Unveiling the Character of the Frequency in Power Systems

The system frequency is a very complex electromechanical variable in a power system. The complexity comes from an appropriate understanding of the phenomena related to the frequency creation and its measurement and estimation. The objective of this paper is to present a comprehensive explanation of the concept of frequency and its potential character in the operation and control of power systems. The significant contribution of this paper is an explanation of the electro-mechanical nature of the frequency, and the introduction of the non-pure frequency concept related to need to measure the frequency from the voltage signal at any bus and the pure-frequency coming from the electro-mechanical character of the frequency generated at the synchronous generators. An illustrative simulation example is used to demonstrate the two characters of the frequency proposed in this paper.