Quasi-Z-source-based multilevel inverter for single phase PV applications

The use of multilevel inverters in Photovoltaic (PV) applications have attracted major attentions in both industry and academic research. This paper presents a PV system based on a single-phase Quasi-Z-Source (QZS) multilevel inverter with a great reduction in number of switches. The introduced inverter is based on a Multilevel DC link (MLDCL) structure and an H-bridge inverter. The MLDCL consists of cascaded half-bridge units with each unit having a PV cell and two switches as the main components. To regulate the PV voltage, a QZS network is considered in each unit in order to reach the desired level of voltage and the system would be able to perform in a wider range of PV output voltage in a more reliable and efficient system. A detailed analysis is applied to 180 W single phase stand-alone PV system with three cascaded half-bridge QZS networks and a 60 Hz H-bridge. Each QZS module in the proposed structure has the advantage of having an independent control scheme, using which each unit can effectively achieve the distributed maximum power point (MPP). The system is simulated to verify the proposed concept and theoretical analysis using Matlab/Simulink. The feasibility of the proposed topology is also confirmed through the experiment on a 60 W system.