Transient Synchronization Stability of Grid-Following Converters Considering Nonideal Current Loop

The widely deployed grid-following converters (GFLCs) may lose synchronization under grid disturbances, presenting a critical challenge to the power electronics penetrated power grid. Existing methods for analyzing transient synchronization stability often assume an ideal current loop in order to keep the system model at low order. However, such approaches based on a simplified second-order model can lead to optimistic stability prediction and inappropriate design. This article applies a full-order model to explore the effects of the nonideal current loop. The unstable periodic orbits (UPOs) that determine the basin of attraction of the stable equilibrium point are located via a numerical continuation method. Moreover, the essential bifurcations leading to the emergence and disappearance of  UPOs are identified. A design principle with consideration of the effects of the nonideal current loop is derived to enhance the transient synchronization stability of GFLCs. Experimental results are provided to verify the analytical findings.