Abstract: The decoupling control of doubly-fed induction generator（DFIG）based wind turbine determines that its active power output has no way to respond to frequency changes of the power grid.When the wind power penetration continues to rise,the frequency modulation pressure of power grid will also increase.In order to make wind power better serve grid frequency modulation when it is incorporated into the power grid as a new frequency modulation power source,a coordinated primary frequency modulation strategy between DFIG-based wind turbine and synchronous generator is proposed based on variable coefficient.The variable coefficient of DFIG-based wind turbine is defined and set in different operating modes,so that it can determine the frequency modulation output according to the current spare capacity.By coordinating the frequency modulation output between DFIG-based wind turbine and synchronous generator,the dual goal of reducing the frequency adjustment pressure of synchronous generator and the amount of abandoned wind can be realized to keep frequency deviation within the allowable range.Simulation results show that the frequency modulation strategy presented can make the reserved active power of DFIG-based wind turbine participate in frequency regulation more fully while effectively reducing the pressure of power grid to a great extent.