A Hierarchical Transactive Energy Management Framework for Optimizing the Reserve Profile in District Energy Systems

District energy systems (DESs) have become a popular form of satisfying comprehensive energy demands for different types of loads in multiple local buildings. For DESs, the operational flexibility could be maintained by energy conversion and storage facilities. This paper proposes a hierarchical optimization framework for leveraging and aggregating the DES flexibility to provide contingency reserves. To characterize and quantify the flexibility in individual DESs, the concept of available reserve profile, which is measured by a set of indices, is established. A two-stage robust optimization (RO) model is developed for calculating the indices, which considers the uncertainties associated with wind power and ambient temperature. The lower stage of the two-stage model is managed by district energy system operators (DESOs) which submit reserve profiles to the district energy system coordinator (DESC) at the upper stage, which is responsible for the coordination process. Correspondingly, information privacy is preserved using a coordinated data-sharing strategy. Using reserve profiles submitted by multiple DESOs, the DESC applies the proposed coordination model to provide a certain reserve capacity schedule to DESs, which satisfies the stated objectives. The coordination model is formulated and solved based on the special ordered set (SOS) technique and particle swarm optimization (PSO) algorithm. A test system is developed to illustrate the technical viability and economic feasibility of the proposed technique.