Estimation of an Unbalanced Grid Impedance Using a Three-Phase Power Converter

Abstract

This paper proposes a real-time method for estimating an unbalanced grid impedance using a three-phase converter. In the method, a periodic single-frequency or multi-frequency excitation signal is added to the converter voltage reference. The converter measures currents and voltages at the point of common coupling. The impedance estimate is obtained from the measurements using sliding discrete Fourier transform (SDFT). The method is experimentally validated.