Source current detection type active filters

The source current detection type active filter (AF) has a merit of robustness to the load variation, but a problem of resonance between the AF and an LC filter often arises if an LC filter is connected in 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 totally improved in addition to suppressing the resonant current. In this paper, the theoretical analyses of resonance, a design of the disturbance-observer based AF and the simulation results are reviewed