Abstract: In order to study the coupling between the wind turbine power and each link of the unit and the influence on the output power of the unit,a double-fed wind turbine is used as an example,Firstly,the energy functions of each subsystem are derived taking into account the tower shadow effect,wind shear and wind speed. Then,the energy variation of each subsystem and the oscillation characteristics of the unit output power are analyzed considering the damping of the turbine and wind speed variation. Finally,the power propagation mechanism and power oscillation characteristics of wind turbine are analyzed through energy changes on the PSCAD/EMTDC platform. The simulation results show that the energy of each subsystem increases greatly when the low frequency oscillation power of the turbine passes through the negatively damped DFIG. The output power of the turbine contains low frequency oscillation and sub-synchronous oscillation,and the amplitude and frequency of oscillation vary with wind speed and damping of the turbine. The energy consumed by the DFIG is mainly determined by the wind turbine subsystem when the wind speed changes.