Analysis and Enhancement of Transient Synchronization Stability for Grid-Connected VSG Considering Reactive Power Coupling and Fault Current Limitation

Existing studies has shown that fault current limitation and reactive power coupling can diminish the transient synchronization stability of virtual synchronous generators (VSG). However, there is limited literature that quantitatively analyzes these factors and proposes a comprehensive method considering the conflict between these two aspects simultaneously. To tackle this contradiction, this article investigates the intrinsic interrelationships between these two aspects using the phase model. It is revealed that there is a conflicting tradeoff between reactive power coupling and current limitation. Moreover, stable boundaries for the VSG are derived. Based on the stable boundaries, a practical transient stabilizing strategy with an adaptive reactive power droop coefficient is proposed, comprehensively integrating the transient stability, fault current limitation and reactive power coupling. Meanwhile, this strategy also ensures that the VSG maintains its voltage-source behavior during faults. Finally, the feasibility and effectiveness of the boundaries and the proposed control strategy are verified through experimental results.