【作者】 李兰芳；

【导师】 刘开培；

【作者基本信息】 武汉大学 ， 电力电子与电力传动， 2004， 硕士

【摘要】 近年来，电能质量问题日益引起电力部门和用户的广泛关注。为了采取合理的措施来提高电能质量，必须首先建立电能质量监测分析系统，对电能质量进行正确地检测、评估和分类。本文在总结原有的电能质量分析方法的基础上，提出采用小波变换和傅立叶变换相结合的方法进行电能质量分析。 本文首先系统地介绍了电能质量现象及其理论基础，对各种电能质量扰动的分类、定义、特征及其产生的原因进行了详细的阐述，并简要介绍了我国电能质量标准。其次，对傅立叶变换、短时傅立叶变换和小波变换这三种方法的基本原理及其在电能质量分析领域的应用现状做了探讨和比较，分析了各种方法的特点及其适用条件。进而，通过对大量典型信号的仿真分析确立了电能质量分析算法，并验证了该方法的优越性。 实际的电能质量信号可能含有高频突变部分和噪声部分。小波变换的自适应性使其对电能质量扰动信号的消噪有着传统的低通滤波器无法比拟的优点。本文采用小波消噪的方法对信号进行预处理，获得了良好的效果。 基于信号的奇异性检测理论，利用小波分解的高频系数是否具有模极大值作为区分稳态和非稳态现象的判据。利用快速傅立叶变换方法对谐波、闪变和纯正弦波等稳态现象进行分析。利用小波变换的快速算法——Mallat算法来确定非稳态扰动的持续时间和扰动波形，从而区分各种非稳态扰动现象。 最后，本文从电能质量在线监测的角度出发，采用基于小波变换和傅立叶变换的电能质量分析方法，设计了以TMS320VC33为核心的硬件监测系统，并采用C语言编程实现电能质量分析算法。更多还原

【Abstract】 In late years, power quality issues have captured considerable attention from both utility companies and their customers in many countries. To improve the electric power quality, a monitoring and analyzing system must be established to detect, estimate and classify different disturbances. Traditional monitoring and analyzing system have put emphasis on steady voltages and currents, a new analyzing method based on wavelet transform and Fourier transform has been presented in the thesis.In the thesis firstly the theoretical background of power quality phenomena is introduced. Secondly, three transform-based methods, which are Fourier transform, short-time Fourier transform and wavelet transform, and their applications are described and discussed in detail. Then the analysis algorithm of electric power quality is posed by massive simulation and analysis.Real power quality signals may comprise high-frequency useful part and noise part. Self-adapting quality makes wavelet denoising prior to low-pass filter. Wavelet denoising is presented as a pre-processing tool for power quality signals in the thesis.Based on the theory of signal strangeness detect, the maxima modulus in high frequency of wavelet resolving can be used as a criterion to classify steady and non-steady state phenomena. As to steady state phenomena, the traditional signal analysis tool FFT is used for harmonic analysis and flicker. By means of the Mallat algorithm, the lasting time and disturbance waveform can be extracted, so non-steady state interruptions can be identified exactly.Finally, considering on-line monitoring and measurement system of power quality, based on wavelet transform and Fourier transform for power quality analysis, the hardware system is designed base on TMS320VC33, and the software is programmed in C language in the thesis.更多还原