Research On The Impacts Of Electric Vehicles Charging And Discharging On The Power System And Its Optimal Strategy

With increasingly deteriorating problems of energy resources exhaustion andenvironment pollution, the electric vehicles (EVs) have attracted more attention dueto their great advantages in energy-saving and emission-reducing. However,large-scale disordered charging of EVs will have a negative impact on the distributionnetwork, which is better to be reduced by studying the influence ofcharging-discharging events on the distribution network and the correspondingoptimization strategies. Based on the ordered charging-discharging approach used forEVs, this paper is focused on the optimization of load curve in a system with EVs, thereduction of voltage deviation, the smooth of power fluctuations of EVs’ chargingstation with photovoltaic (PV), and the enhancement of the integration capacity ofrenewable energy sources. The work in this dissertation is summarized as follows:(1) Two charging modes, disordered charging and ordered charging-discharging,are proposed in this work, respectively, for the description of EVscharging-discharging probability characteristics and power expectation, with thepurpose of studying the optimization of EVs ordered charging in a scenarioconsidering load peak. An optimization model is established as well, aimed towardsminimizing the load peak. Additionally, the impacts of peak valley price and users’responses on load curves in a system with EVs are analyzed in detail and thencompared with the situation in which EVs are charged with disordered strategy.Furthermore, impacts of EVs ordered charging on load curves in a system with EVsare studied under different levels of users’ response. Subsequently, impacts of EVsordered charging-discharging on the optimization of different types of load curves arediscussed under the same level of users’ response. Finally, the relationship betweenusers’ responses and load peak is analyzed in detail.(2) In order to research the economic benefit of EVs orderedcharging-discharging, a multi-objective optimization model is proposed to maximizethe total social profits and users profits, with the optimized solution set obtained.Then, the economic benefit of EVs ordered charging-discharging and their impacts on load curve are discussed based on three typical scenarios. Besides, the sensitivityproblem is analyzed on critical parameters that significantly influent the total socialprofits and users profits, based on which feasible suggestions are put forward on thepremise of no dramatic reduction of the total social profits, and to raise users’enthusiasm of responding the ordered charging-discharging policy.(3) Considering that EVs disordered charging will aggravate voltage deviationand deteriorate power quality of distribution systems, an optimization model isproposed in this work to solve the problem of voltage deviation in a distributionnetwork with EVs. Then, the effects of EVs ordered charging-discharging areanalyzed on the voltage deviation improvement and economic benefit. In addition,based on the analysis of voltage deviation and loss characteristics of distributionsystem operated in typical scenarios, the quantity configuration of EVs is suggestedfor each node in a distribution system.(4) The model of time-sharing control for EVs charging and the method ofswapping batteries charging-discharging control are proposed in this work, aimedtowards utilizing the adjustable capacity of EVs ordered charging and swappingbatteries charging-discharging effectively, smoothing the power fluctuations ofcharging station with PV, and improving the integration capacity of renewable energyresources. Firstly, the physical structure and control structure of EV station areproposed. Then, the characteristics of frequency field of each unit in the station areanalyzed in detail. Last but not least, the smooth effect of power fluctuations isstudies based on time-sharing control of EVs charging and swapping batteriescharging-discharging control, with their pros and cons discussed as well. Finally,feasible suggestions are put forward to further smooth the power fluctuations of thePoint of Common Coupling (PCC), and the optimal configurations are also proposedfor PV capacity, EVs charging power, and swapping batteries capacity.