High Step-Up DC-DC Converter with Two Transformers for Low DC Renewable Energy Systems

A high efficiency, low profile, and high step-up dc-dc converter is proposed for low dc voltage renewable energy systems. The proposed converter employs an active-clamp technique with the complementary pulse width modulation (PWM) controller. Multiple transformers can be employed for a low profile design as well as multiple resonant rectifiers for the soft-switching operation of the output rectifying diodes. Two resonant-current paths formed by leakage inductance and output resonant capacitors achieve zero-current switching (ZCS) turn-off of the rectifying diodes. This ZCS turn-off is very desirable for reducing switching power losses for high step-up applications. An 800 W parallel output prototype of the proposed converter was built. An efficiency of 95% was obtained at the rated load for a 30 V input voltage. Detailed analysis of power losses and experimental verification of the proposed converter with two transformers are presented in this paper.