Research On Double-loop Control Strategy Of Bridgeless 2nd＿DBPFC Converter

The wide application of power electronic equipment in modern production and power system has immensely accelerated the development of China’s industry and the improvement of daily living standards,but the problem of harmonic pollution caused by it is becoming more serious.In order to suppress the harmonic pollution and improve the Power Factor greatly,the technology of power factor correction emerges at the right moment.Among them,bridgeless Boost PFC converter has been widely used because of its advantages of reducing on-loss,simple control and good output waveform.In order to further improve the power quality,I do a more in-depth research on the bridgeless Dual＿BOOST＿PFC(DBPFC)converter to,mainly include:Firstly,based on the traditional bridgeless Boost PFC converters,this thesis analyzes the topology of several improved bridgeless Boost PFC converters widely used at present,and compares their performance features.The bridgeless 2nd＿DBPFC converter,which is more suitable for inductive current continuous mode(CCM)and has the advantages of low on-loss and low common-mode interference,is selected as the research object of this paper,then,the model analysis of this converter is carried out,and the traditional double-loop PI control method of bridgeless 2nd＿DBPFC converter is studied.Secondly,the influence of voltage fluctuation on the DC side of bridgless2nd＿DBPFC converter is analyzed,and a voltage outer loop control strategy based on fractional PI is introduced.A fractional PI controller(FOPI)is used to compensate for the low bandwidth and slow dynamic response of the PI controller.The stability of the output side of the controller is analyzed,and the corresponding parameter tuning is given.At the same time,in order to further improve the current tracking voltage capability of bridgeless 2nd＿DBPFC converter,enhance the power factor and decrease the total harmonic distortion,a virtual super local optimization current inner loop control strategy is established.The work model of virtual dq mode is established by coordinate transformation method,and the steady-state bias of AC is reduced.Combined with a super local optimization control strategy,the defects of the current controller based on mathematical model which is sensitive to parameter changes and internal and external disturbances are improved.Finally,the feasibility of the new double-loop control strategy is proved by simulation.Finally,the experimental prototype of bridgless 2nd＿DBPFC converter is built,and the hardware design and software flow of the system are given,including the selection of main circuit components,the hardware circuit design and software design flow of corresponding modules.The experimental results verify the correctness and superiority of the new double-loop control strategy.