Considering the fluctuation of wind power in seconds exerts an influence on the frequency stability of power grids

it is required to smooth the output power of wind turbine generators. Currently

the wind turbine-depended methods for smoothing wind power usually lead to frequent pitch adjustment

therefore

a power smoothing control method coordinating the rotor speed and pitch angle regulation is proposed. By separating the upward and downward regulation of pitch angle

the conventional constant-speed(upper speed limit)control is redesigned as the rotor speed range control so that the variable-speed operation at any pitch position is available and the kinetic energy buffer of wind rotor can be more adequately used to smooth wind power fluctuations. Correspondingly

while guaranteeing the smoothing effect

the proposed method can effectively reduce the frequency and amplitude of pitch actions

and alleviate the pitch servo fatigue and blade stress. Finally

the proposed method is verified by the wind turbine simulator based experiments.