Comparative Analysis of the Digital Measurement Methods of Active Power with the Application of Approximation Polynomials

In this article, a comparative analysis of digital methods for the measurement of active power with the application of approximation polynomials is performed. Zero-order and first-order polynomials are considered. For each of the applied approximating polynomials, a measurement algorithm is proposed; the methodological error for the case of sinusoidal current and voltage is analyzed; recommendations to reduce the measurement error have been developed. Analytical relations are obtained allows to choose the values of the sampling frequency and the measurement time. It is shown that approximation by zero-order polynomials is much more efficient than approximation by first-order polynomials. For the case of applying the approximation polynomial of the zero-order, the methods for reducing the methodological measurement error are proposed. These methods are based on the adjustment of the number of averaged samples, the adjustment of the initial phase of the signal and the combined adjustment of the number of averaged samples and the value of the initial phase (combined technique). To apply the proposed methods, an additional measurement frequency converter is required. The reliability of the analytical relationships is confirmed by the coincidence of the analytical results and the results of simulation modeling at control points. By using software package Simulink, simulation modeling was performed to evaluate the effectiveness of the considered methods for the active power measurement.