Need for Load Modeling in Short Circuit Analysis of an Inverter-Based Resource-Dominated Power System

Short circuit models of transmission networks have not commonly included loads. The reason is that the fault current from synchronous generators are many times higher than the load current and highly reactive, and hence omission of load current does not reduce the accuracy of short circuit results. Nevertheless, this modeling practice may no longer be appropriate to an inverter-based resource (IBR)-dominated grid or grid region; the fault current of an IBR is comparable to load current and, depending on inverter terminal voltage, can have a considerable active component. This article studies the impact of load modeling on fault analysis of IBR dominated grids. Specifically, the paper identifies potential simulation inaccuracy issues caused by lack of load modeling under IBRs and provides considerations to reduce the error and increase the fidelity of short circuit results. If these inaccuracies are not addressed, they may impact the behavior of protection relays in the simulation and risk incorrect protection relay configurations. This is turn could create risks of relay misoperation or failure to operate during power system disturbances.