Quasi-Electromechanical Oscillation Analysis of VSG Grid-Connected System Based on Small-Signal Model

VSG is a pivotal control strategy for GFM, designed to enhance the damping and inertia of power systems, thereby bolstering their stability. Despite its benefits, VSG can induce a QEO due to dynamic interactions between the GFM and the power system. This QEO, is different from control issues, contrasts with the EO associated with conventional SG, which is rooted in electromechanical factors. To address this phenomenon, the influence mechanism of VSG on QEO of the system is studied. First, a comprehensive control model for the VSG is established and its efficacy in providing damping and inertia is assessed. Subsequently, a small-signal model for the VSG when connected to the grid is developed. Utilizing this model, the system’s characteristic roots and the trajectories of principal state variables, elucidating the impact of VSG control parameters on QEO are analyzed. The validity of the models and the underlying mechanisms are confirmed through extensive simulations. Furthermore, for the key problems that need to be solved urgently in the application of VSG in power system with renewable energy, further thinkings are prospected.