Estimation of Symmetrical Component Phasors and Frequency of Three-Phase Voltage Signals Using Transformations

This paper proposes a simple and computationally efficient algorithm for estimating the frequency and symmetrical component phasors from three-phase time-domain voltage signals utilizing the concept of transformation. A simple least-squares algorithm is proposed to extract the frequency of the signal based on its components in the rotating reference frame. Further, it is shown that the positive and negative sequence component phasors can also be extracted by utilizing the trajectory of the three-phase voltage signals in two rotating reference frames. Unlike the existing approaches, the proposed algorithm estimates the frequency and symmetrical component phasors without utilizing any phase-locked loop or complex transformations. The proposed approach is validated using simulation studies carried out on (a) three-phase test signals that comprise of harmonics, off-nominal frequencies, and unbalances and (b) standard test signals indicated in IEEE Std. C37.118.