Research And Design Of DC/DC Converter For Hydrogen Fuel Cell Electric Vehicle

Fuel cell electric vehicles have become a research hotspot in the field of new energy electric vehicles due to their advantages of high efficiency,cleanliness and fast fueling.However,the fuel cell output voltage is limited by the cell voltage,and the output characteristics are soft,and the electric vehicle cannot be directly supplied with power.A DC/DC converter is usually externally connected to the fuel cell output to improve its output characteristics and control the output power according to the power supply requirements of the electric vehicle.In this paper,the topological structure of fuel cell DC/DC converter under different applications is compared.Combined with the output characteristics of 40 KW hydrogen fuel cell and the working voltage range and power control requirements of the whole project,an interleaved parallel phase-shifted full-bridge ZVS DC/DC is designed.Converter,the main work content is:(1)Introduce the working principle,output characteristics and several factors affecting the output characteristics of a 40 KW hydrogen fuel cell power reactor.(2)Analyze the advantages and disadvantages of the isolated and non-isolated high-power DC/DC converter topologies,and introduce their common control methods.The common topology and characteristics of the on-board DC/DC converter are described.For the 40 KW hydrogen fuel cell in this project,an interleaved parallel phase-shifted full-bridge ZVS DC/DC converter is proposed,and the working principle of the phase-shifted full-bridge circuit is analyzed.(3)Establish a mathematical model of the interleaved parallel output ripple of the DC/DC module,and analyze the relationship between the output current ripple and the duty cycle D.An interleaved parallel phase-shifted full-bridge simulation model was built on the MATLAB/Simulink platform to verify the correctness of the staggered topology to reduce the output current ripple.(4)Design the DC/DC hardware system.The method includes designing a high-frequency transformer in a phase-shifted full-bridge circuit by using the Ap method;calculating a selection switch tube according to an input current level input current;calculating a resonant inductor and a DC-blocking capacitance parameter;and calculating an output filter parameter according to an output ripple requirement;The circuit,the drive circuit,and the CAN communication circuit are designed one by one.(5)According to the output characteristics of the hydrogen fuel cell,a control strategy for outputting the power limit of the DC/DC converter when the hydrogen fuel cell outputs a low voltage section is designed.According to the DC/DC output characteristics requirements of electric vehicles,two operating modes of constant voltage output and constant current output are designed,and the system automatically switches modes according to the output current demand.The software based on TMS320F28069 is designed on the CCS platform,including system control strategy algorithm program,communication processing program,fault handling program and so on.(6)Finally,a DC/DC converter prototype for a 40 KW hydrogen fuel cell electric vehicle was developed and experimentally verified on the prototype.The experimental results verified the rationality of the hardware parameter design and the feasibility of the control strategy.