The Method of Reducing the Active Power Measurement Error With Non-Simultaneous Sampling of Voltage and Current

Abstract

It is known that active power is defined as the average value of the instantaneous power over a time which is multiple of the period of the input signal. For digital measurement devices, finding instantaneous power requires multiplying discrete samples of input voltage and current. Nowadays, there are a large number of low-cost multi-channel ADCs. The considered devices contain one measurement channel and an additional multi-channel multiplexer. Such a device allows to consistently samples of different input signals. In this case, the resulting samples will refer to different time samples, which results to the additional measurement error of instantaneous and active power. The application of approximating polynomials can significantly reduce the measurement error of these parameters. In this paper, we consider the use of polynomials of zero (stepwise), first (linear), second (parabolic) order, as well as a third (cubic) polynomial. Analytical expressions are obtained, which are allows to estimate the measurement error of the active power in the case of the application of these polynomials. Options for constructing interpolators based on the proposed approximating polynomials are proposed. Simulation results are performed by the Matlab software package. The reliability of the obtained expressions is confirmed by the coincidence of their results with the results of simulation modeling at control points.