Method for generator frequency evaluation under unpredictable changes in measurement interval size

The method of frequency estimation of the simultaneously and independently operating generators under unpredictable changes in the measurement interval size is studied. Errors arising under the method application due to the transiency of the oscillator frequencies on the frequency estimation interval are considered. The first error component is related to the deviation of the measurable generator phase due to the inherent generator frequency instability; and the second one is determined by the unpredictable changes in the oscillator frequency on the measurement interval. It is noted that the decrease of each of the components imposes incompatible requirements on the duration of the time length. On the basis of the known relations identifying the potentially reachable value of the root-mean-square frequency deviation from the nominal value, the expressions determining the optimum time length are obtained. As a criterion when choosing the time length, the minimum of two errors sum is considered. The analytical relations determining potentially reachable accuracy of the frequency estimates are presented. The unbiasedness, efficiency, and consistency of the estimates obtained are proved.