Research On Symmetric Tapped Quasi-Z Source Inverter And Application

Inverter is the main device in the power conversion system; its structure wasdeveloped recently. Z source inverter was first proposed by Professor PengFangzheng in Michigan University. Technical indicators of the inverter directly affectthe overall performance of the power conversion system, boost capacity is the maintechnical indicator and to some extent restricts the application of Z-source inverter,Based on this, scholars have put forward some quasi Z source inverter. Comparingwith the classical Z-source inverter, some quasi-Z source inverter’s boost capacity isnot enough high, and some quasi-Z-source inverter structure is more complex.In response to these phenomena, this thesis designed an improved inverter, which issymmetric tapped quasi-Z source inverter, and discussed its performance andapplications.Firstly, this thesis analyses the working principle of Z source inverter, comparesthem in boosting capability and device stress, and discusses their modulation strategyand application. Then, this thesis designs the main circuit of the symmetrical tappedquasi Z source inverter, proves the feasibility of the design of the inverter structurethrough the analysis of working principle, proves the performance of the symmetricaltapped quasi Z source inverter in the improvement of boosting capability and thelower device through the analysis of boosting capability and device stress. In addition,this thesis introduces the design method of capacitor and inductor in the symmetrictapped quasi-Z source inverter.Finally, combining with the characteristics of the symmetric tapped quasi-Zsource inverter, this thesis discusses its application. This thesis highlights the saidboosting capability of the symmetric tapped quasi-Z source inverter throughcomparing with the classic Z source inverter In the study of off grid wind powergeneration system. In the research of grid connected wind power generation system,application of current tracking control shows that symmetric tapped quasi-Z source inverter can be controlled with unity power factor grid connected. In the research ofelectric vehicle drive system, the DC bus voltage compensation delays the drop of theinverter AC voltage. In the research of UPS system, the characteristic that air throughratio regulates voltage level makes higher stability of the output voltage of thesymmetric tapped quasi-Z source inverter.