Region-Based Stability Analysis for Active Dampers in AC Microgrids

Active dampers and other damping approaches are commonly applied to mitigate high-frequency resonance of ac microgrids with multiple parallel interface converters. The parameter mismatch of control diagram and passive components in active dampers and other parallel converters will influence the effectiveness of resonance damping. Traditional stability analysis of multiple parallel converters mainly utilizes root loci of system eigenfunction with single parameter changing. In this paper, to achieve a reasonable selection of parameters and characterizing the variation of multiple parameters simultaneously and intuitively, a region-based stability analysis approach is proposed. To enhance the computational efficiency of obtaining the intuitive stability region, a kernel ridge regression approach is applied to derive an approximate analytical expression for the stability region. The stability region established with multiple dominant control parameters of active dampers and other converters can provide reference for control parameter design, guaranteeing the effectiveness of active resonance damping. Moreover, the effects of circuit parameter mismatch in the region-based stability analysis are also taken into consideration to increase the robustness of the stability region and providing guidelines for the selection of passive components (i.e., filter inductance and capacitance). Compared to the traditional analysis approach, the proposed region-based stability analysis can depict the stability region when multiple dominant parameters vary with an error band indicating the impacts of parameter mismatch. Simulation and experimental results verify the effectiveness of the proposed region-based stability analysis.