Enhanced Transient Stability of Grid Forming Inverter with Modified Active Power Loop during Symmetrical Voltage Sag

Grid Forming Inverter (GFMI) is one of the promising solutions to provide inertia and maintain stability, especially in low inertia grids. To protect the inverter from large currents during the disturbance, the current is limited. During disturbances such as voltage sag, power becomes uncontrollable, which depends on the level of sag and maximum current rating of the inverter. This uncontrollable reduced power may lead to the power angle instability. Existing methods improve the stability by varying the damping coefficient and inertia transiently. These methods rely on the fault detection and switching mechanism. This paper proposes a Modified Active Power Loop (MAPL) to enhance the power angle stability with constant inertia and damping coefficient without fault detection and switching mechanism. To improve the dynamic performance during fault recovery, Finite Control Set - Model Predictive Control (FCS-MPC) is designed in this paper with current limiting capability.