Research On AC And DC Integrative Charging Pile System For Electric Vehicles

As the infrastructure for the energy supply of electric vehicles,the charging pile system must be built in the same scale as the number of electric vehicles.Moreover,the intelligent charging of electric vehicle charging pile system will further promote the entry of China's automobile industry into the era of electrification.This paper designs an AC and DC integrated charging pile system,which integrates the DC charging mode and the AC charging mode in the same pile.Firstly,the hardware structure of AC and DC integrated charging pile system is studied,and the overall structure of the charging pile system is designed.The design and device selection of the central controller,human-computer interaction unit,credit card charging unit,communication system,recording storage unit and other functional modules of the charging pile system were carried out.At the same time,the topological structure of the charging power system of the charging pile system was studied.The front stage rectifier circuit and the rear stage DC-DC conversion circuit are included.Based on the hardware structure of the charging pile system,the DC charging mode and AC charging mode of the AC and DC integrated charging pile system are designed.Different control schemes for charging mode selection are studied to better meet the user's choice of the charging mode of the charging pile.Then,the core unit of the charging pile system is deeply studied,and the pre-stage rectifier of the charging power module is designed.A mathematical model is established for the VIENNA rectifier circuit,and a double closed-loop control of the current inner loop and the voltage outer loop is designed.Aiming at the three-level characteristics of VIENNA rectifier circuit,a method to simplify the three-level space vector pulse width modulation conversion into two-level space vector pulse width modulation is designed in this paper.At the same time,a methodfor controlling the voltage balance of the capacitor midpoint by adjusting the action time of the short vector is designed.Furthermore,the designed VIENNA rectifier is built on the MATLAB/smulink software platform.The steady-state performance and dynamic performance of the rectifier system were simulated separately.It can be seen from the simulation results that the current side harmonic content of the VIENNA rectifier is low,the voltage balance at the midpoint of the DC side capacitor is not offset,the output voltage is stable at the given value of the system,and the dynamic response is rapid.Finally,the human-computer interaction interface and charging power module are experimentally studied.The friendliness of the designed interactive interface of the charging pile system was verified.At the same time,the charging power module of the charging pile system was tested,and the parallel experimental data of the power module was tested in constant voltage mode and constant current mode.