Analysis and mitigation of subsynchronous oscillations in a radially-connected wind farm

Subsynchronous oscillations (SSO), especially, subsynchronous resonance are potential problems in series compensated power system. A fixed speed wind farm employing single cage induction generator (IG) and double cage IG connected to series compensated line are prone to SSR problem. This paper presents some investigations on SSO resulting from induction generator effect (IGE) with the wind turbine generator (WTG) modelled either as single cage IG or double cage IG. Eigenvalue analysis is carried out for various levels of series compensation for different sizes of wind farm with varying power outputs. Eigenvalue analysis is validated by the electromagnetic transient simulations using PSCAD/EMTDC software. The possibility of steady state SSR (IGE) and transient SSR is investigated in depth using PSCAD/EMTDC for the modified IEEE first bench mark (MFBM) model. SVC is employed for mitigating SSR. A new voltage regulator (VR) model of SVC is proposed and linear state space model of SVC is developed. Eigenvalue analysis conducted with the proposed voltage regulator reveals that the proposed VR model is more effective in mitigating SSR compared to VR models that are reported in the literature.