Research And Design Of Integrated Converter Of Electric Vehicle Power Supply Based On Bidirectional LLC

With the increasing use of electric vehicles and the continuous improvement of infrastructure such as charging piles,people are demanding higher and higher standards for vehicle power systems,and they are eager to have higher efficiency and integration of vehicle power systems.Based on the Two-way Energy Transfer of Transformer Integration solution for electric vehicle charging and DC/DC integrated converter,as well as the 4-11 type bidirectional LLC circuit topology.A novel circuit topology of integrated converter for electric vehicle power supply based on bidirectional LLC with high efficiency and high integration is proposed in this paper,and it is deeply researched and designed.In this paper,the resonant principle of the integrated converter is analyzed.The equivalent circuit model of the integrated converter is established by using First Harmonic Approximation analysis method.Based on the equivalent circuit model,the steady-state characteristics of the integrated converter,such as the DC output gain varying with the resonant parameters and the switching conditions of the ZVS on the inverter side,are studied.The small signal model of integrated converter is established by using the extended function description analysis method,and the control-output transfer function of integrated converter is deduced.Based on the amplitude-frequency characteristic curve of the control-output transfer function of the integrated converter,the dynamic characteristics of integrated converter with varying load and switching frequency are studied.In this paper,the resonant working principle of integrated converter and the failure of MOSFET switch are analyzed in detail.Based on First Harmonic Approximation analysis method,the equivalent circuit model of integrated converter is established,and the expression of DC output gain of integrated converter is obtained.The influence of different resonant parameters on DC output gain of integrated converter is analyzed,and the realization conditions of ZVS switching on the inverting side of integrated converter are obtained.The small signal model of the integrated converter is established by using the extended function description analysis method,and the control-output transfer function is deduced,which lays a foundation for the design and selection of the dynamic compensator of the integrated converter.In order to make the integrated converter have higher power conversion efficiency,the efficiency and loss of the integrated converter are researched and the efficiencyoptimization principle of the integrated converter is obtained.Based on the principle of efficiency optimization,the optimal design formula of DC/DC mode excitation inductance is obtained by time domain analysis.Based on the maximum power charging curve of the power battery pack,the harshest operating point of the vehicle charger mode is selected,which matches the ZVS soft-switching characteristic of the converter with the charging curve characteristic of the power battery pack and avoids the reactive power loss caused by the redundant design margin.According to the design index of the integrated converter,the resonant parameters of the integrated converter are designed to optimize its efficiency,and a set of resonant parameters design flow suitable for the integrated converter is summarized.In this paper,a Simulink simulation model of integrated converter is built in Matlab.and the realization of soft switch of the integrated converter is simulated and analyzed,which verifies the rationality and effectiveness of the designed resonance parameters.The key power devices and peripheral hardware circuits of the integrated converter are designed.The experimental platform of the integrated converter is built.The open-loop low-voltage experiment is carried out to verify the feasibility of the peripheral hardware circuit design.The experimental results show that the integrated converter can realize ZVS switching on of the inverter side switch and ZCS switching off of the rectifier side diode at the most critical operating points in the two working modes.The maximum power conversion efficiency of the integrated converter is over 95%,which verifies the efficiency of the integrated converter.