| Electric vehicles have been widely promoted in various countries due to the continuous increase of traditional fuel vehicles and the continuous emission of greenhouse gases,which has brought serious environmental pollution,and the continuous decline of fossil fuel reserves.The bi-directional full bridge DC/DC converter is an important part of the hybrid power system of electric vehicles.Because it can effectively control the input voltage and improve the system efficiency,it is favored by many researchers at home and abroad.However,there are still some problems in bidirectional full bridge DC/DC converters,such as high return power and limited soft switching range.Therefore,the DC/DC converter with bidirectional full bridge topology is studied in this thesis,and the backflow power optimization strategy and fuzzy adaptive PID control are proposed to improve the transmission power and dynamic performance of the converter.The specific research contents are as follows:The bi-directional full bridge DC/DC converter with single-phase shift control is studied,and its working modes are divided into six types.According to its working modes,the steady-state mathematical model is established,and the power characteristics are analyzed.The simulation results show that the bi-directional full bridge DC/DC converter with single-phase shift control has higher return power,which greatly reduces the transmission efficiency of the converter.The dual phase-shift control is studied.Compared with the single phase-shift control,a phase-shift angle is added to the primary side H bridge,and its operation mode can be divided into eight kinds.The steady-state mathematical model is established and the power characteristics are analyzed.Then the reflux power optimization strategy is proposed.The minimum reflux power under different voltage conversion ratios and different transmission power is analyzed,and the combination of the minimum reflux power is obtained.Finally,the effectiveness of the optimization strategy is verified by simulation and comparison with the single phase-shift control.The control quality of the PID control algorithm with fixed parameters will not fully reach the set value because the bidirectional full bridge DC/DC converter is a nonlinear system,when the parameters of the converter change or the input voltage or load is disturbed.In order to improve the performance of bi-directional full bridge DC/DC converter,the fuzzy adaptive PID control algorithm is applied to the bidirectional full bridge DC/DC converter system,and compared with the traditional PID control algorithm underload disturbance.Through simulation and comparative analysis,it is concluded that the fuzzy adaptive PID control algorithm can improve the dynamic response performance of the system.Build a bidirectional full bridge DC/DC converter experimental platform,including hardware circuit design and software design.The hardware circuit includes high frequency transformer,sampling circuit,driving circuit and suitable MOS transistor.Software design includes system main program and PWM program.Finally,the effectiveness of the control strategy is verified by the analysis of the experimental results. |
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