Cooperative Operation Optimization Of Microgrids Integrated With Gas And Electricity In Energy Hub

Most of the public energy infrastructures in traditional energy network,such as power system and natural gas system,are planned and operated independently.With the restructuring of power system and the guidance of decentralization,distributed energy system has been widely used.In the process of distributed energy development,there are gradually multiple energy hubs in the same geographical location to meet the users'multiple load needs.Under the guidance of low-carbon policy,renewable energy such as wind energy and photovoltaic energy are widely integrated into distributed energy hubs.Multiple uncertainties bring challenges to the operation control of the system,which makes it of great significance to formulate economic,low-carbon and efficient operation schemes of energy hubs.In this paper,the energy hub in the gas-electricity integrated energy microgrid is taken as the basic research unit,and the supply of multi-energy is considered at the load side.Considering the efficiency characteristics of energy hubs in gas-power network,the uncertainties of renewable energy and cooling,heating and power loads,and the impact of low-carbon policies on cost,efficiency and other operational objectives,the gas-electricity co-operation optimization under market environment was carried out.The main research contents are as follows:Firstly,the energy hub is taken as the basic research unit in the integrated energy microgrid,and the energy conversion model in the energy hub and the integrated energy network model composed of the energy hub are established.The coupling matrix of energy conversion is formed based on the models of various conversion elements and energy storage elements of energy hubs,and the integrated energy network model of energy hubs is derived from the coupling matrix of energy conversion.The power network and natural gas network are modeled by node power balance and power flow constraints.Finally,the optimization problems of single energy hubs and integrated energy micro-networks are put forward.The potential value of gas-electricity coordination in integrated energy microgrid is also analyzed.Secondly,the efficiency of energy hubs with different roles in integrated energy microgrid is analyzed.In efficiency analysis,three typical energy hubs are selected,i.e.,the combined cooling,heating and power supply system with gas-electricity supply as the production-consumption model,the combined cycle gas generator set with high efficiency gas-electricity conversion and the gas-electricity separation energy supply system as the production-consumption model respectively.Operating modes can be divided into power supply mode,gas supply mode and mixed energy.supply mode according to the mode of energy selection,which is conducive to the rapid decision-making of energy hubs when switching in gas-power network.In efficiency analysis,the efficiency under different thermal and cooling load scenarios is compared by simplified model,which provides a basis for the performance analysis of energy hubs when market conditions,energy policies and operational objectives change.Thirdly,the robust optimal operation model of energy hub in gas-electricity integrated energy micro-grid under load uncertainties is established,and the power supply mode,gas supply mode and mixed energy supply mode selected by the switching of energy network are analyzed and compared.Firstly,a Lagrange two-stage relaxation solution model is constructed based on minimum-maximum regret criterion and dual optimization theory.The original problem is transformed into an inner candidate maximum regret optimization problem and an outer relaxation minimization problem.Then,an improved particle swarm optimization algorithm based on simulated annealing is used to solve the problem.The validity of the model is verified by simulation calculation and the decision-making is further analyzed.Conservative degree,prediction accuracy level,energy price level and seasonal characteristics of load affect the optimization results,which provides conditions for the operation optimization of gas-electricity integrated energy micro-grid composed of multi-energy hubs.Then,a multi-objective coordinated optimization operation model of energy hub including renewable energy generation equipment under low-carbon policy is constructed,and the operation cost and efficiency are selected as the multi-objective optimization.According to the price of carbon tax,the emissions are converted into economic targets,which together with the primary energy consumption cost constitute the economic targets,and the output-input energy ratio of energy hub is taken as the efficiency target.Renewable energy subsidy system takes into account the grid access subsidy system under pricing mode and the quota system under quantitative mode.Under the quota system,the tradable green certificate is introduced to compensate the cost of.renewable energy generation.Through Pareto optimization,the effects of different subsidy systems on the cost and efficiency of energy hubs are analyzed.The analysis results can be used as the basis for decision-making under different operational objectives of decision-makers.Finally,a master-slave game model based on Stackelberg game is established in view of the structural characteristics of energy pricing formulated by operators in integrated energy microgrid and energy hub adopting corresponding energy strategy according to price.As the dominant player of the game,microgrid operators aim at maximizing their own profits,while energy hubs aim at maximizing their utility.The existence and uniqueness of the feasible solution of the game are proved.After the game equilibrium is reached,the Lyapunov optimization method based on queuing theory is used to transform the uncertain disturbance into the cumulative energy demand sequence for the impact of renewable energy and load uncertainties.The sequence is stabilized by minimizing Lyapunov drift and the penalty weight is set to constrain the cost.Because Lyapunov optimization only needs to give the perturbation range for uncertain perturbation without specific distribution parameters,it greatly simplifies the solving process,and can coordinate stability and economy by adjusting the weight.The feasibility and effectiveness of this method are verified by simulation calculation.