【作者】 黄方能；

【导师】 陈陈； 黄成军；

【作者基本信息】 上海交通大学 ， 电力系统及其自动化， 2008， 博士

【摘要】 现代电力系统迅速发展,以大机组、超高压、长距离、重负荷为特点,是一个典型的强非线性、高维、动态大系统。随着大型电力系统的互联以及各种新设备的使用,在使发电、输电更经济、高效的同时也增加了电力系统的规模和复杂性,再加上快速励磁系统的普遍使用和电力市场竞争机制的引入,电网运行在稳定极限边缘的可能性也大为增加。由于输电走廊的饱和及电网公司的商业化运作,依靠建设新输电线路来增加输送容量将会越来越困难,因此低频振荡现象成为大型互联电网安全运行的重要问题。而通过采用新型FACTS装置来改善系统运行工况,提高线路输送容量是一个现实且理想的选择。本文针对利用UPFC(统一潮流控制器)阻尼系统振荡这一问题,对UPFC的数学建模,其稳定控制器的设计与优化,以及提高稳定控制器的适应性等方面进行了研究。主要成果归纳如下:建立UPFC的小扰动模型。电力系统低频振荡问题属于小扰动稳定性的研究范畴,UPFC的数学建模必须要满足小扰动分析的要求,还应同时考虑计算时间及计算精度两个方面。本文推导出一个适用于小扰动分析的UPFC模型,此模型简明精确并包括控制系统及稳定控制器。因为低频振荡是一个全局性的问题,因此该数学模型经过模块化处理,使其便于和系统无缝连接。设计UPFC稳定控制器,将系统特征值与发电机转矩系数相结合,对振荡模式进行分析。利用现代控制理论建立包括UPFC的全系统状态方程,同时利用经典控制理论中的频域法设计UPFC稳定控制器,巧妙利用两种控制理论的内在联系指导UPFC稳定控制器的设计,同时基于全系统状态方程,分析稳定控制器的最佳安装位置及理想的阻尼信号,使稳定控制器充分发挥其功能。提出“转矩面积”的概念,并优化UPFC稳定控制器。稳定控制器投入运行的一个问题是可能会恶化系统同步转矩,转矩面积则同时考虑阻尼转矩系数及同步转矩系数两个因素。利用转矩面积优化设计稳定控制器,可以确保系统同时具有足够大的同步转矩和阻尼转矩。首先利用STATCOM(UPFC简化运行方式)-单机系统推导和验证转矩面积概念,然后在4机系统中利用转矩面积优化UPFC稳定控制器,取得了预期效果。把智能软计算方法应用于UPFC稳定控制器的设计,提高其自适应程度。综合模糊理论和线性理论的优点,设计基于模糊理论的UPFC线性稳定控制器。建立系统运行方式库,利用模糊推理规则优化组合线性稳定控制器,使得稳定控制器的鲁棒性明显增强,最后对一个曾发生低频振荡的系统进行仿真计算,模糊UPFC线性稳定控制器的效果令人满意。更多还原

【Abstract】 Modern power systems, characterized by large capacity units, Extra High Voltage, long distance transmission, heavy load demand, are typical nonlinear, high dimensional, large-scale and dynamic systems. With the interconnections among different power systems, and the increasing numbers of newly introduced devices, a lot of issues on system security and stability raise up while the system size and complexity grow and make the generation and transmission more economic and efficient.More and more large-capacity generators with fast control excitation systems are put into operation. Along with the introduction of the competition mechanism by power marketing, the possibility of operating at the stability limit increases. Further more, since that transmission corridors are almost saturated; it is difficult to enhance transmission capability of power grid by building new transmission lines. The low frequency oscillation occurs more often in the large-scale interconnected system, which threatens the safety of system operation. Designing UPFC stabilizers for the purpose of damping power oscillation is an effective measure to improve system stability. The thesis presents systematic study on mathematic model of UPFC, optimization and Adaptive critic design of the UPFC stabilizer, et al. The main achievements are as follows:A small signal model of UPFC, which could be used in small signal analysis of power system, is established. Both calculation velocity and accuracy are considered during the model-establishing procedure. Furthermore, modular design enables it to communicate with other programs easily. The dynamic characteristic of capacitor voltage is taken into account. Besides, the bus voltage control, dc voltage control and power flow control, etc are included. With high precision, the model could be used in further study of the small signal stability in power system.Oscillation mode is analyzed by using system eigenvalues and the generator torque. The mathematical model including UPFC is derived based on modern control theory; meanwhile, the stabilizer is designed based on classic control theory. Design Procedure is controlled by the intrinsical link between modern control theory and classic control theory. In a multi-machine power system, the optimal location of stabilizers could be determined and the effective feedback signal could be obtained by the state-space equation. Further, the stabilizer could be implemented according to the results. The proposed method improves the damping level significantly and shown by simulation.A novel torque area method is proposed. For a modal frequency, the electrical damping and synchronizing torque coefficients are two main factors that influence the stability of power system, Damping and synchronizing torque components will be affected by the STATCOM stabilizer. By using torque area method, the design of STATCOM stabilizer is optimized and further more, it could maintains sufficient synchronizing torque as well as damping torque. In a 4-machine system, the stabilizer is also optimized; simulation shows the method is effective.Intelligent Soft Computing Methods is used to Design UPFC stabilizer to enhance stabilizer’s adaptability. Typical linearized system models, namely model bank, are taken into account and corresponding linear stabilizers for various models are designed. Furthermore, the similarity between real system model and the model bank is evaluated by fuzzy logic, and the results obtained are used to adjust the weight of each linear stabilizer, and the whole procedure is adaptive according to system operating conditions. Therefore, the stabilizer works effectively and continuously. Finally, the simulation for a poor-damped power system is studied. Results shows that the proposed stabilizer improves the damping level significantly.更多还原