Cooperative power management in DC microgrid clusters

Abstract

A distributed control method is proposed to handle load sharing among dc microgrids. While microgrids manage the internal load sharing, a higher level controller is required to provide load sharing among microgrids within a cluster. Power transfer between microgrids enables maximum utilization of resources and suppresses stress and aging of the components, which improves the reliability and availability, reduces the maintenance costs, and expands the lifespan of the distribution network. The proposed control mechanism uses a cooperative approach to adjust voltage set point for each microgrid and, accordingly, navigate power flow among them. Loading mismatch among neighbor microgrids is used in an updating policy for voltage adjustment. In case of any mismatch, the controller tunes the voltage to mitigate the mismatch and, eventually, equalize the loading percentage of all neighbor microgrids. While the voltage adjustment policy plays among microgrids, at a lower level, each microgrid propagates the voltage set point across all of its sources. Load sharing performance is analytically studied for the proposed controller. Simulation studies are performed on a cluster of four microgrids, where an excellent performance is reported. Contingency studies are also performed to illustrate the resiliency of the proposed method against the loss of communication links, so long as the communication graph has a spanning tree.