Research On Key Technology Of High Power DC Fast Charging Pile

The development of electric automobiles is inseparable from the perfection of charging facilities.Therefore,it is very important to develop a high-power DC fast charging pile to improve the popularity of electric vehicles.This paper is based on the"research and design of 120kW DC charging pile" project of Anhui Duojie Electric Co.Ltd,and designs its core parallel component 15kW DC charging module.The DC charging module designed in this paper is mainly composed of two parts,front stage AC/DC transform circuit and post stage DC/DC transform circuit.Through the analysis and comparison of the advantages and disadvantages of various AC/DC and DC/DC transform circuit and the scope of application.In order to meet the requirements of high power factor of DC charging module,the front stage are selected two three-phase VIENNA rectifying circuits with staggered parallel.At the post stage,two series full-bridge LLC resonance conversion circuits are selected to meet the requirements of high efficiency and soft switching technology of DC charging modules.Firstly,the operating principles and equivalent circuit of single-phase and three-phase VIENNA rectifier circuit are analyzes in details.Based on this,the three-phase VIENNA rectifying circuit is controlled by interval partition,and the parameters of circuit are designed.Then,software Matlab/Simulink is applied for modeling and simulation,and waveform analysis.Secondly,the operating principles and the equivalent circuit model of full-bridge LLC resonance conversion circuits are analyzes in details.Their static characteristics are analyzed,and the parameters of resonant cavity are designed.Modeling,simulation and waveform analysis are done with PSIM software.Then,the TMS320F28335 chip is used as the core of the control system,and the software and hardware circuit of the DC charging module is designed.Eventually,a prototype of 15kW DC charging module is produced and the test results are analyzed in detail.By analyzing and comparing the experimental results,it can be seen that the power of the front stage AC/DC transform circuit is better because of the correction,and the DC side output voltage is stable.The post stage DC/DC transform circuit can realize soft switching technology.The prototype has high efficiency and good output characteristics.The method proposed in this paper has good feasibility and has certain engineering application value.