Résumé

This paper presents an analytical methodology for designing the LCL input filter of a converter for fuel cell applications. Fuel cell railway systems are powerful and must supply the traction system for several decades. Industrial concerns focus on fuel cell lifetime, and the power converter must support higher currents than previously. To ensure optimal performance and longevity, the current ripple in the fuel cell must be minimized, which stresses the usual tradeoff between inductor size, switching frequency, and efficiency. This tradeoff formulation changes significantly when a first-order input filter is replaced with a third-order input filter: the ripple in the fuel cell benefits from the increased order, and the switching frequency can be increased if the filter is designed to allow Zero Voltage Switching (ZVS) due to the high current ripple at the filter output. For SiC devices, turn-on losses are higher than turn-off losses, so ZVS provides a significant reduction in switching energies, enabling a much higher switching frequency.