电力系统谐波检测与去噪声方法研究
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电力系统谐波检测与去噪声方法研究(任务书,开题报告,论文13000字)
摘 要
我们普遍认为电力系统中的设备产生的各次畸变的电网波形就是谐波。即使电源的供电频率都是50HZ，但如果存在非线性负载时，非线性负载在工频电压或电流作用下，会产生非50HZ之外的其它频率的正弦电流或者电压，这些正弦电流或者电压就是人们称的电力系统谐波。当电网中存在谐波时，系统的供电质量会下降，电能的使用效率也随之降低。谐波的存在会导致器件过热，使系统设备的使用寿命降低。严重的使设备绝缘老化，发生故障。
本文首先基于傅里叶变换和小波变换的电力系统谐波检测的原理，分析傅里叶变换存在的不足。考虑到傅里叶变换的不足提出一种更加合理的检测方法—利用小波变换检测谐波。综合这两种检测结果准确把握信号的局部细节，再次根据小波阈值去噪原理对谐波信号中的噪声信号进行处理，最后通过MATLAB进行仿真测试。从检测的结果可以得出相应结论。最后根据小波阈值去噪声的原理，使用三种不同的小波阈值函数对谐波信号中的噪声信号进行处理。
关键词：电网谐波 谐波危害 傅里叶变换 小波变换 小波阈值去噪
Abstract
It is generally believed that the power system waveform is the harmonic wave in the power system. Even if the power supply frequency is 50Hz, but if the presence of nonlinear load, nonlinear loads in the power frequency voltage or current will produce other frequency 50Hz sinusoidal current or voltage, called the sinusoidal current or voltage is people power system harmonics. When there is harmonic in the power grid, the power supply quality of the system will be reduced, and the efficiency of the use of power can also be reduced. Sometimes the presence of harmonics will reduce the service life of the system equipment, because the harmonics will cause the device to overheat. Severe equipment insulation aging, failure.
Firstly, based on the principle of Fourier transform and wavelet transform for power system harmonic detection, this paper analyzes the shortcomings of Fourier transform. A more reasonable detection method based on Fourier transform is proposed, which uses wavelet transform to detect harmonics. The two kinds of detection results accurately grasp the local details of the signal, and then again according to the principle of wavelet threshold denoising to deal with the noise signal in the harmonic signal, and finally through the MATLAB simulation test. Corresponding conclusion can be drawn from the results of the test. Finally, according to the principle of wavelet threshold denoising, the noise signal in the harmonic signal is processed by three kinds of different wavelet threshold functions.
Key words: power grid harmonic，harmonic hazard，Fourier transform，wavelet transform， wavelet threshold denoising
目 录
第1章 绪论 1
1.1研究的目的和意义 1
1.2国内外研究现状及关键技术发展 1
1.2.1国内外研究现状 1
1.2.2关键技术发展 2
1.3本文主要研究内容 3
第2章 谐波的特性及危害 4
2.1谐波的定义 4
2.2谐波的来源 4
2.3电力系统谐波的标准 4
2.4谐波的危害 5
2.5本章小结 6
第3章 基于小波变换的谐波检测原理 7
3.1 傅里叶变换的局限性 7
3.2小波变换 7
3.2.1小波变换原理 7
3.2.2多分辨分析 8
3.2.3小波函数 9
3.3本章小结 11
第4章 小波阈值去噪原理 12
4.1小波阈值去噪方法 12
4.1.1小波阈值去噪基本思路 12
4.1.2小波基的选择 12
4.1.3分解层数的选择 13
4.2 小波阈值去噪函数 13
4.2.1 缺省阈值去噪 13
4.2.2 penalty阈值去噪 14
4.2.3 Birge-Massart阈值去噪 14
4.3本章小结 14
第5章 仿真实例 16
5.1生成谐波信号 16
5.2谐波信号的检测 16
5.3去噪声仿真 19
5.4本章小结 24
第6章 总结与展望 25
参考文献 26
致 谢 27