The Risk And Optimal Charging/Discharging Strategy For Regional Electric Vehicles To Access Distribution Network

As a new type of transportation tool,electric vehicle plays an important role in saving energy and reducing emissions and alleviating the crisis of renewable energy.It has drawn wide attention from all over the world.With the development of electric vehicles,disorderly charge-discharge behavior of large-scale electric vehicles may adversely affect the power grid load.In order to ensure the reliability and safety of smart grid in the environment of high-penetration electric vehicles,it is of great significance to explore the theories and methods of safety risk assessment applicable to large numbers of electric vehicles connected to the power grid.At the same time,as a mobile load,electric vehicles can be rationally charged and discharged to realize the "peak load-shifting " so as to reduce the impact on the power grid.Therefore,it is an urgent issue that a proper charge-discharge dispatching of electric vehicles should be implemented to achieve coordination and optimization of power grids and users.In this paper,a comprehensive assessment of the risk of electric vehicles accessing the distribution network will be conducted to guide the friendly access of electric vehicles in the grid.At the same time,in order to reduce the risk of electric vehicles on the distribution network,the dispatch of electric vehicles in the region will be carried out to achieve the coordination and optimization of power grids,middlemen and users.This paper first introduces the V2G(vehicle to grid)technology of electric vehicle access grid,electric vehicle charging mode and electric vehicle load modeling.Then,consider the influence of electric vehicle charging on the power grid,the risk indexes of distribution network are established from different perspectives,the K-L transformation is used to extract the principal component information,further use of multi-attribute decision-making based on the comprehensive evaluation of node importance comprehensive risk assessment.Finally,in areas including residential areas and industrial and commercial areas,taking into account the access of electric vehicles,the charge and discharge load requirements of grid side under optimal load fluctuation and economic cost are studied,and consider the relationship between electricity consumption at user side and electricity price,the middleman side guides the user through rebate to coordinate charging and discharging.The results show that electric vehicle charging mode provides the basis of calculation for the risk evaluation and the optimal charge and discharge dispatching strategy of the electric vehicle access distribution network.The K-L transformation and comprehensive evaluation method for node importance based on multi-attribute decision making is used to evaluate the comprehensive risk,access to different share of electric vehicles on the grid to bring the overall risk,according to the rule of the comprehensive risk under the share of each electric vehicle,it can guide the number of rapid-charging electric vehicles in a certain area.Taking into account the access of electric vehicles,the goal of minimizing the fluctuation of power load on the grid side and minimizing the charging charges is to achieve the "peak load-shifting " of the grid;the charging and discharging load required by the power grid is the constraint condition,the user side reachs the regional charge and discharge according to the shortest path,with the minimum number of charge and discharge times and waiting time as the goal,middleman side by adjusting the price to guide the user charge and discharge to meet the demand of grid power load,through the algorithms of multi-objective genetic algorithm,dijkstra algorithm,0-1 programming and so on,the coordination optimization of grid side,middlemen side and user side can be realized.