| DC charging piles are an important part of the new energy industry.Designing safe,reliable and fully functional DC charging piles has great engineering significance.Firstly,according to the functions of electric vehicle DC charging piles,this paper puts forward the overall design scheme and technical parameters of high-power DC charging piles,and introduces and analyzes the composition and working principle of the whole charging pile system in detail.In order to solve the problem of charging high-power equipment,this paper proposes to design the working mode of the full charge,so that it can be applied in a more abundant charging scene.In the overall scheme,each sub-module of the charging pile is modularly designed according to function.The whole system mainly includes the main control module,the high-power power module,the human-machine interaction unit,the electric energy metering unit and the radio frequency card reader unit.The main control module realizes the information interaction with the peripheral device,the data collection and processing,and the control function;the high-power power module provides the direct current for the electric vehicle,and the three-phase input alternating current is converted into the direct current output through the pre-stage PFC circuit,and the latter stage passes two The three-phase star-type LLC converter completes the wide-range adjustment of DC power in series;in order to solve the problem of user operation interface,a user-friendly interactive interface is designed,and the user can select the charging mode through the touch screen,and complete the radio frequency card reading module.The settlement of charging transactions and other functions.This paper mainly introduces the core part of the main control module and power module.In order to solve the problem of system task scheduling and improve the real-time nature of the task,the main control system uses STM32F407ZGT6 as the control core,which is more integrated than the design of the dual control board structure.The embedded FreeRTOS real-time operating system is used for design.Using the chip of ARM as the main control chip;the CAN communication protocol part conforms to the national standard off-board communication protocol standard;the design of the read/write card module based on MFRC522 realizes the communication with the Mifarel card Function;human-computer interaction interface is designed with DGUS configuration software,and peripheral RS232 circuit design for communication with main control board is designed;energy metering module adopts an intelligent three-phase electric meter of Zhengtai Company,and completes module according to multi-function electric energy meter communication protocol Design of the communication and program parts.The charging pile designed in this paper is a high-power double-gun DC charging pile,which is composed of ten power modules.Each power module adopts a two-stage structure.This paper also studies and designs the pre-stage PFC circuit.In order to improve the overall efficiency of the charging pile,reduce the input current harmonics,and improve the power factor,the front stage uses a three-phase three-level VIENNA rectifier variable structure,and the traditional diode clamp,flying capacitor type clamp circuit There are fewer power switch tubes used,and each phase is composed of a pair of reverse-series IGBTs in parallel,which effectively reduces the voltage stress on each power device.The chip used in the control circuit is TI's TMS320F28032.After the circuit design is completed,the simulation is performed by Simulink in MATLAB,and the single-cycle control mode is adopted.Compared with the control strategy of SVPWM,the multiplier in the input voltage and the traditional control method is not needed,and the complicated problem of the control circuit is solved.It has a constant switching frequency,fast dynamic response and good robustness. |
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