Research On Hierarchical Dispatching Strategy For The Microgrid Based On Modified MOEA/D

With the rapid development of new energy,micro-grid has been gradually promoted and applied because of its flexibility and other advantages.Microgrid can effectively solve the problem of connecting the power grid and distributed energy resources,and reach energy complementarity.On the other hand,the economic benefits of the power grid can be further improved through the operation of the microgrid.Therefore,the economic dispatching has become one of the research hotspots of the microgrid.However,with the trend of transportation electrification,large-scale electric vehicles connected to the microgrid have brought various challenges to the safe and economic operation of the microgrid.Therefore,it is of great practical value and theoretical significance to research the optimal dispatching problem of the microgrid,which takes into account V2 G.In this context,this paper takes the environmental and economic dispatching problem as the research framework,and studies the optimization model and method of the microgrid system connected with large-scale electric vehicles.The main contents are as follows:(1)Firstly,the basic principle of distributed energy resources in microgrid is studied,and the power output model of wind generator and photovoltaic cell,the charge and discharge model of energy storage battery and the power output model of diesel generator are established.Then electric vehicles are modeled according to the dual characteristics of onboard energy storage and vehicle,and electric vehicles are divided into two categories: one is subject to the driving habits of users;the other category is completely subject to microgrid dispatching,which is fully dispatchable electric vehicles.Secondly,according to the type of load,the load is divided into dispatchable load and un-dispatchable load,and the transferable load in dispatchable load is mathematically modeled.(2)According to the operation characteristics of each distributed unit,a microgrid hierarchical scheduling strategy considering the user-side is proposed,and the microgrid system is divided into source-load level and source-grid-load level.The consumption of renewable energy can be realized through source-load level dispatching.More importantly,it can well mobilize the enthusiasm of users to participate in grid dispatching in this level,thus improving the reliability and stability of the grid.The objective functions of the source-grid-load level are to minimize the operation cost and the power fluctuation between the microgrid and the main grid.The dispatching object of this level is the output of the power grid and diesel generators.Net load from the first level is also absorbed at the source-grid-load level by the diesel generators and connection lines of the main grid,while the surplus renewable energy is sold to the main grid to gain benefits.Aiming at the hierarchical scheduling strategy,the objective function and constraint conditions of each level are given.(3)The economic scheduling problem of the microgrid is a multiobjective optimization problem,which needs to consider complex unit operation and system constraints,some of which are nonlinear and time-coupled equality and inequality constraints.In this paper,a multi-objective evolutionary algorithm based on decomposition(MOEA/D)is adopted to solve this problem.By introducing the optimization principle and process of MOEA/D algorithm,the algorithm is improved for its poor global search ability and premature convergence.The initialization strategy based on multiple constraints and the replacement strategy based on the improvement of maximum fitness value are designed,and the modified MOEA/D algorithm is obtained.Finally,the modified MOEA/D algorithm is used to solve the hierarchical optimization scheduling model of the microgrid.The dispatching curves of source-load level and source-grid-load level were obtained by simulation,and the output curves of each dispatching unit were analyzed to verify the effectiveness of the microgrid hierarchical dispatching strategy.At the same time,by comparing the simulation results with other scheduling schemes,it is proved that the hierarchical scheduling strategy and the modified MOEA/D algorithm are scientifically effective and have more practical application value.