Short circuit network equivalents of systems with inverter-based resources

Large transmission networks are often represented with short circuit network equivalents to share with neighboring utilities and distribution providers. The computation of network equivalents for short circuit studies is straightforward in systems predominantly based on conventional synchronous generators (SGs). However, the integration of renewable powered plants such as solar and wind parks (WPs) introduces inverter-based resources (IBRs) in the grid with different and nonlinear fault current characteristics. The increasing share of IBRs changes the way power systems respond during disturbances. The application of conventional approach to obtain network equivalents based on the computation of Thevenin equivalent at the point of interest to systems with high share of IBRs will result in misleading short circuit calculations. This paper is the first step in the identification of active nonlinear network equivalents for short circuit studies in systems with IBRs. A new concept of voltage dependent network equivalents (VDNEs) is proposed. Considering the increasing complexity of networks with several and different type of IBR installations, a measurement-based approach using simulated fault currents is proposed to obtain VDNEs. The short-circuit response of VDNEs are validated considering a network with WPs consisting of Type-IV/Full-Size Converter (FSC) wind turbine generators (WTGs).