Research Of A Novel Cascading Bidirectional DC/DC Converter And Control Method

Because the problems on environment pollution and energy shortage had been increasingly serious, electric vehicles all over the world have got the fast development. Bidirectional dc converter as the bridge between energy storage devices and the motor, its existing technology has reached the bottleneck and restricted extension and application of electric vehicles. So researching a kind of bidirectional dc converter which had simple structure, stable and efficiency, reliable control and superior performance will have a great significance for electric vehicles.Firstly, This paper provided an overview of the working principles, circuit topology types, research status and development trend on bidirectional dc converter.Secondly, combining the advantages of the cascading transform, a new type of circuit topology on cascading bidirectional dc converter suited for high power electric vehicles was put forward. Not only low dissipation and high efficiency, but also less components and low cost. The process of high gain during Boost transformation was changed into the two-stage step-up of front-end Boost circuit and push-pull transformer, and using only one active clamp circuit can finish the soft switch of all switching tubes. Using phase shift mode can complete zero voltage and zero current switching of the switching tubes in full bridge converter during Buck transformation. This circuit topology was feasible validated by the simulation.Then, the principle and features of sliding mode control were briefly summarized, and the equal connection between the PWM control and sliding mode control and its chattering problem were analyzed. To promote the performance of cascade bidirectional dc converter, sliding mode control was adopted. According to the transformation principle of the system during Boost and Buck mode, the corresponding variable structure models were established. the sliding mode current controller when Boost mode and the sliding mode voltage controller when Buck mode were designed. The dynamic characteristics and robustness of sliding mode control were better than the corresponding traditional linear control validated by thesimulation.Finally, the main circuit, power circuits, drive circuits and sampling circuits of new converter were hardware designed in detail, and the design of the program flow chart in the software system was completed, a 600 W experimental prototype was made by the implementation of PCB design. The experimental debugging results show that the converter had feasibility when Buck mode.