Digital Control of Multilevel Interleaved GaN DC-DC Converter for Fuel Cell Electric Powertrains

Fuel cells are increasingly recognized as a viable alternative to traditional battery packs in electric vehicles, particularly for long-distance transport requiring reduced weight and extended range. Despite their advantages, the low and load-dependent output voltage of fuel cell stacks (typically below 200 V) requires the use of high-efficiency boost DC-DC converters to achieve the required voltage (400-800 V) for electric powertrains. In this context, gallium nitride (GaN) technology enables switching frequencies exceeding 100 kHz, making it a prime candidate for high-power, high-density DC-DC converters. The main focus of this paper is the development and implementation of an advanced digital control solution tailored to a high-power, multilevel interleaved GaN-based DC-DC converter operating at a 100 kHz switching frequency. The high switching frequency, while beneficial for reducing passive component sizes and improving transient response, introduces significant challenges in synchronization, sampling, and the precise control of multiple interleaved cells. Analog control systems struggle to handle these requirements effectively, motivating the adoption of a digital control strategy that ensures high performance and flexibility. Experimental validation is performed on a reduced-scale prototype, demonstrating the robustness of the control scheme under dynamic conditions, including voltage step changes and load transients. The results confirm the effectiveness of the proposed digital control strategy in maintaining accurate voltage regulation, current sharing, and capacitor balancing, even under the demanding operating conditions imposed by high switching frequencies.