Bidirectional DC/DC Converter And Integrated Control Strategy Research For Electric Vehicle

The development of electric vehicles is becoming more and more fast,and the DC/DC converter plays an indispensable role in electric vehicles.The DC/DC converter is developing towards high integration,high conversion efficiency,high control precision,small size and light weight,and digitization.And continuously improve the structure of the DC/DC converter,improve the function.The control strategy is innovative,which can control the converter work efficiently and improve the work efficiency.In the aspect of converter integration,the structure or operation of the motor is generally considered in the integrated design,so as to reduce the volume and achieve functional integration.In this paper,the DC/DC converter is redesigned on the basis of electric vehicle motor drive system and control strategy.Firstly,the driving system of AC motor of electric vehicle,the advantages and disadvantages of various speed regulation modes are introduced.The working principle of inverters and DC/DC converters in the drive system of EV and the frequency conversion speed regulation mode are analyzed.The shortcomings of DC/DC converters in the traditional drive system of EV are concluded,and the L-LLC full-bridge converter is proposed.It can effectively improve the shortcomings of traditional DC/DC converters for electric vehicles.Secondly,according to the requirements of DC/DC converter for electric vehicle,the topology,working principle,voltage gain,switching stress,soft switching and efficiency of L-LLC full-bridge converter are analyzed.It is concluded that L-LLC fullbridge converter has good voltage regulation performance,easy to realize zero-voltage conduction,high efficiency and stable operation.But the traditional control method is not suitable for L-LLC full-bridge converter,so an integrated control method is proposed.The L-LLC full-bridge converter is divided into three modes: boost mode,step-down mode and reverse mode.The integrated control method realizes the conversion of the three modes according to the acceleration,deceleration and speed signals of the electric vehicle,and realizes the operation of the whole motor drive system.Finally,a 3 kW L-LLC full-bridge converter is designed according to the actual electric vehicle motor parameters,including the selection of components,the calculation of dead-time,the selection of the best working area and the design of driving circuit.The simulation results show that under the integrated control method,motor speed regulation and power transmission can be achieved well.The L-LLC full-bridge converter can achieve zero-voltage conduction,good voltage regulation performance and high efficiency.The results show that the L-LLC full-bridge converter designed in this paper is reasonable and the integrated control method is correct and effective.