Based on the past engineering experiences

the influences of background harmonic voltages on the shunt hybrid active power filter are studied by analyzing the current canceling system and active inverters. It is found that harmonic voltages may cause system resonances and/or DC voltage rising for active power filters (APFs). Based on these results

two methods are presented to minimize the influence of harmonic voltages. The first one is by selecting suitable system parameters to void resonances and therefore minimize the harmonic voltage of APF. The second one is by controlling DC voltage or using purpose designed return circuits. The simulation results show that the effectiveness of the proposed methods.