Design And Realization Of Multi-function Charging Converter For Electric Vehicle

In recent years,with the booming development of the electric vehicle industry,the electronic equipment in vehicles has shown a trend of miniaturization,integration,and high power density.Breakthroughs in electric vehicle charging technology have contributed to the rapid development of the electric vehicle industry.In this thesis,a multifunctional charging converter for electric vehicles is designed.The converter can switch between different working modes through different closing combinations of four mode selection switches.By using the method of "topology multiplexing",a set of power electronic components and control systems are shared between different functions,so the miniaturization and light weight of the vehicle charging system are realized,and the economy of the charging system is improved.At the same time,adopting a unified thermal management strategy can improve the stability of the vehicle charging system.The main content of this paper is as follows:(1)Selection of main power topology and control strategy.Firstly,after analyzing and comparing the advantages and disadvantages of different traditional electric vehicle charger topology,the main circuit topology of this design is selected.Secondly,through theoretical calculation and analysis,the selected topology is verified,and its control strategy is analyzed and discussed.Finally,the interleaved Boost PFC was selected as the front-stage for power factor correction(PFC),and the full-bridge LLC resonant converter was used as the post-stage and multiplexing part to achieve DC/DC conversion of different power.(2)Design and simulation of the pre-stage power loop and control circuit.Firstly,the working principle of interleaved Boost PFC circuit and the influencing factors of the duty ratio of switch PWM control signal in the circuit are studied.Based on this,the parameters of the energy storage inductor and output capacitor in the circuit are calculated and the power components are selected according to the requirements of the high voltage DC bus voltage in this design.Secondly,the peripheral circuit of the control chip UCC28070 is designed.Finally,the designed circuit is simulated and analyzed by using the PSPICE software.(3)Design and simulation analysis of the main power loop and control strategy of the post-stage multifunctional DC / DC converter.Firstly,the working principle of the full-bridge LLC resonant converter is studied,and the voltage gain function expression and input impedance expression are calculated and analyzed.According to the input impedance characteristics of the resonant circuit,the working area of LLC resonant converter is divided into three parts,and the working characteristics of each area are analyzed.After these,a multi-function DC/DC control strategy is designed,and the control strategy adopts digital control.According to the stability index,the parameters of PI controller are calculated.Finally,the parameters of the resonant network and the two output transformers were designed,and the designed circuit was simulated with PSIM software.In the end,through the debugging and testing of the experimental prototype,the paper verifies that this design saves a lot of components compared with the traditional vehicle charging system,and has higher efficiency,which proves its value in practical engineering applications.