A Grid-Connected PV System Based on Quasi-Z-Source Inverter With Maximum Power Extraction

               This paper presents an approach to link photovoltaic arrays with the AC grid using Z-source inverter (ZSI) and quasi Z-source inverter (QZSI) topologies. These topologies boost the DC-link voltage and invert it to AC voltage in one stage, resulting in a reduction in the overall system size and cost. The paper presents a control technique that fixes the DC-link voltage on the inverter bridge terminals, tracks the maximum power point (MPPT), and controls the amount and quality of power injected into the grid using unity power factor. The proposed control algorithm utilizes two independent control variables, shoot-through duty cycle (ST) and modulation index, to decouple the control of the DC and AC sides. The effectiveness of the proposed control technique is verified through simulations of a grid-connected PV system. The results demonstrate that the proposed system can efficiently extract maximum power from PV arrays while regulating the DC-link voltage and ensuring unity power factor operation. The operation accuracy of Quasi-Z-Source is validated by performing several simulations in MATLAB/SIMULINK software.

Keywords: Decoupling control, grid connected, maximum power point tracking, photovoltaic, standalone, unity power factor, z-source inverter.