一种高精度六谱线插值FFT谐波与间谐波分析方法

加窗插值快速傅里叶变换(Fast Fourier Transform, FFT)算法因其便于在嵌入式系统实现而被广泛应用于电力系统谐波检测,可改善因非同步采样和非整周期截断造成的频谱泄漏与栅栏效应,提高FFT分析的精确度。针对目前常用的加窗插值算法存在的不足,在分析五项最大旁瓣衰减(Maximum-Sidelobe-Decay, MSD)窗频谱特性的基础上,提出一种基于五项MSD窗六谱线插值FFT的谐波与间谐波分析算法。该算法利用紧邻峰值谱线频点的六条谱线进行加权运算,充分考虑峰值频点左右对称谱线所蕴含的信息以提高分析精度。通过数据拟合求出窗函数对应的插值修正公式,简化了运算过程。仿真结果表明,五项MSD窗六谱线插值FFT算法设计实现灵活,抑制频谱泄漏效果极好。相比于其他常见的四谱线插值FFT算法,该算法具有更高的谐波、间谐波检测精度。

A high precision approach for harmonic and interharmonic analysis based on six-spectrum-line interpolation FFT

The windowed interpolation FFT algorithm can be implemented easily by embedded systems, so it is widely used in power system harmonic detection, which can restrain the spectrum leakage and fence effect caused by non-synchronous sampling and non-integer cycle truncation in order to improve the analysis accuracy of FFT. Aiming at the shortcomings of common windowed interpolation algorithms, the spectral characteristics of 5-term MSD window are analyzed and a harmonic and interharmonic analysis algorithm based on 5-term MSD window and six-spectrum-line interpolation FFT is proposed. The algorithm uses six spectrum lines close to the peak spectrum line frequency point to perform weighted operations, the information contained in symmetric spectrum lines is considered. Through data fitting, the practical interpolation correction formula corresponding to the window function is obtained, which simplifies the operation process. Simulation results show that the algorithm can be designed and realized easily, it can also restrain the spectrum leakage effectively. Compared with other common four-spectrum-line interpolation FFT algorithms, the algorithm has higher accuracy in harmonic and interharmonic detection. This work is supported by National Natural Science Foundation of China (No. 51467004).