Research On Control Strategy Of Large-scale Electric Vehicle Group Participation In Power System Frequency Regulation

In order to cope with the current increasing energy crisis,renewable and clean energy has developed rapidly.Among them,electric vehicles,as the main development targets to replace traditional oil vehicles,have extremely broad development prospects.At present,with the expansion of the global electric vehicle scale,research on the interaction technology between electric vehicles and power grids has also deepened.Among them,the use of electric vehicles to participate in power grid frequency regulation is a hot topic of current research.However,the disordered charging of electric vehicles after entering the network will have an adverse impact on the grid,and the low charge and high discharge of the electric vehicle battery will damage the battery life.In order to solve the above problems,this thesis has carried out research on the large-scale electric vehicle group participation in power grid frequency regulation(FR)research:(1)In view of the difficulty in the scheduling of large-scale electric vehicles to the dispatching center,this thesis proposes a clustering strategy for large-scale electric vehicles.Firstly,according to the operating rules of different types of electric vehicles and the will of the owner,combined with the creditworthiness of the electric vehicles participating in the FR and the time margin of the FR,the electric vehicle clusters that are connected to the network at different times are divided into several sub-clusters.On this basis,the hierarchical control structure is designed.Through the grouping and stratification strategy of electric vehicles,the control difficulty of the dispatching center can be reduced,and communication congestion can be reduced.(2)In view of the current problem of individual electric vehicle constrained by large-scale electric vehicles as a whole,this thesis proposes a controllable FR capacity prediction strategy to solve the needs of different electric vehicle users.Considering the target SOC of the electric vehicle and the expected departure time for packet frequency regulation,it is divided into a FR group and a unidirectional charging group,and then the frequency regulation component is a bidirectional FR group and a one-way FR group,and finally predicts the controllable electric vehicles under different groups.Capacity,and then proportionally allocate the FR demand according to the hierarchical FR structure.This strategy can make the predicted controllable capacity change in real time,thus reducing the frequency regulation capacity of the traditional unit,and thus getting better frequency regulation effect.(3)For the impact of the frequent charge and discharge conversion of the electric vehicle battery on the battery life,the module for limiting the number of charge and discharge cycles of the battery is added on the basis of the original electric vehicle FR model,and the bidirectional FR can be performed when the number of times is limited.When the number of times exceeds the limit,the current charge and discharge state can only be maintained for frequency regulation.After the constraint is added,the corresponding controllable FR capacity is improved,and the life of the battery is prolonged.(4)For the fast frequency regulation characteristics of electric vehicles,this thesis divides the FR demand signal into frequency division,distributes the high frequency signal to the electric vehicle,and distributes the low frequency to the traditional FR unit,which ultimately has better frequency regulation effect.Aiming at the influence of the scale of electric vehicles on the auxiliary frequency regulation of electric vehicles,the influence of the number of electric vehicles on the frequency regulation effect is verified by simulation.As the electric vehicles increase within a certain range,the controllable frequency regulation capacity is larger and the frequency regulation effect is better.