Resonant harmonic filters: their optimization and limits of effectiveness

Resonant harmonic filters (RHFs) are effective devices for reducing supply current harmonics when only those load generated current harmonics to which they are tuned are present and there are no distribution voltage harmonics. Other current harmonics, as well as the supply voltage harmonics may deteriorate the effectiveness of RHFs. This is because of resonances of the RHF with the distribution system inductance. The filter performance can be improved if parameters are selected using an optimization procedure that takes into account the presence of both the voltage and current minor harmonics and the filter resonance with the distribution system reactance. Unfortunately, at some level of current and voltage distortion, even filter optimization is not capable of increasing filter effectiveness. There are some limits of effectiveness in such conditions. This paper presents a method for finding the limits of RHF effectiveness by analyzing the effectiveness of optimized RHFs at increasing distortion level