交流信号RMS值频率偏移误差的准正交抵消算法

摘要

The way to calculate the RMS (Root Mean Square) value of AC signal is introduced and a quasi orthogonal cancellation algorithm is proposed to eliminate the RMS calculation error caused by signal frequency deviation or signal sampling frequency deviation, which gets two sample sequences, with the difference of 1/4 sampling length between their starting points, calculates respectively their MS (Mean Square) values and then gets the square root of the average of two MS values. Compared to the traditional RMS algorithm, it, without the synchronous tracking of signal frequency/phase and the obvious increase of calculation load, significantly cancels the RMS calculation error caused by frequency deviation, even nearly eliminates it when the frequency deviation is not serious. Its effect of error cancellation worsens noticeably when the input signal contains harmonics, though it remains effective.%介绍交流信号的均方根(RMS)值计算方法.针对由于信号频率或信号采样频率偏移造成的RMS值计算误差,提出一种准正交抵消算法,该算法取2个采样起点相差1/4采样长度的单周期信号采样序列,求取采样序列的均方(MS)值,再对其均值取开方.同传统RMS算法相比,该算法无需对采样信号进行频率、相位的同步跟踪,计算量几乎没有增大,即可大幅抵消信号RMS值的频率偏移误差；尤其是在频率偏差不大时,该算法几乎可以完全抵消RMS值的频率偏移误差；当输入信号包含谐波时,该算法的频率偏移误差抵消效果受到显著影响,但仍有可观抵消效果.