on the positive-negative sequence separation method of multi-dq coordinate rotation transformation and the S-transform method was carried out.Finally,in order to verify the correctness of the method,a simulation model was built in MATLAB/Simulink.The results show that the positive and negative sequence separation detection method based on multi-dq coordinate rotation transformation meets the real-time requirements of voltage recovery control,which lays a theoretical foundation for engineering design.

Key words: voltage sag, multi-dq coordinate rotation transformation, S-transform, dynamic voltage recovery