Synchronization Stability Enhancement Methods for Grid-Forming Converters with Current Limiters

Grid-forming (GFM) converters are envisioned to provide essential services to enhance the stability of future power electronics-defined power systems. A physical limitation of power electronics is their low overcurrent capability, leading to the development of current limiting control for GFM converters. However, the use of current limiters restricts the power transfer capability of GFM converters and makes them more prone to losing grid synchronization during severe disturbances. Many methods which aim to enhance the synchronization stability of GFM converters with current limiters have been proposed. This paper reviews several of these methods and examines their efficacy in three types of common grid disturbances: frequency drops, voltage sags, and phase jumps. The methods investigated in this paper are chosen to represent the two main categories: control loop modification methods and feedback signal modification methods. It is found that the control loop modification methods maintain synchronization during all three types of disturbances by minimizing frequency deviation through the provision of extra damping, while the feedback signal modification methods can improve synchronization and exhibit faster recovery if appropriate disturbance-related terms are introduced as feedback signals.