A Bi-Layer Optimal Dispatch Method of Energy in Freeway Micro-grid Systems

With the advancement of China's "dual carbon strategy", the usage of new energy in transportation and the transformation of energy have developed rapidly.In areas with no power grid or weak power grid in western China, where wind and solar resources are sufficient, micro-grids can be used to supply power to facilities in road areas. However, freeway micro-grids have problems such as large longitudinal span, discrete distribution, unbalanced output, and high construction and operation costs of distribution networks along the roads.Therefore, the mobile energy storage dispatching equipment is introduced into the freeway energy system.On this basis, a model of freeway micro-grid with mobile energy storage system is developed, and a newly two-layer structure for dispatching cost mechanism and energy dispatching is proposed.Meanwhile, the micro-grid system for freeway has a long-distance strip structure, which would cause communication burden for the micro-grid sub-controller dispatch.To solve this problem, a distributed bi-layer optimization dispatching strategy using the alternating direction multiplier method is proposed.This method decomposes the global problem into local problem, which is solved through parallel optimization, and each micro-grid only needs to communicate with adjacent micro-grids to exchange the information of expected energy demand.The system takes the minimum total operating cost of the freeway micro-grid as the coupling variable, which is relaxed through the augmented Lagrangian penalty function.As a result, the original optimization problem is decoupled into independent sub-optimization problems of each system.A bi-layer loop solution method is used to obtain the global optimal scheduling plan.A numerical simulation analysis is carried out and show that the utilization rate of renewable energy has increased by 15.3%, ensuring the economic benefits while achieving energy use in freeway.