Energy management strategies of a fuel cell/battery hybrid system using fuzzy logics

Hybrid power systems with fuel cells and batteries have the great potential to improve the operation efficiency and dynamic response. A proper load management strategy is important for both better system efficiency and endurance of hybrid systems. In this paper, a fuzzy logic algorithm has been used to determine the fuel cell output power depending on the external power requirement and the battery state of charge (SoC). If the power requirement of the hybrid system is low and the SoC is low, then the greater part of the fuel cell power is used to charge the battery pack. If the power requirement is relatively high and the SoC is also high, then the fuel cell and the battery are concurrently used to supply the required power. These if-then operation rules are implemented by fuzzy logic for the energy management of the hybrid system. The strategy is evaluated using simulation and experimental results. The results show that the operation efficiency of hybrid system was improved and the battery SoC maintained at reasonable level. The control scheme can be used to optimize the operational efficiency of hybrid power generation system. (c) 2005 Elsevier B.V. All rights reserved.