A Digital Zero-Phase Filter for Measuring High Frequency Emissions (Supraharmonics) in Electrical Distribution Networks

With the high penetration of power electronic interfaces and the increased use of power line carrier communication, high frequency (HF) emissions (supraharmonics) in the range of 2-150 kHz are emerging as a new power quality issue in distribution networks. Both IEC 61000-4-7 and IEC 61000-4-30 recommend the use of a high pass (HP) filter during measurement/analysis of these emissions. However, the filters used so far in HF measurements have non-linear phase characteristics making phase details unsuitable for further analysis. As a solution, this paper proposes a digital, offline, zero-phase HP filter having near ideal magnitude characteristics and a zero phase response.