【作者】 陈婷；

【导师】 李开成；

【作者基本信息】 华中科技大学 ， 电气工程， 2016， 硕士

【摘要】 电网中的大量谐波存在给电力系统安全运行带来极大的威胁。谐波分析是电能质量研究的热点之一,电参量测量作为谐波分析的一个重要分支,是电能质量分析的主要依据。傅里叶分析(Fourier Analysis)是电力谐波测量的应用最常用方法之一。由于电网波动,在非同步采样情况下,基于傅里叶分析的谐波检测方法存在频谱泄露和栅栏效应等问题,从而给谐波信号的准确测量带来困难。加窗插值算法能够有效减小傅里叶分析方法的缺陷,提高电力谐波参数的检测准确度。插值余弦窗由于函数结构和修正算法简单,是目前应用最广的窗类型。本文通过考察插值余弦窗,提出基于插值幂型正弦窗函数的谐波检测方法。基于快速傅里叶变换(Fast Fourier Transform,FFT)的加窗插值方法主要包括窗函数设计和插值算法设计两部分。论文通过回顾多种常用窗函数,并借鉴余弦窗函数的构建方法,改进Nuttall系数设计思路,提出正弦组合窗构建方法;通过解读插值算法基本思想,将余弦三谱线插值算法改进应用于正弦窗修正;结合卷积定理设计卷积窗,提升窗函数性能,提高算法检测的准确度。论文通过窗函数特性分析和数学公式推导,探讨正弦组合窗和余弦组合窗的内在关系,定义了幂型正弦窗函数,并提出幂1的正弦窗是幂型正弦窗的最基本单元,为窗函数的构建提供了另一种思路。论文结合MATLAB仿真,综合分析了基频波动、采样频率变化、窗口长度变化、直流偏置、噪声、数字量化和谐波共存等多种影响因素下的测量误差。结果表明,这种基于加正弦窗插值算法具有检测精度高、抗干扰性强等优点。论文还通过仿真不同幂型正弦窗及其卷积窗,分析了它们的时频域特性和谐波检测性能,以满足谐波分析的不同需求。论文最后围绕可视化设计理念,开发了一套插值幂型正弦窗设计平台。软件具有很好的的幂型正弦窗设计与插值拟合功能,能够完成任意正整数谐波的分析,帮助设计者摆脱了重复式的编程作业,提高开发效率。论文研究表明,基于插值幂型正弦窗的谐波检测方法具有很高的谐波参数提取能力,算法实时性和鲁棒性好等诸多优点,并且函数构造简单、灵活多变、易于移植和衍生,从而为电力系统谐波测量方法提供更广的选择空间,具有很好的理论和应用价值。更多还原

【Abstract】 The existence of numerous harmonic waves will severely endangers the safety operation of electric power system. Harmonic analysis is one of power quality research focuses. Harmonic parameters estimation provides important basis for power quality analysis, which becomes an important branch of harmonic analysis. Fourier analysis is one of most commonly used methods in electric harmonic detection. However, because of the fluctuation of system frequency, the harmonic detection based on Fourier analysis, which under asynchronous sampling, will rise to the phenomenon of frequency spectrum leakage and fence effect, which brings difficulty to accurate measurement of harmonic signals. Window-added and interpolated FFT can effectively reduce impact of spectrum leakage and fence effect, and enhance the accuracy of harmonic detection. Due to cosine window FFT interpolation is easy to structure and correction, it becomes one of the most widely used methods. This thesis analyzed cosine windowed interpolation and proposed an approach for harmonics detection based on power-type sine windowed interpolation FFT. In the approach, the sine window function not only inherits the cosine window function features, but also has more flexible forms, which extends the field of window function.The construction of windowed interpolation FFT method mainly includes two parts: one is windows function design and the other is interpolation function design. This thesis gave a review of many commonly used window function, fully referenced to the constructor methods for cosine windows, presented some thinking to improve Nuttall coefficient design, to the construct sine-class window. The thesis adjusted interpolation by three spectral lines method for cosine windows to sine windows, after grasping the basic idea of interpolation. Moreover, the thesis proposed convolution windows for the performance of windows as well as the accuracy of the harmonic analysis improvements. This thesis discovered the internal relations between cosine-class and sine-class windows by means of time-frequency analysis and mathematical formula, and defined power-type sine windows, promoting that the sine window with exponent one is the most basic unit for power-type sine windows. The definition gave an alternative approach for power-type sine windows construction.Combined with MATLAB software, this thesis made a comprehensive error analysis of factors having an influence on harmonic detection, which included the variety of fundamental frequency, sampling frequency, length of data, DC bias, noise level, quantization bits, harmonic content, and so on. The results indicated that, the power type sine windowed interpolation FFT method has high detecting precision and strong anti- interference capacity. In order to meet different demands of harmonic analyze, the thesis analyzed the time-domain and frequency-domain characteristics of different power type sine windows and their convolution windows with simulated tests.Finally, around the visual design conception, the thesis developed a platform for power type sine windowed interpolation FFT with powerful power type sine windows design and interpolation capability, which can carry out the analysis of integer harmonic efficiently. It can help designers to get rid of repetition of programming and enhance developing efficiency.This thesis showed that, the harmonic detection method based on power type sine windowed interpolation FFT performs good ability in parameter extraction, and has high-detection-rate and robust. Besides, functions are convenient for realization, flexible, and have good portability. It has theoretic and practical merits for offering a much wider choice of harmonic detecting methods for the power system.更多还原