Calculation of Power Grid Partition Short-circuit Current With Negative Sequence Voltage-supported Distributed Generation

With the high proportional inverter-interfaced distributed generation (IIDG) connected to the power grid, the short-circuit current calculation considering the influence of the IIDG is faced with serious challenges. In order to overcome the shortcomings of the existing short-circuit current calculations in dealing with the high proportional IIDG power grid, a power grid partition short-circuit current calculation considering the negative sequence voltage support capacity of the IIDG during the faults is proposed in this paper. Firstly, the necessity of active negative sequence voltage support during the low voltage ride through of IIDG is analyzed, the positive and negative sequence output characteristics of IIDG during the voltage drop are analyzed, and a controlled current source model of the fault equivalent sequence component is established. According to the distribution characteristics of IIDG in the power grid, and based on the multi-regional Norton equivalence and node tearing method, the large-scale power grid is divided into multiple subnets and main power grids containing the IIDG. The equivalent port output current of each subnet is obtained by the iterative method, and the current is transmitted to the main power grid. According to the injected currents, the main power grid solves the short-circuit current by the iterative method. Through the interface information interaction between the subnets and their main power grid, the fast short-circuit current calculation of large-scale power grid with high proportional IIDG under the negative sequence active support strategy is realized. Through calculation and comparative analysis, the advantages of the proposed algorithm in convergence speed are verified over the traditional global iterative calculation with the IIDG. The accuracy of the calculation is verified by the PSCAD simulation. © 2023 Power System Technology Press. All rights reserved.