Coupling Mechanism Analysis and Stabilization Improvement for Hybrid System With GFL and GFM Converter Under Grid Faults

The dynamic coupling between grid-following (GFL) and grid-forming (GFM) converters, as well as their interaction with synchronous generators (SGs), may have a significant influence on the control characteristics of renewable energy converters and the operating modes of SGs during grid faults. This coupling complicates the transient synchronous stabilization of hybrid power systems. This study focuses on the hybrid system integrating GFL with GFM converters. Initially, an equivalent mathematical model is developed based on the synchronous mechanisms of different power sources. Subsequently, using the phase plane and space vector diagram methods, the interactions among various power sources and their effects on the transient stabilization of the system are analyzed. Finally, a collaborative strategy for improving transient synchronous stabilization is proposed. This approach involves adjusting the current and the power reference values of the GFL and GFM converters, respectively, to maintain the equilibrium points of each power source approximately constant before and after grid faults. As a result, it minimizes the dynamic interaction between power sources and enhances the overall transient stabilization of the hybrid system under the voltage dip scenarios.