Dynamic aggregation of doubly-fed induction generators (DFIGs) for stability analysis of wind power systems

The doubly-fed induction generators (DFIGs) are widely applied in wind power conversion. The wind turbines are operated under speed control or power control, and suffered from wind disturbance or network contingency. Full expression of each DFIG involves many differential equations and lots of calculation effort. Dynamic equivalence is valuable to improve the calculation efficiency for the wind power systems. A dynamic equivalence method is presented for the DFIGs in this paper. The wind speed and power coefficient are aggregated by the control modes differentiating the wind speed below or over the rated value. The wind turbines, the drive trains, the induction generators, the converters and the control systems, are given by the capacity-weighted mean values. The wind disturbance and the network contingency are applied to validate the equivalence error. The terminal voltage, the active and reactive powers of the wind farm, the rotor power angle and the frequency of the synchronous generators before and after aggregation are compared, showing desirable accuracy and calculation efficiency.