大型双馈风电机组故障穿越关键技术研究

发布时间：2018-12-28 21:47

【摘要】：大规模风电接入电网给电网安全运行和管理带来了较大的挑战。为此，新的电网规范要求风电机组应保证具备故障穿越（Fault ride through, FRT）能力。因此，研究风力发电故障穿越的问题具有重要的理论和实际意义，关系着风力发电进一步发展，是风力发电大规模并网运行的关键技术之一。在众多的风力发电拓扑结构中，由于双馈风电机组具有的诸多优点和良好的运行性能，其一直占据着世界风电市场的主要份额，是国际风力发电机组研制的主流技术之一。然而，和其他结构的机组相比，双馈感应电机（Doubly fed induction generator, DFIG）风电系统的故障穿越能力最具挑战性。主要是双馈感应电机定子绕组直接接入电网而导致的对电网故障尤其是电压故障特别敏感和有限的变换器容量造成的。因此，改善双馈风电机组故障期间的瞬态行为以满足现代电网所提的故障穿越要求正在成为广泛关注的焦点，具有重要的理论和实际意义。当双馈风电机组遭受对称电压跌落时，为满足双馈机组故障穿越要求需要解决的两个主要问题是双馈电机转子过电流和变换器直流母线过电压。而这直接威胁着变换器的安全和双馈机组的不间断并网运行。而当电网电压发生不对称跌落故障时，除了故障严重时出现过电流外，更多关注的是双馈电机输出有功无功以及电磁转矩中的二倍频振动问题和直流侧纹波问题。因此，本文针对上述热点问题进行了全面、深入、系统地研究，主要完成的工作和取得的成果为： 1）基于空间矢量的表征，完成了双馈感应电机在两相αβ自然坐标系和dq同步旋转坐标系下的数学建模，及其转子侧和网侧变换器及其控制策略在同步坐标系下的建模。在电力系统专用仿真软件PSCAD/EMTDC的环境中，搭建了完整的更精确的双馈风力发电机组仿真平台，用于仿真验证所提故障穿越方案的有效性和可行性。 2）利用定子（静止）坐标系下双馈异步电机的空间矢量数学模型，在不同程度和不同类型的电压跌落故障（不对称故障主要包括单相对地和两相短路故障）情况下，对双馈感应电机的瞬态行为（定子磁链瞬态、转子开路电压瞬态和转子电流瞬态）进行了具有一般意义的理论分析。尤其是对转子故障电流进行了更为详细的研究，考虑了不同频率电压分量在转子回路中造成的阻抗的差别以及转子侧变换器输出电压对转子故障电流的影响，推导出了转子故障电流在对称、不对称电压故障条件下的精确表达式，并通过仿真验证了该表达式的正确性，并讨论了影响转子故障电流表达式准确性的因素。通过这些简单明了地分析，揭示了制约双馈感应风力发电机故障穿越运行的机理，为双馈机组寻求合适的故障穿越方案奠定了理论基础。 3）从控制策略的角度出发，基于转子侧变换器传统矢量控制技术，研究了不同电压前馈补偿项对双馈风电机组故障穿越能力的影响，并简化了前馈补偿项中瞬态磁链的评估方法，解决了考虑定子瞬态特性后需评估定子电阻的问题，而定子电阻的评估通常是很困难的。考虑到双馈异步电机具有的非线性特性，，线性的控制策略在电压跌落时系统性能恶化的问题，研究了典型非线性控制策略——滞环控制器在改善双馈机组故障穿越性能方面的效果。事实上，从能量平衡的角度出发，故障期间双馈电机定转子过电流产生的原因是故障期间出现的能量不平衡造成的。因此，为了缓减故障期间能量的不平衡，从而提高双馈机组的故障穿越能力，研究了减载增速的双馈机组故障穿越方案。仿真验证了上述策略在改善双馈机组故障穿越能力方面具有的各自的特点和优势，这些策略均能够不同程度的提高双馈机组的穿越能力。最后，分析了变换器对双馈机组穿越能力的影响。 4）研究了crowbar电路保护技术、主要包括不同旁路电阻对系统的影响评估以及阻值的优化，比较了crowbar电路不同控制策略对双馈机组故障穿越的影响以及crowbar电路保护技术存在的问题。针对双馈机组故障期间在crowbar电路保护下存在的过速问题，研究了基于紧急变桨和crowbar保护协调的故障穿越方案。为了彻底解决crowbar电路存在的电机失控问题，研究了包括转子串电阻保护和定子串电阻保护的保护技术。其中，评估了两种串联保护不同限流电阻对系统的影响，并比较了二者的优缺点。最后，提出了基于转子串电阻保护的联合双馈机组故障穿越解决方案，并通过仿真验证了该方案的有效性和可行性。 5）研究了双馈风电机组基于动态电压恢复器的故障穿越方案。首先分析了动态电压恢复器应用中涉及的一般问题，其中包括拓扑结构、基本原理、补偿策略等。并针对动态电压恢复器在双馈机组中应用的特殊性，选择了合适的拓扑结构和补偿策略、分析了主回路的主要参数的确定方法，最后，通过仿真验证了在动态电压恢复器的保护下双馈机组成功穿越全电压故障（包括低压、零压、高压、单相对地以及两相对地故障）及其改善双馈机组瞬态性能的能力。
[Abstract]:The large-scale wind power access grid brings great challenges to the safe operation and management of the power grid. For this purpose, the new grid specification requires the wind turbine to ensure that the fault-through (FRT) capability is provided. Therefore, it is of great theoretical and practical significance to study the problem of wind power generation, which is one of the key technologies of large-scale wind power generation and network operation. In many wind power generation topologies, because of the many advantages and good running performance of the double-fed wind power unit, it has always occupied the main share of the world wind power market, and is one of the mainstream technologies developed by the international wind generating set. However, the fault-crossing ability of the double-fed induction generator (DFIG) wind power system is most challenging as compared to the other structures. mainly due to the direct access of the stator winding of the double-feed induction motor to the power grid, and is caused by the particularly sensitive and limited transformer capacity of the voltage fault. Therefore, it is of great theoretical and practical significance to improve the transient behavior during the fault of the double-fed wind turbine to meet the fault crossing requirements of the modern power grid. When the double-fed wind turbine unit is subjected to the symmetrical voltage drop, the two main problems that need to be solved to meet the fault crossing requirement of the double-feed unit are the over-current of the double-feed motor and the over-current of the DC bus of the converter Pressure. This directly threatens the safety of the converter and the uninterrupted supply of the dual feed unit. Line. In case of an asymmetric drop fault of the grid voltage, the two-frequency-frequency vibration problem and the direct current-side ripple question in the output active and reactive power and the electromagnetic torque of the double-feed motor are more concerned in addition to the overcurrent which occurs when the fault is serious Therefore, this paper has carried on the comprehensive, in-depth, systematic research, the main work and the achievement of the above-mentioned hot issues. 1) Based on the characterization of the space vector, the number of the two-phase induction motor in the two-phase synchronous rotation coordinate system and the dq synchronous rotation coordinate system is completed. learning and modeling, and its rotor-side and net-side converter and its control strategy in synchronous coordinate system In the environment of PSCAD/ EMTDC special simulation software of power system, a complete and more accurate simulation platform of double-fed wind generating set is set up, which is used to simulate and verify the effectiveness of the fault crossing scheme. feasibility. 