This paper describes a new controller of active power to improve the power system transient stability, using active wind power based on a doubly-fed induction generator (DFIG). In order to balance demand and generation, any deficit or excess of power system will be compensated by the DFIG, a Field-oriented control is used to control of the power flow exchanged between the DFIG and the power system. The rapid controllability of injected active provided by wind turbines is used to improve the transient stability. A simplified wind turbine model based on power injection is proposed in this paper. The transient stability is examined with numerical simulations based on relative rotor angles criteria. The Critical Clearing Time is used as an index for evaluated transient stability. In order to demonstrate the interaction between the wind turbine and the transient stability improvement, proposed methodology is tested in the WSCC3 nine-bus system connected to a wind farms in the case of three-phase short circuit fault on one transmission line for different energy margin injected in power system.