Pseudo single stage flyback current source inverter for grid connected PV applications

Abstract

Pseudo single stage flyback current source inverter designed for photovoltaic applications is presented in this paper. The proposed inverter consists of flyback current source converter and h-bridge unfolding stage. The proposed system is intended to do the following functions: extract maximum power for the Photovoltaic (PV) module, inject a sinusoidal current into the grid. Flyback converter is designed to operate in Discontinuous Conduction Mode (DCM), the purpose of DCM operation is to inject a sinusoidal current into the grid without measuring the grid current. Rectified sinusoidal modulation is used to control the flyback converter switch. The purpose of this modulation strategy is to let the output of the flyback converter current to be a rectified sinusoidal waveform. H-bridge unfolding stage is used to convert the rectified current at the fundamental frequency of the grid voltage to full sinusoidal current. All switches of the h-bridge unfolding circuits are operating at fundamental frequency of the grid. Operating at fundamental frequency reduces the switching losses of the h-bridge inverter to be approximately zero.