| After the industrial revolution,human society’s development has fallen into the predicaments of energy shortage and environmental pollution.Traditional energy utilization mode is extensive and hard to sustain,which prompts people to gradually turn focus to renewable energy source(RES)exploitation and sustainability construction.Under this background,microgrid(MG)technology comes into being,and related demonstration projects are constantly completed and put into operation.Moreover,the concept of Energy Internet spreads and endows MG with new time connotation,making it transit from single electricity to multi-energy complementation with electricity as the core,and MG is changing into the platform of integrated energy utilization.Wide-area interconnection and multi-energy coordination have become the main evolution directions of traditional microgrid incorporating into energy revolution and expanding self-application value.This thesis revolves around multi-energy complementation and carries forward the research on MG optimal operation from aspects of basic model,dispatch method and control strategy.Firstly,based on the analysis of energy flows,including cooling,heating,electricity and natural gas,their physical carriers and coupling relationships are selected as the study entry points,and mathematical model of multi-energy complementary microgrid(MECMG)is established.Then,from microgrid cluster and single MG layers,respectively,dynamic optimal dispatch methods are proposed to realize energy’s cooperative management and MG’s orderly operation.Finally,facing source-load uncertainty and electricity-gas coupling scenarios,coordinated control strategies are investigated to provide theoretical guidance for MG dispatch problems.The specific work of this thesis is as follows:1)Considering typical energy-supply units like gas turbine,waste heat boiler,absorption chiller and power to gas,the structure of electricity-oriented MECMG is designed,which covers all energy interaction scenes,such as electricity-heating,electricity-cooling,and electricity-gas.The power output characteristics of energy-production,energy-conversion and energy-storage units are particularly clarified,and the steady-state transmission models of electricity and gas networks are set up based on Distflow and Weymouth equations.Also,energy hub(EH)is employed to achieve the abstract description of multi-energy system’s input-output relations,and its modified model is derived for the proposed MECMG.2)Adapting to MG’s future evolution into microgrid cluster(MGC)and MECMG,for MGC,a tri-layer multi-agent system architecture is built to facilitate mutual action among generation unit,MG and MGC via agents’ cooperation.Given that low time resolution,large prediction error and poor optimization performance exist with one single scale,a multi-time scale energy optimization scheme is thus put forward for MGC,including day-ahead scheduling,day-in rolling and real-time adjustment.For MECMG,operation indexes,reflecting system economy,safety and efficiency,are proposed,and an EH-based multi-objective optimization model is established with complex energy coupling relations clearly depicted.Besides,membership function is used to process these indexes into their satisfaction degree,and the original optimization problem is finally transformed into a single-objective problem through linear weighted sum method.3)To meet the dispatch and control demands of MG under subdivision scenarios,in uncertainty scenario section,based on the probability distribution functions of wind speed,solar radiation and load power,typical MG scenarios are generated by Latin hypercube sampling and simultaneous backward reduction.Combined with stochastic programming theory,scenario method-based optimization model is then built.To tackle the adaptive problem of scenario method’s results,extreme scenario is thus introduced and a robust MG optimization scheme is further studied based on extreme scenario method.In coupling scenario section,considering the information security problem of multi-energy system,a decentralized dispatch concept is introduced and the principle of alternating direction method of multipliers(ADMM)is elaborated.Then,decoupling and iteration mechanism analysis is implemented for the electricity-gas system’s interconnected boundary,and the decentralized optimization model of electricity-gas MG is proposed accordingly based on ADMM.Besides,nonconvex and nonlinear constraints in this model are handled by second order cone relaxation and incremental piecewise linearization techniques. |
