Coordinated Control Strategy for Interconnected DC Microgrids

This work proposes a power sharing strategy for interconnected DC microgrids (DCMGs), where two subgrids are connected through an interlinking bidirectional converter (IBD). One of the subgrids has a storage unit and PV unit as renewable energy sources (RESs), whereas the other subgrid has PV as RES. To ensure proper power management among the subgrids, a power management strategy using storage subgrid control and IBD control is developed. In the storage subgrid, considering the SoC and charging/discharging power of the battery, a DC bus-signaling method is implemented. To regulate the DC bus voltage in the RES subgrid and to manage power flow, an improved IBD control strategy is proposed. The proposed battery controller and IBD controller can resolve the oscillation and overshoot associated with the voltage transition. The proposed DCMG has a single storage unit, thereby reducing the overall operating cost. Further, with the proposed DC bus-signaling, the PV controller switches its mode from maximum power point tracking to voltage regulation mode and vice versa. Therefore, generation and storage coordination is achieved. The proposed power management scheme is decentralized as it uses DC bus voltages as an information carrier. Thereby, it reduces dependency on the communication line and improves reliability. The effectiveness of the proposed strategy is verified in MATLAB Simulation.