Energy management strategy for battery/supercapacitor/fuel cell hybrid source vehicles based on finite state machine

In recent years, fuel cell vehicles have attracted attention for their zero emission and environmental friendship. The sole fuel cell system cannot satisfy the dramatical change of motor power demands. In addition, the power fluctuations will damage the fuel cell stacks and shorten the cycle life of fuel cells. Therefore fuel cell systems are always combined with other energy storage devices like batteries and supercapacitors to increase the power density of the power system and fulfill the load power demands. The management strategy of the hybrid propulsion system is a significant technique for the vehicular power system. In this work, a finite state machine based management strategy is first proposed for both the battery/fuel cell and battery/supercapacitor/fuel cell system. The power capabilities of the battery and supercapacitor have been considered as important parameters in the management strategy. Moreover, an optimal oxygen excess ratio control is presented to maximize the fuel cell output net power. To evaluate the performance of the fuel economy and dynamic property, both the simulations and experimental verifications with the real physical system are given, and the real driving cycle of urban dynamometer driving schedule is utilized. The experimental and simulated results indicate that the proposed method is able to guarantee the required power during most of the driving cycles.