Transient Stability Analysis of Wind Turbines with Induction Generators Considering Blades and Shaft Flexibility

Increasing levels of wind turbine generation in modern power system is initiating a need for accurate wind generation transient stability models. Long flexible blades maybe have influence on the transient responses of wind generator systems with the increase in size of wind turbines during an electrical fault. In order to exactly analyze the transient stability of wind generator systems, by using the equivalent lump mass method, a three-mass wind turbine equivalent model is proposed considering both the bending flexibility of the blades and the torsional flexibility of the drive-drain shaft between the wind turbine and induction generator. Combined with the electrical transient models of a grid-connected squirrel cage induction generator, the transient behaviors of the wind turbine system are simulated during a three-phase fault. The results of transient stability analysis are also compared with the traditional two-mass shaft model and one-mass lumped model, respectively. In addition, the effects of the different bending flexibility and inertia constant ratio of blades and hub on the transient stability of large wind turbines are also analyzed. The results have shown the three-mass equivalent model including both the blades and shaft flexibilities may be more appropriate to accurately analyze the transient stability, and the parameters of the blades stiffness and inertia constant ratio of blades and hub have an important effect to the transient stability of wind turbine systems.