【作者】 王艳；

【导师】 张艳霞；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2010， 博士

【摘要】 智能电网是当今世界电力系统发展变革的最新动向,被认为是2l世纪电力系统的重大科技创新和发展趋势。智能电网的最终目标是实现电网的数字化、信息化、自动化和互动化,使电网达到智能、坚固、高效和可靠。作为智能电网重点研究对象之一的广域保护系统是解决现有保护存在的独立、片面工作问题,确保大型互联电网的安全性和稳定性的不可或缺的组成部分。本文对智能电网中的广域保护及其相关问题进行研究。提出了基于广域信息的防连锁过载跳闸保护。以重要母线为单元,利用正常运行时存贮在广域网调度中心的节点阻抗矩阵中的相关元素,估算各支路的过载电流系数以分析过载支路开断后有无引起连锁跳闸的可能,及时告知调度中心采取防连锁跳闸的措施,以防大面积停电。该保护原理简单、计算速度快,对保证电网的安全稳定运行具有重要意义。提出了基于多Agent技术的防连锁过载跳闸保护方案。阐述了Agent的基本思想,分析了多Agent防连锁过载跳闸保护的框架结构及其内部各模块的功能与配合,提出了基于Agent技术的防连锁过载跳闸保护方案,故障时可以有效地缩短后备保护动作时间,过载时通过对过载电流系数的实时判断,防止连锁过载跳闸情况的发生。对电网广域测量系统及数字化变电站中多采样率转换的问题进行了研究。数字化变电站中的电子式互感器及广域相量测量单元(PMU)中用到的各测量点的互感器并非同一型号,其采样频率不完全相同,因而需要将多采样频率信号转换为同一采样频率。通过对不同采样频率信号内插、抽取和凯赛窗低通滤波三者的级联,实现了任意分数倍采样频率的转换。在此基础上,提出了基于全波傅氏的数字窄带滤波算法,在频率转换的同时对有用信号进行滤波,实现对采样信号不失真的频率归一化。所提方法简单、快速、有效,可用于电力系统安全稳定的分析、控制和广域保护。对基于广域信息的六线输电系统的选相及测距进行了研究。将广域测量系统得到的输电线路两端电气量进行六序分解,利用六序分量中同正序故障分量(同杆双回线)或反正序故障分量(六相输电)的传输线长线方程测得故障距离。之后利用两端电气量和故障距离再借助长线方程求得故障点的各相电流,依据故障点相电流的幅值特征判断故障相。该方法测距精度高,又能实现故障选相,且选相原理清晰、逻辑简单可靠,不受故障点过渡电阻和线路分布电容电流的影响,随着系统运行方式的变化可自适应调整选相判据的定值,为六线输电系统的距离保护提供了有效的选相逻辑。更多还原

【Abstract】 Smart grid is present situation of the development and changes in power systems, and it is considered as the most important technology innovation and development trend in power systems during 21st century. The final goal of smart grid is realizing the digitalization, informatization, automatization and alternation so that the smart gird would be established intelligently, strong, efficiently and reliably. As one of the most important investigated subjects for Smart grid, wide area protection system can resolve the unilateral and independent problem of the protection at present. Wide area protection system can also keep the large-scale power grid secure and steady, and it is indispensable. In this paper, wide-area protection of Smart grid and related issues has been discussed.A principle of preventing chain over-load trip based on wide-area information is proposed. Taking the important buses as units, the over-load current coefficient of each branch is calculated using relevant elements of the node impedance matrix in the normal operation conditions stored in the wide-area scheduling centre. The possibility of chain over-load trip caused by over-load branches is then estimated based on these coefficients, to help control centers take timely measures to prevent chain over-load trip and large-scale blackouts. The protection has simple principle, fast algorithm. It is also of great significance to the power grid safe and stable operation.A new method of wide-area protection against chain over-load trip (PACOLT) based on multi-Agent technology (MAT) is discussed in this paper. After expounding the Agent technology, and analyzing the structure of wide-area PACOLT based on MAT and the function and cooperation of all the inside modules, a new theory of wide-area PACOLT is proposed to prevent the Chain over-load trip and insure the reliability and continuity of power supply.In this paper, Wide area measurement system (WAMS) and Multi-sample-rate for Digital substation are studied. Because current (voltage) transformers and Phasor Measurement Unit (PMU) of Wide area measurement system in digital substation are different in type and sampling rates, it is necessary to convert them to the same rate. In this paper, sampling rate conversion in a rational factor is realized through cascade connection of extraction, interpolation and low-pass filter. A digital narrow band-pass filter algorithm based on full cycle Fourier algorithm is proposed. This algorithm can not only obtain the useful frequency component fast and effectively, but also realize the normalization of signals’sampling rate without distortion. The method Proposed is simple, fast, effective and can be used for security and stability of power system analysis, control and wide-area protection.Phase selection and fault location of Six-line transmission system based on Wide area measurement system are studied in the paper. This paper introduces the six sequence variables method to analysis the electrical signals gained from the end of transmission lines, and uses the same positive sequence (the parallel transmission lines system) or the opposite positive sequence (six phase transmission system) signal’s long line equation to locate fault point. With the help of long line equation, the fault currents can be calculated form the location of fault and electrical signals gained from the end of transmission lines. The method proposed has high fault location accuracy and can select the right fault phase. The theory of the phase selection is clear and the logical of the protection is simple and reliable. It is also free from transition resistance and distributed capacitance current influence. This method can adjust the criterion of fault phase selection when operation mode is changed. It can provide effective phase selection logic for six-line transmission systems.更多还原