Study Of The Probability Simulation Of Electric Vehicle Charging Load And Its Impact To The Loss-of-life Of Distribution Transformer

This thesis was supported by National Natural Science Foundation of China(51277184) and independent research project of State Key Laboratory of PowerTransmission Equipment&System Security and New Technology(2007DA10512709209).With the increasing pressure from energy saving and environmental protection, theresearch of new energy vehicles has been accelerated. The electric vehicle, one of thenew energy vehicles, has gained the preference of the public with its superiormechanical property. Our government strongly supports the development of electricvehicles, and also actively supports the construction of its facilities. Moreover, westrongly conduct the demonstration projects to promote the popularity of electricvehicles. However, with the massive charging of electric vehicles, significant impactswould be brought to the distribution network, such as the decreased power quality,increased network losses and decreased equipment utilization and so on. Therefore,before the integration of large-scale electric vehicles to the distribution network, it is ofgreat significance to study the probability simulation of electric vehicle charging loadand its impact on the distribution transformers. The main content of this paper is asfollows:1）According to the different energy supply modes, useage modes and chargingmethods, this paper establishs a hierarchical classification structure of electric vehicles.Then combined with the characteristics of charging power and state-of-charge (SOC) ofdifferent types of electric vehicles, considering that the plug-in hybrid electric vehicles(PHEV) have to two operating modes, this paper improves the initial sampling methodsof SOC. Taking into account the length of the charging time which may influnce theconsumer’s device of when to start charging, we finally propose a probability simulationmethod for multiple kinds of EVs containing PHEV.2) According to the different proportions of conventionally-charged EVs andfastcharged EVs, four indexes (the increment of peak load, the duration of peak load,the maximum smoothing index of load curve and the average smoothing index) areproposed to evaluate the impact on the distribution network. Then a method isestablished to configure the proportion of EV in different charging methods. Finally,based on the field data of a distribution network and the IEEE-34node example, the optimal proportion of EV in different charging methods are made combined with theMonte Carlo simulation of charging load.3) In the case of both charging load and local load simultaneously accessed to thedistribution transformer, considering the harmonic currents generated by the charging ofelectric vehicle, combined with the equivalent circuit of electric vehicle chargers, thispaper proposed an calculation process of evaluating the impacts of distributiontransformer operating parameters, which is caused by the EV charging load. Based onthe probability simulation of electric vehicle charging load, this calculation process alsouses the analytical calculation method of harmonic voltage and harmonic current.