【作者】 邹旭东；

【导师】 康勇；

【作者基本信息】 华中科技大学 ， 电气工程， 2005， 博士

【摘要】 常规能源、电力紧缺及供电环境问题日益突出,利用可再生能源如风能,作为未来最重要的清洁替代能源之一,对于缓解能源匮乏具有非同寻常的意义。和常规风力发电系统相比,由于变速恒频交流励磁双馈风力发电系统配置的变频器在转子回路,仅处理双向流动的转差功率,不仅具有变频器体积小、重量轻、成本低的特点,而且实现了机电系统的柔性连接。本文围绕变速恒频交流励磁双馈风力发电系统及其相关控制技术展开研究。本文揭示了双馈发电机与普通异步电机和同步电机的区别和联系。建立了双馈发电机的等值电路模型,详细分析了双馈发电机中功率、转矩等关键物理量之间的相互关系。在此基础上,定性分析了双馈发电机运行特性、功率流动关系、稳态运行性能、静态稳定等问题。分析认为,在双馈发电机功率控制方式下各控制量之间的相互关系是复杂的、耦合是严重的。首次提出了三种适合双馈发电机分析和控制的复矢量模型,分析了三种复矢量模型之间的相互关系和适用场合。建立了双馈发电机在两相同步旋转坐标系下的数学模型,揭示了双馈发电机并网运行和独立运行在定子磁场定向控制策略下的内在统一和区别。重点研究了并网运行双馈发电机的控制目标、控制方式、运行特性和系统功率流动等关键技术及其实现方法,并依据内模原理,运用复矢量模型首次分析了系统耦合量的不同处理方式。研究表明,采用矢量控制可实现并网运行双馈发电系统定子端口有功和无功功率的解耦控制。分析了风力机捕获最大风能的运行原理,解释了传统的恒速恒频发电方式风能利用率低的根本原因。建立了风力机的数学模型,对基于背靠背电压源变换器,带风力机模型的并网型双馈发电系统进行了详细研究,指出采用最大风能捕获控制可实现系统有功功率、无功功率和转速的独立控制。并就实验室如何采用他励直流电动机模拟风力机输出特性曲线,分析了实现原理,建立了相关的数学模型,给出了相应的控制策略。常规待并发电机的端电压和电网电压存在差别时并网,对电网冲击的影响以及待并发电机如何获得同期条件进行了详细的研究。建立了双馈发电机空载并网系统的数学模型,研究了间接定子磁场定向控制策略。并针对常规并网方式中的先励磁后并网再切换控制策略的顺序,首次提出了双馈发电机直接并网方法,将常规的并网顺序改变为先并网后励磁,从而系统可直接工作在正常的发电模式,而无需控制算法的切换。降低了系统成本,大大简化了系统控制的复杂程度。本文研究了位置辨识与转速辨识之间的相互关系以及它们对控制系统性能的影响。通过辨识,只要知道转子位置就一定可以知道转速。换个思路,本文首次提出将更多还原

【Abstract】 With the lack of general energy source、electric power and the worsening of power supply circumstance problems increasingly,it is provided with very important meanings to partially solve energy lack by using renewable energy source such as wind energy as the one of the most important clear substituted energy source in the future. Comparison with the general wind energy generation system,because of equipped transducer of VSCF AC excitation doubly fed wind energy generation system located at rotor loop,it not only possesses the characteristics of small cubage、light weight and low cost but also realizes flexible connection of mechanical-electric system,which only deals with slip power in double direction. VSCF AC excitation doubly fed wind energy generation system and its control technology is studied in this paper. In this thesis,the difference and relation between the general asynchronous and synchronous motor and DFIG is opened out. The equivalent-circuit model of DFIG is established , and the interrelations of key physical parameters such as power 、electromagnetic torque are discussed. For this basis , issues about operational characteristics、power floating、static operation performance and static state stability are qualitative analyzed. It concludes that the interrelations of control parameters under power control mode of DFIG are complicated,and the coupling is serious. Three kinds of complex-vector models suited for DFIG to analyze and control are proposed for the first time,and the interrelations and applications situation of it are analyzed. Mathematics model of DFIG in the synchronous rotary coordinate is established,and the internal unification and difference between grid-connected and stand-alone DFIG controlled with stator-flux-oriented scheme is analyzed. The key techniques and realization methods of control target、control mode、operational characteristic and system power floating of grid-connected DFIG are mainly studied,and the different disposals of system coupling variables by applying complex-vector model based on Internal Model Control (IMC) theory are also analyzed. It concludes that the essential reason is by using vector-control to realize high performance and obtain decoupling control of active power and reactive power at stator port of DFIG. Operational theory based on maximum wind energy capture of wind turbine is analyzed,and the essential reason for low utilization-ratio of wind energy by using the traditional CSCF generation mode is explained. Mathematics model of wind turbine is established,and grid-connected doubly fed generation system by using back-to-back voltage-source converter with wind turbine model is mainly studied. At the same time,to realize independent control of system active power、reactive power and rotor speed by adopting maximum wind energy capture control is pointed out. Then,how to use separate-excitation DC motor to simulate output characteristic curve of wind turbine in the laboratory condition is supplied. Realization theory、mathematics model and relative control scheme is also given. The influence on impact of grid-connection and how to obtain synchronization condition while the general generator voltage is different from grid voltage is mainly studied. Mathematics model of DFIG no-load grid-connection system is established,and indirect-field-oriented control scheme is studied. Doing excitation before grid-connection then switching control scheme for the sequence of the general grid-connection mode,this paper proposals a direct grid-connection method for the first time. The new sequence is direct grid-connection before excitation so that system can directly operate in nature generation mode without switching control algorithm. It reduces system cost and greatly simplifies the complex degree of system control. The interrelation and the influence on control system performance of position estimation and rotor speed estimation is studied. If we know rotor position we can know rotor speed by all means according to estimation. Changing another thought,this paper presents a rotor speed estimation method of Model Reference Adaptive Control (MRAC) theory rotor-flux-based applying to position estimation system for the first time,design thoughts、stability and improving methods of it are also analyzed. It concludes that rotor speed estimation and position estimation can track the practical value at last,and is provided with definite robust ability but influenced on rotor initialization position. At the same time,it provides a new ideal for such systems with rotor position,namely can get estimated position by estimated rotor speed without estimating rotor position directly. This paper studies several important loops of system experiment. During the course of obtaining rotor position to use gray-code absolute-photoelectrical-encoder,a gray-code data-reference table is presented to simplify programmer design. A new method for rotor initialization position oriented suited for engineering application is presented for the first time. It is easily realized without considering connection mode of stator and rotor windings. To realize function of voltage space vector in rotor side,a mathematics model of connecting inductance to rotor port in rotor-side converter in the synchronous rotary coordinate is established. The structure and simplified condition of control system based on current control mode or speed control mode is mainly analyzed. Operation theory and realization method of stator-flux-angle in engineering based on digital phase-locked-loop (PLL) orreal-time numeration are presented respectively,and applications situation of real-time numeration is analyzed. A small signal model for stability analysis of DIFG system is established,and the influence on system stability caused by rotor position and current loop bandwidth is pointed out. In experiments,several different operational status based on current loop、current control mode and speed control mode of grid-connection and stand-alone in DIFG system sub-synchronous operation are mainly investigated. It concludes that experimental analyses are in accord with analyses in theory,and anticipative purpose is given.更多还原