Comprehensive Phasor Domain Short Circuit Analysis of Bulk Power Transmission Systems in Presence of Inverter-Based Resources

Phasor domain fault analysis of bulk power systems uses a linear model, where generators are represented as Thevenin equivalents and loads are neglected. However, due to the highly nonlinear, current-limited, and proprietary behavior of controllers dictating the response of renewable sources to faults in the power grid, this model breaks down. This paper significantly advances the state of research in this field by proposing a framework that can correctly perform short circuit analysis in bulk power grids for any penetration of inverter-based resources, without neglecting loads. Unlike previous methods that approximate the total fault current as sum of the contributions of all source currents, this framework uses the fundamental properties of bus impedance matrix to accurately determine the part of source current that actually reaches the fault. Additionally, in cases where the voltage fluctuations in two successive iterations are large, the proposed framework breaks down this large change into small changes, which solves the convergence issue reported in literature for faults electrically farther away from the source. The method is tested for accuracy, convergence, and scalability by comparing its results with results from time-domain simulations of faults on the IEEE 39-bus transmission system.