基于多峰谱线插值的间谐波检测新方法

An Interharmonic Estimation Method Based on Chirp Z Transform and Correction Algorithm of Four-peak Spectral Line

插值FFT算法根据检测到的频率分布修正FFT结果,而实际中间谐波频率很难确定,当间谐波信号附近含幅值较大的谐波信号时,FFT的栅栏效应可能降低检测精度。利用频率识别能力较强的线性调频Z变换(CZT),用检测得到的与估计值邻近的4条离散频谱幅值估计间谐波参数,并根据多项式逼近推导了插值修正公式,在CZT谱频率分布指导下进行插值修正,使各次谐波和间谐波参数的检测精度得到一定程度提高,仿真证明了该方法的可行性和正确性。

Interpolation FFT algorithms correct the results of FFT according to the detected frequency distribution. However, the distribution of interharmonics and harmonics in actual signal usually can not be ascertained beforehand. And when there are harmonic signals with large amplitude near interharmonic signal, the inherent picket fence effect of FFT will reduce the precision of detection. A method for interharmonic measurement is presented based on chirp Z transform （CZT） and correction algorithm of four - peak spectral lines. The accurate estimated value of frequency distribution of interharmonic signal can be obtained hy means of CZT, and the parameter of interharmonics can be estimated to form the amplitude of four neighboring peak spectral lines. The polynomial approximation method is used to obtain the simple correction formula of Blackman - Harris window interpolation algorithm, and the interpolation and correction is carried out according to the distribution of CZT spectra. So the estimated results are modified and more accurate parameters of various orders of harmonics and interharmonics are obtained. The simulation results show that the proposed method is feasible and proper.