Fault analysis of microgrid and adaptive distance protection based on complex wavelet transform

With the development of microgrid technologies, the impacts brought by distributed generation (DG) on the distribution network protection has not been improved effectively. Therefore, this article analyzed the fault characteristics of IBDG (inverter-based distributed generations) and that of microgrid composed by IBDG; built the simulation model of IBDG with P-Q control and that of IBDG with U-F control, as well as simulation models of microgrid under islanding operation mode and grid-connected operation mode, analyzed the fault characteristic while different faults occured in transmission line. They all provide a basis for microgrid protection. In a microgrid composed by IBDG, fault current magnitude cannot be used to determine the fault and the use of Fourier algorithm will cause frequency leakage. Thus, an adaptive distance protection algorithm based on an improved wavelet algorithm for digital filtering is proposed. At last, this article built the coordination optimization model and got the relay setting value using ant colony algorithm. The action time of the relays in general is shortest.