High gain single-stage inverter for photovoltaic AC modules

Abstract

In this paper, a high gain single-stage buck-boost grid-connected system is proposed. The proposed system consists of a high voltage gain - high efficiency - switched inductor buck-boost converter (SIBBC) and a folded cascade H-bridge inverter. The proposed converter switch is derived with a sinusoidal modulation, so that the converter output voltage is a rectified sine wave which requires only a folded cascade as a second stage. Therefore, H-bridge is used to fold converter output voltage at fundamental frequency that eliminates the switching loss. The proposed system is used to connect the PV module to the grid with achieving maximum Power Point Tracking (MPPT) control; AC module. The converter operates in DCM to inject a sinusoidal current into the grid with unity power factor. The proposed dc-ac system has some advantages such as low cost, small size and simple control. In addition, the grid connection, MPP, and unity power factor controls are executed through only one switch, the converter switch. A prototype has been built and tested for validation. Some selected simulation and experimental results have been provided.