Research And Design Of Bidirectional DC/DC Resonant Converter Applied To On-board Charger

With the shortage of world's energy and increasing environmental pollution,the development of electric vehicles has attracted more and more attention.Compared with the traditional fuel cars,electric vehicles are driven by electric power,and electric energy is renewable energy,which greatly alleviates the current situation of energy shortage.In addition,electric vehicles do not exhaust emissions,which will not cause air pollution.At present,our country has formulated corresponding policies to encourage the development of electric vehicles and has made great progress.With the promotion and popularization of electric vehicles,the power electronics industry is facing new opportunities and challenges.The high voltage battery pack on electric vehicle is the main device to supply the electric energy needed,and the function of on-board charger is to charge high voltage battery pack.At present,the commonly used chargers on the market are mostly unidirectional,that is to say the energy can only flow in a single direction and charge the battery pack through the grid.With the increasing demand of people,the research on bidirectional on board charger gradually becomes popular.Bidirectional on board charger requires energy to flow in both directions.In addition to charging the battery,it can also invert the battery energy into 220VAC and achieve grid connection or act as power supply for other devices.Like the unidirectional charger,the bidirectional charger is also composed of a two stage circuit.The former stage AC/DC and the postscript DC/DC,two stages all require bidirectional energy flow.This paper first investigates the commonly used bidirectional DC/DC topology,analyzes the application of different topologies and their respective advantages and disadvantages,and ultimately determines the bidirectional DC/DC topology used in this paper,using asymmetric CLLC bidirectional resonant converter.Then the working status of the bidirectional resonant converter is introduced.The working principle of the forward and backward converter is analyzed in detail,and how to realize the soft switching of the converter is analyzed.The forward and backward voltage gain expressions are mainly deduced.It is analyzed that how different parameters affect the voltage gain curve.The design guidance of resonance parameters is given.According to the requirements of the prototype index,the resonant parameters of resonant tank are designed and the resonant inductor,resonant capacitor and magnetizing inductance are determined.The selection method of converter components and the design method of magnetic components are introduced followed by the converter loss analysis.Finally it introduces the software control methods and control processes.Software and hardware design methods are explained for the bidirectional resonant converter.Finally,according to the previous design,a 3.3kW prototype is made and debugged.The simulation results and experimental results of bidirectional resonant converter are given.The simulation waveforms and experimental waveforms are analyzed in detail.It can be seen from the simulation and experimental results that the converter can work stably under different output voltage and load conditions,and both the forward and backward voltage gain can meet the requirements.At the same time,the forward and backward efficiency curves are given and the forward and backward maximum efficiency of the prototype is respectively 97.8%and 98.0%.It is verified that the feasibility of this design method of bidirectional resonant converter.