2) Using the space vector mathematical model of the double-fed asynchronous motor under the stator (static) coordinate system, the voltage drop fault (asymmetric fault mainly including single-to-ground and two-phase short-circuit) in different degrees and different types The transient behavior of the double-fed induction motor (stator magnetic chain transient, rotor open-circuit voltage transient and rotor current transient) is of general significance in the case of a barrier In particular, the rotor fault current is studied in more detail, the difference of the impedance caused by the different frequency voltage components in the rotor circuit and the effect of the output voltage of the rotor-side converter on the rotor fault current are considered, and the rotor fault is derived. The accurate expression of current under the condition of symmetrical and asymmetric voltage fault is obtained, and the correctness of the expression is verified by the simulation. The mechanism of the fault crossing operation of the double-fed induction wind-driven generator is revealed through these simple and simple analysis, which lays the foundation for finding the proper fault crossing scheme for the double-feed unit. Based on the traditional vector control technology of the rotor-side converter, the influence of different voltage feedforward compensation terms on the fault-crossing ability of the double-fed wind power unit is studied based on the traditional vector control technology of the rotor-side converter, and the transient state of the feedforward compensation term is simplified. The evaluation method of the magnetic chain solves the problem that the stator resistance needs to be evaluated after the stator transient characteristics are taken into account, and the evaluation of the stator resistance It is often difficult to take into account the non-linear characteristics of the double-fed asynchronous motor. The linear control strategy is a problem in the performance of the system when the voltage drops. The typical non-linear control strategy _ hysteresis loop controller is studied to improve the fault crossing of the double-feed unit. The effect of performance. In fact, starting from the angle of energy balance, the reason that the double-feed motor stator-stator overcurrent occurs during the fault is the energy that occurs during the fault Therefore, in order to reduce the unbalance of energy during the fault, the fault-crossing ability of the double-feed unit is improved, and the double-feed machine with no-load-increasing speed is studied. The simulation verifies the respective characteristics and advantages of the strategy in improving the fault-crossing ability of the dual-feed unit, which can improve the double-feed by varying degrees. The crossing ability of the unit is analyzed. Finally, the double-feed unit of the converter is analyzed. 4) The influence of different bypass resistance on the system and the optimization of the resistance value are studied. The influence of different control strategies of the crowbar circuit on the fault crossing of the double-feed unit and the crowbar circuit are compared. The problem of the protection technology is a problem in the protection of the crowbar circuit during the fault of the double-feed unit, and the protection based on the emergency and crowbar protection is studied. In order to thoroughly solve the problem of the runaway of the motor in the crowbar circuit, the resistance protection and the stator string of the rotor are studied. The protection technology of resistance protection, in which the effect of two series protection different current-limiting resistors on the system is evaluated, and The advantages and disadvantages of both are compared. Finally, the fault crossing solution of the combined double-feed unit based on the resistance protection of the substring is put forward, and the method is verified by the simulation. The validity and feasibility of the case are discussed. 5) The dynamic electricity of the double-fed wind power unit is studied. In this paper, the general problems involved in the application of the dynamic voltage restorer are analyzed, including the topological structure. In the light of the particularity of the application of the dynamic voltage restorer in the double-feed unit, the appropriate topological structure and compensation strategy are selected, and the main circuit is analyzed. The method of the determination of the parameter is finally verified by the simulation. The fault of the full-voltage (including low-voltage, zero-voltage, high-voltage, single-to-one and two-to-one-to-one-to-one) and the improvement of the double-feed unit under the protection of the dynamic voltage restorer is verified by the simulation.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM315

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