DFIG characteristics based line protection of active distribution network

The high permeability integration of the distributed wind power accessed to the traditional network, topological structure has changed from radialized to active. The amplitude and phase of the fault current are changed greatly and it is difficult for the traditional three-current protection to adapt this. By analyzed the fault transient characteristics of the doubly-fed induction wind generator (DFIG), used FFT algorithm to decompose the current waveform. The significant variation of the frequency characteristics of DFIG short-circuit current is got in this paper. According to the analysis above, a new line protection based on the current frequency difference was put forward in this paper. The new protection calculated the frequency by the way of instantaneous frequency calculation, and distinguished the fault area comparing the fault current frequency difference of both ends of the line. Based on the local power grid, the active distribution network simulation model was built in PSCAD, the simulation results show that the proposed method can operate correctly in different conditions and the protection scheme can be provided into complicate distribution network in the future.