An iterative scheme to hierarchically structured optimal energy management of a microgrid

In this paper we address the optimal energy management of a microgrid composed of multiple sub-units, each one including one or more buildings sharing some common resources. The goal of the microgrid operator is to match a given electrical energy profile agreed with the operator of the main grid. We propose a decentralized solution scheme based on a hierarchical structure involving three layers: single building, sub-unit, and microgrid operator. At the level of each building, thermal and electrical energy requests are minimized while guaranteeing a certain comfort and quality of service to the building occupants. Optimization of the use of common resources (storages and technological devices) is performed by each sub-unit based on the energy requests of the buildings composing the sub-unit and the cost signal received by the microgrid operator. Each sub-unit minimizes its electrical energy cost as computed based on its own cost signal, while the microgrid operator updates all cost signals based on the outcome of the decentralized optimization, so as to coordinate the sub-units and match the given reference profile. A numerical example shows the efficacy of the approach.