A new method for noninvasive measurement of grid harmonic impedance with data selection

摘要

The paper presents a new, noninvasive method for the measurement of power grid harmonic impedance. The method is a robust variant of transfer function estimation method. Its novelty lays in the way of selecting local harmonic impedance estimates for averaging, based on input–output coherence estimates, which immunizes it against background voltage variations. The method is validated by simulation including varying background voltage harmonics, both forfixed and slowly varying harmonic impedance. It has also been tested with noisy and nonsynchronously sampled signals. The method is compared with another noninvasive method with data selection. Simulation results clearly show that the proposed method returns lower estimation errors. Also, its computational complexity is significantly reduced compared with the reference one. The presented results of afield test conducted at medium-voltage/low-voltage substation prove that the method works well in real conditions. Copyright © 2015 John Wiley & Sons, Ltd.