【作者】 肖运启；

【导师】 徐大平；

【作者基本信息】 华北电力大学（北京） ， 热能工程， 2008， 博士

【摘要】 随着常规能源短缺和环境污染问题加剧,风能作为可再生绿色能源,对其开发利用十分必要。变速恒频双馈型风力发电系统具有转子励磁变频器容量小、成本低,机电系统柔性连接,风能捕获能力强等特点,成为目前风电开发的主流机型,其交流励磁控制技术也成为重要的研究方向。受国家自然科学基金项目“大型变速风力发电混杂系统全工况优化运行控制策略研究(项目号: 50677021)”的资助并作为该课题部分内容,本论文在广泛分析国内外有关资料的基础上,重点研究了变速恒频双馈型风电机交流励磁控制和优化运行技术,并在网侧变换器控制方案、最大风能追踪控制方案、变频器系统建模方法等方面进行了改进,主要研究内容及创新成果如下:1.分析了风电用交直交变频器的系统结构、控制目标和数学模型。为提高有功电流的实际响应速度,增强母线电压抗扰动能力,在传统的网侧变换器直接电流控制方案的基础上,创新的提出了一种应用模糊控制器将单位功率因数和母线电压稳定综合考虑作为无功电流参考设定的方案。仿真表明新方案有效。2.分析了双馈发电机的运行原理、等值电路、功率特性和数学模型。为研究变速恒频运行中双馈发电机稳定性变化规律,应用小扰动分析法,得到发电机对象在典型工况点上的线性模型加以分析,结果表明双馈发电机对象在正常工作转速范围内都具有稳定性,并且在由亚同步或超同步向同步速变化的过程中,稳定性变化趋势一致。3.分析了风力机的功率特性和风力发电系统运行区域及控制目标。建立了双馈发电机双闭环矢量控制系统,研究了功率控制模式和转速控制模式下发电机系统的调节原理和动态特性。针对已有的最大风能追踪方案在稳态和动态性能上存在的问题以及风速测量的不准确性,创新的提出了一种新型模糊最优转速追踪控制方案,将转速、功率和风速变化量都作为模糊控制器输入,以增强模糊推理应对渐变风速的能力。模拟自然风速激励下的仿真结果表明,新方案提高了机组低风速运行区域风能捕获能力。此后,为实现发电机最低损耗运行,根据双馈发电机损耗特性与无功功率的关系,提出了一种应用模糊控制器进行最优无功设定的方案,仿真结果表明此方案能够自适应发电机系统参数摄动而保持最低损耗运行,提高了发电机的运行效率。4.结合风力机变桨距控制,分析了双馈风电机准同期并网、自同期并网和零功率解列控制策略。仿真验证了机电系统协调工作对提高机组并网和解列控制水平的作用。5.分析总结了常规风电机组对象建模仿真方法。针对应用Matlab/Simulink/PSB对交直交变频器建模仿真存在运算量大、耗时长的问题,创新的提出了一种交直交变频器系统简化模型,既能够合理反映变频器系统工作原理和外部特性,又具备运算简洁高效的特点,适合于风电机组系统级控制策略的仿真研究。接下来,研究了双馈发电机跨并网全过程建模仿真方法,为并网控制策略有效性验证提供了仿真平台。更多还原

【Abstract】 Due to continually diminishing reserves of normal energy sources and environment pollution, it is very necessary to develop wind power as its renewable and clean characteristic. Variable-speed constant-frequent (VSCF) wind power generation system with doubly-fed induction generator (DFIG), that excited by inverter located at rotor loop, possesses characteristics of smaller capacity, lower cost, flexible connection of mechanical-electric system, higher wind power capturing capability. Therefore, it becomes the mainstream developing type, and its AC-excitation control technology becomes an important research direction. Supported by the National Science Foundation of China Project ’Research on optimizing control strategy overall operating condition for variable wind turbine hybrid system (NO: 50677021)’ and as a part of it, this thesis studies AC-excitation control and optimal operation technology for VSCF doubly-fed wind turbine based on the full analysis on the references from domestic and aboard. Improvements on net-side converter control strategy, the maximum wind energy capturing control strategy and converter system modeling method are taken; primary contents and original contributions of this thesis can be summarized as follows:Firstly, system structure, control targets and mathematic model of AC/DC/AC converter employed by wind power generation are analyzed. Aimed at improving active current tracking speed and enhancing DC-bus anti-disturbance ability and based on the ordinary direct current control strategy for net-side inverter, a novel control strategy with a comprehensive reactive current adjusting target of both power factor keeping and DC-bus voltage maintaining, using fuzzy logic controller, is originally proposed. Simulation results indicate its efficiency.Secondly, operation function, equivalent-circuit model, power relation and mathematic model of DIFG are analyzed. In order to study DIFG stability characteristic during VSCF operation, the small disturbance analysis method is adopted to establish and study DIFG linear models on several typical operating points. Results show that DIFG is stable in normal operating speed range, and has the same stability varying trends as operating from sub-synchronize or sup-synchronize to synchronize speed.Thirdly, power characteristic, operating field and control target of wind turbine are analyzed. DIFG double closed-loop vector control strategy is established; regulating principle and dynamic characteristic in active power control mode or speed control mode is discussed. To solve the problems of stable and dynamic control ability excited in the normal maximum wind energy capturing strategies, and wind velocity measuring inaccuracy, a novel fuzzy optimal speed tracking strategy is originally proposed, in which variations of rotating speed, generation power and wind velocity are input into fuzzy logic controller together, in order to enhance fuzzy deduction efficiency for wind that gradually changed. Simulation results with natural wind model indicate the wind generation capturing ability improvement of the novel strategy, during the operating field that below rated wind velocity. After that, aimed at the lowest loss operation for DIFG, an optimal reactive power reference control strategy using fuzzy logic controller is presented, based on relation between loss characteristic and reactive power of DIFG. Simulation results indicate its effectiveness for adopting DIFG characteristic varying, maintaining lowest loss and improving operating efficiencyFourthly, considered with wind turbine pitch control strategy, cutting-in and cutting-out control strategies for DIFG are analyzed. Simulation results validate the effect on improving operating performance by mechanical and electric corresponding action.Fifthly, normal modeling methods for wind power generation system simulation are summarized and analyzed. As AC/DC/AC converter model built by Matlab/Simulink/PSB library blocks needs lots of time for calculation during simulating, a novel simplified model of AC/DC/AC converter system is originally proposed. It can not only discribe the work principle and outer characteristics of the converter system reasonablely, but also save calculating time, which is suitable for simulation in wind power generation system level. After that, a modeling method for DIFG whole process simulation across cutting-in operation is discussed and accomplished, which supplied a simulating platform for cutting-in control strategy validation.更多还原