Short-circuit calculation approach of grids with high proportion of inverter-interfaced generator stations

• A short-circuit model for the IIGS under decoupled sequence control is proposed, which takes into account the nonlinear fault characteristics differences among units within the station caused by active power inconsistency. • Node voltage equations for the fault total content are established based on the composite sequence network. • A short-circuit calculation approach based on the secant method for solving node voltage equations has been proposed to address the convergence issues of traditional iterative methods under weak grid conditions. In short-circuit calculation for grids with a high proportion of inverter-interfaced generator stations (IIGSs), the single-unit multiplication model for IIGS can result in significant calculation errors, and the common iterative method can not guarantee convergence in weak grids. First, to improve the accuracy of short-circuit analysis, a short-circuit model of IIGS under decoupled sequence control (DSC) is proposed in this paper, which considers variations in the fault characteristics between units by cluster aggregation calculation. Secondly, to address the convergence issue of iterative methods under weak grid conditions, a node voltage equation-solving method based on the secant method is proposed. The node voltage equations are derived from the fault composite sequence network. Finally, case studies verify the accuracy of the short-circuit calculation model of IIGS and the short-circuit calculation approach.