电机测试中谐波分析的高精度FFT算法

FFT ALGORITHM WITH HIGH ACCURACY FOR HARMONIC ANALYSIS IN THE ELECTRIC MACHINE

快速傅立叶变换在非同步采样情况下存在较大的误差 ,因而无法在电机测试过程中获取准确的谐波参数。为了减小非同步采样对快速傅立叶变换的影响 ,提高电机测试中的谐波分析精度 ,该文通过加窗和插值对原算法进行了改进。该文先是对非同步采样的泄漏效应进行了简要说明 ,然后详细分析和推导了加Blackman Harris窗的插值算法 ,并借助MATLAB软件求解高次插值方程得到准确的频率偏移量 ,进而得出较准确的谐波参数。在此基础上 ,对插值公式作适当改动 ,可以进一步提高各种情况下特别是泄漏程度较严重时的计算精度。该文最后提供了一个模拟分析实例 ,分析结果进一步验证了改进后算法在非同步采样时 ,仍然具有非常高的分析精度。

The FFT has a higher error when used with a sample sequence which is not synchronized with the signal,which makes that the electric harmonic parameters can not be gotten accurately.To reduce the influence of an unsynchronized sample sequence on FFT and to improve the precision of harmonics in electric machine testing, This paper improves the algorithm by using windows and interpolation methods.This paper first discusses the leakage of FFT briefly and then analyzes the interpolation algorithm on Blackman Harris window in detail. With the new algorithm,we can get the accurate frequency offset and other accurate harmonic parameters by solving high order interpolation equation with the help of MATLAB language.After this,we make a little change to the interpolation formula,which can make the calculating accuracy be further improved on every condition especially for the severe leakage.An example of simulation is given and validates that the improved algorithm holds a very high precision when used for the unsynchronized sample sequence.