New method for assessing the utility harmonic impedance based on fuzzy logic

• Published in: IET generation, transmission & distribution transmission & distribution, 2017-07, Vol.11 (10), p.2448-2456
• Main Authors: Zebardast, Abolfazl, Mokhtari, Hossein
• Format: Article
• Language: English
• Subjects: background harmonic fluctuations; constrained recursive least squares algorithm; CRLS; fuzzy if‐then rules set; fuzzy logic; fuzzy set theory; least squares approximations; noninvasive method; PCC; point of common coupling; power system harmonics; recursive estimation; Research Article; three‐point data selection technique; utility harmonic impedance
• ISSN: 1751-8687; 1751-8695; 1751-8695
• DOI: 10.1049/iet-gtd.2016.0881

This study proposes a novel non-invasive method for estimating the utility harmonic impedance. Since the major concern about non-invasive methods is the dependency of the accuracy of the results on background harmonic fluctuations, proper measured samples are selected using a three-point data selection technique to increase the method accuracy. Then, a new non-invasive method for the evaluation of the utility harmonic impedance at a point of common coupling (PCC) based on fuzzy logic is presented. In the proposed method, fuzzy logic is applied to the constrained recursive least squares algorithm (CRLS) by designing a set of fuzzy if-then rules. Due to the changes in the quantities at a PCC$\lpar V_{{\rm pcc}}\comma \; I_{{\rm pcc}}\rpar $(Vpcc,Ipcc) because of the changes in the utility and customer sides, these rules are used to determine the magnitude of the forgetting factor of the CRLS in order to estimate the utility harmonic impedance. Analysis of the simulation and real field test results for different cases show that the proposed method is effective in reducing the harmonic impedance calculation error caused by the fluctuations of the background harmonic.