Research On Energy Conversion Method Of Multi Port Electric Vehicle Based On Bridge Buck-Boost

In the face of increasingly severe energy and environmental problems,the global fuel vehicle industry is accelerating the strategic transformation to new energy vehicles.In order to make electric vehicles have better endurance ability and inherit the usage habit of traditional fuel vehicles,people put forward higher requirements on the rapidity,convenience and reliability of electric vehicles' power battery charging.In recent years,the fusion technology between photovoltaic modules and electric vehicles,energy conversion technology between electric vehicles,V2G(Vehicle to grid)application technology of electric vehicles,and battery management system have become research hotspots.Aiming at the improvement of electric vehicle endurance and its role in the future smart grid construction,this paper proposes a bridge Buck-Boost multi-port electric vehicle energy conversion circuit architecture and its control method based on electric vehicle energy conversion requirements.The energy conversion system is composed of on-board photovoltaic charging circuit,inter-vehicle energy conversion circuit,power grid and electric vehicle energy conversion circuit,energy management and battery management subsystem.In order to obtain high cost performance,bridge Buck-Boost circuit is used between ports.The main function of the bridge Buck-Boost circuit in the on-board photovoltaic charging circuit is to track the maximum power point of photovoltaic modules,so as to realize the quick and efficient charging of electric vehicle.According to the different state of solar illumination and battery,the energy generated by PV photovoltaic modules is managed,so as to increase the endurance of electric vehicle and reduce the wear and tear of electric vehicle batteries and increase their service life.The energy conversion circuit between electric vehicles adopts the H4 bridge Buck-Boost circuit.Due to the symmetry of the two ports of Buck-Boost circuit,it is convenient to realize the bidirectional control of energy,so as to realize the energy conversion between electric vehicles.In the port where the grid charges the electric vehicles,the grid side adopts the two-way AC-DC inverter,and the battery side adopts the H4 bridge Buck-Boost circuit,which can realize the energy interaction between the grid and the electric vehicles as well as realize the V2G application.In this paper,the H4 bridge Buck-Boost circuit is shared among the ports,the soft switch implementation technology of the Buck-Boost circuit of the H4 bridge is studied,and the staggered parallel technology is used to meet the power level expansion,so that the high power density of the bridge Buck-Boost multi-port electric vehicle energy conversion system can be realized.The multi-port circuit adopts the constant voltage and constant current charging mode for battery charging to ensure the rapidity and safety of battery charging as well as the service life of the battery.In order to make the change of system can run efficiently and orderly,the paper studies the energy management method can switch circuit,energy management plays the role of a macro-control for electric vehicles energy conversion system,gives the energy flow between each port of monitoring and control,combining it with battery management system can realized the new electric vehicle in a safe and reliable operation of the system.The battery management System(BMS)in this paper adopts a distributed architecture.One main control panel can Manage several Battery acquisition panels.This architecture has good scalability and is universal for vehicles with different power levels.The paper studied the open circuit voltage method and neural network correction ampere-hour integral battery SOC(State of Charge)estimation method,to solve the change in battery capacity problem of integral method for estimating SOC precision,and can solve the initial value of SOC estimation of SOC,which can effectively improve the accuracy of Ann when integral method for estimating SOC.On the basis of theoretical research and simulation,an experimental prototype of multi-port electric vehicle energy conversion system is built for Buck-Boost circuit of non-isolated H4 bridge.Among them,the power level from the photovoltaic module port to the vehicle battery is 1.1Kw,and the power level between the batteries of the electric vehicle is 3.3Kw.The battery management system is designed based on TI's digital chip and battery monitoring management.Finally,the feasibility and superiority of the proposed vehicle-mounted photovoltaic charging circuit based on bridge Buck-Boost multi-port electric vehicle system are verified by experiments.