Performance of Synchrophasor Estimators in Transient Conditions: A Comparative Analysis

Transient amplitude or phase changes in current or voltage waveforms may seriously affect synchrophasor estimator's accuracy and responsiveness. The IEEE Standard C37.118.1-2011 specifies test conditions as well as accuracy and response delay limits for different types of disturbances. In this paper, the performances of three state-of-the-art techniques based on phasor Taylor's series expansion specifically conceived to track phasors in dynamic conditions are analyzed and compared with the one-cycle discrete Fourier transform estimator under the effect of amplitude step changes, phase step changes, and linear frequency variations. Several simulation results show that the total vector error (TVE) tends to increase linearly with the step size. However, the peak TVE increments for a given step size are quite similar for all the considered techniques and are dominated by amplitude or phase errors, depending on whether the step affects the waveform amplitude or its phase, respectively. In this paper, the response times of the considered estimators for two different TVE thresholds are also analyzed and compared as a function of the step size, to assess their compliance to the requirements of the standard. Further simulation results show that in the case of linear frequency variations, responsiveness is not an issue and the TVE values of all estimators lie within the same worst case boundaries as those related to the case of static off-nominal frequency offsets.