Experimental verification of disturbance observer based active filter for resonance suppression

In case of the harmonic compensation based on the detection of the line current, a problem of the resonance between the active filter (AF) and an LC filter often arises if an LC filter is connected parallel to the AF. Thus the disturbance observer is introduced to solve this problem. By the estimation of the harmonics disturbance using the proposed disturbance observer, the compensation characteristics of the AF is improved and the resonant current can be compensated. In this paper, the theoretical analyses of resonance, a design of the disturbance observer based AF and the experimental results are presented.