A Novel Method for Noninvasive Estimation of Utility Harmonic Impedance Based on Complex Independent Component Analysis

This paper presents a new noninvasive method for calculating utility harmonic impedance at the point of common coupling (PCC). The proposed method is based on a statistical signal-processing technique, known as independent component analysis (ICA). The complex ICA technique is applied to the equations derived from Northon equivalent circuit model at the PCC in order to estimate the utility harmonic current values. Then, the estimated values of the utility harmonic current are used in an optimization problem to calculate the utility harmonic impedance. Due to considering the utility harmonic current variations in utility harmonic impedance calculation, the proposed method is relatively robust against the background harmonic fluctuations. The results obtained from computer simulation and a real case study verify the effectiveness of the proposed method.

I. Introduction

Utility harmonic impedance is an important parameter in the harmonic study of electrical networks. It is generally used at the point of common coupling (PCC) for designing filters, verification of harmonic limit compliance, predication of system resonance, and evaluating the harmonic voltage emission level. Determining utility harmonic impedance is comparatively a challenging task. Besides computer simulation techniques, which need detailed data of system components, direct measuring of utility harmonic impedance is also favorable in many applications. The major advantage of the direct measuring of the utility harmonic impedance is its independence from detailed system data which are often hard to access. Furthermore, the measurement can be carried out from time to time to consider the effect of system changes on the value of the utility harmonic impedance.