Research On The Impact Of Plug-in Electric Vehicles On The Operating Life Of The Distribution Transformer

In the coming years, there is a high likelihood that large numbers of electric vehicles will be used in the world including China in the future according to “Global EV outlook,understanding the electric vehicle landscape to 2020”. But a great many electric vehicles plugged into the grid can have a significant impact on the distribution network such as increasing the load of the distribution network, impacting the heat capacity and life of the distribution transformers. State Grid Corporation of Hebei and Jiangsu are also facing the problem that a large number of electric vehicles will plug in. And therefore it is necessary to study the impact on the loss of life of distribution transformers with the rapid development of electric vehicles. This paper studies the impact on the operating life of the distribution network transformer when a large number of electric vehicles are plugged into the grid simultaneously and draws up the charging strategy to reduce the loss of life and impacts. It provides a guarantee for the development of electric vehicles and the control of the fog and haze. The paper assumes two Chinese electric vehicle pilot cities in North China and East China as the research objects on the basis of China electric vehicles development project and carries out the researches in residential living areas of this cities.Firstly, the paper sets up electric vehicle charging load model. The model takes into account the type of electric vehicle, charging strategy, charging power, charging frequency, the state of charge of battery, the electric vehicle market penetration, the start time of charging, the traveling distance each day and so on. It establishes the Chinese non-control charging model of electric vehicles and off-peak control charging model on the basis of that in order to study the impacts on the distribution network.Then it constructes the transformer hot spot and life evaluation model by MATLAB programming. While the electric vehicle charging load is superimposed to the residential living areas to study the effects on distribution transformers with different areas. It compares the uncontrolled charging and the non-peak charging specifically from the electric vehicle market penetration, the ambient temperature and the charging strategies.Finally, it proposes smart charging strategies based on Particle Swarm Optimization in order to meet the users’ demand for electric vehicle charging and minimize the loss of life of the transformer. They can be divided into the control of electric vehicle charging time and the control of electric vehicle charging current depending on the optimization objectives. The smart charging strategies, the uncontrolled charging and the non-peakcharging are compared to verify the smart charging strategies’ validity.