Hierarchical Energy Management Strategy for an Islanded Networked Microgrid Considering Flexible Inter-Microgrid Power Exchange

The networked microgrid (NMG) interconnects multiple microgrids (MGs) to improve load shedding and utilization of renewable energy sources (RES) effectively. However, using centralized energy management system (EMS) strategies for NMG may suffer from communication and computational burden, while decentralized EMS are costly and focus on local optimization. This paper presents a hierarchical EMS strategy for an islanded NMG. Firstly, the strategy is developed to minimize the operating costs within independent MGs. Based on the shortage/surplus MG results, the strategy is designed to make optimal decisions on a flexible inter-microgrid power exchange plan. Dispatchable distributed generators (DGs) share power to shortage MGs for load shedding minimization. In contrast, energy storage systems (ESSs) are used to maximize the utilization of surplus RES in the NMG. The NMG topology is configured in a radial or mesh structure to fulfill the network requirement. The proposed strategy is implemented on an islanded NMG test system of four interconnected IEEE MGs with different sizes (6, 9, 18, and 7 buses) and topologies (radial and mesh). The simulation results of decentralized and hierarchical energy management strategies for the NMG are presented under normal and abnormal operation modes. The results reveal that the proposed strategy reduces the total NMG operating costs by 36.56% and 53.10% under normal and abnormal conditions with zero load shedding and unutilized RES compared to the decentralized strategy.