Research On Multi-Energy Complementarity Modelling And Coordinated Operational Optimization Of Distributed Multi-Energy Microgrids

As the basic unit and organizational form of the future Energy Internet,the multi-energy microgrid is an autonomous regional network based on the multi-energy complementarity and integrated optimization of a variety of distributed energy sources such as wind,solar,natural gas,etc.It can not only convert/condition different RESs through several energy conversion and storage devices into desirable qualities and quantities to be consumed by electricity,heat/thermal,gas loads,but also integrate into public electric and natural gas networks.The high-penetration wind and solar power is a process energy with spatial-temporal fluctuation,which cannot be easily stored and controlled.Their inherent intermittency and volatility are the main source of system uncertainty and have raised concerns regarding the multi-energy real-time supply-demand balance and efficient economic operation in power systems.This work was supported in part by the National Natural Science Foundation of China“Investigations on multi-energy coupling mechanisms and distributed group coordination dispatch for biogas-solar-wind microgrids”under Grant 51877072,in part by Huxiang Young Talents Programme of Hunan Province under Grant2019RS2018,in part by Hunan Strategic Industries Scientific and Technological Project“Research and development of key technologies on integrated energy management system for industrial Microgrid energy internet”under Grant 2017GK4028,in part by Hunan Provincial Innovation Foundation for Postgraduate under Grant CX2018B166.The research is conducted from the aspects of multi-energy complementarity modelling and coordinated operational optimization of distributed multi-energy microgrids,which includes coupling modeling and characteristic analyzation of individual microgrids as well as integrated energy flow optimization and energy/communication sharing/trading mechanism design of interconnected microgrids.A more comprehensive basic research methods and optimized operation scheme of multi-energy microgrids can be formed,and the main contributions are summarized as follows:1.A multi-source multi-product framework for coupled multi-carrier energy supplies with a biogas-solar–wind hybrid renewable system is proposed.In this framework,the biogas–solar–wind complementarities are fully exploited based on digesting thermodynamic effects for the synergetic interactions of electricity,gas,and heating energy flows,and a coupling matrix is formulated for the modeling of production,conversion,storage,and consumption of different energy carriers.The multienergy complementarity of biogas–solar–wind renewable portfolio can be utilized to facilitate the mitigation of renewable intermittency and the efficient utilization of batteries,and a multicarrier generation scheduling scheme is further presented to dynamically optimize dispatch factors in the coupling matrix for energy-efficient conversion and storage,while different energy demands of end-users are satisfied.2.An integrated model of P2A to exploit the inherent operational dispatchability of nitrogen-ammonia(N₂-NH₃)cycles for high-renewable multi-energy systems is proposed.In this model,the steady-state electrolytic process is mathematically formulated into a thermodynamic system based on thermo-electrochemical effects,and the long-term degradation process of P2A is transformed as the short-term degradation cost to characterize its cost-efficiency.Furthermore,the enhanced utilization of P2A is explored to form a renewable energy hub for coupled multi-energy supplies,and a coupling matrix is formulated for the optimal synergies of electrical,ammonia and thermal energy carriers.An iterative solution approach is further developed to schedule the hub-internal multi-energy conversion and storage devices for high-efficiency utilization of available hybrid solar-wind renewables.3.A distributed multi-energy management framework for the coordinated operation of interconnected biogas-solar-wind microgrids is proposed.In this framework,each microgrid not only schedules its local hybrid biogas-solar-wind renewables for coupled multi-carrier energy supplies based on the concept of energy hub,but also exchanges energy with interconnected microgrids and via the transactive market.The multi-microgrid scheduling is a challenging optimization problem due to its severe constraints and strong couplings.A multi-microgrid multi-energy coupling matrix is thus formulated to model and exploit the inherent biogas-solar-wind energy couplings among electricity,gas and heat flows.Furthermore,a distributed stochastic optimal scheduling scheme with minimum information exchange overhead is proposed to dynamically optimize energy conversion and storage devices in the multi-microgrid system.4.A distributed multi-period multi-energy operational model for the interconnected microgrids is proposed.In this model,energy hubs function as distributed decision-makers and feature the synergistic interactions of generation,delivery,and consumption of coupled electrical,heating,and natural gas energy networks.The multi-period multi-energy scheduling is a challenging optimization problem due to its strong couplings and inherent nonconvexities within the multi-energy networks.The original problem is thus reformulated as a MISOCP and subsequently solved with a sequential second-order cone programming(SOCP)approach to guarantee a satisfactory convergence performance.Furthermore,a fully-distributed consensus-based ADMM approach with only neighboring information exchange required is developed to optimize the multi-energy flows while considering the local energy-autonomy of heterogeneous energy hubs.5.A peer-to-peer(P2P)transactive multi-resource trading framework for multiple multi-energy microgrids is proposed.In this framework,the interconnected microgrids not only fulfil the multi-energy demands of with local hybrid biogas-solar-wind renewables,but also proactively trade their available multi-energy and communication resources with each other for delivering secured and high quality of services.The multi-microgrid multi-energy and communication trading is an intractable optimization problem because of their inherent strong couplings of multiple resources and independent decision-makings.The original problem is thus formulated as a Nash bargaining problem and further decomposed into the subsequent social multi-resource allocation subproblem and payoff allocation subproblem.Furthermore,fully-distributed ADMM approaches with only limited trading information shared are developed to cooptimize the communication and energy flows while taking into account the local resource-autonomy of heterogeneous microgrids.