The Reactive Power Measurement Method of Harmonics Based on the Application of IIR Filters

Along with active and apparent power, reactive power is one of the most informative indicators of electrical power for the field of power electrical networks. Reactive power parameters include: harmonic reactive power, reactive power in a given frequency band, and reactive power of the main spectral component. To measure the reactive power of individual spectral components, time-domain measurement methods supplemented with low-pass or band-pass filters can be used. This implementation requires significant costs associated with the additional implementation of digital filters. This paper considers a group of digital methods for measuring reactive power in the time domain, which uses a pair of digital filters of the voltage and current channels simultaneously for the tasks of isolating the spectral component of interest and performing a phase shift of signals by an angle equal to
$\pi/2$
. The class of digital IIR filters of even order is considered as the filters used. The complex transmission coefficient of the proposed phase shifter is obtained. A method is proposed for calculating the parameters of the proposed phase shifter based on the known frequency of the isolated spectral component and the maximum deviation of the input signal frequency from the nominal value. The influence of sampling frequency and input signal frequency on the error in reactive power measurement was assessed. The errors in measuring reactive power arising from the imperfection of the magnitude response and phase response of the proposed phase shifter are estimated. To assess the methodological component of the error caused by the finite deviation of the signal frequency, a simulation model is proposed, performed in the Matlab and Simulink packages.