The Research Of Pure Electric Car Battery Charging System

With energy saving and strengthening of environmental protection consciousness, under the force promoting of government and automobile manufactures in the world,the electric cars are rapid development,especially electric cars. Because of its true realization "zero emissions,"become one of important city green traffice tools. Power battery is the only power supply and the key technology of pure electric vehicle, it directly restricts the service life, travlled distance and economic cost etc. Lithium battery because of its small volume, light weight, long cycle, no memory effect, monomer working voltage and price advantage high etc advantages, become the first choice of power electric cars, are widely used in aviation, maritime, transportation, communications and other high-tech areas. Along with the wide application of lithium batteries, the charging and discharging technology is also more and more scientific and reasonable. This topic is used to polarization pulse fast charging. This method can make the battery fast charging to50%-80%capacity in half an hour, to the battery polarization and reduce gassing, prolong the life of the battery. In order to ensure the safety and durability of the battery, add the battery management system, real-time monitoring and management work condition of the battery, the equilibrium charge and discharge, ensure the safety and reliable of the the battery and vehicle.Lithium battery charging and discharging system mainly include reversible PWM rectifier equipment, two-way DC/DC charging and discharging device, battery management system device and lithium battery packs. the system of the rectifier part adopts three-phase voltage source PWM rectifier, provides stable reliable dc voltage, realize the unit power factor, power two-way flow, low harmonic pollution, such as performance, and its working principle, the mathematical model and control strategies carried on the detailed analysis. Charging and discharging part choose two-way DC/DC converter, though its buck charge and discharge boost control,and choose polarization pulse fast charging to shorten the charging time, Lengthened Service Life. PWM rectifier and DC/DC converter constitute V2G, realize electric power two-way exchange composition of the power grid and the electric car, has the energy conservation, the environmental protection characteristics. In order to ensure the safety and reliability of the the battery and vehicle, The system has set up the lithium battery management system, real-time and effective control power battery of the electric vehicle,through to protection the current,voltage and temperature of the lithium battery charge and discharge,edtimate the SOC value, Finally through the CAN bus and other control system of information transmission, and realize the battery charge and discharge balance, heat balance management, etc. Make charging and discharging device tend to be more human nature, intelligence, and more simplification, and meet the daily needs.This topic through the MATLAB/Simulink software, for the system are respectively the PWM rectifier and DC/DC converter part modeling simulation and waveform analysis, to the simulation waveform, Finaly giving the simulation waveformthe of the whole system, it is shown that the lithium battery realize polarization pulse fast charging, two-way reversible power flow, unity power factor, low harmonic pollution, small overshoots etc. To meet the needs of the electric vehicle charging device.