Mallat电力谐波检测方法分析与仿真
近年来，越来越多的非线性设备在电力系统中被广泛使用，谐波问题日益严重，对 电网造成危害，而谐波检测是解决谐波问题的前提，为治理谐波污染提供依据。
本文首先介绍了谐波的定义，传统的几种谐波源以及谐波的影响，并论述了五种较 常见的谐波检测方法，比较它们的优劣。然后研究基于傅里叶变换的检测方法，分析算 法中的频谱泄漏和栅栏效应，提出用窗函数来减小频谱泄漏。用 MATLAB 软件进行 FFT 算法仿真，在非整周期同步采样时加窗函数，仿真后信号幅值误差减小。接着研究小波 变换检测法，主要研究 Mallat 算法，分析该算法中存在的频率折叠。在仿真中，由于滤 波器的非理想特性，出现了虚假频率，对此做了算法改进，使仿真结果与理论值相符。 最后，用小波函数对含噪声的信号进行降噪，证明了小波变换法也适用于信号的降噪处 理。78758
关键词 电力谐波 检测方法 傅里叶变换 小波变换
毕 业 设 计 说 明 书 外 文 摘 要
Title Analysis and Simulation of Power Harmonic Detection Method
Abstract In recent years, with the widely use of more and more nonlinear electronic device, the harmonic problem is increasingly serious,harming the power network。 Harmonic detection is the precondition of solving the harmonic problem and provides the basis for controlling the harmonic pollution。
Firstly, the definition of harmonic,several traditional harmonic sources and the influence of harmonic are introduced。 Then,five common harmonic detecting methods are discussed and their merits and demerits are compared。 Next,the detection method based on Fourier Transform is studied and the spectrum leakage and fence effect is analyzed in the paper。 To reduce the spectrum leakage, a window function can be used。 Through the MATLAB simulation,the window function is verified useful when conducting the non integer period sampling。 And then, the detection method based on Wavelet Transform espically the Mallat algorithm is studied。The frequency folding of the algorithm is also analyzed。 After simulation, an improved algorithm is proposed to solve the false frequency condition due to the non ideal characteristics of the filter。 Finally, the wavelet function is used to reduce the noise,and it is proved that the wavelet transform method is suitable for the signal denoising。
Keywords power harmonic detection method Fourier Transform Wavelet Transform
目 录
1 绪论 1
1。1 课题研究背景及意义 1
1。3 本文章节安排 2
2 电力谐波分析与检测 3
2。1 电力谐波分析 3
2。2 电力谐波检测方法 5
2。3 本章小结 8
3 快速傅里叶变换检测方法研究与仿真