Research On Key Technology Of Grid-friendly Electric Vehicle Management And Control

To tackle with the crisis of energy and environment and achieve the clean energy and electricity substitution,electrical vehicles(EVs),as the representative of new electricity usage technology,are developing rapidly.With large-scale renewable energy and stochastic and surging EV charging loads integrated,the grid faces great pressure during its operation and control process,which leads to more demand of energy storage.Meanwhile,the treatment of the large quantity of retired EV batteries is a hard and emergent problem.Given the above background,this thesis studies some related key problems,based on the idea that using the retired EV batteries to form an energy storage system(ESS)and further to support the grid to integrate EV loads.The final purpose is to integrate EV loads into the grid efficiently while making the best of the retired EV batteries,and then both of them can be integrated into the grid in a friendly way.Firstly,EV loads modeling and characteristic analysis is carried out.A methodology of EV load modeling,which considers the effect of the battery,the charging device and the user behavior characteristics as well as electricity price,is proposed.The characteristics of EV loads are analyzed by referring practical EV data.The proposed EV load modeling methodology includes a numerical method of single EV load modeling,which considers the time-varying and voltage dependent characteristics of the load,and a method of aggregate EV loads modeling,which considers the stochastic characteristics of the loads.Secondly,the key technology of forming a reconfigurable retired EV battery ESS is studied.To get the aging process characteristics of the retired EV battery ESS,an aging and inconsistency coevolution simulation model of the battery pack is proposed,which is further used to guide the classification of the retired EV battery.To cope with the bad consistency and reliability of retired EV batteries,based on dynamic reconfiguration theory and reconfigurable topology design principles,a control methodology of dynamic reconfiguration and charging or discharging of the battery pack,which considers the balance of aging,is designed.According to the simulation results,in the aging process,the proposed methodology can effectively reduce the inconsistency of battery cells and significantly increase the capability of the battery pack.Finally,the application of the retired EV battery ESS in EV loads and renewable energy integration is studied.By analyzing the power and energy change mechanism of the designed ESS in aging process,the operation and control methods in different aging and energy demand conditions of the ESS are proposed,which can be used in the management and control of EV loads and renewable energy output power.Based on the operation and control methods and the ESS's load or output power management index,the performance of the ESS in the aging process is analyzed.In the studied cases,results show that the ESS can operate at least five years with all its designed functions implemented.The application of the designed ESS for reduction in distributed photovoltaic(PV)or EV integration curtailment is analyzed in a practical case.The analysis proves that the ESS can help to achieve the local consumption of the distributed PV and EV loads and improve the load factor of the transformer of distribution networks.