Research On Switch-Embedded Cascaded Switched-Inductor Quasi-Z-Source Inverter

With the continuous development of China's economy and industry,electricity has become an integral part of all walks of life.As resources and environmental problems caused by excessive exploitation of coal and petroleum resources have become more serious,new energy and renewable energy generation systems have received attention and development.An inverter,as an important power converter,can be used as an interface between new energy and renewable energy sources and the load or power grid,providing high-quality power for the load or power grid.Z-source and quasi-Z-source inverters are simple in structure and superior in performance,which overcome the theoretical limitations of voltage-type inverters and current-type inverters and are the focus of research in this field for more than a decade.This thesis will further study Z-source and quasi-Z-source inverter topologies,and optimize the topologies to make it more applicable to photovoltaic,wind power,new energy electric vehicle and other broad fields.Firstly,this thesis introduces the research status of Z-source and quasi-Z-source inverters,and summarizes the strengths and weakness of a dozen of existing classical topologies.According to the defects of insufficient boost capacity and excessive device stress in the traditional quasi-Z-source inverter,three kinds of switch-embedded cascaded switched-inductor quasi-Z-source inverter topologies are designed;the working states and working principles are studied in respective.And comparisons are made individually with traditional quasi-Z-source inverter in two aspects of boost performance and capacitor voltage stress.Secondly,the appropriate control scheme is selected by taking a second level switch-embedded cascaded switched-inductor type I quasi-Z-source inverter topology as an example.By applying Matlab to fully simulate the first,second and third-level forms of the switch-embedded cascaded switched-inductor quasi-Z-source inverter.At the same time,the second level forms of the above three topologies are compared and analyzed by Matlab simulation in the following aspects:working principle,boosting performance and stress intensity.Based on the above analysis,the simulated results demonstrated the most optimal second level switch-embedded cascaded switched-inductor quasi-Z-source inverter.Finally,this thesis takes the optimal second level switch-embedded cascaded switched-inductor quasi-Z-source inverter as an example,designs the parameters according to its working principles and builds an experimental prototype,confirming that this circuit topology has superior performance with high boost capability and low capacitor voltage stress.