A Novel Secondary Power Management Strategy for Multiple AC Microgrids With Cluster-Oriented Two-Layer Cooperative Framework

Reducing time consumption of economical power allocation operation among multiple microgrid (MG) clusters can significantly enhance the balance efficiency between power supply and load demand. In this article, a novel secondary power management strategy with cluster-oriented two-layer cooperative (TLC) framework is proposed, by which both the power sharing requirement for all DGs within each MG cluster and the economical power allocation demand among multiple MG clusters can be simultaneously realized during the secondary control process. In the framework, all cluster-head distributed generators (DGs) constitute the upper control layer, which enable the economical power allocation operation among multiple MG clusters, and all noncluster-head DGs constitute the lower control layer allowing the power sharing adjustment within each MG cluster. All the power mismatches across the TLC framework are fed back in the primary control to generate the frequency/voltage nominal set-points. Sufficient conditions, in terms of control time constants of the TLC framework and connectivity of the two-layer cyber network, are derived to guarantee the stability of the entire multiple MG cluster system with both power balance and power generation constraints. Specially, both the lower and upper layer controllers are designed based on a sparse two-layer cyber network, allowing different numbers of heterogeneous DGs in each MG cluster. The effectiveness of the control methodology is verified by the simulation of a multiple ac MG cluster system in MATLAB/SimPowerSystems.