A flexible power management strategy for PV-battery based interconnected DC microgrid

In this paper, a coordinated power-sharing strategy for interconnected DC-microgrid (DC-MG) is proposed. The DC-MG consists of two subgrids with an interlinking bidirectional DC/DC converter (IBDDC). Each subgrid has a secondary-1 controller based on a state of charge (SoC) balancing based droop control strategy of the battery unit (BU). The proposed droop strategy regulates the DC bus voltage according to the SoC of BU. With the SoC balancing based droop method, BU with higher SoC supplies more power to the microgrid (MG) as compared to low SoC BU. The SoC information of batteries in all subgrids is communicated through low bandwidth communication (LBC). In case of failure of LBC, a secondary-2 controller is implemented for the battery controller to regulate the DC bus voltage considering the SoC of BU. Secondary-2 does not depend on the communication line. Considering the levels of DC bus voltages, a secondary power regulating controller is introduced for IBDDC. Further, a coordinated power control strategy is proposed for distributed generation to avoid overcharging of batteries. The whole system operates in a distributed way without a central controller. The proposed strategy has been verified in MATLAB/Simulink.