随着风力发电的大规模并网运行，风力发电机组的稳定运行对电网安全尤为重要。本文以双馈异步风力发电系统为对象，针对系统并网后的动态稳定性和故障穿越问题进行了研究。对双馈发电机系统的数学模型和控制策略进行了总结和比较，依托国家科技支撑计划的支持，参与研制了一套1.5MW双馈异步风力发电机用变流器，并将其应用在实际运行的兆瓦级双馈异步风力发电机组上，实现了系统的长时间稳定运行。深入分析了双馈发电机系统并网运行时的小扰动动态稳定性问题。分别对定子磁链定向和定子电压定向两种矢量控制策略对双馈发电机系统稳定性的影响进行了研究，建立了包含双馈电机转子电流及矢量控制调节器动态的双馈发电机系统高阶小信号模型，采用“定子磁链恢复因子”的概念对定子磁链定向双馈发电机矢量控制系统的动态稳定性进行描述，得到了系统稳定边界的解析描述。通过对简化模型的解析推导和复杂模型的数值计算，详细分析了弱电网下定子电压定向双馈发电机矢量控制系统的动态稳定特性，采用“等效线路电抗”的概念对基于锁相环的定子电压定向双馈发电系统的失稳机理进行了解释。对电网电压长期不平衡和暂态电网电压跌落两种异常工况下双馈发电机系统的稳定运行问题进行了研究，提出了相应的控制策略。基于对称分量法建立了不平衡电压下双馈发电系统的数学模型，对负序电压引起的有功和无功脉动进行了分析。在此基础上，提出了基于比例谐振（PR）调节器的正序电网电压定向双馈发电机及网侧变流器的矢量控制策略，对控制效果进行了仿真和实验验证。为实现电网电压深度跌落时双馈风力发电机系统不脱网运行，提出了一种双馈发电机定子绕组并网时的变流器再投入控制策略，并以该控制方法及有源Crowbar技术为基础，设计了双馈发电系统的低电压故障穿越控制策略。此外，本文还对用于双馈风力发电机测试试验的对拖方案进行了分析和试验研究，设计了基于四种起动策略的双馈电机对拖试验系统，完成了1.5MW和2MW大功率试验平台的建设和投运。

With increasing wind power penetration, the stability characteristic of wind turbine is particularly important to power grid security. In this dissertation, doubly fed induction generator (DFIG) systems for wind turbine have been studied. Special efforts have been given to the stable operation and fault ride-through of grid- connected DFIG systems. Firstly, the mathematic model and control strategies of the DFIG system are summarized and compared. With the support of China Key Technologies R&D Program, the author participates in the development of a 1.5MW DFIG converter applied in a MW-class variable pitch variable speed wind turbine operating stably in wind farm site for a quite long period.An in-depth analysis on the small signal stability of grid-connected DFIG systems is given. The influences of two types of vector control strategies, stator flux oriented (SFO) and stator voltage oriented (SVO), are studied, and the high-order small signal dynamic model of DFIG system including the dynamic of the rotor current and vector control regulator is presented. The stability of the SFO DFIG system is investigated by a so-called “stator flux recovery factor” method, and the analytically stable region is obtained. The stability condition of the SVO DFIG system is obtained from the analytically derivation of simplified model and numerical simulation of detailed model, and the instability reason of DFIG system based on phase-lock-loop (PLL) can be explained by a so-called “equivalent line reactance” concept.The stable operation and control strategy of DFIG systems under two abnormal conditions, long-term unbalance of grid voltage and transient voltage drops, are studied. The model of DFIG system under unbalanced voltage is presented based on the symmetrical component theory, and the impact of negative sequence voltage on the active and reactive power pulsations of wind turbine is analyzed. According the analysis results, a novel positive-sequence voltage oriented DFIG vector control strategy based on proportional-resonant (PR) regulator is presented. Simulation and experimental results of the proposed method are given. In order to achieve fault ride-through of DFIG systems during the grid voltage drops, a novel control method is given for the re-starting of DFIG converter when the stator windings are connected with power grid. Based on the proposed method and active crowbar technology, the DFIG fault ride-through method is presented.The doubly fed back-to-back motor drive system used for DFIG testing platform is investigated by theoretical analysis and experiments. Four starting methods are considered, and a 1.5MW and 2.0MW doubly fed motor drive systems are developed.