The Study Of Fast-charging Control Strategy Of Lithium-ion Battery On Electrical Vehicle

Combustion of fossil-based fuel is one of the main contributors to the greenhouse gas emissions in most countries.Traditional Vehicles are powered by gasoline.With gradually depleting fossil fuels and deteriorating environmental problems,massive attentions have been focused on energy conservation and emission reduction among the governments and the whole society.Lithium-ion batteries are a new type of power batteries,which closely relates to range of vehicles.After launched,batteries get a warm response and receive high raise,because lithium-ion batteries have many advantages.Electric power is highly efficient.However,after electrical vehicles are introduced into the market,the vehicle-mounted batteries suffer dispute due to the low charging efficiency and long charging time.The rapid charging system on Lithium-ion batteries has important economic significance for development of electrical vehicles.Firstly,the paper investigates the development of charging methods.Battery model and charging process are analyzed to help learn more about lithium-ion batteries.Besides,many kinds of charging way are studied.To solve the problem of low efficiency,fuzzy control is brought into the process of fast charging on lithium-ion batteries.Fuzzy inference is calculated according to two subsets of change gradient of terminal voltages and charging current.All above work is to determine the suitable charging current for extend the battery life.Secondly,with the increasing adoption of plug-in electric vehicles(PEVs),it is critical to develop efficient charging coordination mechanisms that minimize the cost and impact of PEV integration to the power grid.Three-phase voltage-source PWM rectifying circuit is chosen to avoid harmonic pollution.Mathematical model of this circuit on three-phase stationary coordinate is established,and mathematical models on two-phase synchronous rotating reference frame by transformation of coordinates are elicited.To realize the net side current sinusoidal and operate with unit power factor,the direct current control strategy of double closed-loop is chosen to control charging circuit of lithium-ion batteries.What’s more,circuit of no-dissipative energy and improved equalization strategy are used to eliminate the effect on shorting the battery life of difference between unit cells.Polarization phenomenon when charging can be removed by intermittently stopping charging the battery.Lastly,detailed hardware and software circuits are designed.Extensive simulations show that the proposed scheme performs very closely to the fast charging control strategy.The experimental results initially verify the effect of fuzzy control on fast charging system.