Impacts of Interactions between Grid-forming and Grid-following VSCs on Stability of Hybrid System Connected to Weak Grid

This paper investigates the effects of interactions between grid-forming and grid-following Voltage Source Converters (VSCs) on the stability of a hybrid system connected to weak grid. Initially, the stability analysis model and the interaction analysis model for the hybrid VSCs connected to weak grid are developed. The self-impact and interaction-impact components are delineated to quantify the degree of interaction between grid-forming and grid-following VSCs. Subsequently, the self-impact and interaction-impact components of VSCs are integrated with participating factors analysis. By exploring the magnitude-frequency characteristics of the interaction components under various operating points and control parameters, the analysis not only tracks the migration of system eigenvalues but also elucidates the underlying physical mechanisms driving these changes. Specifically, the impact of the interaction between grid-forming and grid-following VSCs on the hybrid system's stability is traced to the energy exchange and phase coupling between their core synchronization control loops through the weak grid impedance. Finally, the aforementioned analytical results are corroborated through both simulation and experimental validation.