Application of the Quadrature Demodulation Technique for the Active Power in a Given Frequency Band Measurement

Currently, active power in a given frequency band is the most informative parameter of the active power. To measure this parameter, a method based on extracting a DC component of instantaneous power by applying spectral analysis can be applied. Typically, a discrete Fourier transform (DFT) is used to obtain the DC component of the instantaneous power signal. An alternative approach is based on the application of quadrature demodulation, which is more accurate than DFT. For the case of applying a quadrature demodulator, the study of the influence of the signal frequency deviation on the measurement error of active power has been carried out. In the article, analytical expressions are obtained that allows to calculate the measurement error in the cause of frequency deviation and the quadrature demodulator parameters. An approach based on additional measurement of the frequency and adjustment of the quadrature modulator parameters is considered, which can significantly reduce the active power measurement error. The tasks of influence of the instrumental error components of the measurement channel on the active power measurement error when using the considered measurement method are investigated. Additive, multiplicative components, linearity error and quantization error are considered. Analytical expressions have been obtained that make it possible to evaluate it influence on the active power measurement error. By applying the Simulink software package, a mathematical simulation model has been established, which makes it possible to estimate the active power measurement errors for the considered measurement method. The reliability of the obtained expressions is confirmed by the coincidence of the simulation results and analytical modeling results which are performed in Simulink software package.