Flexible Interlinking and Coordinated Power Control of Multiple DC Microgrids Clusters

Abstract

Multiple distributed dc microgrids (MGs) in a close vicinity can be connected to each other to form a dc MG cluster. Especially with isolated bidirectional dc-dc converters (IBDCs) as the active interconnected devices, flexible power control and electrical isolation among the dc MGs can be realized. A novel coordinated power control framework for such a cluster has been proposed in this paper, in which the dc MGs adopt the standard droop control, and a unified control is proposed for the IBDCs. In normal operation, autonomous flexible interlinking power control among the distributed dc MGs can be achieved through the unified control of IBDCs, making the demand of the power terminals to be proportionally shared among the slack terminals in the dc cluster. Furthermore, with the unified control, if one of the dc MGs loses dc voltage control capability due to the outage of its slack terminal, the interlinked IBDCs can transfer to dc MG support control mode automatically and seamlessly without control scheme switching and operation mode detection. In addition, when there is a dc bus fault in one of the subsystems, the interconnected IBDC can lockout its control signals and isolate the dc fault, to ensure stable operation of the rest of the dc MGs within the cluster. Finally, PSCAD/EMTDC based simulation verifications and experimental results obtained from a hardware prototype have been provided.