【作者】 张艳萍；

【导师】 张建华； 黄伟；

【作者基本信息】 华北电力大学（北京） ， 电力系统及其自动化， 2008， 博士

【摘要】 电源距离的扩展、负荷恒功率化趋势的加大以及厂网分开后电力市场的逐步推进,使得大电网的电压稳定问题尤其是受端系统的无功电压问题日趋严重,对于经济发达、人口集中、能源缺乏的大型城市负荷中心的影响更为突出。以典型的受端系统北京电网为例,2005年夏季高峰负荷期间,北京地区从外网受电比例已经达到约75%,任何一个受电通道出现问题都有可能造成电网发生严重的事故,因此大都市受端系统的薄弱性足以引起我们的关注。本文以北京电网电压稳定分析项目为背景,对受端系统的小扰动电压稳定问题进行了深入研究,主要内容如下:静态分析方法一直被广泛应用于实际系统的分析,但在应用中存在很多概念不清甚至混用的问题。本文在受端系统发生电压单调下降失稳机理的研究中深入讨论了静态电压稳定研究中系统运行极限的深刻含义,对出现率较高的关键词语,如电力网极限输送能力、系统最大负荷功率点、潮流极限、P-V曲线拐点、潮流雅克比矩阵奇异点、鞍结分叉点等进行了分析研究,并对其相互关系进行了讨论与论证。P-V曲线法是静态分析方法实用化程序中最常用的一种静态电压稳定分析方法,但很多学者认为,当负荷不被假设为恒功率负荷模型时系统就不存在负荷功率极限,P-V曲线拐点也不再对应负荷能力极限、不再是电压稳定临界点。本文对计及电压负荷静特性模型情况下的系统潮流运行情况进行了深入研究,分析了系统稳定运行临界点的特征;对不同电压特性负荷指数α取值下的P-V曲线进行了解析,对非恒功率模型下潮流极限、负荷能力极限、系统负荷功率极限、P-V曲线拐点、潮流雅克比矩阵奇异点的物理含义及相互之间的关系进行了论证;研究了负荷特性对系统静态电压稳定性的影响。小扰动特征分析方法已被广泛应用于多机系统的低频振荡功角稳定问题,本文主要对小扰动特征分析法在电压稳定分析中的应用进行了研究,通过研究状态变量与系统状态方程系数矩阵特征值之间对应关系,确定系统失稳临界点处影响系统电压稳定性的关键因素以及系统可能发生的失稳模式。利用小扰动电压稳定分析方法研究了动态负荷感应电动机与空调负荷对系统电压稳定性的影响。无功电压问题是受端系统中存在的主要问题,也是影响受端系统电压稳定性的重要因素。静止无功补偿器(SVC)作为一项成熟的技术已被广泛应用于现代电力系统的负荷补偿与输电线路补偿。本文针对北京电网存在的问题重点研究了SVC在电网中的应用特性,针对传统U-I特性在实际系统应用中的缺点提出了改进的U-I特性,并给出了详细的特性方程描述以及重要参数调差率的选择方法。网络结构是电力系统安全稳定运行的基础,本文重点研究了电磁环网在电网发展中出现的必然性及对系统稳定运行的不利影响,以及分层分区运行在都市电网发展中的必然趋势。通过详细分析北京电网讨论了网络结构的合理优化方法与分层分区供电原则。更多还原

【Abstract】 As the expansion of power supply distance, the enlargement of load characteristic of constant power tendency as well as the gradual advancement of electric power market after the electric power plant and network separate, these factors make the voltage stability question for the large electrical network, especially the reactive voltage question for the received system more and more serious, and this influence is more sensitive to the load center of economy developed, population concentration, the energy deficient large-scale city. We take the Beijing electrical network as the example, which is a typical received system, in 2005 summer peak load period, the received electricity proportion of the Beijing area network from the outside grid already has achieved approximately 75%, the serious accident may be happened for the electrical network if any received channel appears the question, therefore we should pay more attention on the weakness of received system for the metropolis. This thesis based on the project of voltage stability analysis of the Beijing electrical network, deeply studies on the small disturbance voltage stability question of the received system, the main content of research as follows:Although, the static analysis method is widely used in actual electric power system, there are many concepts that are unclear or even confused. In the analysis of instability mechanism due to voltage’s dropping monotonously,the meaning of operation limit of the static voltage stability is thoroughly discussed in this thesis. Key words and expressions which have comparative high occurrence frequency, such as network maximum power transfer capability, maximum load power point, power flow limit, flex point of P-V curve, singular point of power flow Jacobian Matrix, saddle node bifurcation, and so on, are analyzed, and their interrelations are discussed and demonstrated.In the analysis of static voltage stability, P-V curves arise as an appealing method in practice. However, many scholars believe that when loads are not supposed to be constant power loads, there is no power limit, consequently, the flex point of P-V curves does not correspond to load capability limit or is no longer the critical point of voltage stability. The operation of power flow, taking account of the model of static characteristic of load, is studied deeply in this thesis, and the characteristic of the critical point of stable operation is analyzed; P-V curves under different load index of voltage characteristicαare also analyzed, the physical meanings of load flow limit, load capability limit, load power limit of system, flex point of P-V curves, power flow Jacobian Matrix singular points, and their interrelations are discussed under non-constant power loads, the effects of load characteristic to static voltage stability of power system is studied. The eigenvalue analysis method of small disturbance has been widely applied to power angle stability analysis under the low frequency oscillation in multi-machine system. This thesis mostly studies the application of this method in voltage stability analysis, and determines the key factors at the critical point of instability that affect voltage stability as well as the probable instability mode that system may occur. The effects of dynamic induction motors and air conditioners to voltage stability are studied through small- perturbation voltage stability analysis.In modern power system, Static Var Compensator, as a mature technology, has been widely applied to the load compensation and transmission line compensation. This thesis is key to study the application characteristic of SVC in power grid, and proposes an improved U-I characteristic according to the demerits of application of conventional U-I characteristic in actual system.The network topology is the foundation of secure and stable operation of electric power system, this thesis mainly studies the inevitability of the appearance of electromagnetic loop network and its bad effects to stability,and the tendency of the operation mode of voltage-grading & district-dividing in the development of metropolis grid. The rational optimization method of network topology and power supply principle of voltage-grading & district-dividing are discussed by analyzing Beijing grid in detail.更多还原