Orderly Charge And Discharge Strategy Of Electric Vehicles Based On Complex Network Under V2G Mode

With the problems,including energy shortage,environmental pollution and global warming,the country has vigorously promoted the development of electric vehicles(EVs).As a new means of transportation which is clean with zero emission and low noise,EVs play an important role in saving energy and protecting the environment.As EVs become more and more popular,their impact on the power system is also increasing.When lots of EVs are connected to the distribution network,the charge load added with the original grid load aggravates the load peak-valley difference and the pressure on the distribution network.In order to play the role in saving energy and protecting the environment,how to reasonably formulate an orderly charge-discharge strategy for EVs becomes the primary problem to be solved.When EVs are connected to the distribution network to be charged and discharged,it will affect the distribution network from time and space.It will not only change the load,but also change the topological connection structure of the power network,and then change the topological evolution process of the distribution network.However,there are few literature studies on the impact of network topology.In this article,based on the shortcomings of the existing orderly charge-discharge strategies for EVs,the traditional modeling method of complex power network is improved.Through fully considering the integrity and interactivity of EVs connected to the distribution network,this article studies the orderly charge-discharge strategy for EVs from time and space.The main work is as follows:(1)Aiming at the interaction between the distribution network and EVs during the charge-discharge process,based on the complex network theory,the dynamic evolution model of distribution network under Vehicle-to-Grid(V2G)mode is proposed,which can analyze the relationship between the distribution network topological statistical and electrical characteristics.The model is used to study the impact of the space-time distribution of EV load on the two distribution network characteristics under three charge-discharge modes.(2)Based on the community structure and the travel chain theory,the orderly charge-discharge strategy for EVs in V2 G mode is proposed,meanwhile optimization factors are allocated to charge station nodes inside and outside the neighborhood network and the optimum charge-discharge sites are selected for EVs.The statistical characteristics of the orderly charge-discharge model are defined,and then the effectiveness of the proposed strategy in suppressing the node voltage drop,reducing the network loss and balancing the power flow of the distribution network is verified in terms of network topology and network electrical characteristics.(3)The optimization problems of EVs connected to the distribution network in terms of time and space are considered comprehensively.In terms of time,the minimum load fluctuation of the distribution network and the minimum charge cost of users are taken as objective functions.The battery capacity constraint and the transformer capacity constraint of the distribution network are considered comprehensively.In terms of space,based on the minimum average fluctuation in the number of EVs connected to the charge stations in one day and the minimum choosing disappointment of users,the number constraint of EVs connected to the charge stations and the distance constraint between the charge stations and EVs are considered comprehensively.As a result,the multi-objective space-time orderly charge-discharge strategy for EVs is proposed.The genetic algorithm is adopted to solve the multi-objective optimization problem of different numbers of EVs connected to the distribution network and the optimization effectiveness of this strategy is verified in terms of time and space.