A Modified Cockcroft-Walton Quasi-Z Source Inverter with High Voltage Gain for Photovoltaic Systems

This paper proposes a modified cockcroft-walton quasi-Z-source inverter (MCW-qZSI). The proposed inverter is conceived by embedding a boost cell reorganized and derived from the Cockcroft-Walton voltage multiplier into a traditional quasi-Z-source. Compared with the existing quasi-Z-source topology, it has a stronger voltage boost capability under the same total number of turns. The proposed circuit possesses all the advantages of a quasi-Z-source, such as continuous input current and common ground between input and output ends, while achieving high voltage gain at a small duty cycle, which results in a larger modulation index and higher output quality. In addition, the steady-state principle of the proposed inverter is analyzed. Also, its boost capacity, device voltage, current stresses, and superiority in magnetic devices are studied in detail. Then compare that with two typical (quasi-) $\mathrm{Z}$ sources. Finally, a prototype of the proposed MCW-qZSI has been produced with an output power of 720 W. Theoretical analysis and experimentation results are both given to verify the feasibility of the proposed MCW-qZSI.