Research Of Sliding Model Variable Structure Adaptive Control Of New Energy Vehicles Bidirectional DC-DC Converter

The bidirectional DC-DC converter which has the advantage of high efficiency,light weight, small volume has become not only the core of switching power but also thecore of energy flow control device in Hybrid Electric Vehicle(HEV).The HEV-mountedbidirectional DC-DC converter works in the complex environment with the condition ofsevere changes, and DC-DC converter itself is composed of switching devices, which hasthe time-varying and nonlinear characteristics. The converter must meet the requirementof fast response and strong robust in actual use, which the traditional linear control can’tmeet the needs of the HEV. The advanced control ideas are studied in this paper. Aimingto improve the dynamic and static performance of the DC-DC converter, the main workis as follows:(1) The topology of DC-DC converter is analyzed, and in the basis of topologyanalysis，The bidirectional half bridge converter which has the advantage of small currentstress and simple structure is selected as the research object, and the basic principle isintroduced in this paper.(2) The state space average method is selected to establish the model of bidirectionalhalf bridge converter working in the Buck and the Boost state based on the analysis ofworking principle of the double half bridge DC-DC converter. The transfer function isbuild by the he small signal analysis and the parameter is calculated by the parametercalculation. The model is established in Matlab/Simulink environment. The simulationresult shows that the open loop of the bidirectional DC-DC converter has big systemovershoot and long adjustment time，so the open loop control can not meet the practicalapplication.(3) The sliding mode variable structure control method is introduced when thebidirectional DC-DC converter work as the Buck converter. The appropriate sliding modesurface and the reaching law are selected and the control effect is verified inMatlab/Simulik. The simulation results show that compared with PI control, thesuppression system overshoot become smaller，rapidity of system is greatly improved andthe robust is become stronger. Then the sliding parameters and reaching law parameterswhich have influence on the sliding mode variable structure control performance areanalyzed.(4) Two big problems which are the chattering and weak adaptive ability of thesliding mode variable structure control are found.In order to solve the issues, the ideasare proposed by combining adaptive control and fuzzy control method. The adaptivecontrol can make the reaching law parameters adjust adaptively by the deviation and thecontrol signal can be diffused by the fuzzy control. The adaptive fuzzy sliding modeadaptive control agorithum is built in Matlab/Simulik. The results show that the chatters will be effectively woken by the adaptive fuzzy sliding mode adaptive control. The robustperformance is verified by the sudden resistance simulation, the results show that theadaptive fuzzy sliding mode adaptive control still has good dynamic performance underthe sudden resistance simulation.