【作者】 武艳华；

【导师】 黄纯；

【作者基本信息】 湖南大学 ， 电力系统及其自动化， 2006， 硕士

【摘要】 近年来,随着电力电子技术的广泛应用,电力系统谐波污染日益严重,成为影响电能质量的公害,谐波及间谐波问题已经引起广泛关注。本文首先简单介绍了谐波及间谐波的产生、危害以及各种检测算法,分析比较了各种算法的优缺点,对其中的基于傅立叶变换的理论和现代谱估计理论进行了较为详细的介绍,阐述了本文的学术背景和实际意义。其次对傅立叶变换的基本理论、基本形式以及实际应用中应注意的问题进行了详细的阐述,对传统的基于加窗DFT的谐波检测方法的误差原因及减少误差的方法进行了分析,并介绍了各种不同的余弦窗函数,进而简要分析了几种常见的频谱校正方法。在频谱校正方法的基础上,文章给出了一种基于DFT频谱校正的谐波及间谐波检测算法,并通过仿真实例,证明在选取合适的时间窗长度、采样点数以及相应的窗函数时,算法可以比较精确地测量出各次谐波及间谐波的各项参数。但是该算法不适用于检测频率间隔很近的谐波和间谐波。然后,文章提出了一种基于现代谱估计的间谐波检测算法,算法应用AR模型和扩充Prony模型进行间谐波检测。由于AR模型的递推算法Burg算法存在谱线分裂现象,文中选择使用Hamming窗加权的Burg算法来递推AR模型,修正后的Burg算法明显减轻了谱线分裂现象,具有较好的抗噪声能力,但无法得到间谐波的相位信息。因此文中还使用了Prony模型来检测间谐波,Prony模型检测精度高,但是由于模型本身受噪声影响比较大,选择Prony模型时算法的抗噪声能力较差,只适用于信噪比较高的情况下。上述研究证明,在间谐波检测领域,特别是对离谐波频率较近的间谐波检测中,现代谱估计理论有着许多DFT算法及其校正算法不可比拟的优势,将其引入电力系统间谐波检测中是有效可行的。最后对全文工作做了总结,对如何进一步提高谐波和间谐波检测精度以及检测技术的发展趋势做出了展望。更多还原

【Abstract】 In recent years, along with the extensively application of the power electronic technology, the pollution of the harmonics becomes more and more seriously and it influences the electric power quality seriously. As a result, harmonics and inter-harmonics problems have attracted widespread attention.Firstly, this paper introduces the derive, harm and lots of detection algorithms of harmonics and inter-harmonics, analyses the advantage and disadvantage of every algorithm, and then details the Fourier transformation theory and the theory of modern spectral estimates, which elucidates the research background.Secondly, this paper details the basic theory of Fourier transform, and the problems which must be paid attention to in the practical application. The reasons of the error caused by the traditional electric signal detection methods based on the windowed DFT are thoroughly analyzed. Besides, many cosine windows are introduced.Based on the spectrum correction theory, we propose an algorithm which is suitable for harmonics and inter-harmonics measuring. The simulation of the Matlab proves that the algorithm can meet the demand of harmonics and inter-harmonics detection when choosing suitable length of data window, sampling frequency, and corresponding windows. However, this algorithm is not fit for the detection of the signals whose frequencies are very close to each other.Therefore, using the AR model and the Prony model to measure the inter-harmonics, an inter-harmonics measuring algorithm which is based on advanced spectral estimation is presented. Because of the spectral line splitting of the Burg algorithm, the recursive algorithm of the AR model, we choice the Hamming weighted Burg algorithm in this paper. The modified Burg algorithm can weaken the spectral line splitting effectively. However, the AR model can’t gain the phase of the inter-harmonics. So the Prony model is adopted to detect the inter-harmonics. Although the Prony model can achieve high precision, it is much more sensitive to noise and can be applied only under the higher SNR circumstance. The studying results show that the advanced spectral estimation is more predominant than DFT algorithm and its corrected algorithms in the field of inter-harmonics measuring, especially for the inter-harmonics which is too close to harmonics. Hence, it is effective and feasible to introduce the advanced spectral estimation into inter-harmonics measuring.更多还原