Research On Coordinated Optimal Scheduling Of Micro Energy Grid With CCHP System And Energy Storage

Faced with the dual challenges of the global energy crisis and environmental pollution,the existing energy production and consumption patterns can no longer meet the demands of social development.Meanwhile,with the proposal of energy internet,integrated energy systems and other concepts,new ideas have been provided for the efficient and economical utilization of energy.Among them,as one of the development trends of future distributed energy systems,the micro energy grid for intelligent buildings,residential communities and isolated islands has attracted extensive attention.Extended from microgrid under the background of energy interconnection,micro energy grid is a kind of mini integrated energy interconnection system.In this network,the advantages of various energy networks,such as electric power,heating and natural gas,are complemented and coordinated to meet the needs of users for multi-type of loads,such as cooling,heating and power.At the same time,the renewable energy such as wind,solar and geothermal energy can be full used by adjusting measures to local conditions.This paper study on the optimal operation of micro energy grid,and the main contents are as follows:Firstly,the concept of micro energy grid is given and the mathematical model of micro energy grid is proposed based on the framework of energy hub.This energy hub model can intuitively reflect the coupling characteristics and energy flow process between micro-sources,including energy input,energy conversion,energy storage,energy collection and distribution,and energy output five major links.Micro energy grid has grid-connected and islanded two operation modes and different scheduling strategies are proposed respectively.On this basis,the operation characteristics of distributed micro-sources inside micro energy grid are analyzed in detail so as to construct the mathematical models including wind turbine,photovoltaic cell,CCHP system,ground source heat pump,fuel cell and energy storage devices.The refined construction of energy hub model lays a theoretical foundation for the methods and strategies of micro energy grid dispatching optimization.Secondly,in order to analyze the economical and energy-saving effects of heat pump and energy storage devices,an optimization model of micro energy grid with heat pump and energy storage is proposed in grid-connected mode with time-of-use electricity price.Based on the lowest system operating cost during the scheduling period,the micro energy grid optimization scheduling model including wind turbine,photovoltaic cell,micro turbine,ground source heat pump,energy storage and fuel cell devices is established.This model is solved with mixed integer programming method to obtain start-stop statuses,optimal outputs and total operating costs of each units and energy storage devices,and then compare it with traditional microgrid scheduling model.The simulation results indicate that by introduce heat pump and energy storage into micro energy grid can enhance the flexibility of CCHP system through changing energy coupling relation between cooling,heating and power,and realize coordinated scheduling and conversion of various energies.According to the analysis of peak-load shifting and energy-saving indicators,heat pump has higher energy conversion efficiency,which can greatly reduce the fuel consumption and improve the utilization of energy.In addition,energy storage devices can effectively adjust the load peak-to-valley difference.Finally,over all considering the characteristics of energy coupling and conversion,operation characteristics of distributed units and energy storage devices,an economic optimization model of islanded micro energy grid considering multi-type demand responses is proposed.Without the effective voltage and power support of the main grid,it is difficult to maintain the energy real-time balance just through the scheduling of internal micro-sources.Therefore,in view of the operation characteristics of islanded micro energy grid,this paper analyzes from the perspective of cooling,heating and power multi-type demand responses.The controllable loads are essentially equivalent to virtual micro-sources,which is incorporated into the system operating cost through the demand response cost so as to participate in the economic energy scheduling of micro energy grid.This paper selects typical summer and winter days to formulate corresponding scheduling strategies,and mixed integer programming is used to solve the model.The simulation results show that by introducing demand responses of cooling,heating and power,the flexibility of energy supply for islanded micro energy grid can be effectively improved,which eventually contributes to reduce the total operating costs.