Effects of damping on the performance of resonant harmonic filters

The effectiveness of resonant harmonic filters (RHFs) in harmonic suppression is the resultant of two different types of resonance that affect the filters´ effectiveness in an opposite manner. They are the resonance of the filter branches and the resonance of the entire filter with the distribution system inductance. Damping these resonances by reduction of the filter Q-factor affects the filter performance in a complex way. There are suggestions in the literature on RHFs that such a damping would improve the filter effectiveness. Unfortunately, no quantitative information to support such a suggestion is available. This paper presents the results from a study of the effect of the Q-factor on the filter effectiveness and on the loss of active power in the filter.