Accuracy of the Synchrophasor Estimator Returned by the Interpolated DFT Algorithm under Off-Nominal Frequency and Harmonic Conditions

In this paper analytical expressions are derived for the synchrophasor amplitude and phase estimation errors achieved by the Interpolated Discrete Fourier Transform (IpDFT) algorithm when a steady-state harmonically distorted waveform at off-nominal frequency is weighted by a Maximum Sidelobe Decay (MSD) window. The derived expressions allow to separately analyze the contributions of the fundamental spectral image component, harmonics, and off-nominal frequency on the estimator Total Vector Error (TVE). Also, the related curves depicted in the plane of relative amplitude error and phase error allow to visually assess the overall accuracy of the IpDFT phasor estimator in the case of either pure sine-wave or harmonically distorted sine-waves. These curves are useful to analyze the robustness of the IpDFT algorithm to off-nominal frequency and harmonics.