Extremum Seeking as a Tool for Active Damping of Active Front-End Converters

Active damping control is necessary to mitigate the resonance issues associated with the grid-connected active front-end converters equipped with LCL harmonic filters. Nonetheless, the performance and stability of active damping are highly susceptible to uncertainties due to the grid impedance variations and aging-related drift in LCL filter parameters that can lead to a mismatch between actual and modeled resonance point thereby causing deterioration in performance or even instability. This article addresses this important practical issue by proposing a novel real-time optimization-based self-tuning algorithm to adaptively change the resonant frequency of active damping control as per variations in grid and filter conditions. The approach benefits from the concept of extremum seeking as a framework to estimate actual resonant frequency. The approach is experimentally validated on a two-level three-phase converter interfaced with a dSPACE rapid control prototyping system. The results demonstrate that the proposed approach is a straightforward and effective way of obtaining the performance and stability certainty of active damped AFE systems regardless of the grids they are connected to.