Small Signal Stability Analysis of Grid-Following Inverter-Based Resources in Weak Grids With SVGs Based on Grid Strength Assessment

Recently, the increasing penetration of the renewable energy generation, i.e., inverter-based resources (IBRs), is challenging the grid operation. Besides, static var generators (SVGs), due to its high flexibility and controllability, have been widely-used in renewable energy generation for providing voltage support. However, the strong interaction among grid-following IBRs and SVGs may cause serious small signal stability issues, especially in weak grids. To ensure the secure operation of modern power systems, it is important to analyze the small signal stability of grid-tied IBRs with SVGs. This paper proposes a short-circuit ratio (SCR) based method for quantifying small signal stability of a single-IBR infinite-bus system (SIIBS) with a SVG located at arbitrary bus, in which SCR is a metric for quantifying small signal stability of a SIIBS from the viewpoint of grid strength. Furthermore, the key factors for the impact of a SVG on the stability of a SIIBS are investigated from the viewpoint of grid strength. Simulation results based on MATLAB/Simulink verifies the efficacy of the proposed SCR- based method.