A single-tuned harmonic filter is a passive harmonic filter widely used to eliminate harmonics in power systems.
Minimizing the impedance of the filter at the corresponding harmonic frequency makes the harmonic voltage produced by the harmonic current generated by the non-linear load a minimum. This is the principle of filtering in a single-tuned harmonic filter.
While eliminating the corresponding harmonic, the single-tuned harmonic filter affects the fundamental power factor. That is because the single-tuned harmonic filter itself is capacitive at the fundamental frequency. In the past, most power systems were inductive at the fundamental frequency, so in general, their capacitive characteristics played a positive role in raising the power factor of power systems. But nowadays, with the widespread use of power electronic devices, there have been more and more loads that are non-inductive at the fundamental frequency in the power systems. In this case, using conventional single-tuned harmonic filters results in the decrement of the fundamental power factor and the increment of transmission loss. In order to overcome these disadvantages, it is necessary to develop a new type of filter that eliminates harmonics but does not influence the fundamental power factor.
Ji Kuk Ryol, an institute head at the Faculty of Electrical Engineering, has proposed a novel single-tuned harmonic filter, which can remove harmonics with the fundamental power factor unchanged.
The proposed filter can be applied to filtering the harmonics made by a load whose fundamental power factor is 1 or capacitive.
You can find more information in his paper “Novel Single Tuned Harmonic Filter not Affecting Fundamental Power Factor” in “Journal of Electrical Power & Energy Systems” (EI).