Coordinated power sharing among multiple subgrids in a photovoltaic-battery based DC microgrid

In this paper, a coordinated power sharing strategy for multiple subgrid-based dc microgrid (DCMG) is proposed. The DCMG has an SPV (storage-PV) subgrid and two PV subgrids connected through interlinking bidirectional converters (IBCs). In the SPV subgrid, a charging/discharging power and state-of-charge (SoC) of battery-based droop strategy have been implemented for the battery controller for dc bus voltage regulation. In PV subgrid, IBC regulates its dc bus voltage. Further, for coordinated power-sharing, a correction factor-based coordination control strategy for IBC has been proposed. With the proposed coordination strategy, a small change in load demand has been taken care of by the PV subgrid without affecting the state of the battery. Moreover, the battery has been accorded the last priority to respond to the change in load demands in the DCMG. With the proposed strategy, a low SoC battery charges 1.28%/min faster than the conventional strategy. Similarly, a high SoC battery charges 1.07%/min slower than the conventional strategy. Hence, deep discharge and overcharge of the battery are avoided. With the coordination strategy, a higher capacity subgrid takes more load demand than a weak subgrid. The effectiveness of the proposed strategy is verified with MATLAB simulation and OPAL-RT real-time digital simulator.