Improved Mode-Adaptive Droop Control Strategy for the DC Microgrid

The mode-adaptive droop control (MADC) strategy enables bus voltage regulation and power sharing between the distributed energy resources (DERs) in the direct current (dc) microgrid without communication systems. The conventional MADC strategy may fail to provide acceptable voltage regulation and power sharing performance in large dc microgrids where the voltage drops across the dc lines are not negligible. This paper proposes an improved MADC strategy for the dc microgrid. The proposed control strategy minimizes the adverse effects of the aforementioned voltage drops on the bus voltage regulation and the power sharing between the DERs in the dc microgrid. The performance of the proposed control strategy is investigated under various operating conditions and disturbance scenarios, using a detailed and realistic dc microgrid study system that is modeled in the PSCAD/EMTDC software environment. The study results indicate that the proposed control strategy: 1) effectively maintains the power balance in the dc microgrid; 2) accurately regulates the dc bus voltages under various operating conditions; 3) improves power sharing between the DERs without using communication systems; 4) significantly reduces the circulating currents between the DERs in the islanded microgrid; and 5) enhances the dc microgrid reliability, flexibility, modularity, and scalability.