This paper presents a high step-up converter, which utilizes a three-winding coupled inductor and a rectified voltage-doubler circuit to obtain high step-up gain for fuel cells. The proposed converter functions as an active-clamp circuit, which relieves large voltage spikes across the power switches. Thus, power switches with low-voltage-rated can be utilized to reduce conduction losses and circuit cost. Energy stored in leakage inductances of the coupled inductor is recycled to the output terminal, resulting in efficiency improvements. In addition, the coupled inductor in the presented converter can also have extra windings in order to achieve higher voltage gain. Finally, a prototype circuit with an input voltage of 60 V and an output voltage of 380 V is developed for a 1000 W-rated fuel cell power-generation system to validate its performance, and experimental waveforms and measured efficiency under different input voltages and output power level are demonstrated.

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