A Systematic Review of Non-Invasive Methods for Utility-Side Harmonic Impedance Determination

Abstract

The increasing integration of power electronic based technologies, such as photovoltaic inverters, electric vehicle chargers and high voltage direct current systems, is changing how modern power systems operate. While these technologies improve energy efficiency and grid flexibility, they also introduce challenges associated with increasing harmonic disturbance levels (e.g. equipment overheating, reduced efficiency, etc.). Therefore, effective harmonic management is vital for ensuring grid stability and power quality. Utility-side harmonic impedance specifies the part of harmonic impedance that represents the grid-side (or upstream-side) with reference to a particular point in the network. It is used for designing harmonic filters, predicting system resonances, and in evaluating the level of harmonic voltage distortion caused by a device or an installation connected to the grid. Utility-side harmonic impedance measurement methods fall into two major categories: invasive and non-invasive. Measurements for non-invasive methods are easy to implement, especially at higher voltage levels. Despite the extensive literature on non-invasive methods, there is a lack of a comprehensive review outlining their applicability under different conditions. This paper addresses the aforementioned gap by providing a detailed review of existing non-invasive utility-side harmonic impedance estimation methods, analyzing their advantages and limitations, and identifying conditions under which they are most effective. Moreover, future research directions are discussed with a view to improve utility-side harmonic impedance estimation techniques. Future research should focus on adaptive, AI-based, and data-driven methods for robust utility-side harmonic impedance determination under dynamic network conditions and frequency-coupled utility-side harmonic impedance modelling.