Research On Power Exchange Methods Of EVs Considering The Battery Degradation Cost

As an important constituent part of “Energy Internet”,electric vehicles(EVs)as the flexible resources can consume renewable energy power generation locally through adjusting the charging power and period.It effectively promotes the integration and consumption of renewable energy sources,improves the operation condition of the power system.With the proliferation of EVs,the random charging and discharging behaviors of EVs bring new challenges to the operation of the power system,and EV owners' experience.Based on this background,this paper is conducted from the aspects of battery degradation cost model and the power exchange methods such as vehicle-to-grid(V2G),vehicle-to-home(V2H),vehicle-to-vehicle(V2V),battery-to-battery(B2B),and battery swap,targeting for solving the key technologies of EVs participating in the power exchange with different scenarios,and satisfying the requirements of EV owners and providing assurance for the safety and economical operation of the power system.These studies can promote theoretical and practical guidance for the application of EVs.The main contributions are summarized as follows.1.To tackle the exorbitant battery degradation cost(BDC)results from power exchange,a frequency regulation power hierarchical dispatching method is proposed for reducing the BDC of EVs.In order to calculate the BDC of EVs accurately,the corresponding cost model that considers various EVs is established based on the rainflow counting algorithm.In order to ensure system security,the required FR power is dispatched to FR units and EV aggregators according to the optimization coordinating strategy for reducing frequency fluctuation.Then,EV aggregators further dispatch the power to each EV for reducing the total BDC of EVs.In the dispatching process,various EVs provide FR service in the light of their actual condition such as battery types and state-of-charges(SOCs).According to the sensitivity analysis,the FR regularity of EVs about FR performance is drawn for promoting the quantity of EVs participating in FR and further improving FR performance with cost-efficiency.Extensive case studies are presented to validate the effectiveness of the proposed method.2.In order to promote local consumption of distributed renewable energy sources and reduce customer electricity cost,a hierarchical power exchange method base on family microgrids interconnection and V2 H behavior is proposed.Through coordinating the flexible load and V2 H power,the renewable energy sources are consumed locally.In the lower level,the power exchange between the residential load and available source in each microgrid is performed for the minimum cost and satisfying the electricity requirement through coordinating the flexible load.In the upper level,the power exchange between the unsatisfied load and surplus sources in microgrids is performed.In the whole process,EVs are considered as the interactive flexible load and reduce the total cost through V2 H behavior.Extensive case studies are presented to validate the effectiveness of the proposed method.3.To decrease the adverse impact of a large number of EVs random charging and discharging behaviors on the power system,a hierarchical bipartite graph matching method is proposed to promote transactive V2 V power exchanges in a distribution power system.The power system that EVs plug in is divided into a series of subsystems according to EV locations,where V2 V power exchanges are optimized for scheduling charging/discharging periods among transacting EVs in each subsystem.In the lower level,the power exchange between charging EVs and available sources,including discharging EV and renewable energy sources,in each subsystem is performed.In the upper level,each subsystem's power surplus or deficit will then be regulated by power exchanges among neighboring subsystems and the utility grid.In the power exchange processes,the individual EV's electricity trading price can track that of the subsystem by adjusting respective power exchange objectives adaptively.Several case studies are presented to validate the effectiveness of the proposed method,where transactive V2 V power exchanges are improved and the energy efficiency in a distribution power system is enhanced.4.To solve the power supplement of EVs driving on expressways,a power exchange method considering EVs supplement energy in battery swapping stations(BSSs)is proposed.In order to ensure EVs supplement electricity with costeffectiveness at any time,the power exchange process is hierarchical.In the lower level,EVs are dispatched to BSSs for supplement energy with cost-effectiveness.In the middle level,the power exchange among batteries and the grid is performed for reducing the cost.In the upper level,EVs with high SOC batteries are encouraged to swap low SOC batteries in BSSs for ensuring BSSs can provide the power for EVs with cost-effectiveness.At this level,some low SOC batteries could reduce the charging power and the BSS reduces the total cost.Several case studies are presented to validate the effectiveness of the proposed method.Overall,as the flexible resources,EVs could improve the local consumption of renewable energy sources,satisfy the driving requirement of EV owners and reduce the cost by improving the power efficiency.By decreasing the impact of large-scale EVs charging and discharging behaviors on the power system,an applicable economic dispatch and flexible power exchange for user-side energy management is provided.