Environmental issues and restriction in using of fossil fuels have led to develop renewable energy resources. One of the significant renewable sources which are clean and almost available around the world is wind energy. High penetrated wind farms in power systems can cause reduction of total system inertia and stiffness of the frequency response to the disturbance and short circuit. Consequently it is expected that wind farms are gradually used in load frequency control (LFC) with changing in their performance. Nowadays Doubly Fed Induction Generator (DFIG) due to their particular structure is used in the wind turbines. Kinetic energy that is stored in the rotational masses can be used during load disturbance by shifting to deloaded extraction curve by considering the restriction for the rotor speed of DFIG. Several simulations are carried out to demonstrate the benefits of wind farm contribution in frequency excursion in Maximum power point tracking (MPPT) and deloading area.Using PI fuzzy logic controller (PIFLC) instead of PI conventional in layout of wind farms has been caused to improve frequency behavior and consequently changing in the rotor speed and injected active power by wind farm will be decreased noticeably. Membership function patterns used in the structure of fuzzy logic controller (FLC) will be considered according to optimize one objective function such that this includes different parameters for description of frequency behavior. In order to obtain an optimal performance the genetic algorithm (ABC) is used to determine membership functions parameters. The physical and engineering aspects have been fully considered and to demonstrate effectiveness of the proposed control scheme, a time domain simulation is performed on the power test system. Finally the results are compared with PI conventional for serious load disturbance in terms of frequency behavior, changing in rotor speed and injected active power by wind farm.