Research On Switched-capacitor Multilevel AC-AC Direct Converter

Switched-capacitor converters have become more and more widely used from the DC-DC field to the AC-AC field.Because it can achieve various circuit transformation only through the switch tubes and capacitors,without magnetic components.It has the advantages of small size,light weight,large power density,and low switching tube stress.Thus,from the perspective of multilevel AC-AC direct conversion technology,this article incorporates the ideas of switched-capacitor converters,studing two types of switched-capacitor multilevel AC-AC converters.They are called the symmetrical switched-capacitor multilevel AC-AC converter and the asymmetric switched capacitor multilevel AC-AC converter.Discussion in detail is givern from the working principle,the establishment of equivalent circuit,and the circuit performance analysis in this paper.And MATLAB software is used for function analysis,giving the graphic results.Then in PSIM simulation software,the correctness of theoretical analysis can be verified by building simulation circuit models.In addition,in order to solve the problem that the output voltage is not adjustable,the control scheme is converted from traditional PWM control to phase-shifted PWM control,and small inductors are added to the two types of converters.So,the output voltage can be adjusted through the regulation of the output current by the inductor.And the theoretical analysis and relational expressions are given in this paper.At the same time,the strategy for implementing soft switching is discussed,with implementation conditions and related formulas.Finally,the simulation verifies the reliability of theoretical analysis in the PSIM software.At last,based on the above theoretical analysis and simulation results,experimental prototypes of these two types of converters are made,and control programs are written with the CCS6.0 platform for experimental verification.Then,the research topics and results in this paper are summarized,and the research on switched-capacitor multilevel AC-AC converters is further prospected.