The Application of Digital Filtration for the Active Power Measurement

Abstract

To measure the active power in a given frequency band, a method based on low-pass filtration of the instantaneous power signal can be applied. For active power digital meters, the low-pass filter is implemented digitally. At the same time, infinite impulse response (IIR) digital filters, finite impulse response (FIR) digital filters can be used to perform low-frequency filtering. The article shows that the parameters of the applied digital filter are significantly affected to the measurement error. The application of cascaded integrator-comb (CIC) filters plays an important role. The article shows that when using a complex circuit containing a CIC-filter and a IIR-filter, the smallest measurement error (among the considered digital filters) is shown. Analytical expressions are obtained, which allows to contact the measurement error of active power and the parameters of the applied digital filter. To verify the reliability of the obtained analytical expressions, simulations were performed in the Simulink software package.