With large-scale and high penetration level wind integration,stable and adjustable active power output of wind energy conversion systems like traditional power sources is an urgent requirement for the future power grid operation and dispatch.Active power control (APC) for wind turbines participating in automatic generation control (AGC) has become one of the highly-concerned issues in the main control strategy research of wind turbine.Existing APC methods mainly include the output power control base on the pitch angle control (PAC) and the rotor speed control (RSC).Base on the analysis on energy balance of wind turbine,the principles of the aforementioned APC strategies are summarized in this paper.Then,the performance of PAC and RSC are compared by simulations on the FAST (Fatigue,Aerodynamics,Structures,and Turbulence) code.Results show that RSC possesses a more stable active power output as compared with PAC.Because of the energy buffer of rotor inertia,the frequency and amplitude of pitch angle manipulation can be effectively reduced at low wind speed by RSC method.However,both methods require frequent pitch angle adjustment at high wind speed.It is also pointed out that the power reference exerts a significant influence upon APC performance.