Research On Distributed Charging And Discharging Control Strategy For Electric Vehicles In Residential Areas

With the increasing pressure of energy and environment,Electric Vehicles(EVs)has attracted attention of governments all over the world due to its advantages of environmental protection,energy saving and pollution-free.The user base number of the electric vehicle is increasing year by year,and the residential area will become the main charging place in the future.However,in real life,there is a difficult problem of users charging,the main reasons are:on the one hand,the uncoordinated charging of large scale electric vehicle will cause overload of distribution transformer,which affect the safe operation of power distribution system.On the other hand,the layout of intelligent charging pile in the residential areas needs additional power equipment and upgrading circuit.The investment cost in the early stage is high,so it is difficult to mobilize the enthusiasm of residential property participation.At the same time,state grid sells electricity in the form of time-of-use price,but the cost rate and the time interval of time-of-use price does not adjust dynamically with the actual operation of the state grid,which is difficult to reflect the actual supply and demand.Aiming at the difficulty problem of charging of electric vehicles in residential area under time-of-use price scenario.This paper proposes a distributed coordinated charging and discharging control stategy for electric vehicles in residential area,which realizes the safe and reliable operation of power distribution system and meets the user's charging demand.The main research contents of the thesis are as follows:1)The factors affecting the charging load,such as the charging mode of electric vehicles,user's driving characteristics,the charging characteristics of battery,are analyzed,and a charging load model for a single electric vehicle is established.2)Taking a residential area as an example,the Monte Carlo method is used to simulate the effect of the scale uncoordinated charging behavior and the time-of-use price coordinated charging behavior on the residential area load characteristics.The results shows that the uncoordinated charging will aggravate the load fluctuation,the coordinated charging based on time-of-use price can transfer the charging load to the low price period,but it will have a new load peak at the beginning of low electricity price.3)The distributed coordinated charging control strategy for electric vehicles in residential areas is proposed.First,the computation chip is embedded into the battery management system,which making it has the function of making the charging plan independently,overcoming the problem of power center computation time overhead and centralized controlling the starting and stopping of the charging pile.Second,the architecture of the distributed charging system is constructed for the residential areas,a model that aiming at minimize the user's charging cost based on the real-time guide price is established.The dual theory is introduced into the model to achieve distributed computation.Finally,in order to verify the effectiveness of the proposed strategy,the effects of uncoordinated charging and coordinated charging on load characteristics and user's charging cost are simulated,and the computation time is compared with the centralized control strategy.4)A distributed charging and discharging control strategy for electric vehicle which considering battery loss is proposed.A coordinated charging and discharging simulation example is established by the Vehicle-to-Grid(V2G)technology.The battery loss cost and discharging power are correlated,the model that minimize the user's charging and discharging cost considering battery loss is established,and the dual theory is used to transform the model to solve the problem of coupling constraints which realize distributed coordinated charging and discharging.Finally,the uncoordinated charging,coordinated charging,coordinated charging and discharging control strategy,respectively,is simulated and analyzed.