Fault line selection method of DC distribution network based on transient current fault component

When a unipolar ground fault occurs in a medium-voltage flexible DC distribution network based on a two-level converter (voltage sourced converter, VSC)., the fault current will rise rapidly, and it is necessary to quickly find out the line where the fault occurs. In response to this problem, the unipolar ground fault at the VSC terminal is analyzed, and the variation characteristics of the transient fault current are analyzed and calculated. According to the difference of the transient fault current information of each line, the fault line selection method can quickly and reliably identify the fault within 3ms, and is particularly suitable for the radial flexible DC distribution network. Finally, a medium voltage flexible DC distribution network model was built in PSCAD/EMTDC, and MATLAB was used to verify the protection line selection algorithm. The simulation results show that the proposed line selection method can accurately achieve unipolar grounding of the flexible DC distribution network Fault line selection.