【作者】 杨淑英；

【导师】 张崇巍； 张兴；

【作者基本信息】 合肥工业大学 ， 电力电子与电力传动， 2007， 博士

【摘要】 风力发电作为一种已获得商业化利用并具有较大潜能的可在生能源开发形式，近年来得到了较快的发展，其中变速风力发电技术尤其是双馈型变速恒频(VSCF)风力发电技术以其独特的优势而倍受关注。本文以国家“十一五”科技支撑项目(2006BAA01A18、2006BAA01A20)和安徽省“十五”科技攻关项目(040120564)为依托，在双馈型风力发电系统数学建模、驱动控制策略以及变流器的工程设计等方面进行了深入研究，并获得了一些具有创新价值的研究成果。本文主要研究内容可概括如下：1．建立了针对不同仿真目的和研究需要的双馈电机数学模型，并重点对双馈电机的磁饱和模型和戴维宁等效模型进行了研究。为了简化采用同步发电机对电网特性的仿真，提出了基于受控电压源和电压频率下垂特性对电网运行特性进行模拟的方法，降低了仿真运算量，提高了仿真效率。2．利用了双馈电机的“T”型等效电路对其运行控制机理进行了分析，在此基础上对双馈电机的定子磁链定向矢量控制策略和电网虚拟磁链定向矢量控制策略进行了深入研究，并提出了基于自适应谐振调节器的双馈电机控制方案，使得在无需对转子电流进行坐标变换的情况下实现了对双馈电机转子电流的无静差控制。3．探讨了双馈电机矢量控制系统的控制性能，并对定子磁链定向和电网虚拟磁链定向两种矢量控制系统的稳定性进行对比；针对双馈电机反电势扰动所形成的振荡过程，提出了“虚拟阻抗”控制策略，从而有效地改善了双馈电机矢量控制系统的动态抗扰能力；研究了双馈电机定子磁链的振荡及其抑制措施。4．采用了对称分量法对电网电压不平衡条件下双馈电机的运行特性进行了研究，并对有功功率脉动、无功功率脉动以及电磁转矩脉动之间的关系进行了探讨。重点研究了双同步旋转坐标系(双SRF)不平衡控制策略和单SRF不平衡控制策略，并且针对单SRF不平衡控制策略，首次分析了基于直接转子电压补偿控制方案的理论基础，并针对转子电压补偿控制与转子电流控制之间的耦合作用对系统控制性能的影响，提出了一种解耦控制方案，改善了直接转子电压补偿控制的控制性能。5．研究了双馈电机的无速度传感器控制策略。针对基于定子励磁电流的闭环速度观测方案和基于定子电压幅值的闭环速度观测方案均受双馈电机运行状态的影响且速度观测的动态增益受转子电流相位角影响之不足，提出了定子电流双回路和定子电压双回路两种闭环速度观测方案。在基于转子电流的模型参考自适应(MRAS)速度观测方案中，针对速度观测的动态增益与观测电流矢量偏差角之间的非线性特性，提出了基于转子电流偏差角的闭环速度观测方案，改善了系统的动态响应特性。6．剖析了双馈电机空载定子电压控制的机理，提出了基于PI调节器和谐振调节器并行的以及解耦的空载定子电压控制方案。7．描述了电网电压跌落时双馈电机的电磁过渡过程，并以数学模型对电网电压跌落时双馈电机定转子电流、定子磁链以及电磁转矩的动态响应特性进行了定量分析，讨论了转子电流的控制和电网电压的跌落类型对双馈电机电磁过渡过程的影响。在此基础上深入研究了双馈型风力发电机的低电压穿越(LVRT)控制策略。针对基于转子撬棒的LVRT控制策略，提出了一套完整的控制逻辑，实现了电网故障时风力发电机与电网之间的协调控制和双馈电机不同运行状态之间的平稳切抉；针对基于暂态磁链补偿技术的LVRT控制策略，提出了虚拟电感控制技术，削弱了LVRT控制策略对双馈电机漏感参数的依赖性，改善了双馈电机的LVRT控制性能：针对电网电压恢复时可能形成的电流冲击，研究了基于短暂中断(STI)技术的LVRT控制策略。8．搭建了多套不同功率等级、不同机组类型和不同试验目的的双馈型风力发电机实验室模拟系统，获得了一系列的试验结果。研究了对诸如风机气动特性、转动惯量及传输轴系的动态特性等风力机特性进行模拟的软件算法。尤其是建立了基于MW级“双馈电机对”拖动机组的实验室模拟系统，为大功率双馈型风力发电机的模拟试验提供了必要条件。针对“双馈电机对”拖动机组的起动与运行，研究了双馈电机定子短路转子驱动的矢量控制策略，较好的实现了双馈电机的起动控制和低速运行控制。9．阐述了用于双馈型风力发电机驱动的背靠背变流器之关键部件的工程设计。针对直流母线支撑电容的设计，依据直流母线电压的脉动特性，研究了转子有功功率阶跃响应和电网电压跌落时双馈电机转子有功功率的交流脉动对直流母线支持电容的设计要求：针对LCL滤波器参数的设计，依据网侧变流器交流谐波的特点和滤波要求，研究了LCL滤波器参数的优化设计方案；针对长线驱动du／dt滤波器的设计，依据波的反射机理，研究了几种变流器端du╱dt滤波器和电机端阻抗匹配网络的设计方案。10．设计了2MW双馈型风力发电机驱动变流器的试验样机，并完成了基于“双馈电机对”拖动机组的实验室模拟系统中的试验，且通过了某风力发电机专用试验平台的地面测试试验。更多还原

