Application of a Power Source for Hydrogen Fuel Cell Railway Vehicles in Multiple Resonant LLC Converter with Parallel-Input and Series-Output

All over the world regulation of carbon emission is being reinforced. Therefore, the research is actively underway to use a hydrogen fuel cell, which has high energy efficiency and eco-friendly source as the main power for railroad vehicles. Currently, hydrogen fuel cell railway vehicles adopt the 3-Level boost converter as a step-up converter. However, it does not achieve a high density in hydrogen fuel cell railway vehicles. In this paper, multiple resonant converters are proposed as alternatives to 3-Level boost converters. Multiple resonant converters with parallel-input and series-output not only have large I/O voltage gain but also have benefits in high density, so they are suitable for hydrogen fuel cell railway vehicles. Due to the structure of multiple modules, deviation of the module output voltage can occur. To solve this problem, the frequency/duty control method is proposed. To confirm the validity of the multiple resonant converters with the proposed control method, 400 V input and $667\sim$ 864 V/12 kW output prototype of the 3-Level boost converter and proposed converters are built and tested.