An Optimization-Based Approach for Evaluating Short-Circuit Currents in Power Systems Accounting for Inverter-Based Resources

Abstract

The increasing penetration of inverter-based resources (IBRs) is changing fault behavior in modern power systems, thereby reducing the accuracy of conventional short-circuit calculation methods. This paper proposes a nonlinear optimization-based framework for short-circuit current evaluation that explicitly incorporates the current-limiting behavior of IBRs. To enhance computational performance, a differentiable current-limiting model for IBRs is introduced. By replacing conventional piecewise formulations with smooth transition functions, this approach enhances both numerical stability and algorithmic convergence. The proposed method is validated on a modified IEEE 39-bus system and benchmarked against the iterative short-circuit method proposed by IEEE Working Group C-24. Simulation results demonstrate numerically stable and computationally efficient performance, achieving solution times of less than three seconds for the modified IEEE 39-bus system.