Research On Optimal Dispatching For Flexibility Improvement Of CHP Micro Energy Grid In Island Mode

The combined heat and power(CHP)micro energy grid can realize the joint supply of electricity and heat through energy ladder utilization,which plays an important role in reducing operating costs and improving environmental benefits.Due to the increasingly complex energy structure of the CHP system,and it lacks the energy supply support of the external power grid when operating in island mode.The fluctuations in wind power and photovoltaic output,as well as the uncertainty of the electrical and heat loads,which pose great challenges to the reliable operation of the system,leading wind and light to be abandoned and load reduced.It is an important means to improve the operating flexibility and ensure the stable operation of CHP micro energy grid by fully exploiting the available flexible resources and optimizing the dispatching under the established grid structure.Firstly,the energy supply structure of CHP micro energy grid is introduced in detail.Based on the analysis of the energy flow pattern in CHP micro energy grid in the island mode,the energy supply framework of energy supply equipment,energy storage equipment and demand response load is constructed.The energy supply equipment such as photovoltaic,wind turbine,micro gas turbine,waste heat boiler,heat pump and other energy supply equipment in the system,energy storage equipment and integrated demand response are modeled and analyzed.Secondly,the flexibility of the system is analyzed and quantified.The basic concepts of flexibility in the joint supply system are elaborated.The flexibility resources and flexibility requirements during the operation of the system are analyzed in depth,and the corresponding mathematical models and flexibility evaluation indicators are constructed respectively.Through the analysis of the flexibility balance principle,the relationship between flexible demand and flexible resources is clarified.Then,an optimized dispatching framework for improving the flexibility of CHP micro energy grid is proposed.In order to improve the operation flexibility of the island micro energy grid,a multi-objective day-ahead optimal dispatching model that considers the flexibility goal while taking into account the economic and environmental is established.AHP is used to obtain the weight coefficients of economic goal,flexibility goal and environmental goal.By linearly weighting the membership function of each objective,the multi-objective model is transformed into a single-objective optimization model,and particle swarm algorithm with dynamic inertia weight is used to analyze the model.Simulation result shows that,by building a multi-objective optimal model for "source-network-load-storage" collaborative optimization can not only improve the operational flexibility,but also comprehensively coordinate economic and environmental benefits.Finally,a flexible optimal dispatching framework for CHP micro energy grid considering uncertainty is proposed.Considering the uncertainty of wind,photovoltaic and load in the operation of micro energy grid,a probability distribution model of illumination,wind speed,electrical load and heat load is constructed.The correlation between wind speed and illumination is further considered,then a correlation model of renewable energy output is constructed.On this basis,a fuzzy opportunity constraint model is constructed with economic,environmental and flexibility as optimization goals.Combining the random simulation method and the opportunity constraint method,Latin hypercube sampling and Cholesky decomposition method are used to obtain the correlated variable sample.And then,the membership function of fuzzy variables is used to transform the fuzzy opportunity constraint model into the form of deterministic equivalence class.Simulation result shows that considering the correlation between variables can better characterize the uncertainty of renewable energy output,and it is beneficial to improve the operating efficiency of the system and enhance the system’s ability to cope with power fluctuations by optimal dispatching model based on multi-objective fuzzy chance constraint programming.