Harmonic currents can originate from systems that do not contain energy and in which the sign of the current matches that of the voltage throughout the cycle (e.g. a phase-angle controller for an incandescent lamp). The term ‘wattless current’ is sometimes applied to harmonic currents that do not have substantial voltage harmonics of the same orders to multiply them. The result is a product of current and voltage that is zero. Those harmonic currents have a lot in common with reactive currents:
It should therefore be possible to combat both reactive power and harmonics by similar means.
This is indeed the case. This publication explains how it can be accomplished effectively and how dedicated filters can be created for individual frequencies.
In addition to the general principles and guidelines, this paper tackles the importance of using high-quality components for accurate filter tuning. It discusses whether to compensate centrally or dispersed, and how to choose the inductor for a given L/C ratio. Finally, it warns that special caution must be taken to (i) prevent the filtering out of sound frequencies used by utilities, and (ii) that despite filtering, harmonics should still be taken into account for rating cables and equipment.
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