| At present,the hybrid electric vehicle what is consisted of fuel and battery is being widely promoted by various countries because of its economic and environmental advantages.Among them,bidirectional DC/DC converters are the key subsystems of energy transformation such as electric vehicle powertrain and energy storage.Therefore,this thesis takes the bidirectional DC/DC converter as the research object,and adopts the improved staggered parallel as main topology.the fuzzy sliding mode control strategy is proposed to improve the dynamic performance and stability of the converter.The main research contents are as follows:1.The topology of the interleaved bidirectional DC/DC converter is used to reduce the current stress of the system switch tube,decrease the output current voltage ripple,and improve the power density of the converter.Since there are two inductors in the topology structure that will affect the system output voltage and current ripple,the coupled inductors are used to improve the performance of the magnetic components and the system operating efficiency.The coupled inductance of the interleaved parallel circuit is analyzed and calculated to derive the coupling coefficient for optimum circuit performance.2.The double closed-loop control of voltage and current is established according to the small-signal model of interleaved parallel bi-directional DC/DC converter.In view of the poor dynamic performance and robustness of the traditional PI controller,the sliding mode control theory is used to design a reasonable sliding mode surface.Combined with the fuzzy control theory,an adaptive sliding mode approach is proposed to design a fuzzy sliding mode controller,and the stability of the controller is analyzed so as to improve the dynamic response of the system.This controller can avoid the problems of traditional sliding mode controller,such as chattering and long convergence time.3.Improved interleaved bidirectional DC/DC converter model is built by using MATLAB/Simulink simulation software,which is simulated and compared in different control mode.The results show that the output current and voltage ripple of the interleaved bidirectional DC/DC converter with coupled inductance is smaller,and the coupling coefficient is the best when the coupled inductance is close to 1.According to different control strategies,the results of the interleaved bi-directional DC/DC converter can be obtained.under the same working mode,the robustness and dynamic stability of the sliding mode controller are better than that of PI controller.The fuzzy sliding mode controller has the properties of sliding mode controller and can avoid chattering problem caused by sliding mode control.Finally,the experimental platform is set up,and the hardware and software are designed.According to the experimental results,the effectiveness of the proposed control strategy is verified. |
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