The frequency is an important operating parameter of power systems and electrical equipment, and the frequency measurement is the basis of the operation and monitoring of power systems and electrical equipment and of relaying protection. The frequency of power systems is an important index of power quality, and it is very important for the fault diagnosis of power systems. Larger power system capacity increases the stability requirement of power systems, which consequently leads to higher measurement accuracy of the frequency of power systems.
Many frequency measurement theories and calculation methods have been developed so far. Although they can be used in real applications with relatively accurate frequency measurements and small measurement errors, they are all based on discrete Fourier transform (DFT) under asynchronous samples, and approximate computational methods have been employed for real frequency measurement calculations.
Im Jung Bin, a researcher at the Faculty of Electrical Engineering, used vector theory to accurately measure the frequency under asynchronous sampling conditions for sinusoidal signals with constant frequency offset. He proposed a frequency measurement principle based on the vectors at three sampling points and calculated the frequency based on the calculation of the real and imaginary parts at each sampling point using DFT transform. Likewise, he proposed a frequency calculation method under asynchronous sampling and verified through simulation that the frequency measurement method under asynchronous sampling using three sampling values is accurate.
This provides a method for accurately and quickly measuring the frequency in the development of power measuring devices and protective devices.