【作者】 兰洲；

【导师】 甘德强； 倪以信；

【作者基本信息】 浙江大学 ， 电力系统及其自动化， 2008， 博士

【摘要】 现代电力系统在发电容量和电压等级方面都有较大提高,高压直流输电(HVDC)和柔性交流输电元件(FACTS)的投入运行,以及跨区域电网的互联和电力市场的开放,都增加了系统在结构和模型上的复杂性,并产生了许多不确定因素,为电力系统带来了更多的安全隐患。近年来,世界范围内的多起严重停电事故,使电力系统的安全稳定问题再次引起了人们的重视。电力系统中许多破坏性事故的根本原因都归咎于大扰动下发电机的功角失稳。大干扰功角稳定通常又称暂态稳定,是电力系统安全稳定运行的基础,暂态稳定控制是电力系统安全稳定运行的一道重要屏障。本文的研究主要针对暂态稳定控制策略的相关问题,所作的主要工作包括:第一章,综述了现代电力系统暂态稳定非线性控制的相关问题,包括控制对象、控制方法等问题,简述了非线性系统自适应控制的相关知识及其在电力系统暂态稳定控制中的应用。第二章,研究了多机电力系统中发电机励磁的非线性鲁棒自适应控制问题,考虑了发电机阻尼系数、d轴同步电抗和暂态电抗的不确定性,以及模型误差和外部动态干扰的存在,设计了非线性鲁棒自适应控制规律,保证了发电机功角和频率在原运行点邻域内的收敛性。在所采用的方法中,只要求动态干扰项有界而不需要知道或给定其界限的具体数值,这是该方法的主要特点。在所设计的控制器中,针对每个不确定项,都设计了一个动态估计环节以应对其影响,控制规律保证了所有状态变量的一致最终有界性和系统输出的收敛性,并且,所设计的控制器是分散体地化的,数字仿真显示了控制器在提高系统暂态稳定性方面的有效性。第三章,提出了一类多输入-多输出(MIMO)非线性不确定系统的鲁棒自适应控制方案,并将其应用于设计发电机励磁与调速综合协调控制,对第二章中所采用的单输入-单输出(SISO)系统鲁棒自适应控制设计方法进行了扩展。对于一个n阶非线性不确定系统,假设前n-1个控制量在系统处于稳态时为零,则首先对系统进行增阶,即设前n-1个控制量为状态变量,从而产生n-1个新的控制量替代原有的控制变量,且使系统变为一个2n-1阶非线性不确定系统。控制规律的设计仍采用反步法(Back-stepping),对于每个不确定项,都设计了一个动态估计环节以应对其影响,最终保证了全部状态变量的一致最终有界性和系统输出的收敛性。最后,将所提出的方法应用于发电机励磁与调速综合协调控制设计,给出了发电机励磁和调速综合协调控制规律,并通过数字仿真显示了所设计控制器对于提高系统暂态稳定性的效用。第四章,提出了利用系统动态贯量中心COI(Center of Inertia)信号设计非线性暂态稳定控制器的思想,简称“COI跟踪”思想。一般来讲,系统COI(包括功角COI和频率COI)曲线能够反映系统中所有发电机运转的总体趋势,且其较为平滑,容易跟踪,因此,如果系统中所有的发电机都能够动态地跟踪COI的变化,而不只是停留于原有运行点,则各发电机更容易保持同步,系统暂态稳定性更能够得到保证。广域测量系统WAMs(Wide-area Measurement Systems)技术的发展为该思想的实现提供帮助,各发电机在通过WAMs得到系统COI信息后,动态的跟踪COI的变化以达到同步运行,且一定范围内的WAMs信号时滞是被允许的。根据传统的“分散/本地化”控制思想和本章提出的“COI跟踪”控制思想,采用相同的非线性控制方法设计了两种励磁控制器,数字仿真实验表明,后者更有利于提高系统的暂态稳定性。第五章,提出利用区域COI信号阻尼两区域互联系统功角和频率COI振荡的高压直流输电系统(HVDC)直流功率调制和晶闸管控制串联电容器(TCSC)电抗调节控制方法。HVDC直流功率调制和TCSC电抗调节都能改变区域间传输的有功功率,从而影响系统的暂态稳定性。HVDC和TCSC控制环节均采用一阶环节表示,设计的控制目标是阻尼区域功角和频率COI间的振荡,控制器设计采用非线性鲁棒控制方法,保证了全部状态变量的一致最终有界性和区域间功角及频率COI振荡的收敛。数字仿真表明,所提出方案相比于传统型调制控制器更有利于故障后发电机功角摇摆的收敛,更有利于提高系统的暂态稳定性。所提出的方法同样可扩展应用于多区域互联电网的暂态稳定控制,用于阻尼多区域间的功角和频率COI振荡。第六章,对全文做出总结,并分析了本文中存在的未解决问题及有待进一步解决的问题。更多还原

