Synchronous Frequency Calculation Based on Synchrophasor Measurements

Voltage frequency is a key parameter both in the studies of the power system properties and in its operational management. Many methods have been proposed for determining the frequency, but most of them are highly sensitive to transients and noise, and also have insufficient time resolution. Thus, it is necessary to develop an algorithm for determining the frequency with the minimum error regardless of the transients and noise presence, and in order to study the electromechanical transients in more detail, it is necessary to perform measurements “inside” the industrial frequency period. The methods of digital signal processing were used: sliding parabolas, sliding segments, data approximation by the least squares method. All calculations were made using MATLAB. An algorithm was developed for determining the synchronous frequency based on the synchrophasor data using characteristic points: phase intersections with zero, phase extrema and phase intersections. The computational delay of the developed algorithm is 1.66 ms, which allows its use in real-time calculations. It was determined that during transient the extremum bias significantly affects the accuracy of frequency determination. The algorithm that considers the intersection of phases with zero and the intersection of phases has a higher computational stability and a smaller deviation of the calculated frequency from the given one.