系统采用一阶差分与全周傅氏算法相结合的 值。通过一阶差分去除信号中的直流分量与低 信号中的高频分量，并将信号转换为相量表示-System uses the first difference Fourier algorithm with the whole week combined value. Removal of the signal by the first difference in the DC component and low signal in the high freq