A case study of flicker/interharmonic problems caused by a variable frequency drive

Variable frequency drives (VFDs) are well known harmonic sources. This paper presents a case where such a drive is identified as a flicker source as well. A VFD causes voltage flicker due to the fact that it is an interharmonic source. The interharmonics could beat with the fundamental frequency component, resulting the generation of voltage flicker. Through field measurements and simulation studies, this paper explains how a VFD causes voltage flicker problems and the various factors that have an impact on the flicker generation characteristics of a VFD. This paper can serve as a useful example to guide people who need to troubleshoot voltage flicker problems.