High Step-Up Nonisolated ZVS/ZCS DC-DC Converter for Photovoltaic Thin-Film Module Applications

Photovoltaic (PV) thin-film modules normally present higher voltages at the maximum power points than crystalline silicon ones. This feature makes the usage of low-voltage MOSFETs (<= 100 V) unfeasible in high step-up boost-based converters. In order to solve this drawback, this paper proposes a novel high step-up nonisolated dc-dc converter based on the classical synchronous buck converter with coupled inductor and voltage multiplier techniques. Besides reducing the voltage stress on the active switches, the proposed converter also requires a coupled inductor with lower core-window product, allowing the use of a smaller magnetic device. The resonant operation mode of the proposed converter enables zero-voltage-switching turn-on of active switches and zero-current-switching turn-off of diodes, which increases its efficiency. A 150-W prototype, able to work with a large variety of commercial PV thin-film modules, with 55-85-V input and 400-V output voltages, is built to verify the developed analysis. Experimental results show that the maximum obtained efficiency is nearly 98%, and the weighted California Energy Commission efficiencies are greater than 96.7% over the whole input voltage range.