Cluster-oriented distributed cooperative control for multiple AC microgrids

Matching power transfer between microgrids (MGs) enables maximum utilization of distributed energy resources (DERs), this paper proposes a cluster-oriented cooperative control strategy for multiple ac MG clusters, under which the power sharing among multiple MG clusters can be achieved by an intercluster scheme, whereas the frequency/voltage of all DERs within each MG cluster can also be regulated by an intracluster scheme. By pinning one or some cluster-head DERs from each MG cluster to constitute an intercluster communication network, the intercluster control layer can generate the frequency/voltage references based on the power mismatch among multiple MG clusters. In the intracluster control layer, the pinned DERs propagate these references to their neighbors in an MG cluster, and the frequency/voltage nominal set-points for each DER in the primary control process can be adjusted based on the frequency/voltage errors across the intracluster communication networks. Since the evolutions of intra- and intercluster dynamics may involve different time scales, the upper bound for the ratio of the associated intra- and intercluster time constants is finally derived to guarantee the stability of the whole multi-MG-cluster system. In special, both the intra- and intercluster controllers are designed based on their own sparse cyber networks, allowing different numbers of heterogeneous DERs in each MG cluster. The effectiveness of the control methodology is verified by the simulation of an ac multi-MG-cluster system in MATLAB/SimPowerSystems.