Modeling and Stability Analysis of an Active Filter for DC Current Compensation

The widespread use of power converters and nonlinearloads connected to the grid have caused the emergenceof problems regarding the power quality. Among differentkind of non-linear distortion, there is the issue of the DCcurrent component. In fact, a DC current component flowingin the grid transformers has various detrimental effects, i.e.increased harmonic distortion, increased power losses, andpossible damage due to consequent overheating. This paperproposes a non-linear sensor and a compensator system thatact as an active filter to remove the DC current componentflowing in the power lines. In the first part, the strategy isoutlined and then the stability issue is addressed by meansof a simplified model. Simulation results confirmed that thesimplified model closely approximates the real system. Anapproximated analysis of stability is also presented. Finally wepresent some experimental results that shows the effectivenessof the proposed solution.