Research On Optimal Operation Method Of Distribution Side Multi-micro Grid System Based On Game Theory

Microgrid is an important part of smart grid in the future,which plays an important role in improving the acceptance ability of distributed renewable energy in distribution system and ensuring the reliability of power supply for energy consumers.With the continuous development of renewable energy,the promotion of market reform on energy selling and the maturity of microgrid technology,the number of microgrids in the distribution system is increasing,forming a multi-microgrid system,which brings new challenges to the optimal operation of the distribution system.Therefore,the optimization method for traditional single-agent decision-making will be difficult to solve the multi-objective optimization problem of complex agents caused by multi-microgrid system.Under this background,this paper uses game theory as a tool to explore the power coordination and benefit distribution among different stakeholders,and carries out the research on the optimal operation method of distribution side multi-microgrid system.The main contents of the paper are summarized as follows.Firstly,this paper establishes a typical application framework of game theory in distribution system with multi-microgrid,and gives the general idea of game model application from three aspects:non-cooperative master-slave structure game,cooperative master-slave structure game and cooperative peer-to-peer structure game.The corresponding relationship between the application of game theory and various boundary bars,game type selection and boundary conditions of distribution side multi-microgrid system are analyzed.Besides,the basic content of game theory involved in this paper is introduced.In view of the non-cooperative electricity transaction between distribution operators and multi-microgrid operators,this paper constructs a non-cooperative master-slave game model.Among them,the distribution operator is the leader of the game,and the microgrid operator is the follower of the game.In this paper,the existence of game equilibrium is proved,and the game optimization problem is modeled as a two-level optimization model.Differential evolution algorithm is adopted by the leader to search the optimal internal prices.The followers optimize the internal power dispatch by responding internal prices.After repeated iterations,the optimization results converge to the equilibrium solution of the game.The example analysis shows that the proposed model can get the internal tariff formulation scheme which is better than the grid tariff,and effectively reduce the operating costs of distribution operators and microgrid operators.Aiming at the cooperative power trading between distribution operators and multiple microgrid operators,this paper constructs a cooperative master-slave Nash bargaining model,where the distribution operator is the center of the whole cooperative game,and all microgrid operators can only cooperate with the distribution operator.The optimal costs based on grid prices are set as the breaking point of Nash bargaining.The paper proves that the Nash bargaining model is equivalent to the optimization of social cost of the whole distribution system,and illustrates the stability of cooperative game.The alternative direction multiplier method is used to construct a distributed optimization architecture between distribution operators and multiple microgrid operators.The participants in the game only need to exchange the expected transaction power and transaction price,thus protecting the privacy information of the participants.In the process of distributed optimization,the convergence speed of the original residual is improved by adjusting the optimization parameters adaptively,so that the distributed optimization algorithm can converge to Nash equilibrium solution quickly.Case study shows that the proposed model can get an effective bidirectional clearing price,reduce the operating costs of distribution operators and Microgrid operators,and achieve the optimal social cost of the whole system.Aiming at the direct electricity transaction among multiple microgrids without distribution operator,this paper constructs a Nash bargaining model of peer-to-peer cooperative game.In the model,the network transportation charges of the microgrid operators are considered,and the breaking point of Nash bargaining is that the microgrid operators only trade with the distribution operators according to the grid prices.This paper proves that the Nash bargaining model is equivalent to the social cost optimization of all microgrids,and illustrates the stability of cooperative game.The original optimization problem is transformed into two sequential convex sub-problems:social cost minimization and payment benefit maximization.In this paper,an alternating direction multiplier method is used to construct a distributed optimization architecture among microgrid operators,and two sub-problems are solved in stages.Case study shows that the proposed model can find the expected electricity quantity and price of direct power exchange,reduce the operation cost of microgrid operators to the greatest extent,and achieve the optimal social cost of multi-microgrid.To further verifiy the effectiveness of the above-mentioned optimization method in practical application,this paper builds a virtual power trading platform based on two actual AC micro-grid systems.The paper designs the experimental flow of the actual system,and uses special equipment to verify the reliability of the local equipment.On this basis,this paper validates the three optimal operation schemes under different weather conditions of sunny,cloudy and cloudy days,and analyses the results of the optimal operation cost.The experimental results show that the three optimal operation schemes proposed in this paper are applicable to three different interests of the distribution system.