Per-phase Phasor Modeling of GFL and GFM Inverters for Distribution System Dynamic Studies

A significant increase in inverter-based distributed energy resources (DERs) is expected in the near future. Existing electromagnetic models and sequential electromechanical models of DERs supporting dynamic analysis cannot be extended to largescale three-phase distribution systems usually with unbalanced construction. As such, there is a need for appropriate industry models that can support distribution system dynamic studies. This paper describes the latest phasor models of grid-following (GFL) and grid-forming (GFM) inverters that can capture distribution system dynamics under grid disturbances. The overall modeling performance is examined by test cases including setpoint changes, balanced and/or unbalanced grid faults. The derived models can retain high accuracy with normalized root mean squared errors (NRMSEs) less than 3%, as verified by comparison with controller hardware-in-the-loop (CHIL) testing, MATLAB/Simulink phasor model and/or PSCAD electromagnetic transient (EMT) switching model simulation results.