基于加窗傅里叶变换的弱电网阻抗测量算法

摘要

为了解决基于传统傅里叶变换的弱电网阻抗测量在电网背景谐波干扰和基频偏移时出现严重的检测误差现象,给出了一种改进的检测算法.通过深入分析傅里叶变换以及窗函数的数学特点得出,对信号的非同步采样及传统傅立叶变换较慢的频响曲线衰减速度是引起误差的主要原因.基于此提出采用加窗傅里叶变换算法,以大大提高傅里叶变换主瓣与旁瓣以及旁瓣间的衰减速度,同时适当增加傅里叶变换的频率分辨率以避免加窗之后主瓣过宽引起的主瓣干扰.Matlab仿真和实验结果表明,所提改进算法可有效提高电网阻抗检测的计算精度和抗干扰能力.%In order to solve the error of the weak grid impedance measurement based on the traditional Fourier transform,which is caused by the grid background harmonic interference and the fundamental frequency fluctuation,an improved detection method is proposed.By analyzing the mathematical characteristics of Fourier transform and window function,it is concluded that the slow frequency response attenuation speed of the traditional Fourier transform and signals' asynchronous sampling is the main cause of the error.On this basis,a windowed Fourier transform algorithm is applied to greatly improve the Fourier transform attenuation speed from the main lobe to side lobe as well as from side lobe to side lobe.At the same time,the frequency resolution of Fourier transform is increased to avoid the main lobe interference caused by wide main lobe after windowing.Matlab simulation and experimental results verify that the method proposed is effective to improve calculation precision and anti-interference ability of grid impedance detection.