中文摘要：

以兆瓦级直驱式风电机组为研究对象，进行叶片断裂事故发生后风电机组动态特性分析。通过将风轮载荷模型、机电耦合模型和变桨距控制等多个风电机组子系统模型进行集成，得到较完整的系统整体模型。在风轮载荷模型中，不但考虑气动载荷，也考虑惯性载荷和重力载荷等；变桨距控制充分考虑变桨距机构动力学特性。在Simulink环境下建立风电机组数值仿真模型，并假定叶片断裂后几秒内风电机组尚未停机进行仿真研究。研究结果发现，一个叶片断裂后，风轮旋转力矩出现突变，发电机电磁力矩快速响应风轮机械旋转力矩，风轮转速能控制在设定值附近波动；风电机组能量捕获与转换出现失衡，变流器直流电压、输入电网有功功率和无功功率等都出现大幅度波动，造成对电网的冲击。通过分析叶片断裂后风电机组动态特性，能够为风电机组结构设计、运行控制等提供有益的参考。

英文摘要：

Million watt scale directly-driven wind turbines are chosen as the study object and its dynamic characteristics are analyzed at the condition of a blade fracture accident happening. By integrating the wind rotor loads sub-model, electromeohanical coupling sub-model and pitch control sub-model, the system models of wind turbines are obtained. In the wind rotor loads sub-model, not only the aerodynamic force but also the inertia force and gravity force are considered; in the pitch actuator sub-model, the dynamic characteristics are considered. According to the established wind turbine models, the corresponding numerical simulation models are constructed in Simulink; the simulation is carded out assuming that wind turbines have yet to be stopped after a few seconds of blade fracture. The research results show that when a blade fracture happening, the wind rotor mechanical rotational torque mutates. Since the generator electromagnetic torque tracks quickly the wind rotor mechanical rotational torque, the wind rotor rotating speed remains near the given value. Furthermore, the energy capture and conversion of wind turbines is out of balance; the DC capacitor voltage, the active power and reactive power injected into the grid have dramatic fluctuations which has impact on the grid. Through the research, the dynamic characteristics of wind turbines are obtained when a blade fracture happening which can provide useful reference for wind turbine structure design, operation control, etc.