Research On Bidirectional Full Bridge DC/DC Converter Based On LLC Resonance

With the development of science and technology in recent years,bidirectional DC/DC converters applied in renewable energy power generation,electric vehicle energy management,aerospace power supply and other systems have attracted wide attention.The LLC resonant bi-directional full-bridge DC/DC converter studied in this paper can realize zero voltage opening of the switch tube and two-way energy flow through the reasonable parameter design and control method,and builds a bridge for energy exchange between the energy storage unit and the DC bus.This paper focuses on the performance and control strategy to improve the steady state performance of the converter and realize the bidirectional energy flow.In this paper,based on the LLC resonant topology,the mode analysis and parameter design of two-way full-bridge DC/DC are carried out.This paper mainly analyzes the working process of the converter when it is running forward,describes in detail the working states of the converter in under-resonance mode and over-resonance mode,and studies the key problems.The mathematical model of voltage gain is established by fundamental wave analysis,the working interval of the converter is determined,and the resonant parameters are optimized.Then the defect that the voltage gain is always less than 1 is analyzed by using the mathematical model of reverse operation,and the purpose of boosting voltage is achieved by changing the driving mode of the rectifier.Then,according to the requirements of the thesis,the parameters of the main circuit of the converter are designed,the main device selection is completed by calculating the voltage and current stress,and the design process of high-frequency transformer is introduced in detail.Then,the software and hardware parts of the control system are designed.In order to obtain a stable dc voltage,the PID control algorithm is adopted to conduct closed-loop control of the system through the DSP28335 minimum system board,and the model is built in MATLAB for simulation.In the end,according to the design content,an experimental platform of a bidirectional DC/DC converter system based on LLC resonance is built.The output power of the system is 2.5kw and the output voltage is 500 V.TMS320F28335 is selected as the digital control chip of the whole system.The correctness of the algorithm and the rationality of the software and hardware design are verified by the experimental results.The experimental results agree with the theoretical analysis.