本文主要以变速恒频双馈异步风力发电机系统为对象，针对发电机系统控制策略、系统并网、故障下不间断运行及无速度传感器运行等问题开展理论及实验研究。在此基础上，先后研制成功首套国产化600kW和1.5MW的发电机系统样机，实现了系统的稳定并网运行。论文分析了变速恒频双馈异步风力发电机系统的数学模型和控制原理，重点研究了定子磁链观测问题。首次把改进电压模型方法应用到了双馈风力发电机的定子磁链观测中，改善了矢量控制性能；提出了基于全阶观测器的闭环磁链算法，该方法可以增强系统控制对发电机参数变化的鲁棒性。为了有效弥补发电机参数不准确对并网性能的影响，论文提出一种双馈风力发电机闭环软并网算法，该算法通过控制定子端电压准确跟踪电网电压来抑制并网冲击。此外，论文借助微积运算电路理论，深入研究了电网三相对称电压跌落故障对双馈异步风力发电机系统的影响，并根据理论分析结果，给出几种在电网三相对称电压跌落故障时系统的保护及不间断运行解决方案。为了提高变速恒频双馈异步风力发电机系统的运行可靠性，论文探讨了无速度传感器运行理论和相应的控制方法。提出一种开环无速度传感器算法，该算法实现简单，可以在整个运行过程中实现系统的无速度传感器运行，且具有良好的动态响应。在此基础上，进一步提出一种基于模型参考自适应方法的闭环无速度传感器算法，用以克服发电机参数变化对转速观测造成的不良影响。在权衡现有的双馈风力发电系统和转子斩波调阻系统各自优、缺点的基础上，提出一种新型低成本变速恒频风力发电系统，解决了混合控制中不同模式间的平滑过渡问题，实现了双馈矢量控制与斩波调阻控制的统一。该系统显著简化了转子交流励磁变频器的结构，可在较宽的转速范围内变速恒频运行。论文的理论分析和控制方法实验验证主要在实验室的7.5kW双馈异步风力发电机系统试验平台上完成，文中给出了大量仿真与实验的对比结果。结合风电设备国产化项目的要求，论文对大容量双馈异步风力发电机系统硬件设计和软件实现进行深入研究，自行设计了首套国产化600kW和1.5MW双馈异步风力发电机系统样机，完成了这些系统的现场地面调试及并网和满负荷运行试验。
In this dissertation, Variable Speed Constant Frequency(VSCF) Doubly-fed Induction Generator(DFIG) systems for wind turbines have been studied. Theoretical analysis and experiments have been done on the control strategies, synchronization, Low Voltage Ride-Through(LVRT), and speed sensor-less operation. Also high power VSCF DFIG systems for wind turbines have been implemented, and sychronazation and stable operation have been achieved.Firstly, the mathematic model of the generator system is established, and control principle of VSCF DFIG system for wind turbines is analysed. Moreover, the problem of stator flux observation is emphatically studied. The modified voltage model of flux observation is applied to stator flux observation of DFIG, and the performance of vector control is remarkably improved. In addition, a closed-loop stator flux scheme based on full order observer is presented and proved to be robust to the effects of parameter variation.To effectively decrease the negative influences produced by the inexact generator parameters in synchronization control, the thesis presents a closed-loop synchronization algorithm of DFIG systems for wind turbines, using stator voltage control method, to limit electrical impact when system is connected to the grid. Moreover, by using operational calculous circuit theory, how electric network symmetric voltage sags influence the generator system is analysed, and some system protection and ride though methods according to analysis results are given.In this dissertation studies have also been done on the speed sensor-less operation and its control principle to enhance the reliability of VSCF DFIG systems for wind turbines. The paper presents an open-loop speed sensor-less algorithm of good dynamic response and capable to realize control without encoder in full operation process. Further, it is presented that another closed- loop speed sensor-less algorithm based on Model Reference Adaptive System(MRAS) method to overcome the influence of parameter variation.A novel low cost VSCF induction generator system for wind turbine has been presented through comparing DFIG system and Rotor Current Control(RCC) system. The novel system can make smoothly transition among different operation model, and realize unification of doubly-fed vector control and RCC. The elaborately designed structure of the novel system can evidently reduce the hardware cost and the complexity of DFIG control. It is also able to regulate the active and reactive power output of the generator system respectively, and operate in wide speed range.The experimental validation of theory analysis and control method has been completed in the laboratory’s 7.5kW test system for research of VSCF DFIG systems. Numbers of comparison results between simulations and experiments are carried out and analyzed. By elaborately designing of the control hardware and software of high power system, the author has successfully developed first domestic 600kW DFIG systems and 1.5MW DFIG system according to the demand of real projects, and has completed field synchronization and full load experiments.
