Power Flow-Based Estimation of Short-Circuit Currents From Inverter-Based Resources

The generator side of inverter-based resources (IBRs) interfaced with back-to-back converters is electrically decoupled from the grid. During electrical faults, grid-following IBRs behave as voltage-dependent current sources due to grid code requirements and converter control. This paper presents Newton-Raphson formulations for estimating short-circuit currents from IBRs using novel power flow modeling approaches to address voltage-dependent current sources. The work shows how to represent <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq0</i> current injections, which are typically implemented in control architectures based on phase-locked loops. The power flow formulations are adapted to capture grid codes with different characteristics, such as the injection of negative-sequence currents during unbalanced faults. Comparisons against a field-validated electromagnetic transients (EMT) model reveal mean absolute errors of less than 0.5% for the proposed approach when estimating steady-state short-circuit currents from type IV wind turbine generators under grid-following control.