Abstract: The inverter interfaced distributed generator (IIDG) connected to the distribution network makes the traditional short-circuit current calculation method no longer applicable. The existing short-circuit current calculation for distribution network connected with inverter interfaced distributed generators, based on bus impedance matrix iteration, has two disadvantages-larger calculation amount and longer calculating time, especially when a fault occurs in the middle of the line. The authors, analyzing composite-sequence nets of faulted distribution network and considering the coupling relationship between PCC voltage and output current of IIDG, put forward a new method, which sets three-phase metallic short circuit with no IIDG connected to the system as initial value and uses direct iteration calculation. It is able to fast calculate inter-phase short circuit from IIDG connected to distribution networks because it does not need to generate and process bus impedance matrix and the number of nodes does not affect the calculating time. It is verified that this method is valid and efficient by comparing example simulation calculation with existing calculation methods.

    Key words: distribution network; short-circuit current calculation; inverter interfaced distributed generator; fault characteristic; composite-sequence net