Design of a novel fully-active PEMFC-Lithium battery hybrid power system based on two automatic ON/OFF switches for unmanned aerial vehicle applications

High-performance unmanned aerial vehicles (UAVs) have become increasingly popular in applications across industrial inspection, forest patrol, and aerial photography. For high-performance UAVs, hybrid power systems consisting of proton exchange membrane fuel cells (PEMFCs) and Lithium batteries are usually recommended for improving their flight endurance. In this paper, a novel fully-active PEMFC-Lithium battery hybrid power system is designed for UAV applications. The proposed construction employs an automatic ON/OFF switch in parallel with a DC-DC converter to control the PEMFC and a second automatic ON/OFF switch replacing the commonly used DC-DC converter to control the Lithium battery. With this design, we enable the two energy sources to directly supply power through control of the ON/OFF state of the two automatic switches, thereby significantly avoiding energy loss in the DC-DC converter. The design further allows for separate or joint operation modes of the PEMFC-Lithium battery hybrid power system to be actively selected through combined control of the automatic ON/OFF switches and the DC-DC converter. On this basis, a simple and effective rule-based strategy can be designed for the energy management between the PEMFC and Lithium battery. Experimental results successfully demonstrate the feasibility of the proposed fully-active PEMFC-Lithium battery hybrid power sys-tem, with numerous simulations results showing that the proposed fully-active hybrid power system reduces hydrogen consumption by 5.6 g and improves energy utilization by 7% in UAV applications when compared with the conventional fully-active hybrid power system under the same power requirement. Additionally, the active mode switch control can effectively alleviate voltage degradation of the PEMFC as well as improve the output performance of the Lithium battery, which would effectively extend the service-life of the hybrid power system. This paper successfully demonstrates the advantages of the proposed fully-active PEMFC-Lithium hybrid power system in UAV applications.