A Step-up Seven-Level Switched-Capacitor Inverter with Components Count Reduction for Grid-tied PV Systems Application

This paper proposes a seven-level grid-tied Photovoltaic (PV) inverter based on the switched-capacitor technique with input voltage boosting capability. This topology includes an electrolytic capacitor, eight power switches, and two input dc sources. The output peak magnitude of the proposed inverter is one-half times the input voltage sources. The components count of the proposed inverter is reduced in comparison to recent several-level inverters which are used for grid-tied PV applications. This topology does not require an independent control method for balancing voltage of capacitor and has a self-balancing mechanism for the capacitor voltage. Morover, the Model Predictive Control (MPC) is utilized as current injection technique to produce proper output voltage levels. A capacitor optimal design for resistive load and inductive-resistive load has been analyzed to reduce of volume and size of the proposed inverter.  The theoretical loss calculation of the proposed inverter under different load conditions has been analyzed. The performance of the proposed inverter is simulated by MATLAB/Simulink software and the results are presented under on-grid and off-grid conditions. Finally, a 200W laboratory prototype with 180V maximum output voltage is tested to validate the simulation and the theoretical analysis.