Single-Phase Two-Stage Seven-Level Power Conditioner for Photovoltaic Power Generation System

Abstract

This paper presents a new power conditioner with the inherent benefits of boosting, generation of seven-level output voltage with minimum leakage current in a grid-connected photovoltaic (PV) power generation system. The proposed power conditioner is an upgrade of a front-end multioutput dc–dc boost converter and an asymmetrical seven-level inverter. A high-frequency transformer (HFT) employed in front-end converter produces balanced dc-link voltages to generate the seven-level output voltage. The leakage current caused by the parasitic capacitance of the PV panel is minimized by providing a common-mode conducting path to the inverter. This results in a reduction of the leakage current well below the VDE0126-1-1 grid standards. Furthermore, the proposed configuration utilizes a minimum number of devices for every level generation, which reduces the control complexity and also improves the system efficiency. The dynamic performance of the system is tested for intermittent changes in the PV characteristics for grid-connected operation. The proposed power conditioner is simulated using MATLAB software, and a laboratory prototype of 750 W is developed to validate its feasibility. Finally, a comparison is made with other recently proposed seven-level inverters to highlight the benefits of this power conditioner over others.