Controller-Saturation-Based Transient Stability Enhancement for Grid-Forming Inverters

This article reveals that the saturation block (SB) used with the power-angle control loop can enhance the transient stability of grid-forming (GFM) inverters. Three methods of using the SB in the power-angle loop are examined based on power-angle curves. It is found that all can enhance the transient stability of GFM inverters by either decreasing the acceleration area or increasing the deceleration area. At the same time, the threshold value selection of SB in the three schemes is also explained, considering the tradeoff between the transient stability and the response speed. A holistic comparison of the three schemes recommends the scheme with the SB used for power error adopted by the GFM inverters. Finally, experimental tests confirm the effectiveness and correctness of the analysis.