• This paper develops an improved kinetic energy control method to mitigate output power fluctuations. A low pass filter is introduced to generate the output power smoothing reference. • A fuzzy logic controller is designed to generate the difference coefficient for balancing wind turbine stability and power generation efficiency. • The setting principles of important parameters in the control strategy are discussed, such as the filter time constant and delay time interval. • Experiments are carried out to make up for the lack of experimental verification in this research direction. The output power of wind energy conversion system (WECS) fluctuates randomly due to the intermittence of wind speed, which will endanger the power quality and the stable operation of the grid. This paper develops an improved kinetic energy control method to mitigate output power fluctuations. In this method, a low pass filter is introduced to generate the output power smoothing reference. A fuzzy logic controller is designed to generate the vacancy coefficient for balancing wind turbine stability and power generation efficiency. The proposed method has the advantage in precisely tracking the smoothing command and reducing dependence on energy storage devices. Additionally, the setting principles of important parameters in the control strategy are discussed, such as the filter time constant and delay time interval. The direct-drive permanent magnet synchronous generator based wind energy conversion system (PMSG-WECS) is modeled both in the simulation and experiment platform to verify the effectiveness of the proposed power smoothing strategy.