NEW INTERHARMONIC SUBGROUP DEFINITIONS FOR QUANTIFYING AND LIMITING DISTORTION IN DISTRIBUTION NETWORKS

There are many challenges associated with including interharmonic voltage and current limits in future versions of international Standards (e.g. new IEEE Standard 519). This paper introduces a new definition of interharmonic subgroups based on IEC concept and aimed at overcoming the difficulty of the existing definition in IEC 61000-4-7 in limiting interharmonic distortion. The new subgroups are better able to address the main problem caused by interharmonics, which is light flicker (LF) produced by modern lamp technologies (e.g. LEDs) that cannot be assessed by the IEC Flickermeter (IEC 61000-4-15). A numerical case study is presented to show the effectiveness of the new definitions and, additionally, to test their robustness versus both the desynchronization of the window width used to perform the DFT with system fundamental frequency, and the accuracy requirement of the voltage measurement chain contained in IEC 61000-4-7.