Investigations On The Impacts And Interactions Between Electric Vehicles And Power System

The emission caused by the traditional automotives which reply on burning gasoline anddiesel oil as the main driving force leads to increasingly serious environmental pollution. Inorder to find a perfect solution, each country seeks to develop a brand new energy vehicle foreffectively reducing air pollution problems. The emergence of electric vehicles brings a newhope and direction to improve air quality and change people’s life. Electric vehicle usingbattery as the main driving force not only effectively solve the emission issues, but also it canhelp current power system to improve operation on power supply, which is of a strongcompetitive on promoting automotive innovation.With the popularization and development of electric vehicles, people have paid moreattentions on battery charging and discharge’s problem. Unconsciousness charging behaviorsare engaged as long as driver making decision on consciousness. When developing to acertain scale, it definitely will challenge existing power system and brings a certain impactand influences, such as voltage variations, power quality, system stability, reactive powerbalance. However, the battery from electric vehicle has a characteristic that can storeelectrical energy. With intelligent management strategy, electric vehicles having coordinatedcharging on off peak hours and coordinated discharging on peak hours can help enhancing theeconomy and stability of the power system. The purpose of this study is to analyses a varietyof different types of electric vehicles and charging behaviors, study the impact and influenceson existing power system with electric vehicle charging and discharging, develop theintelligent charging and discharging strategy for peak load shaving.This thesis mainly consists of five parts.With the traditional energy becoming less and less and the air pollution caused by vehicleexhaust being more and more serious, every country is active seeking and developing a newresource or replace energy. Supplied by a battery as main power source, electric vehicle notonly can effectively reduce users’ driving cost and reliance on petroleum, achieve the real"zero" emissions, but also it can increase the efficacy of power system by charging batteriesduring off peak time. In order to further reduce impacts of coordinated charging on theexisting distribution system and the cost to the user, this thesis will proposes a batteryexchange station solution for electric vehicle and its operation model. Assuming modeled onbus and according to the rapid battery exchange character, a simulation is made for maximumannual profit of battery exchange station, minimum the charging impact, meanwhile it helpsusers reduce battery cost and its maintenance problems. Secondly, for further development of electric vehicles in automotive industry, theconstruction of charging facilities is one of the important key for promotion new energyvehicle. For electric bus, battery lease mode is the best option to run the operation effectivelyand have less impact for local distribution system, which is because all recycled batteries canbe charged in coordinated charging station later in off peak time period. With the analysis ofthe charging profile of electric buses, an optimal model for coordinated charging stations’planning and siting is developed to minimize the operation cost. Finally, by employingVoronoi diagram, the solutions of planning and siting strategy is made and illustrated.When the developed charging and discharging technology gain people’s recognition,large-scale of uncoordinated charging must bring some negative impact to current powersystem, or even become a serious threat to the security of the operation. In order to avoid andfind the solution, electric vehicle’s driving behaviors, daily travel route, charging habits, andcorresponding charging load response matrix will be studied. Peak and valley time pricemodel is constructed. Using different charging tariff to affect electric vehicle’s chargingbehaviors, an optimization solution is developed to achieve peak load shaving.The popularity of electric vehicles and the development of battery V2G(Vehicle-to-Grid) technology have brought many conveniences to people’s lives and publicsociety. However, the raise of large scale charging load from electric buses impacts thenormal operation of power system. To minimize that impacts, many experts proposed avariety of V2G (Vehicle-to-Grid) charging strategy for helping improve the operation ofpower system. In order to transform the negative impacts into active benefits for powersystem, this thesis analyses the operation mode of coordinated charging station for electricbuses. Under the conditions of fixed driving hours, fixed bus routes, charging and operationmode are studied, and an optimal function is developed for establishing the coordinated V2Gcharging and discharging strategy, which is based on the battery leased model.The random variation of wind power output brings more uncertainties and challenges tounit commitment in power system. By introducing large scale of coordinated charging anddischarging loads, electric vehicles and battery charging stations that acting as distributiongenerations not only help the traditional generating units reallocating the power output anddecreasing operation cost, but also their mobility and stability of power output cover theweaknesses from wind power’s output. Therefore, a new unit commitment model withcoordinated discharging loads of electric vehicle is developed to minimize the operating costfor traditional generating units. A5-unit24hours unit commitment problem is employed todemonstrate the feasibility of this optimal model.