The Research Of Off-board DC Charging Communication And Security System

Electric vehicle is different from tanditional fuel vehicles,it is being accepted by most of people because it’s non-pollution characteristics.However,the popularity of electric vehicles is also bringing some problems: the charging accidents are growing;the electric vehicles and charging piles are not compatible.The country specially formulated five sets of charging system to avoid some potential unsafe factors and the charging piles differences between different enterprises.Controller Area Network is becoming famous because the increasing of electronic control units in the car,it’s strong real-time performance,strong resistance to electromagnetic interference ability,long-distance tranmission and other advantages make it become the communication bus in the electric vehicles.This paper is supposed to make a set of charging protection system for the charging process of off-board DC charger on the basis of CAN communication.This paper first analyses the state standard communication protocol of off-board DC charger and battery management system,focusing on the six charging process : the physical connection,low voltage auxiliary electrifying,charging shaking hands,charging parameters configuration,charging,the endness of charging.and then taking the possible appearing serious faults as object,study the failure mechanism and resulting influences.the faults studied in this paper are charging side lacking of phase,dc side short circuit,dc side leakge,the over temperature of battery,the unbalance of battery cells.Finally,the paper gives the flow chart of all kinds of fault protection on the basis of CAN communication,and makes charger and BMS as spare for each oher to achieve double protection.The proposed Kalman filter method gives the soc estimation algorithm in charger side on the basis of Thevenin cell model,the charger and BMS do the estimation algorithm at the same time,if the charger does not receive charging termination packet from BMS when it’s algorithm show the battery is fully charged,the charger will automatically stop charging in case of the overcharging accident happening.Electric vehicles is the main travel transportation in the future,the country is advocating the construction of charging infrastructure device for the convenience of electric vehicles charging.In this case,the device safety is very important,this paper analyses several typical faults,draws the flow chart of protection for every fault,so it gives certain references to the development of charging piles.