Transient Stability Analysis for Grid-Forming Inverters Transitioning from Islanded to Grid-Connected Mode

This paper addresses the transient stability of grid-forming (GFM) inverters when transitioning from islanded to grid-connected mode. It is revealed that reconnection GFM main grid can be equivalent a step change active power reference, whose impact closely related with local load, reference inverter, and short-circuit ratio (SCR) grid. Such disturbance may cause lose synchronism To avoid loss synchronization, existence equilibria inverter after reconnecting it examined, considering varying SCR. Then, parametric effects controllers on are characterized by using phase portraits, which shed clear insights into controller design for reliably Lastly, all theoretical findings confirmed experimental tests.