【作者】 段志远；

【导师】 张承学；

【作者基本信息】 武汉大学 ， 电力系统及其自动化， 2009， 博士

【摘要】 区域联网运行已成为现代电力系统的重要特点,伴随着大电网的发展而日益严重的低频振荡问题更加引起电力工作者的关注,尽管有关低频振荡的研究进行了很多,但是仍有很多问题未能很好解决。在所有这些问题中时滞就是一个需要迫切研究的问题,从工程实践的角度来看,时滞的存在往往会导致系统的性能指标下降,甚至使系统失去稳定性。一般认为电力系统稳定器是增强系统阻尼、抑制电网低频振荡的主要措施,实际运行的系统在安装了电力系统稳定器仍然会诱发低频振荡,这就需要从新的角度引入新的控制对象和控制原理,以提高本地振荡模式的阻尼比,抑制低频振荡的发生。传统的电力系统稳定器,往往只采用机组本地信号,虽然对局部振荡模式有很好的阻尼作用,但对区域间振荡模式的抑制效果欠佳。近来受到广泛关注的广域测量系统可以在同一参考时间框架下捕捉到大规模互联电力系统各地点的实时稳态、动态信息,这些信息可应用于电力系统稳态及动态分析与控制的许多领域,给大规模互联电力系统的运行和控制提供了新的方法。广域测量系统给电力系统的运行和控制带来了新的契机,但也带来了新的问题,如反馈信号的传输时延问题,在广域测量系统的环境下,信号传输的时延是不可忽略的。针对目前的研究状况,本文提出了计及信号传输时延的阻尼控制器设计,综合利用若干理论设计了计及信号传输时延的电力系统稳定器、附加调速阻尼控制器和广域阻尼控制器。主要内容和研究成果归纳如下：1.采用Pade逼近的方法对于时延进行建模,分析了信号传输时延对电力系统稳定器控制效果的影响。计算得到了维持系统渐近稳定的时滞稳定裕度,研究表明二阶Pade时延逼近效果较好。对于多机运行方式下,研究了发电机输出有功功率变化对时滞稳定裕度的影响,得出了一些初步的结论。并在此基础上研究了计及信号传输时延的电力系统稳定器设计方法,结合线性矩阵不等式和粒子群优化理论分析计算得出了合适的电力系统稳定器参数,通过仿真分析验证了该方法的有效性。2.研究了附加调速控制器抑制电力系统低频振荡的可行性,并在此基础上探讨了计及信号传输时延的附加调速阻尼控制器设计方法,提出了基于校正补偿原理和基于粒子群优化算法的附加调速阻尼控制器设计策略。通过仿真表明附加调速阻尼控制能够达到抑制电力系统低频振荡的效果。3.探讨了计及信号传输时延的广域阻尼控制器的设计方法,采用二阶Pade时延逼近对时延进行建模,运用粒子群优化算法获得广域阻尼控制器参数,针对广域阻尼控制器的引入会造成原有系统区间振荡范围内特征值数量的增加,提出了基于Routh降阶算法的等效阻尼比的分析方法,对于广域阻尼控制器的引入会造成大干扰情况下相对功角第一摆振荡幅值较大的现象,优化了集中广域控制器的结构参数。通过大扰动和小扰动仿真实验表明,通过以上分析获得的广域阻尼控制器对区间振荡具有很好的抑制效果。对测试系统仿真结果的分析表明论文中提出的理论,能够为电力系统低频振荡研究提供新的分析方法和控制策略,在保障电网安全稳定的同时提高其运行的经济性。更多还原

【Abstract】 Inter-regional connection is an important characteristic of modern power system. As the power grid develop,the increasingly serious low-frequency oscillations problems has become quite prominent. Though there are lots of references concentrating on the low-frequency oscillations problem, many problems have not been yet well solved. Among these problems, the signal transmision delay is a significant problem. A long time delay may be a detriment to system stability and degrade system robustness.The basic function of. a power system stabilizer(PSS)is to add damping to the generator rotor oscillations. PSS based on shaft speed signal has been used successfully on generator unit. However, the low-frequency oscillation still happened even some PSS were installed in generator unit. The new principles of controller design should be study so as to increase damping ratio to the local oscillation mode and inhibit the low frequency oscillation.The input signals of the conventional PSS come from local generator, can damp the local mode oscillations well, but not the inter-area mode oscillations. Wide-area Measurement System can retrieval the real time dynamic and static information of the large scale power system under the same time reference, helping to resolve the problems of the dynamic analysis and control for an interconnected power system, especially the low-frequency oscillation. However, communication delay is a non-ignorable factor for the stability of wide-area control.To improve the existing methods, the damping controller including the power system stabilizer,the governor damping controller and the wide area damping controller considering signals transmission delay for power system is presented for the first time in the dissertation. The main works presented in the dissertation contain:1. The Pade approximation method is used to express time delay, Analysis of the influence of the signal transmission delay on the power system stabilizer, and calculate the delay margin to maintain the system asymptotic stability. Research shows that the second-order Pade approximation has better accuracy. The power system stabilizer considering signals transmission delay is proposed for generators excitation controllers, Simulations in a single-machine infinite bus test system are given to demonstrate the advantages of the proposed.2. The principle of the governor damping control is discussed. The governor damping controller considering signals transmission delay is designed. Simulations in a single-machine infinite bus test system are given to demonstrate the advantages of the governor damping controller.3. The principle of the wide area damping control is discussed, The second-order Pade approximation method is used to express time delay. The equivalent damping ratio conception based on the Routh algorithm is proposed,Simulations in a 4-machine test system are given to demonstrate the dvantages of the wide area damping controller.The theoretical results proposed in the dissertation establishes the control theory and engineering application foundation for the low-frequency oscillations. The economical efficiency can be improved on the promise of safe operation of power grid.更多还原