Modeling and control of a PV based QZSI for grid connected applications

This paper proposes modeling and control system design for PV based Quasi-Z-Source Inverter (QZSI) for grid connected applications. The control system is designed based on the dynamical characteristics of the converter and introduces two cascaded controllers. Firstly, output current controller designed in the stationary frame. The second is DC-link voltage controller. Also, Modified Direct Incremental Conductance Maximum Power Point Tracking (MDIC-MPPT) method is proposed for rapid and accurate maximum power point optimization allowing wide DC-link voltage and Shoot-Through (ST) duty ratio ranges, minimize the voltage stress on the inverter bridge, and prevent overlap between ST duty ratio and Modulation index (M). Simulation results are presented to validate the controller's design. The obtained results are encouraging and promising for practical implementation.