Research On The Control Strategy For Electric Vehicles Charging Load To Participate In System Frequency Response

Under the double-press of environmental pollution and energy shortage, electricvehicle has become the main development direction of new energy vehicles. Thecontinuous expansion of electric vehicle scale brings new challenges and opportunitiesto the safe and stable operation of power system. The grid-connected electric vehiclecan be regarded as a controllable load, which can also act as a distributed energystorage unit. Through the proper control, electric vehicles can effectively assist thesafety and stability of power grid. Therefore, with a consideration of the chargingcharacteristics of electric vehicle, it is of great theoretical and practical importance toresearch on control strategies for electric vehicles to participate in power systemancillary services. It can provide references for the stable operation of power systemand improve the ability to integrate renewable energy into the system.Due to the rapid characteristics in responding to system frequency change,electric vehicles are suitable for power system frequency regulation. How to make useof the charging and discharging characteristics of electric vehicles to suppress thefluctuation of the system frequency and improve the stability of power grid has becomea new research hotspot. Focusing on this topic, the following research has been carriedout in this paper:Based on the decentralized V2G model, a coordinated control strategy for thelarge numbers of decentralized electric vehicles to actively participate in primaryfrequency regulation is analyzed in detail. Due to the characteristics of controllabilityand time flexibility, electric vehicles can make response immediately when thefrequency deviation exceeds a certain threshold. In the proposed control strategy, astepped response pattern is adopted. Electric vehicles adjust their charging ordischarging power properly according to the frequency variations, achieving theinteraction with power grid friendly. Through the control strategy, electric vehiclesmake response asynchronously and actively, namely they participate in response atdifferent points of time. Using the Power System Analysis Toolbox (PSAT), differenttypes of disturbances were simulated, and the results verify the effectivess of theproposed method.Based on the centralized V2G model, electric vehicles participating in powersystem automatic generation control (AGC) is also taken into consideration. Fullytaking into account the advantages of largr-scale electric vehicles and battery energy storage stations, e.g., rapid response and large instantaneous power, a coordinatedcontrol strategy for large-scale electric vehicles and battery energy storage stations toparticipate in system AGC, coordinating with the traditional frequency regulationresources is presented. To achieve the coordination among different frequencyregulation resources while fully utilizing the advantages of electric vehicles andbattery energy storage stations, different response priorities and control strategies areset based on the different operating states. To verify the effectiveness of the proposedcontrol strategy, dynamic simulations for electric vehicles and battery energy storagestations to participate in AGC of a two-area interconnected power system areperformed in the Matlab/Simulink program.In conclusion, this paper focuses on electric vehicles contributing to powersystem regulation services, and control strategies for decentralized and centralizedelectric vehicles to participate in system frequency regulation have been proposedrespectively. The research of this paper could provide a reference for integrating largenumbers of electric vehicles into the grid and effectively assisting the stable operationof power system.