Economy-Durability Oriented Optimization of Power Levels for Fuel Cell Hybrid Electric Vehicles

Fuel cell hybrid electric vehicles (FCHEVs) have emerged as a promising pathway for the decarbonization of medium- and heavy-duty road transport. Nevertheless, most existing energy management strategies assume that the fuel cell output power can be continuously adjusted to track traction demand. However, in practice, fuel cell systems typically operate at a limited number of discrete power levels due to efficiency characteristics, dynamic response constraints, and thermal management requirements. Neglecting this discrete characteristic may result in frequent power fluctuations, accelerated degradation, and a shortened stack lifetime. This paper proposes a joint optimization framework to determine fuel cell power levels while coordinating economy and durability objectives. Both the number of power levels and their specific values are treated as design variables. The proposed power-level strategy is evaluated by comparison with a continuous power strategy under identical driving cycles and constraints. Simulation results demonstrate that the proposed approach yields a smoother, staircase-like fuel cell power trajectory, effectively suppressing high-frequency fluctuations. The proportion of operating points within the high-efficiency region increases from 7.9% to 27.2%. Additionally, the cumulative power roughness is reduced by 38.6%, and the comprehensive cost decreases by 24.8%, indicating improved durability while maintaining economy. These findings validate the effectiveness of the proposed power-level optimization strategy for FCHEVs.