Modeling of Grid-Forming Inverters for Transient Stability Simulations of an all Inverter-based Distribution System

Existing models of grid-forming inverters are typically three-phase electromagnetic models and positive sequence electromechanical models. Neither of them is suitable for dynamic simulations of large-scale three-phase unbalanced distribution systems. In order to investigate grid-forming inverters' impact on the transient stability of large-scale three-phase unbalanced distribution systems, a dynamic model of a grid-forming inverter is developed and implemented in an open-source GridLAB-D simulation environment. The advantage of this method is that it can be extended to full-size three-phase unbalanced distribution systems. Simulation results of an all grid-forming, inverter-based, modified version of the IEEE 123-node distribution system verify the capability of grid-forming inverters to maintain the transient stability of a resilient distribution system.