| Popis: |
In the present era, due to increased power requirements, size and complexity of power system are increasing continuously. As a result, power system protection is a problem of major concern and requires the most attention. In order to have the fast, reliable and proper protection system, the first and foremost thing is the accurate measurement of phasors by protective relays. Hence, a phasor estimation algorithm is a widely researched issue in the literature. New algorithms are being developed day by day. Now the challenge is to develop a precise and fast algorithm which is computationally less complex. Within the purview of phasors estimation techniques, varied algorithms have been proposed in past decades to offer accurate and real-time phasors measurements. Among these Discrete Fourier Transform (DFT) is widely used algorithm. DFT works effectively in presence of harmonics and noise but, its performance deteriorate in presence of decaying DC (DDC) component. Various algorithms have been reported in literature for the removal of DDC so as to have accurate phasors estimation. In this paper, a comprehensive outline of the most common DFT based algorithms is presented. The performance of algorithms is evaluated and compared using simulated signals under the normal operating condition as well as in presence of decaying DC (DDC), severe harmonics and noise. For all the algorithms, phasor parameters (magnitude and phase angle) are estimated. The fundamental frequency is assumed to be known apriori. The obtained simulation results are provided to highlight each algorithm aptness and shortcomings to estimate the phasor. |
