A Novel Three-Phase Isolated LLC and Non-Isolated LCL-T Resonant Converter for Fuel Cell Applications

In this paper, a novel three-phase isolated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{L} \boldsymbol{L} \boldsymbol{C}$</tex> and non-isolated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L C L-T$</tex> resonant converter topologies are introduced for fuel cell applications. In order to improve the fuel cell DC/DC converter efficiency, the current amplitude should be reduced in the power stage components. Cascaded connections of fuel cell blocks through a controllable system enable using higher voltage amplitude and bring the current amplitude lower at the target power. In this way, power losses in the passive components can be reduced, and maximum energy transfer can be established, improving the DC/DC converter efficiency from the fuel cell to the load. The introduced new converter also achieves soft switching (ZVS), minimizing the switching losses in all input and output load conditions. The presented three-phase isolated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L L C$</tex> and non-isolated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L C L-T$</tex> resonant converter systems, fed by three fuel cell modules with an output range of 190380 V, deliver <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$580-730 ~\mathrm{V}$</tex> at 450 kW maximum output power. The results reveal that the proposed systems have the advantage of reducing the size, volume, and weight and increasing the overall DC/DC converter system efficiency compared to the single-phase systems.