A Current-Fed Transformer-Based High-Gain DC-DC Converter With Inverse Gain Characteristic for Renewable Energy Applications

This article proposes a current-fed high-gain high-efficiency dc-dc converter for renewable energy applications such as photovoltaic energy. The converter is based on the modified SEPIC, in which the secondary inductor is replaced with a built-in transformer with differentially connected windings (mSEPIC-DBT). The high voltage gain is achieved through a magnetic-coupling-based VMC, in which the built-in transformer is paired to diodes and capacitors. The capacitors, alongside the leakage inductances of the transformer, form a resonant tank, allowing for the zero-current switching of the diodes, while also blocking dc currents from circulating through the transformer windings, which, in turn, allows employing gapless cores for the transformer, reducing its size. The converter operational stages are discussed and steady-state analysis is performed, from which the design guidelines are derived. The theoretical analyses are validated by an experimental 300-W, 50-kHz laboratory prototype. The experimental results show a full-load efficiency of 96.6% and a maximum efficiency of 96.8% at 90% of the full load, which demonstrate that the proposed converter is a strong candidate for applications that require high voltage gains.