Power Angle Estimation-Based Control Strategy for Operation of Grid-Forming Converters in Very Weak Grids

Paper in proceeding, 2025

Power converters can operate stably with adequate angle stability margins when connected to strong grids. However, under very weak grid conditions - characterized by a low grid short-circuit ratio (SCR) and limited power transfer capacity - the transient stability deteriorates significantly. Specifically, when the SCR drops below 1, the converter may lose its equilibrium operating point, leading to transient instability if nominal power injection is enforced without adaptive control. To mitigate this issue, this paper proposes an enhanced active power control (APC) strategy for grid-forming (GFM) converters. This method integrates realtime grid power angle estimation to dynamically adjust both the active power setpoint and converter frequency, ensuring improved transient stability and sustained synchronization during severe SCR drops. The effectiveness of the proposed approach is validated through experimental results.