Steady state characteristic analysis and stability assessment of doubly fed induction generator based wind power generation System

Based on the mathematical model of doubly fed induction generator (DFIG), this paper analyzed its steady state characteristics and presented the analytic expression of electromagnetic power of DFIG with stator voltage, rotor voltage and the angle between these two voltages as input variables. It has been shown that the DFIG has an extensive stable operation region and all the operating points are stable. By linearizing the DFIG model, stability assessment of stator-flux-oriented system and stator-voltage-oriented system were performed comparably by using small signal stability analysis scheme. It is concluded that the stability feature of a stator-flux-oriented system is impacted by the rotor exciting current, which will restrict the reactive power provided by the rotor. However, for a stator-voltage-oriented system, its stability is independent of the rotor current. Consequently, it is possible to provide as much reactive power as possible while the system keeps stable.