Stability analysis of parallel virtual synchronous generators and suppression of low-frequency oscillations

Abstract With the increasing penetration of power electronic devices in power systems, virtual synchronous generator (VSG) technology has garnered widespread attention for its ability to provide inertia and damping support to the grid. However, while simulating the external characteristics of synchronous generators, this technology also introduces inherent rotor oscillation issues. Particularly in multi-machine parallel operation, insufficient system damping can easily lead to low-frequency oscillations, threatening system stability and equipment safety. To address this issue, this paper first establishes a small-signal model for multi-VSG parallel grid connection. Subsequently, a Phillips-Heffron model tailored for multi-VSG parallel structures is constructed, revealing the fundamental cause of system oscillations under disturbances. Building upon this foundation and drawing inspiration from traditional power system stabilizer design principles, a virtual power system stabilizer control strategy tailored for multi-VSG parallel grid-connected systems is proposed. Finally, the proposed control strategy is validated through MATLAB/Simulink simulations. The simulation results demonstrate that, compared to conventional control methods, the proposed VPSS control strategy effectively suppresses low-frequency oscillations in the system, significantly enhancing overall stability.