As wind speed varies randomly,intermittentlySand uncertainly in the wind farm,wind turbines maximum power outputStracking control can be achieved by regulating rotor speed according to the wind.Base on the analysis abc three-phase axis model of brushless doubly-fed generator (BDFG),the α-β two-phase static axis equations of the winding voltage were derived,and the Euler-Lagrange model of BDFG were construted.The passivity of the electrical subsystem and mechanical subsystem of BDFG were analysed from the energy viewpoint.The passivity-based controller was designed to regulate the speed of BDFG.The flexible damping was added into the controller to improve the system dynamic response and reduce the interference from parameter variations in control system.Modeling on Matlab/Simulink platform and contrasting with vector control and constant damping,the passivity-based controller with flexible damping could faster track the desired value ofSspeed and have better robustness and dynamic performance.