A Methodology for Frequency-Measurement Characterization Based on Increment of Input Signal Phase

It is known that the signals of modern power networks are non-sinusoidal, and in this case frequency measurement methods for sinusoidal signals cannot be effectively applied. The widely applied measurement method, based on cross-zero technique, requires a long measurement time. In a number of problems of power quality parameters measurement, this drawback is significant and necessitates the application of a faster measurement method, which allowing measurements for nonsinusoidal input signals. In this paper discusses a frequency measurement method based on determination of increment of input signal phase. The phase value is determined by applying of the discrete Fourier transform (DFT). An analysis of influence of additive, multiplicative and nonlinear components of the samples error to the frequency measurement error for the considered measurement method is performed. The influence of the measurement system parameters on the algorithmic error component is investigated. Recommendations to significantly reduce of the error have been developed. Analytical relationships that allows to evaluate the algorithmic component of the measurement error are obtained. A simulation model of the considerate measurement method is developed by Matlab software package. The reliability of the analytical relationships is confirmed by the coincidence of the results which are obtained by analytical expressions and the results of simulation modeling at check points.