The effect of the design method on efficiency of resonant harmonic filters

Distribution voltage harmonics and load current harmonics other than harmonics to which a resonant harmonic filter (RHF) is tuned, deteriorate the filter efficiency in reducing harmonic distortion. The paper presents results of a study on dependence of this deterioration on the method of the filter design. The study was confined to four-branch RHFs of the 5th, 7th, 11th, and 13th order harmonics, installed on buses that predominantly supply six-pulse ac/dc converters or rectifiers. The filters under investigation were designed according to two different approaches: a traditional approach and an approach based on an optimization procedure. In the traditional approach, the reactive power allocated to particular branches of the filter and their tuning frequencies are selected at the designer´s discretion, according to recommended practices. In the optimization based approach, the reactive power allocated to particular branches and tuning frequencies are resultants of an optimization procedure that minimizes the bus voltage and the supply current THD in the system with the filter under design.