基于小信号模型的虚拟同步发电机稳定性分析与设计研究

发布时间：2018-08-29 17:14

【摘要】：在全球能源危机和环境污染的背景下,可再生能源因其可开发潜力巨大和清洁环保的特点,近年来得到了快速的发展。可再生能源的分布式发电技术因其可靠性高,相比于大规模的风、光电站对电网稳定性的冲击小,获得了国内外学者广泛地关注。作为一种特殊的分布式发电系统,微电网将分布式电源、负荷、电力电子装置、储能等整合为一个独立的发供电系统,有利于可再生能源的大规模应用,成为目前世界各国研究的热点。微电网中的逆变器作为可再生能源并网的主要接口,其控制策略对微电网的性能有至关重要的影响。由于传统的PQ控制、Vf控制和下垂控制难以满足微电网独立自治运行的需要,越来越多的学者开始关注虚拟同步发电机的概念。本文针对虚拟同步发电机的小信号稳定性和参数设计展开研究,主要研究内容有:1.通过对下垂控制和同步发电机小信号模型的对比分析,证明了下垂控制是虚拟同步发电机的一个特例。针对下垂控制缺乏惯性,受扰后易振荡失稳的缺陷。参考同步发电机引入电力系统稳定器的原理,在下垂控制中引入功率微分项进行改进能够有效抑制振荡。建立了下垂控制引入功率微分项前后微电网完整的小信号模型。对比分析了控制参数与线路参数变化对两种系统小信号稳定性的影响,总结了控制参数的选择方法。进一步地进行了灵敏度分析,研究对比了微电网中各逆变电源状态变量对系统低频模式的参与程度,以及线路参数变化对参与因子的改变。得出结论:线路长度或阻抗比增加为系统提供阻尼,且越靠近该线路的逆变电源获得的阻尼越大;且使用下垂控制时,系统特征根对各逆变电源的主导性更易改变。最后,通过不同工况下的仿真验证了建模、分析与结论的正确性。2.设计了一种无需电流传感器的虚拟同步发电机控制策略。控制策略包括原动机与转子运动方程、电压-无功控制和输电线路功率计算方程3个主要部分。其中创新地采用输电线路功率计算方程计算虚拟电磁转矩,可以使虚拟同步发电机无需电流传感器。建立了虚拟同步发电机的小信号模型,并结合同步发电机相关理论进行分析,系统性地总结了参数设计的方法。主要结论如下:虚拟同步发电机的同步转矩与滤波器参数、输电线路参数、电压-无功控制环节的电压增益、无功增益有关,且无功增益相比于电压增益对同步转矩的影响更大;阻尼转矩与转子方程阻尼系数、原动机频率下降系数有关。惯性时间常数增加将同时减少虚拟同步发电机的阻尼和振荡频率。虚拟同步发电机的输出电压与无功功率的关系则与电压增益和无功增益有关。最后通过多种参数工况下的仿真实验验证了所总结的参数设计方法的正确性。3.设计了一种与同步发电机具有一致响应的虚拟同步发电机控制策略,控制器包括:原动机与转子运动方程、虚拟励磁控制、虚拟电磁暂态控制、双PI控制器几个部分。建立了一致性虚拟同步发电机的小信号模型。通过分析发现,一致性虚拟同步发电机的部分控制参数和电路参数对系统小信号稳定性的影响也符合“虚拟同步发电机的同步转矩与滤波器参数、输电线路参数有关,阻尼转矩与转子方程阻尼系数、原动机频率下降系数有关”的结论。同时对重新设计的虚拟励磁控制环节和双PI控制器参数的设计方法进行了研究,得出了参数设计的方法。最后通过仿真实验验证了一致性虚拟同步发电机与同步发电机具有一致的响应。
[Abstract]:Under the background of global energy crisis and environmental pollution, renewable energy has been developed rapidly in recent years because of its great potential for development and clean environmental protection. The distributed generation technology of renewable energy has high reliability. Compared with large-scale wind, the impact of photovoltaic power station on the stability of power grid is small, and has won scholars at home and abroad. As a special distributed generation system, micro-grid integrates distributed generation, load, power electronic devices and energy storage into an independent power generation and supply system, which is conducive to the large-scale application of renewable energy and has become a research hotspot all over the world. Due to the traditional PQ control, Vf control and droop control are difficult to meet the needs of independent and autonomous operation of microgrid, more and more scholars begin to pay attention to the concept of virtual synchronous generator. The main research contents are as follows: 1. By comparing droop control with small signal model of synchronous generator, droop control is proved to be a special case of virtual synchronous generator. A complete small-signal model of microgrid is established before and after power differential term is introduced into droop control. The effects of control parameters and line parameters on small-signal stability of the two systems are compared and analyzed, and the selection methods of control parameters are summarized. Sensitivity analysis is carried out, and the participation degree of each inverter state variable in the low frequency mode of the system and the variation of the line parameters in the system are compared. The dominance of the eigenvalues of the system is easier to change when the system is droop controlled. Finally, the simulation results under different operating conditions verify the correctness of the modeling, analysis and conclusion. 2. A virtual synchronous generator control strategy without current sensor is designed. The control strategy includes the motion equation of the prime mover and rotor, voltage-reactive power control. And the three main parts of the transmission line power calculation equation, in which the virtual synchronous generator does not need current sensor by innovatively using the transmission line power calculation equation to calculate the virtual electromagnetic torque. The main conclusions are as follows: the synchronous torque of virtual synchronous generator is related to filter parameters, transmission line parameters, voltage gain of voltage-reactive power control link, reactive power gain, and the effect of reactive power gain on synchronous torque is greater than that of voltage gain; damping torque and rotor equation damping coefficient, prime mover frequency The relationship between the output voltage and reactive power of the virtual synchronous generator is related to the voltage gain and reactive power gain. Finally, the simulation results under various parameter conditions show that the proposed parameter design method is correct. Veracity. 3. A virtual synchronous generator control strategy is designed, which has the same response as the synchronous generator. The controller consists of several parts: the motion equation of the prime mover and rotor, the virtual excitation control, the virtual electromagnetic transient control and the double PI controller. The influence of some control parameters and circuit parameters of the VSR on the small signal stability of the system also conforms to the conclusion that the synchronous torque of the VSR is related to the filter parameters, the transmission line parameters, the damping torque is related to the damping coefficient of the rotor equation and the frequency drop coefficient of the prime mover. The design method of parameters of virtual excitation control and double PI controller is studied, and the method of parameter design is obtained. Finally, the simulation results show that the consistent virtual synchronous generator and synchronous generator have the same response.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM31

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