Torsional oscillation characteristic and resonance analysis of the grid-following PMSG-based wind-driven system considering virtual inertia control

Most permanent magnet synchronous generator (PMSG)-based wind systems currently employ grid-following control, relying on a phase-locked loop (PLL) for grid connection. However, it leads to a lack of inertia support in the system. To address this, virtual inertia control (VIC) is essential for improvement, but it introduces new impacts on the grid-connected PMSG-based wind-driven system. The first impact is the deterioration of torsional oscillation damping. This paper establishes a small-signal model of the grid-connected PMSG-based wind-driven system using the damping torque method and small-signal analysis. It derives the transfer function of electromagnetic torque and speed difference considering VIC, explaining the mechanism and influence of VIC parameters on torsional oscillation damping characteristic. The second impact is the resonance between torsional, PLL, and low-frequency oscillations. This paper uses open-loop resonance analysis and eigenvalue analysis methods are employed to investigate the resonance mechanism between quasi-electromechanical timescale (QET) oscillations and predict the corresponding root locus using the residue method. Finally, the effectiveness of the theoretical analysis is validated through a simulation case study of PMSG-based wind-driven system connected to the four-machine two-area (FMTA) system using the SIMULINK platform.