Application of Filtration as a Measurement Method of Reactive Power Parameters

Reactive power is one of the most important parameters of the signals of modern electrical power grids. In this case, the most informative parameters are the reactive power of the main spectral component and the reactive power of harmonics. To measure these parameters, there are lot of methods that are not highly accurate or difficult to implement. The paper discusses a new approach based on the application of a low-pass and band-pass filters to provide a phase shift equal to ±π/2. The basic principles of performing measurements by this approach are considered, analytical expressions are obtained for calculating the reactive power error. The case of application of a second-order low-pass filter and a second-order band-pass filter is considered in detail. The features of the application of this approach for the case of applying filters of a higher order are analyzed. Approaches are proposed to improve the measurement accuracy by additional measurement of the frequency or root mean square value (RMS) of the signal and adjusting the filter transfer coefficient. A method has been developed for calculating filter parameters in accordance with the required reactive power measurement error, the nominal frequency of the measured harmonic, the relative frequency deviation and the signal spectral composition.