【Abstract】 The generation capacity and voltage grade have been greatly improved in modern power systems. At the same time, the structure and the model of the systems become more complicated, and many uncertain factors are brought to the system because of the application of HVDC and FACTS, the interconnection of the area power systems, and the open of the power market. These bring many hidden troubles of the system security. Many severe accidents in power systems all over the world in these years arouse again the focus on power system security. Many severe accidents in power systems ascribe the loss of angle stability under large disturbances. Angle stability under large disturbances is always called transient stability and is the foundation of the operation of the power systems. So, transient stability control is an important barrier of the power system security.The topics discussed in this paper are on transient stability control strategies in power systems, and they are:Ⅰ. A survey of transient stability control is made, which includes control objectives, control techniques and so on. And a brief introduction of nonlinear system adaptive control theories and their implications in power systems is made.Ⅱ. A nonlinear robust adaptive excitation controller is designed for the generators in multi-machine power systems. The uncertainties of damping coefficient, synchro reactance and transient reactance on d axis of the generators, and the model errors and outer disturbances are considered. The controller guarantees the convergences of the generator angle and frequency in a small neighborhood of the prime operation point. A characteristic of the designed controller is that the model errors and outer disturbances are requested only to be bounded but the boundnesses are needless. In the designed controller, a dynamic estimator is designed for each uncertain iterm, the globally uniformly ultimately boundedness of all state variables and the convergency of the system output are guaranteed, and each controller is decentralized or local. The digital simulation displays the validity of the designed controller used to improve power system transient stability.Ⅲ. A nonlinear robust adaptive controller is designed for a MIMO nonlinear system with uncertain parameters and model errors, and is applied to the integrated control of generator excitation and turbine governor. The work in the above chapter which is on the SISO control of nonlinear system is extended in this chapter to MIMO control of nonlinear systems. An increase-order operation is made, first, if the anterior n-1 control variables of an n-order nonlinear system convergence to zero, and the n-1 control variables are regarded as state variables, that brings n-1 new control variables. Then, the whole system becomes to be a 2n-1 order nonlinear uncertain system with n control variables. At the end, using back-stepping technique, control laws are designed for each control variable to guarantee the globally uniformly ultimately boundedness of all state variables and the convergency of system output. The design method is applied to the integrated control of generator excitation and turbine governor to improve transient stability of power systems. The digital simulation displays the effectiveness of the designed controllers.Ⅳ. A "COI-tracking" concept is proposed for the design of transient stability excitation controller in multi-machine power systems. Generally, the COI curves of the power system can reflect the global trend of the changings of all generators in transient time, and the curves are usually smooth. So, if all generators in the power system track the dynamic COI of the system, but not try to stay at the initial operation point, the generators could keep synchronous more easily and the transient stability of the system could be greatly improved. The development of WAMs technique could help the realization of proposed global control concept, and the time delay of WAMs signals within a certain range is acceptable. With the proposed concept, an excitation controller is designed for generators using back-stepping technique and is contrasted with the decentralized/local controller designed by the same technique. Digital simulations show that the proposed excitation controller using COI-tracking concept can improve transient stability of the power system obviously and is much better that the other one.Ⅴ. Using area COI to design the power modulation controller of HVDC and reactance controller of TCSC, to damp the swing between two-area interconnected power systems is proposed. Direct current power modulation of HVDC and the reactance modulation of TCSC can affect the active power transfered between areas and, further, affect the stability of the power system. The models of HVDC and TCSC modulation are expressed by one order models in this paper. With the objective of damping the swing between the area-COI of the two areas, nonlinear robust controllers are designed for power modulation of HVDC and reactance modulation of TCSC. The globally uniformly ultimately boudedness of all state variables and the convergency of the swings between area-COIs are guaranteed. Digital simulations show that the designed controllers are better than the conventional modulation controllers in improving power system stability. The proposed concept could also be extended to the damping control of multi-area power systems.Ⅵ. At the end, a conclusion is made for the whole paper. Some open problems in this paper are discussed.更多还原