In order to analyze the transient dynamics of power system with grid-connected wind farms

an accurate transient model of wind turbine is the foundation of the research work. According to the structure of the wind turbine

the mechanical transient model is divided into three parts

i.e.

aerodynamic model

rotor and tower dynamics model

and drive-train model. The classical method of theoretical mechanics is proposed to analyze the three parts

taking into account of the mutual influence among subsystems link

the model interface is modified and the mechanical subsystem model is proposed. A 3 MW doubly-fed wind turbine model is built with MATLAB/Simulink. After linearization of the model

the root locus is extracted with Control System Toolbox

and the main factors affecting the stability of drive-train speed is figured out. Finally

in comparison with conventional mechanical transient models

simulation is carried out in time domain

and the results validate the model higher precision. This work is supported by National Basic Research Program of China (973 Program) (No. 2012CB215200).