Research On Bidirectional DC-DC Converter For Hybrid Electric Vehicle

With the continuous development of the economy and society,people's material living standards are rising steadily,and cars have almost become the standard for human convenience.However,the continuous increase in car ownership has greatly facilitated people's lives,but also brought a series of serious environmental pollution problems and resources and energy shortages.Energy-saving,environmentally-friendly and economical electric vehicles have gradually been favored by people.The emergence of bidirectional DC-DC converters provides the possibility of solving the problems existing in traditional electric vehicles,and a composite power source composed of a super capacitor is used as an auxiliary power source to drive the electric vehicle.In this paper,a hybrid electric vehicle equipped with a composite power source is considered.Its special application and complex driving conditions are considered.The main topology used in this paper is obtained by interleaving and paralleling the basic converters,and the dynamic performance of the converter is improved through traditional and improved control strategies.The research contents of the thesis are as follows:First,the domestic and foreign research status of electric vehicles and bidirectional DC-DC converters for automobiles is briefly introduced,and then the control technology of bidirectional DC-DC converters is briefly described.According to the design requirements of bidirectional DC-DC converters for electric vehicles,the bidirectional half-bridge converters with smaller voltage and current ripples are selected through comparison,and then the main topology used in this paper-interleaved parallel bidirectional DC-DC converters is obtained from the interleaved parallel.The working principle in different modes is analyzed in detail,and its main parameters are designed.Secondly,small-signal mathematical modeling is performed for Buck and Boost modes,and traditional controllers with different operating modes are designed respectively.Simulation analysis shows that the controller design under the traditional control strategy is more reasonable.Aiming at the problems of traditional control strategies,Buck mode uses an improved single-cycle control method,and Boost mode adopts the control method of introducing voltage feedforward on the input side and increasing voltage feedback on the output side.Compared with the traditional control simulation,it shows that the improved control strategy is significantly better than the traditional control.Finally,the simulation under different control strategies is further verified,and the software and hardware circuits of the system are designed on the basis of this.The software part mainly designs the main program of the system and the ADC interrupt subroutine.The hardware part mainly designs the driving circuit,voltage sampling circuit and current sampling current based on the analysis of the entire system's working mode.