A Method for Reducing the Dynamic Error of Power Frequency Measurement for the Case of Quadrature Demodulation Application

Currently, the quadrature demodulation method is widely used to measure the frequency of the power grid in conditions of both sinusoidal and polyharmonic input signals. Along with the signal phase increment method, this approach is the most common in practice and widely studied in the theoretical field. One of the problems of this method is the presence of a significant dynamic error caused by transients in the output filter of the demodulator. The modification proposed in this article is intended to reduce this problem by using two demodulators in parallel. The error of frequency measurement when using a demodulator is considered. The basic idea of the applied modification is analytically shown and its effect on the final error of frequency measurement is obtained. The variants of the modified demodulator construction are considered, their advantages and disadvantages are indicated. The influence of the initial phase of the demodulator reference signals on the frequency measurement error is considered. The estimation of the final error of frequency measurement using this technique has been performed, and an analytical expression for its evaluation has been obtained. The measurement of the RMS and the initial phase of this technique is considered. The problems that arise when performing such a measurement are identified and ways to solve them are outlined. With the help of Matlab and Simulink software packages, simulation models were built to evaluate the correctness of the obtained analytical expressions.