Non-isolated high step-up converter based on combination of Flyback and Forward for power conditioning of photovoltaic and fuel-cell systems

In this paper a dc/dc converter with large boost ratio arising from isolated interleaved half-bridge converter is proposed that its operation is based on the combination of the Forward and Flyback converters having the merit of minimizing the core size of coupled-inductors. The drawbacks of conventional boost converter do not pose a major problem in the proposed converter because of employing the active clamp structure with asymmetrical pulse width modulation, which limits a suddenly huge increase in the voltage stress of switches and makes the soft switching possible. The secondary windings of coupled inductors operate as voltage sources in series with the voltage doubler capacitors, so the voltage conversion ratio heightens; consequently, the designer is under no obligation to use the coupled inductors with extreme turn ratio. At final, a 500 W laboratory prototype operating at switching frequency 50 kHz and output voltage 380 V by utilizing a input source 20 V is simulated to prove the theoretical analysis.