Topology Research Based On Quasi-Z-Source DC-DC Converter

Under the dual background of the increasing scarcity of traditional energy sources and the increasingly prominent environmental crisis,the rapid development of switching power supplies has provided powerful support for the application and promotion of new energy technologies.Nowadays,with the gradual improvement of people's awareness of environmental protection and the positive implementation of relevant policies in the fields of electric vehicles and distributed power sources,DC power plays an indispensable role in industrial production and daily life of residents.The DC-DC converter,as a connecting point between the DC power supply and the load,has become a long-term research hotspot in the field.Therefore,it is of great theoretical significance and great practical value to study a DC-DC converter with simple circuit structure,excellent performance and good economy.At present,there are mainly defects in DC-DC converter,such as small booster factor,high voltage stress of capacitor,limited voltage regulation range and so on.The current novel quasi-Z-source DC-DC converter can overcome the above problems and show good performance.Based on the quasi-Z-source DC-DC converter,this thesis focuses on the topology of the main circuit,and improves the two aspects of the output port and the impedance source network,and puts forward the quasi-Z-source DC-DC double output converter and the improved quasi-Z-source DC-DC converter respectively.Both converters retain the quasi-Z-source network and inherit all the advantages of the quasi-Z-source converter,satisfying the current demand for miniaturization and output diversification of the power supply.Referring to the analysis method of quasi-Z-source converter,the working principle,control method and performance of the new topology are analyzed and studied.The expressions corresponding to the equivalent circuit diagrams in different states are listed and the boost factor,capacitor voltage,and voltage across the switching device are derived.Taking a double output converter as an example,the small signal modeling is completed by state averaging method and disturbance method in the Z source network,and the influence of the network device parameters on its static and dynamic performance is analyzed.It can provide a reference for selecting appropriate device parameters and realize the dual output function.Taking an improved converter as an example,comparison is made with traditional Z-source converters and quasi-Z-source converters from four aspects of performance of the boost capacity,the capacitor voltage stress,the inductor ripple current and the switching voltage stress.Using Matlab software visually shows the difference between the three topologies and verifies that the improved converter has significant advantages.Then,by means of connecting unit modules in series with the improved converter,the extended quasi-Z-source converter is explored and the conclusion that the unit module can not be increased infinitely and the quantity is suitable to be increased is obtained.Finally,the experimental prototype of the two converters is built,and the experimental data of the prototype are tested under the different conduction duty ratio and compared with the theoretical value.Within the allowable range of error,the feasibility of the two converters and the correctness of the theoretical analysis and derivation of the formula are proved.