采样时间和采样频率对基于加窗插值算法介损角测量的影响

为减少非同步采样时DFT算法计算介损角的误差,将加汉宁(Hanning)窗插值谐波分析法和加布莱克曼-哈里斯(Blackman-Harris)窗插值谐波分析法用于介损角的测量。介绍了两种算法的原理,比较了两种算法受采样时间和采样频率影响上的差别。结果表明:两种算法误差随采样时间增加呈振荡下降趋势,加汉宁窗插值算法极小误差值点为0.02 s的整数倍附近,极大误差值点为0.01 s的奇数倍附近,加布莱克曼-哈里斯窗插值算法在0.01 s的整数倍附近有极小误差,中间存在极大误差值;两种算法达到基本的精度时要求采样时间至少为3~5个工频周期左右,采样频率不小于500 Hz即可;在一定范围内,前者计算所得介损角的精确度对采样时间较敏感,前者的精确度对采样频率不敏感,后者的精确度对采样时间和采样频率都较敏感。

Influence of sampling time and sampling frequency on dielectric loss angle measurement based on windowed interpolation algorithm

In order to reduce the error of dielectric loss angle measured by Discrete Fourier Transform(DFT) in asynchronous sampling,Hanning windowed interpolation harmonic analysis algorithm and Blackman-Harris windowed interpolation harmonic analysis algorithm were used to measure dielectric loss angle.The principle of the two algorithms were introduced,accuracy influence of sampling frequency and time were compared.The results indicated that error of the two algorithms decreased vibratingly with the increase of sampling time.As for Hanning windowed interpolation harmonic analysis algorithm,the time of the maximal error point was about integer multiple of 0.02s,and the time of the minimal error point was about odd multiple of 0.01s.As for Blackman-Harris windowed interpolation harmonic analysis algorithm,the time of the minimal error point was close to integer multiple of 0.01s,and the maximal error point was in the middle.If accuracy requirement was satisfied,the two algorithms needed at least 3～5 power frequency period and furthermore sampling frequency should be higher than 500Hz.In some conditions,the former is sensitive to sampling time,but not sensitive to sampling frequency;the latter is sensitive to both sampling time and sampling frequency.