Transient Stability Analysis and Damping Enhanced Control of Grid-Forming Wind Turbines Considering Current Saturation Procedure

The grid-forming wind turbine (GFM-WT) is prone to transient instability during grid fault, due to the control switch of current limitation. However, the existing work ignores the transient instability issues caused by current saturation procedure, failing to fully reveal the instability mechanism. To deal with the problem, this article analyzes the current saturation procedure of GFM-WT after grid faults. It is pointed out that there exist two current saturation conditions, i.e., the current saturation mode instantaneously (CSMI) and the current saturation mode subsequently (CSMS). Then, the transient stability of GFM-WT is analyzed considering above new operational modes. It indicates that the transient characteristic of power angle will be reshaped during current saturation procedure. Based on it, a damping enhanced control method is proposed to improve the transient stability, by damping the power angle overshoot during current saturation procedure. Finally, the analysis and proposed control method are verified by the experiments.