Impact of large scale wind farm integration on power system transient stability is studied in this paper. The transient stability mechanism of wind turbines based on doubly-fed induction generator (DFIG) is analyzed theoretically. Then the dynamic model of wind turbines based on DFIG is used to study the impact of wind power integration on the transient stability of the grid

and the comparison of different impacts on the grid transient stability is conducted between the wind turbines based on DFIG and the substituted synchronous generator with same capacity in the same connection point. The digital simulations verify the theoretical analysis. It is concluded in the paper that the wind farm integration based on DFIG into the power system is better than that of synchronous generation units at a same point in the power system as far as system transient stability is concerned.