Comparative Analysis of the Active Power Measurement Methods in Time Domain

摘要

Active power is one of the most informative parameters of the power grids signals. Signals of present power grids are non-sinusoidal. There are harmonics, noise and flicker (sinusoidal or rectangular). For this reason, the methods used to measure active power must take into account the above signal features. The article discusses two of the most popular measurement methods of the active power in the time domain: the method based on averaging the instantaneous power and the method of low-pass filtration of instantaneous power. For these methods, analytical expressions are obtained that allows to estimate the measurement error of active power in the case of a polyharmonic input signal. Simulation modeling was performed to evaluate the metrological characteristics of the considerate methods in Matlab. The research of influence of the signal parameters on the measurement error is performed. The implementation features, advantages and disadvantages of each method are considered. Approaches to improve the accuracy of the active power measurements when performing additional measurements of power frequency are proposed. It is shown that in the case of using a moving average (single-stage) filter, both considered methods are equivalent. The reliability of analytical expressions is confirmed by comparing of the analytical and simulation modeling results at check points.