Digital Control of a Multilevel Interleaved DC-DC GaN Converter for Fuel Cell Traction Applications

Nowadays, fuel cells represent a promising alternative to replace battery packs for electric vehicles where weight or the limited range is a concern. With respect to a battery pack, built up to 800 V, the output voltage of fuel cell stacks is rather low (typically below 200 V) and it is strongly dependent on the load current. Therefore, the integration of a fuel cell in an electrical powertrain needs a DC-DC converter. To maximize the power density, the gallium-nitride (GaN) technology represents an interesting solution as it allows unprecedented performance in terms of switching frequency. As the rated voltage of available GaN devices is limited to 650 V, multilevel solutions must be employed for DC-DC converters whose output is 800 V. As the switching frequencies are usually above 100 kHz, the control of such converters is challenging, especially when multiple interleaved switching cells must be controlled. The literature reports several publications focusing on the adopted topologies for DC-DC conversion, while few papers deal with the digital control of such multilevel DC-DC converters. Therefore, the goal of this paper is the digital control applied to a high-power multilevel interleaved GaN DC-DC converter for an electrical powertrain fed by fuel cell.