An Approach to Improve the Power Frequency Measurement Accuracy Based on the Application of Low-Pass Filtration

In the task of measuring the frequency of an electrical power networks, the zero crossings technique is most often applied. It is known that the main causes of error for this method are signal flicker and noise. Signal harmonics can increase influence of noise and flicker on frequency measurement error. For this reason, increase of the accuracy of this method can be achieved by suppressing input noise and flicker. To solve this problem, low-pass or band-pass filtration can be applied. To solve this problem application of digital filters with finite (FIR) and infinite (IIR) impulse response is considered in the paper. Among FIR filters the filter based on application of Kaiser window is considered. Among IIR filters the Butterworth, Chebyshev filters of the first and second type, elliptic filter are considered. The application of the moving average filter for solving this problem is considered. The estimation of the dynamic error component, caused by the application of low-pass filter, is performed. The influence of the maximum filter stopband rejection on the frequency measurement error is considered. The simulation model in Matlab/Simulink environment is performed that allows to estimate the error of frequency measurement for cases of sinusoidal and nonsinusoidal periodic input signals which are distorted by noise and flicker.