Research On Control Technology Of The Bidirectional DC/DC Converter On Electric Vehicle

In recent years,With the progress of science and technology and The popularization of new energy technologies,The bidirectional DC/DC converter has been widely used in various uninterruptible power systems,electric vehicle energy management systems,solar photovoltaic power generation systems and spacecraft power systems.Especially in the pure electric vehicle energy management system,the bi-directional DC/DC converter is indispensable,and it is the key component of the new energy vehicle to realize the whole vehicle energy control and to improve the vehicle driving performance.Therefore,the bidirectional full bridge DC/DC converter applied to pure electric vehicle is selected as the object of study,and its control technology is deeply studied.For bidirectional full bridge DC/DC converters,the input to output voltage range is large,the voltage and current stress of the tube is small,and it is easy to implement soft switching,and has high power density,and can transmit more power under the same capacity.It is the preferred topology for high power applications.However,in conventional phase shift control,there is the problem of power return,which makes the efficiency of the converter lower,especially when the input and output voltage amplitudes do not match.Therefore,this thesis focuses on double phase shift control,the switching process of the converter under two control strategies,the traditional phase shift control and the double phase shift control,is analyzed in detail,the transmission power,return power and soft switching conditions of the two are compared and analyzed.It is concluded that the converter has smaller return power under dual phase shift control,and makes it easier to implement soft switching.The Boost converter model is established by the method of state space averaging,based on the modeling of the Boost converter,the mathematical model of the bidirectional full bridge DC/DC converter for the pure electric vehicle is established.The steady-state and dynamic small signal model of the converter under dual phase shift control is obtained.A double closed loop control system of current inner loop and voltage outer loop is designed,the fuzzy PID control algorithm is designed by combining traditional PID control algorithm with fuzzy control algorithm,The simulation analysis shows that the control system designed in this paper has good control effect and stable output voltage,which verifies the correctness of the theoretical analysis in this paper.