基于数字化变电站IED接口的数据处理算法

Data Processing Algorithms Based on IED Interface in Digital Substation

在当前的数字化变电站中,过程层的合并单元(merging unit,MU)将等间隔采样的采样值报文发送到智能电子设备(intelligent electronic device,IED)进行处理。为提高测量精度和保护特性,IED首先要将等间隔数据转换成等相角数据;另外,MU的采样率不等于2N(N为每周期采样点数),无法进行快速傅里叶变换(fast Fourier transform,FFT)计算,若在测控装置中直接采用离散傅里叶变换(discrete Fourier transform,DFT)算法,则计算量太大。为得到等相角的数据,同时减小计算量,适应FFT算法,文章设计了一套适应数字化变电站IED接口的数据预处理算法,包括数字低通滤波、频率跟踪校正、采样率转换(sampling rate conversion,SRC)等,并使用MATLAB对数据预处理过程进行了仿真验证,结果表明,该算法计算量较小,精度较高。

In digital substations, the message of sampled value acquired by equal interval sampling is send to intelligent electronic device （IED） by merging unit （MU）, where the message is processed. To improve both measurement accuracy and protective characteristics, in IED the sampled equal interval data is converted into the data with equal phase angle; besides, because the sampling rate of MU is not equal to 2N, here N is sampling points within a period, so it is impossible to perform fast Fourier transform （FFT）, however if discrete Fourier transform （DFT） were directly adopted in measuring and controlling devices, the calculation burden would be too heavy. In order to obtain the data with equal phase angle, lighten calculation burden and suit to FFT algorithm, the authors design a data pre-processing algorithm suitable to IED interfaces in digital substation, in the proposed algorithm digital low pass filtering, frequency tracking and correction, sampling rate conversion and so on are included. The data pre-processing is verified by MATLAB and verification results show that the calculation burden of the proposed algorithm is lighter and the calculation results are of higher accuracy.