Optimal energy flow in integrated energy distribution systems considering unbalanced operation of power distribution systems.

• Operation of integrated energy systems in distribution level is modeled. • Constraints of electrical, natural gas, and heating networks are considered. • The electrical network is modeled as an unbalanced three-phase distribution system. • Optimal energy flow of integrated energy distribution system is formulated. • A new method is applied to solve the load flow of unbalanced electrical network. This paper focuses on the operation optimization of the integrated energy distribution systems, including electrical, natural gas, and district heating distribution systems. According to the unbalanced nature of the electrical distribution networks, a comprehensive model of the unbalanced electrical distribution network is established. A non-iterative three-phase load flow method, based on holomorphic-embedding, is proposed and implemented for solving the load flow of the unbalanced radial distribution electrical network. The energy flow of natural gas and heat networks are modeled and solved by a graph theory-based method. Teaching-learning based optimization algorithm is implemented to solve the optimization problem, considering various constraints of the proposed integrated energy distribution system. The objective is minimizing the total operation cost of energy flow in multi-carrier energy networks. The performance of the proposed method is validated in an integrated energy distribution system, including a 19-bus unbalanced radial electrical network, a typical 20-node natural gas, and a 30-node district heating network. The results verify the effectiveness of the proposed integrated energy system operation and applicability of the proposed optimal energy flow. [ABSTRACT FROM AUTHOR]