Modeling and control of a wind-turbine-driven DFIG incorporating core saturation during grid voltage dips

Doubly-fed induction generator (DFIG) has been widely used in the variable-speed constant-frequency (VSCF) wind energy generation system. In traditional vector control scheme, the reduced DFIG model with both stator flux transients and the effect of flux saturation neglected was employed to simplify the rotor current inner-loop controllers processed by standard PI regulation, which can perform well in normal grid condition. However, once grid voltage dip occurs, the performance is degraded with rotor over current so as to deteriorate the fault-ride through (FRT) capability of the DFIG wind-energy generation system. In this paper, a complete mathematical DFIG model is proposed. The model taking into account magnetic saturation and its influence on the transient performance of the DFIG during grid voltage dips is analyzed. Finally, simulation was carried out on a 2 MW wind-turbine driven DFIG system. The validity of the developed saturated model and the influence of flux saturation on the determination of the transient performances of DFIG under grid voltage dip fault are all confirmed by the simulated results.