Distributed Secondary Control of DC Microgrid via the Averaging of Virtual Current Derivatives

This article presents a novel distributed secondary control method for dc microgrids. The method improves existing results by considering the effects of transmission line impedances and constant power loads (CPLs) on system stability. Specifically, a new parameter named "virtual current derivative (VCD)" is defined, which simplifies system analysis and facilitates the improved control design. It is shown that through the dynamic averaging of VCDs, the dc microgrid system model can be reduced to a second-order one regardless of the number of converters connected. This second-order model facilitates the stability analyses of the dc microgrid, thereby leading to a sufficient condition for determining the allowable CPL upper bound. Simulation and experiment studies are conducted to verify the proposed method.