Multi-Stage Cascaded Quasi Z-Source Inverter System for Renewable Energy Applications

Multi-stage cascaded quasi Z-source inverter (qZSI) features a lesser shoot-through duty ratio for the same boost factor of the input voltage, but the traditional qZSI has the disadvantage of possessing increased shoot-through ratio and very high component stress at the same voltage boost factor. The whole idea of this work is to present a multi-stage cascaded quasi Z-source inverter for application to photovoltaic power system. Three-stage cascaded qZSI is obtained by adding two diodes, two inductances and three capacitances to the traditional quasi Z-source network. Due to the cascaded structure and qZSI topology, the proposed system acquires all the advantages of impedance inverter that can realize boost/buck function in a single-stage with improved reliability, lower component rating, constant DC current from source and good power quality. Besides, the three-stage cascaded solution the shoot-through duty cycle by 25% at the same voltage boost factor. The topological characteristics of three-stage cascaded qZSI system is analysed and operating principles are discussed. An experimental prototype is built to test the three-stage cascaded qZSI module. Simulation and experimental results are presented to demonstrate the validity of the proposed system.