| Nowadays,the level of science and technology in the world is constantly developing rapidly,and the demand for energy by human beings is also increasing.The problems such as urban environmental pollution and energy crisis that accompany it have intensified.Pure electric vehicles have low energy consumption,low environmental pollution,and high energy efficiency.Pure electric vehicles are already the trend.The bidirectional full-bridge DC-DC converter,as a connecting bridge between several important parts of the electric vehicle power system,is very important to improve the overall performance and reliability of the vehicle.Therefore,for the improvement of the transmission efficiency and power density of the bidirectional fullbridge DC-DC converter,the research on the miniaturization and modularization of the bidirectional full-bridge DC-DC converter,the improvement of the system's work,and the improvement of control strategies have become the power electronics applications.Popular research directions.In this article,the two-way DC-DC converter,the key link of energy conversion in pure electric vehicles,is taken as the research object,and the purpose of effectively reducing the return power of the system in the full range of operating conditions is the research purpose.The development history,topology structure and control method of the bidirectional DC-DC converter are introduced first,and the topological advantages of the bidirectional full-bridge DC-DC converter are systematically explained.The working mode of the bidirectional full-bridge DC-DC converter under single and double phase-shifting control strategy is analyzed in detail and the related mathematical model is established.Based on the analysis of the mathematical model,the relationship between the system characteristics,transmission power,and recirculation power of the single and dual phase shift control strategies and the phase shift angle was quantitatively analyzed.By comparing the advantages and disadvantages of the control strategies and combining the advantages of the two phase-shifting controls,this paper proposes a hybrid phase-shifting control strategy based on natural segmentation,which can select the optimal phase-shifting angle during the operation of the converter.The system has the lowest backflow power,which improves the operating efficiency of the system.After that,the small-signal modeling of the bidirectional full-bridge DC-DC converter is performed,and the mathematical model of the relationship between the internal and external shift comparison and the output voltage disturbance is derived.The transfer function of the system is obtained and the PI controller is designed.The stability of the closed-loop feedback control system of the converter is analyzed according to the Bode diagram to complete the closed-loop design of the converter.In order to simulate and experimentally verify the characteristics analysis and control optimization strategy of the bidirectional DC-DC converter in this paper,a converter system model is built based on MATLAB / Simulink platform,and the above analysis and design are simulated and verified.By designing the hardware and software of the DC-DC converter,a set of experimental system platform is built and the analysis and proposed optimization strategy of this paper are verified by experiments.The experimental results show that the hybrid phase shift based on natural segmentation The control strategy can effectively reduce the return power in the full range of operating conditions,thereby improving the transmission efficiency of the bidirectional DC-DC converter. |
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