Research On High Set-up Z-source Inverters

High set-up wide input inverter plays an important role in the field of new energy development, it can boost the low output dc voltage of new energy into high alternating output voltage. As a research spot of high set-up wide input inverter, Z-source inverter has adavantages of no dead time, low THD and high reliabilty. It is of important research value to further improve the performance and efficiency of ZSI.This paper first derivated circuit topologies of coupled-inductor based quasi-Z-Source inverter, then operating principle and modulation strategy of CL-ZSI are introduced, comparison of voltage gain, device stress, and the volume of coupled inductor of different topologies are made in details, at last characteristic of the coupled inductor based quasi-Z-source inverter are summerized.Secondly, based on the switched-inductor quasi-Z-source inverter, one diode is replaced by the capacitor, quasi-Z-source inverter based on voltage lifting unit is proposed. Operation principle and the characteristics of VL-ZSI are analyzed, boost raio improved compared to ZSI. Then the two inductors in voltage lifting unit are coupled to save volumn, if turn ratio changed above 1, the diode worked in off state in all the switching period can be saved, coupled inductor quasi-Z-source inverter based on voltage lifting unit was proposed, quantity of passive components is reduced. The leakage inductor of the coupled inductor can be used to suppress the current flow the diode. Influence of the leakage inductor, turns ratio, shoot-through duty cycle and the average input current on the boost ratio is given in details, a prototype is made in the lab to verify the analysis.Then, the author extended the application of Z-source inverter to the isolated situation, put forward an asymmetric phase-shifted full-bridge Z-source inverter, operation principle of APSFB-ZSI is given and experiments are made in the lab. In order to reduce the sampling circuit and decrease the voltage stress of the diode in Z-source network, a symmetric phase-shifted full-bridge Z-source inverter is put forward. Design principle of the parameters is listed, a prototype was made in the lab to verify the theoretical analysis.Finally, to avoid the shoot-through state in the prior DC/DC stage and keep the high reliability of the whole Z-source system, this paper proposes a symmetric interleaved dual switches forward Z-Source inverter. The prior DC/DC stage is interleaved dual switches forward converter. Operation principle of IF-ZSI is introduced, parameters design and component selection of IF-ZSI are given. A prototype rated 3k W was made to verify theoretical analysis.Aiming at overcoming the shortcoming of Z-source inverter and further improving the voltage gain, topologies of high set-up Z-source inverter are proposed and studied in this pape. Within a shorter shoot-through time to achieve the same gain, conduction losses of IGBTs/MOSFETs in shoot-through state can be greatly decreased, and the the efficiency of ZSI can be improved.