Short-circuit Sequence Network Model of DFIG with Different Slips

The contribution of doubly fed induction generator (DFIG) to ac system short-circuit current can not be ignored with large wind power integrations. The traditional methods, which neglect the influence of DFIG or take DFIG as a load, are inevitably to introduce error in short-circuit current calculations. In this paper, analytical formula of DFIG short-circuit current under voltage dips is derived based on a mathematical model. The sequence network models of DFIG with different slip speed are developed and can be implemented in short-circuit calculation program. Simulations in Matlab/Simulink verify the accuracy of the proposed models of DFIG. It is demonstrated that DFIG with larger slip we can adopt the constant impedance model of induction motor, while the model with transient potential and transient reactance is suitable for the DFIG with smaller slip.