An improved interharmonic grouping scheme based on IEC 61000-4-7

The interharmonic group concept adopted by the IEC 61000-4-7 is very useful for addressing the need to monitor interharmonics in power systems. This paper shows that grouping spectral bins into interharmonics and harmonic components of 5Hz resolution could yield misleading information for cases where an interharmonic component´s frequency is very close to a harmonic frequency. Since interharmonics in such cases can cause more severe waveform modulation, the interharmonic grouping scheme needs to be improved. A signal processing method that can separate interharmonic and harmonic components in close proximity is, therefore, proposed in this paper to address this need. Field data analysis showed that the proposed method was able to extract interharmonic and harmonic components correctly.