基于三谱线插值FFT的电力谐波分析算法

快速傅里叶变换在非同步采样和数据非整数周期截断的情况下存在较大的误差,无法得到准确的谐波参数。为此,文章提出一种改进的加窗插值傅里叶变换算法进行电力谐波检测。该算法通过分析加窗信号傅里叶变换的频域表达式,利用谐波频点附近的3根离散频谱的幅值确定谐波谱线的准确位置,进而得到谐波的幅值、频率及相位。推导的三谱线插值修正算法能够进一步提高谐波分析的准确性。基于该算法,通过多项式拟合的方式,得出了一些典型窗函数的谐波分析实用修正公式。通过仿真,验证了相比目前常用的双谱线插值修正算法,该算法在加相同窗函数情况下具有更高的计算准确度,从而验证了该算法的有效与实用。

An Algorithm for Electrical Harmonic Analysis Based on Triple-spectrum-line Interpolation FFT

The fast Fourier transform(FFT) will have a greater error in the cases of non-synchronous sampling and in a truncated non-integral period,thus accurate harmonic parameter values can not be obtained.For this reason,an improved interpolation windowed FFT algorithm was presented in this paper to analysis electrical harmonics.The algorithm used the three neighboring spectrum lines to locate the accuracy position of the harmonic spectrum line through analyzing the discrete-time Fourier transform of the windowed signal,and then the accurate results of the frequency,phase and amplitude could be obtained.By the triple-spectrum-line Interpolation FFT,the accuracy of the harmonic analysis results could be improved.Based on the algorithm,the practical rectification formulas for harmonic analysis were obtained by using the polynomial approximation method.The simulation results have verified that the algorithm has a better precision than the double-spectrum-line interpolation algorithm using the same window.Thus the effectiveness and practicability of the algorithm have been verified.