An Approach of Reducing the RMS Measurement Error for the Measurement Method Based on Averaging of the Squares of Samples

At present, the most popular method of the RMS measurement is based on averaging of the squares of samples. This method is highly accurate and easy to implement on a modern microcircuits. The main disadvantage of this measurement method is the significant influence of the signal frequency deviation on the measurement error. Existing methods to reduce the effect of frequency deviation assume its additional measurement, which complicates the overall implementation. This paper proposes an approach based on compensation of the measurement error by determining several RMS measurements for different initial phase of the input signal. The proposed method shows high efficiency for stationary signals or signals with a slow parameters change (in comparison with the measurement time), which is specify by modern power grid signals. In this paper, analytical expressions are obtained that allows to estimate the RMS measurement error when applying the proposed approach. Digital methods of providing a phase shift are considered. The analysis of the influence of the phase shift deviation on the RMS measurement error is carried out. By application of the Simulink software package, a simulation model of the RMS measurement transducer, which implements the proposed measurement method, has been proposed. The reliability of the obtained analytical expressions is confirmed by the coincidence of the simulation modeling results and analytical expressions results at check points.