Electric Vehicle Aggregator Control For Grid Frequency Regulation

With the growing popularity of electric vehicles(EVs),orderly and reasonably unified management of the charging of EVs has emerged as an important problem.This paper proposes a charging control strategy using EVs to participate in grid frequency regulation based on an aggregator.In light of the sensitivity of battery life to the number of instances of charging and discharging,the droop characteristics of a virtual synchronous generator are simulated by controlling only the charging power of the EV,and a modified sectional droop control strategy is proposed.Virtual inertial damping is added to simulate the inertial damping characteristics of the synchronous generator to solve the issues of inertia and damping and allow the system to operate safety and stably.Firstly,this paper considers the huge impact on power grid caused by the access of a large number of EV,expounds the necessity and importance of reasonable and orderly control of EV charging.Secondly,according to the characteristics of the long-time stop and cluster of private EV,puts forward a framework of centralized control of EV charging by means of cluster.Making use of the advantages of EV's participation in system frequency regulation,meanwhile considering the users' charging demand and the effect of frequent charging and discharging on EV battery life,the power-frequency droop characteristic of synchronous generator is simulated by EV aggregator through the G2V mode.In this paper,two power primary allocation strategies are proposed for each EV aggregator at the rated frequency and changing frequency,respectively,which making EV aggregator participate in the regulation and control of the grid in the form of controllable load,effectively avoid the negative impact of large scale EV charging on the grid.Aiming at minimizing the influence to the owner,the secondary charging control strategy of each EV in the aggregator is proposed,which not only reduce the loss of the battery due to frequent charging and discharging,but also ensure the normal charging of the EV and bring the FR profits for the electric car owners as well.Taking into account that the EV is access to the grid through the power electronic interface,whose frequency response speed can reach milliseconds,in order to eliminate the rapid change of the EV charging power caused by the rapid changing frequency,the inertia damping part is added to the frequency detection end,and to some extent,the fast change of EV charging power is restrained.In this paper,MATLAB/Simulink software is used to build the simulation model,and the effect of the EV aggregator taking part in frequency regulation under the droop control strategy is verified.The simulation results show the effectiveness and superiority of the proposed control strategy.