Adaptive Impedance Design for VSG in Variable Speed Pumped Storage Hydropower Converters Under Strong Grids

This paper introduces a novel adaptive impedance control strategy for Virtual Synchronous Generator (VSG) systems in variable Speed pumped storage converters to enhance stability under strong grid conditions. Through detailed modeling of the grid-side converter (GSC) and VSG control, we identify instability risks associated with traditional methods, particularly in high short-circuit ratio (SCR) environments. Using root locus and impedance Bode analysis, the study demonstrates the limitations of conventional approaches in managing grid impedance variations. To overcome these challenges, we develop an adaptive control law based on Lyapunov stability theory, allowing real-time adjustments of virtual inertia and damping. Simulations confirm that the proposed method significantly improves stability, suppresses oscillations, and ensures robust performance across a wide range of SCRs, offering a reliable solution for the integration of renewable energy in modern power systems.