Stability Improvement Method of VSC-HVDC Grid-Connected System under Weak Grid Based on SVG Impedance Reshaping

Currently, with the rapid development of power systems, reactive power compensators have become widely utilized in new energy grid-connected systems. However, this widespread use has introduced several stability challenges. To improve the stability and stability margin of new energy grid-connected systems with static var generators (SVG), an active damping control strategy is proposed. The output impedance of SVGs varies with the short circuit ratio (SCR) of the system. The output impedance models of SVG and voltage source converter-based high voltage direct current (VSC-HVDC) systems with the proposed control strategy are derived. Then, the efficacy of the proposed strategy in improving stability margin is analyzed based on the generalized Nyquist stability criterion (GNC). Finally, the simulation results in PSCAD/EMTDC confirm that the impedance reshaping strategy effectively enhances the interaction stability between the SVG and the weak grid.