Research On The Fault Analysis And Protection Control Of Electric Vehicle Charging And Discharging Station

Electric vehicle is an important link to realize clean substitution and alleviate the energy crisis by replacing fuel with electric energy.The large-scale development of electric vehicles has led to the construction of the supporting charging pile and charging station.The DC electric vehicle charging and discharging station is compact in structure and low in transformation grade.Its power is high and can control the energy flow in two directions to meet the application of V2G technology.It is beneficial for distributed new energy to access to power grid,and has become a hotspot.However,as the intersection of AC and DC network,The station contains a lot of power electronic equipment,which leads the fault anasysis more complex,so we need more effective protection method.Therefore,it is necessary to consider the control strategy of the converter and other power electronic equipment for the fault analysis of electric vehicle charging and discharging station.The characteristics of the fault are summarized,and suitable protection method for the site is studied.This paper provides theoretical support for the large-scale application and protection design of electric vehicle charging and dischargingr station.Firstly,the basic classification of electric vehicle charging station is compared,and the superiority and practicability of the DC mode are determined.The physical structure and operation control structure of DC charging and discharging power station are analyzed.Based on PSCAD/EMTDC,the circuit model of the station is established,such as the AC/DC converter,DC/DC converter and power battery.And a method for selecting the working mode of the power station is proposed.Secondly,the dynamic process of symmetric short circuit fault(three-phase short circuit and DC short circuit fault)in the station is analyzed from the power and electronic component level.The fault characteristics are summarized and the calculation method of the fault voltage and current is derived.For the asymmetric fault,the influence of the eontrol strategy on the fault current is studied,and the calculation method of short circuit current considering the control strateg is derived and the cause of harmonic generation on the AC and DC side is analyzed.All kinds of fault conditions are simulated in PSCAD model,and the correctness of the derivation is verified.Finally,the protection requirement of the station is summarized.The corresponding protection methods are proposed based on the results of fault analysis.