Application of Simulink for Research of a Frequency Measurement Method Based on Quadrature Demodulation Technique

Abstract

Currently, there are a large number of frequency measurement methods. Most of it can only be applied to a sinusoidal input signal. Other methods are limited in practical application due to the significant measurement time. The measurement method based on the application of quadrature demodulation technique is devoid of these drawbacks. This method is promising for frequency measurement tasks in modern power grids. The basic principles of frequency measurement method based on a quadrature demodulator are described. By using the simulation modeling which is developed in Simulink software, the frequency measurement error of this measurement method was investigated. The application of Butterworth and Chebyshev infinite impulse response (IIR) digital filters is considered. An analytical dependence is obtained that relates the frequency measurement error and filter parameters. Approaches based on the application of post-filtration and averaging are proposed, which allows to significantly reduce the frequency measurement error by the considered method. The relationship between the parameters of the post-filter and the final error of frequency measurement is investigated. A method for choosing the post-filter parameters is proposed. The reliability of the obtained analytical expressions is confirmed by the results of simulation modeling which is performed in Simulink software package.