Design And Research Of Bidirectional Full-bridge DC-DC Converter For New Energy Vehicles

In order to alleviate the problems of energy security and environmental pollution caused by excessive use of fossil energy,new energy vehicles have been vigorously developed in recent years.As an indispensable power converter in new energy vehicles,bidirectional DC-DC converter must have many advantages such as high power density,high voltage ratio,good dynamic characteristic and so on.In this paper,a bidirectional fullbridge DC-DC converter experimental platform is designed,and its research and analysis are carried out in many aspects such as synchronous rectification,voltage spike suppression and soft start.Firstly,this paper introduces the existing non-isolated topology and isolated topology of bidirectional DC-DC,then analyzes the current research status of several isolated topologies,and selects the main topology of bidirectional full-bridge DC-DC converter based on phase-shifted full-bridge circuit.Based on phase-shifted full-bridge control and PWM full-bridge-boost control,the working principle of forward and reverse operation of the converter is analyzed,which provides theoretical basis for hardware design and closedloop control of the converter.For the forward mode of the converter,the driving waveforms required for synchronous rectification and the existing self-driven synchronous rectification hardware scheme are analyzed.The sampling software method realizes synchronous rectification,which improves the working efficiency without increasing the hardware cost.For the reverse mode of the converter,the reason why the voltage spike occurs when the converter is loaded is analyzed,and the specific calculation process of the voltage spike is given,and the active clamp circuit is used to suppress it.The startup impact problem in reverse operation is also analyzed,and the reverse soft start is implemented by software.Secondly,the hardware design of the related circuit of the bidirectional full-bridge DCDC converter is completed.The simulation model and bidirectional closed-loop controller are built in simulink according to the hardware parameters,and the accuracy of hardware parameter design is verified.Referring to the closed-loop control mode in the simulation,the bidirectional drive and closed-loop control of the converter are realized by TMS320F28377 D program.Finally,a 400V/48 V 500W experimental platform was built and experiments were carried out to obtain relevant experimental waveforms.Soft switching and synchronous rectification are realized when the converter works in the forward direction,so it has high efficiency.After the introduction of the active clamp circuit,the reverse operation of the converter can load normally,and the reverse soft start is realized by the software scheme.In both forward and reverse operation,the converter exhibits better dynamic load capability and smaller steady voltage ripple,and has smooth commutation capability.