Flexible energy management of hybrid hydrogen-electric power system considering temperature-induced characteristics in unmanned aerial vehicle applications

In hybrid hydrogen-electric unmanned aerial vehicle (UAV) applications, efficient energy management for the hybrid hydrogen-electric power system (HEPS) combining the hydrogen fuel cell (HFC) module with the lithium battery (LiBa) module is vitally important for the long-term and steady power supply. However, conventional energy management strategies (EMSs) generally assume a constant ambient temperature and employ fixed control thresholds for power allocation. This assumption is unsuitable for UAV missions involving rapid altitude changes, during which the time-varying ambient temperature alters the operating characteristics of both power sources, particularly the maximum power point (MPP) of the HFC and the maximum available capacity (MAC) of the LiBa. Consequently, fixed-threshold EMSs may result in inappropriate power allocation and hinder efficient cooperative operation of the two power sources under changing flight conditions. In this study, a flexible energy management strategy for the hybrid HEPS considering its temperature-induced characteristics is proposed for UAV applications. At first, the hybrid HEPS architecture for the UAV is analyzed, and models of the HFC module and the LiBa module are established. Then, to accurately reflect the variations in the MPP and the MAC of the two energy sources under dynamic ambient temperature conditions, nonlinear compensation schemes are constructed in accordance with temperature-induced characteristics of the two energy sources, respectively. Moreover, to achieve efficient energy management for the HEPS, the flexible EMS with nonlinear compensation schemes is developed. Finally, simulations and experiments are carried out to validate the effectiveness of the flexible EMS for the HEPS in UAV applications. Compared with the traditional rule-based EMS, the proposed flexible EMS improves the UAV endurance by 11.6% and 14.6% under two operating conditions, respectively.