电压质量论文.doc

毕业设计（论文） 题 目 电网电压质量分析 算法的设计与仿真 专 业 电气工程及其自动化 2007 年专业：电气工程及其自动化 班级：电气031班 作者： 指导教师： 职称：教授 答辩日期：2007-06-18 摘 要 随着科学技术和国民经济的快速发展，各种工业生产对电力系统电能质量的要求越来越高。然而，现代电力电子设备和非线性负载的大量使用又造成电能污染日趋严重，电能质量成为电力部门及其用户日益关注的问题。另外我国电力行业改革，电能作为一种特殊商品，按质论价也是大势所趋。因此对电能质量进行检测与分析具有重要的意义。 电能质量主要有五项基本指标:电压偏差、频率偏差、谐波偏差、电压波动和闪变、三相电压不平衡。本文介绍了这五项标准的基本概念。目前电能质量的分析方法有傅立叶变换法、短时傅立叶变换法和小波分析法，本文所述的电能质量监测是采用快速傅立叶变换(FFT)分析方法。本文主要对电能质量的有关指标:谐波含量、三相不平衡的计算和检测方法，进行了详细地阐述，对FFT实际应用中的问题进行了研究，通过实际算例探讨了采样方法、窗函数加权等影响谐波计算精度的因素。这些方法都是在MATLAB中通过仿真完成的。得到了对电压质量分析具有指导意义的结论。 关键词：电能质量，谐波含量，三相不平衡，傅立叶变换 Abstract With the rapid development of science technology and national economy, diverse kinds of industry production demand higher power quality; moreover, with the widely application of modern power electronics technology, power quality is deteriorated increasingly; therefore, more and more close attention is paid to power quality by both electric department and consumers. Power as a kind of special merchandise, there is a tendency of its price scaled according to its quality. So detecting and analyzing power quality are very significant. I There are five prime indexes of power quality: voltage deviation, frequency deviation, harmonic content, voltage fluctuation and flicker, three phase unbalance. This paper presents the concept of these five indexes. At present, Fourier transform, short time Fourier transform and wavelets analysis are the main analysis methods of power quality. While power quality presented in this paper uses fast Fourier transform. Then some indexes of power quality: harmonic content and three phase unbalance are discussed at length. Finally some measurements are summarized, the harmonic analysis method based on FFT is discussed, and some practical issues in the application of FFT are investigated. The factors which affect the calculation precision of harmonics, such as sampling and weighting of window function are anal