An Impedance-based Equivalent Method for Wind Farms with PMSGs to Evaluate Power System Oscillation Stability

In power systems, the large-scale wind farms integration poses new vibration stability issues. To ensure the efficiency of the calculations, the wind farm is replaced by a single unit for oscillation stability analysis in the literature always. It ignores the dynamic interaction within the wind farm and can lead to unreliable results, however. In this thesis, a wind farm with PMSGs is decomposed into a diagonal matrix with M blocks, which are equivalent PMSG subsystems, using the eigenvalue decomposition technique. PMSGs means M-coupled permanent magnet synchronous generators. Based on this, matrix perturbation theory derives a reduced-order impedance-based model for the wind farm, which can characterize the dynamic interaction within the wind farm. Intuitively, in the proposed model, a wind farm is represented by several equivalent PMSGs connected in parallel to two wind farms. Then, numerical simulations and hardware-in-loop experiments show that the proposed method can accurately assess the vibration stability margin of the integrated power system in wind farms. The proposed equivalent method significantly reduces the design effort and ensures its accuracy, which is suitable for real-time simulation of vibration stability analysis.