Research On Vienna Rectifier Based On Improved Sliding Mode Variable Structure Control Strategy

In recent years,with the continuous deterioration of the natural environment and the consumption of fossil energy,more and more countries and people realize the importance of protecting the environment and using cleaner energy.New energy vehicles are an important transformation direction.Electric vehicles gradually take the lead in the competition with their great advantages.It has become the representative of energy-saving vehicles in the new era,and the number of users who choose to use it has gradually increased.At this time,how to further improve the charging speed of new energy vehicles in unit time has become a hot research topic.Compared with other rectifiers,Vienna rectifier has the advantages of fewer power devices,higher power factor,lower harmonic content of network side current,lower voltage stress of switch tube and no dead zone of switch.It can be widely used in the field of vehicle charging with unidirectional energy flow.In this paper,the Vienna rectifier is taken as the research object.By analyzing its structural characteristics,a sliding mode inner loop controller based on the variable coefficient double power approach law and an improved sliding mode outer loop controller with disturbance observer are proposed.The research contents are as follows:Firstly,the main circuit topology and model structure of Vienna rectifier are analyzed and introduced,and two rectifier models with different switch device structures are introduced,which are transformed into ideal switch models.The working states of Vienna rectifier under 8 different switch states in a certain current range are analyzed,and its working principle is introduced.Three traditional sitting modes of Vienna rectifier are established Mathematical model under the standard system.Secondly,after fully understanding the working principle of the Vienna rectifier and the advantages and disadvantages of the traditional control methods of the Vienna rectifier,the double closed-loop sliding mode variable structure control strategy of the Vienna rectifier is studied in depth.However,the double closed-loop control strategy of the traditional sliding mode variable structure control strategy can improve the dynamic response speed and anti-interference ability of the system,but there is chattering phenomenon.Based on this problem,in the third chapter,a direct power sliding mode control based on the variable coefficient double power approach law is proposed.The improved variable coefficient double power approach law can improve the system's rapidity,robustness and effectively suppress the system chattering.The direct power control does not need to use the phase-locked loop,and does not need to collect the voltage phase information and synchronous coordinate change at the network side In the outer loop,the integral sliding mode control based on the exponential approach law is adopted to suppress the voltage overshoot and enhance the robustness and rapidity of the system.In addition,in view of the disturbance caused by the change of external environment,the disturbance caused by the change of load,the estimation error in the process of system design and the disturbance caused by the aging of internal circuit components,the fourth chapter proposes the sliding mode variable structure control based on the disturbance observer,which estimates the unknown disturbance through the disturbance observer and compensates the feedback to the controller input And then improve the system robustness.Finally,the model is built in MATLAB/Simulink simulation platform,and the Vienna rectifier experimental machine platform is built.The performance of the proposed control strategy is verified by simulation and experiment.