Enhanced interpolated dynamic DFT synchrophasor estimator considering second harmonic interferences

Abstract

In the future, phasor measurement units are expected to be applied in distribution networks (DNs) for their control and monitoring. Because of the widely used power electronic devices in DNs, harmonics are widely present in a voltage/current signal. Particularly, second harmonics have the most significant uncertainty contributions to synchrophasor estimation, which is especially true when a short cycle observation window is used for a fast response. Based on the interpolated dynamic discrete Fourier transform (IpD2FT), this paper introduces an enhanced IpD2FT (e-IpD2FT) synchrophasor estimator that considers second harmonic interferences. First, the adaptive equivalent filters of the IpD2FT are given. Based on these, the optimal frequencies where the IpD2FT has the least second harmonic interferences are then searched using an enumeration method, and the e-IpD2FT synchrophasor estimator is accordingly proposed. Instantaneous frequency responses and several simulation tests show that the e-IpD2FT performs much better than the IpD2FT in second harmonic suppression, and can meet the P-class response time requirements and most of the M-class accuracy requirements of the IEEE standard C37.118.1 only over a three-cycle window.