【Abstract】 As a renewable energy technology already commercially available and with great potential to be further exploited, wind power generation experienced fast development in the last two decades. Variable-speed wind-energy conversion systems (WECS), especially the doubly fed induction generator (DFIG) -based WECS attract big attention for their exclusive advantages. With the support of "The National Eleventh Five-Year Research Programme of China" (2006BAA01A18、2006BAA01A20) and "The Tenth Five-Year Research Programme of Anhui Provience"(040120564), a number of the key topics, such as modeling of DFIG-based WECS, driving control strategies, engineering design of the back-to-back converters, and so on, are studied in this dissertation. It is through these studies that some innovative results are achieved.The main contents of the dissertation can be summarized as:1. Different mathematical models of DFIG are derived for different purposes in simulation and research, and the stress is put on the model with flux saturation and the Thevenin’s equivalent model. In contrary to the complexity of the method of simulating the characteristics of the power grid by using synchronous generators, a method with less computation and higher efficiency is proposed to perform the simulation by controlled voltage source with frequency-droop and voltage-droop in accordance to its output active and reactive power respectively.2. The T-type equivalent circuit of DFIG is used to analyze its control mechanism, on which based the study on the stator-flux and the grid-flux-oriented vector control is carried out, and an adaptive resonant regulator-based control strategy, by which errorless control in steady state is achieved without any frame transformation for the rotor currents, is proposed.3. The performance of the vector control of DFIG is discussed, and comparison is made on the stability of the stator-flux and the grid-flux-oriented vector control strategies. To improve the disturbance-rejection from the back-EMF, a strategy of "virtual impedance control" for the DFIG controller is proposed. Analysis is done on the oscillation and its damping of DFIG’s stator flux.4. The symmetrical component method is adopted to study the behavior of DFIG under unbalanced grid voltage, and the correlations among the pulsations of the stator-side active power, reactive power and the electromagnetic torque are investigated. The unbalance control strategies are studied based on either the dual synchronous reference frame (SRF) or the single SRF. As one of the single SRF-based control schemes, the mechanism of the direct rotor-voltage compensation control is proposed and fully analyzed in the dissertation. To overcome the influence of the coupling between the rotor-voltage compensation and the rotor-current control, a decoupled control scheme is put forward, by which the system performance is improved.5. Several typical sensorless control strategies of DFIG are studied. The speed observation based on either the stator excitation current or the stator voltage are both affected by the DFIG’s operation modes, and the dynamic gains of both observers are also affected by the phase angles of the rotor currents. To overcome the above mentioned disadvantages, two speed observers, i.e. stator-current dual loop coordinated observer and stator-voltage dual loop coordinated observer, are proposed. And to overcome the nonlinearity between the dynamic gain of the speed observer and the deviation angle of the observed rotor current vector, for the rotor current -based model reference adaptive system (MRAS) speed observer, a deviation angle-based speed observer is proposed, consequently the system dynamic performance is improved.6. The mechanism of the no-load stator voltage control of the DFIG is analyzed, and two control approaches, one is based on a hybrid regulator composed of an adaptive resonant component and a PI component and another is based on a decoupled controller, are proposed.7. The electromagnetic transfer process of the DFIG during grid voltage dip is described, and the dynamic responses of the stator currents, rotor currents, stator flux and the electromagnetic torque to the grid voltage dip are quantitatively analyzed by modeling, meanwhile, the affection of rotor-current control and the types of the dip to the transfer process is discussed. Based on above study, several typical control strategies for improved LVRT performance of DFIG-based WT are further investigated. For the rotor-side crowbar-based LVRT control strategy, a set of control logic is put forward, with which the coordinated control between the WT and the power grid during grid fault and smoothly switching between different DFIG’s operation states are achieved. For the transient flux compensation-based one, a virtual inductance control scheme is proposed to relieve the dependence on the leakage inductance of DFIG and reach better performance. For the current surge, which maybe happens at voltage recovery, the "Short Term Interruption" (STI)-based LVRT control strategy is researched.8. Several sets of test benches, with different power level, different types of machine sets, and different experimental purposes, are built, and a series of experimental results are achieved. The software calculation method of WT’s dynamic behavior, such as wind turbine aero-dynamics, mechanical load moments, and gearbox and shafts dynamics, following which the prime motor is operated, is studied. Especially a test bench based on dual-MW-level DFIGs is set up, which is indispensable to simulating high power level DFIG-based WT. To meet the requirements of the start-up and low-speed operation of the drive system, rotor-side driving vector control of DFIG with its stator-side short circuit is researched, and good operation performance is obtained.9. The key parts engineering design of the back-to-back converters, driving the DFIG-based WT, is presented. For the DC-link capacitor design, the requirements to cope with load perturbation and the rotor-side active power pulsation during grid voltage dip are studied, according to the DC-link pulsation behavior. For the LCL filter design, the optimizing design schemes of the LCL filter are studied, according to the harmonic distribution in the AC side of the grid-side converter and the filtering requirements. For the long lead filter design, several converter-side du/dt filters and motor-side impedance matching networks are analyzed and designed, according to the wave reflection mechanism.10. A converter prototype, for 2MW DFIG-based WTs, is designed, with which the experiment has been taken on the dual-DFIGs-based test bench above mentioned. And the on-ground test on a dedicated test bench for WT has been accomplished.更多还原