Abstract：The traditional fault calculation method in the case of distribution network with multi-point Tconnected inverter interfaced distributed generator（IIDG）has the problems of complicated calculation process and large calculation amount. Therefore，a fault calculation method for new distribution systems with T-connected IIDG was proposed. Firstly，according to the type of power supply，the fault network of distribution network was divided into two types：the subnets with traditional units and the branch subnets with IIDG. Secondly，in order to avoid the huge amount of calculation caused by the nonlinear components in the system，the virtual voltage source method was used to perform regional iterative calculation on the branch subnet to determine the output of IIDG. Finally，the IIDG in the distribution network was replaced by the equivalent constant current source，and the system fault characteristic values satisfying the accuracy requirement was obtained by linear variation method. The simulation results show that the proposed method is correct and effective，and it simplifies the solution process of fault characteristics quantity in the new distribution system with IIDG under the premise of ensuring the calculation

accuracy，and greatly shortens the solution time.

      Key words：new distribution system；inverter interfaced distributed generator（IIDG）；fault characteristics；

virtual voltage source；equivalent constant current source；region iteration