A new frequency measurement algorithm in the presence of harmonics using instantaneous phasor quantities

The frequency is an important parameter for monitoring, control and protection of power systems. This paper describes an algorithm for frequency measurement from estimates of voltage and current phasors. The cosine of the sampling angle, the angle between phasors estimated at two consecutive sampling instants, is calculated from three and five consecutive real components of phasors. The information is then used to estimate the frequency. The algorithm was implemented on a TMS320C26 digital signal processor of a digital fault recorder, and is described in this paper. Results from tests conducted by using simulated data are also presented.