Blackman-Nuttall窗FFT序列重构四谱线插值介损角测量方法

Four spectral interpolation dielectric loss angle measurement method based on Blackman-Nuttall window FFT sequence reconstruction

采用快速傅里叶变换(FFT)在非同步采样时会产生频谱泄露和栅栏效应,影响介质损耗角的测量精度。为提高介质损耗角的测量精度,该文提出并建立一种基于Blackman-Nuttall窗FFT序列重构的四谱线插值介损角测量方法,对采样信号加Blackman-Nuttall窗进行FFT获得离散频谱序列,通过五点变换重构离散频谱序列,然后对重构后的序列进行四谱线插值修正得到电压和电流信号的基波相位,最后由两者的基波相位得到介质损耗角。通过在频率变化、采样点数变化、初始相位变化、直流分量变化、谐波分量变化和不同信噪比的噪声下仿真实验,表明该方法具有较高的介质损耗角测量精度。在与已用加窗傅里叶变换法相比,该方法运算量小、测量精度高,适用于对介质损耗角的精确测量。

The use of fast Fourier transform(FFT)in asynchronous sampling will produce spectrum leakage and fence effect,which will affect the measurement accuracy of dielectric loss angle.In order to improve the measurement accuracy of dielectric loss angle,a four spectral line interpolation dielectric loss angle measurement method based on FFT sequence reconstruction of Blackman Nuttall window is proposed and established in this paper.The sampled signal is FFT with Blackman Nuttall window to obtain discrete spectrum sequence,and the discrete spectrum sequence is reconstructed through five point transformation.Then,the reconstructed sequence is interpolated with four spectral lines to obtain the fundamental phase of voltage and current signals.Finally,the dielectric loss angle is obtained from the fundamental phase of the two.Through the simulation experiment under the noise of frequency change,sampling point change,initial phase change,DC component change,harmonic component change and different signal-to-noise ratio,it shows that the method has high accuracy of dielectric loss angle measurement.Compared with the existing windowed Fourier transform method,this method has the advantages of less computation and higher measurement accuracy,and is suitable for accurate measurement of dielectric loss angle.