Research On Key Technologies Of Combined Three-phase Single-stage Full-bridge PFC Converter

The single-phase single-stage bridge PFC converter is a common topological structure for single-phase power usage.By combining three single-phase single-stage bridge PFC converters connecting to the three-phase power grid in modular form,a combined three-phase single-phase single-stage full-bridge PFC converter is proposed.This converter shows advantages in three-phase high-power applications.However,the research on this type of topology is still in the early stage,with many problems remain unsolved,including the voltage spike problem in the single-phase module,the control strategy and voltage ripple problem in the combined three-phase single-phase single-stage full-bridge PFC converter.In this article,the mentioned aspects will be researched in detail.First,to improved the reliability of the single-phase full-bridge module,the voltage spike on the primary side of the transformer is researched.After clarifying the topological structure and working principle of single-phase bridge PFC module,the equivalent model during switching is established.On this basis,he reason of the voltage peak of transformer primary voltage is studied,and the active clamp is theoretically proved.Besides,a improved active clamping circuit is proposed to limit the inrush current of clamping switch during zero-crossing period of input current.By doing this,the reliability of single-phase full-bridge module is improved without affecting the normal function,which is the ideal foundation of combined three-phase single-phase single-stage full-bridge PFC converter.To obtain a combined three-phase single-phase single-stage full-bridge PFC converter,three single-phase full-bridge modules are delta-connected in the primary side and parallel-connected in the secondary side.In this paper,the topology structure of the combined three-phase single-stage bridge PFC converter is introduced in detail,and a module power balance algorithm under unbalanced power grid conditions is proposed.On this basis,the output voltage ripple components of the converter are analyzed,and the influence of converter parameters and grid conditions on the ripple is studied.To eliminate influence of the output voltage ripple on the performance of the converter,a segmented digital filter is proposed to solve this problem effectively.Under the unbalanced grid condition,the 100 Hz frequency ripple will appear at the output side of the combined three-phase single-stage bridge PFC converter,which affects its DC output characteristics.To solve this problem,a ripple absorption circuit is proposed to suppress the voltage ripple.Based on the output voltage ripple characteristics of the converter,the corresponding ripple detection and ripple suppression control strategies are proposed.In addition,this paper also introduces the design criteria of the main components of the ripple absorption circuit in theoryFinally,on the basis of detailed theoretical research and simulation analysis,experimental platforms for the single-phase bridge PFC module and the combined three-phase single-stage bridge PFC converter was built,and all the above theories were verified and fully proved.