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1、摘 要摘 要风能作为可再生能源，受到了世界各国的关注。风力发电成为近年来发展最快的能源，在电网中的比重越来越大。交流励磁双馈电机变速恒频风力发电技术被认为是最有前景的风电技术方案之一，对此，本文从理论与实践上进行了深入全面的研究。本文建立了双馈电机在三相静止坐标系和同步旋转坐标系里的数学模型，推导并分析了双馈电机定转子之间的功率传递关系(有功功率和无功功率)。在此基础上，研究了双馈电机电网电压定向矢量控制策略，针对转子位置初始误差造成的转子电流矢量定向偏差降低矢量控制性能的问题，提出了一种补偿控制策略，可以在不需要知道转子初始位置的情况下，实现转子电流矢量的准确定向。结合风电系统并网控制的实际
2、情况，提出了双馈电机分段并网控制策略，给出了各个控制器的一种设计方法，并对各个阶段控制策略的切换问题进行了讨论，避免了因切换容易引起的冲击问题。双PWM变换器的控制技术是双馈电机变速恒频风力发电技术的核心，其中，网侧变换器为转子侧变换器提供恒定的直流电压，网侧变换器的控制性能关系到整个系统的稳定问题。为了提高网侧变换器的抗干扰能力，本文基于输入输出的功率平衡关系，提出了一种改进的前馈控制策略，增强了系统对于电网电压幅值变化（三相对称）和负载变化的抗干扰能力。将该控制策略的思想应用于双PWM变换器的协调控制，给出了计算电流环参考的具体办法。LCL型滤波器在大功率三相电压型PWM变换器中应用越来越
3、广泛。本文分析了LCL型滤波器在开关频率处各支路电流之间的关系，根据参数选择的约束条件推导出了一个方程组，将滤波器设计的各个约束条件转换为对方程求解的约束条件。提出了一种实用的设计方法，给出了程序式的设计步骤，大大简化了LCL型滤波器的设计过程。针对双馈电机风电系统无功功率的给定问题进行了研究。在分析双馈电机风力发电系统功率关系的基础上，提出了考虑网侧变换器无功发生能力时系统无功功率发生极限的计算方法。考虑网侧变换器在其功率允许范围内的无功发生能力，系统动态无功极限为定子与网侧变换器的无功极限之和。在此基础上，对双馈电机风电场无功功率分析及控制策略进行了研究。提出了强电网条件下双馈电机风电场对
4、当地用户进行就近无功补偿的策略，给出了相应的风电场无功功率分配原则。从而使双馈电机风电场在实现风电机组变速恒频优化运行的同时，充分发挥了整个风电场的无功处理能力，参与所连电网的无功调节。最后，对双馈电机高性能的矢量控制以及网侧变换器控制策略进行了实验研究。为此，本文研制开发了以双PWM变换器为核心的交流励磁双馈电机变速恒频风力发电系统的实验室模拟平台，对所提出的控制策略作了系统实验研究。该平台以双DSP为控制核心，可以实现系统的统一协调控制。关键词 风力发电；变速恒频；双馈电机；交流励磁；双PWM变换器-IX-AbstractAbstractWind energy has drawn worl
5、dwide attention for being renewable resource and wind power of today has become the worlds fastest growing energy. Penetration level of wind power into the grid becomes higher and higher. AC excited Doubly Fed Induction Generator (DFIG) Variable Speed and Constant Frequency (VSCF) wind power scheme
6、is considered as one of the most dominant schemes, on which this paper researches theoretically and experimentally. Mathematical model of DFIG in three-phase stationary coordinate system and synchronous coordinate system were made and power relationship between stator and rotor was analyzed, includi
7、ng active power and reactive power. Furthermore, grid voltage oriented vector control strategy was implemented to control DFIG. In order to compensate initial error of rotor position from the encoder, which may deteriorate performance of vector control, a controller was proposed and no initial posit
8、ion information is necessary for rotor current vector orientation. Applying the compensation controller to DFIG wind power generation system, stagewise control strategy was proposed for connecting DFIG to the grid. Overall controllers were designed and implemented and the problem led by switching be
9、tween different controllers was solved, which makes smooth transition of every stages.Successful control of dual PWM converter is most important for DFIG wind power generation system. As the front-end of dual PWM converter, grid-side converter provides constant DC link voltage for the rotor-side con
10、verter and makes great contribution to the stability of overall system. An improved feedforward control strategy was proposed based on the power balance between the input and the output. The proposed method can improve the robustness of grid-side converter to disturbances from both grid voltage ampl
11、itude fluctuation (symmetry) and load variation. Applying such a principle to the overall control of dual PWM converter, the method calculating current reference was derived.LCL type filter is commonly used in high power applications as grid interface of three-phase voltage source PWM converter. Bas
12、ed on relationship between currents through branches of the filter at switching frequency, a set of equations were got according to the constraints of the filter parameter selection. The design process of the filter becomes that of solving the equations. A novel design method was proposed and step-b
13、y-step design procedure was given, which makes the task very straightforward.Determination of reactive power reference of DFIG wind power generation system was investigated. A method is proposed to calculate the reactive power limit of the system based on the power relationships of overall system. C
14、onsidering the reactive power capacity of the grid-side converter, total reactive power includes that of both stator and the converter. Furthermore, reactive power analysis and control of wind farm made up of DFIG wind power generation unit were studied. A reactive power compensation strategy for th
15、e local user using DFIG wind farm was developed and the distribution algorithms of reactive power demand were given. With VSCF optimized operation of each generation unit, DFIG wind farm contributes to the reactive power regulation in the grid at its full reactive power capacity.Finally, for the pur
16、pose of experimental research on high performance vector control of DFIG and control strategy of grid-side converter, a simulation platform of AC excited DFIG VSCF wind power generation system was built, of which dual PWM converter is main part. With Dual DSPs as the heart of the control part, overall control strategy of the converter can be implemented.Keywords wind power; VSCF; DFIG; AC excitation; dual PWM converter目 录目 录摘要I
