The operational control of the wind turbine,such as blade pitch control and/or speed control of the turbine rotor,is one of the useful methods to reduce the temporal variation of wind turbine output.For the optimization of the control method,the response of turbine performance has to be clarified with respect to the changes in operational condition.We have examined the effects of wake inertia on the response of turbine performance when the blade pitch and the rotor speed are temporally changed under stationary inflow condition by using numerical calculation.The calculated results provide relationship between the responses of the wake-induced velocities on the rotor plane and the aerodynamic performance.