As the power output of fuel cell system cannot respond quickly to dynamic power loading, it is necessary to combine other power sources. The battery is chosen as an auxiliary energy source to store the energy recovered from braking, and a super capacitor is also used because of its high power density. In order to distribute the power flow among the above three-power hybrid system, based on Pontryagin's minimum principle, this paper formulates an energy management strategy, focusing on the relationship between co-state and state of charge. The results show that although the relationship between the co-state and the state of charge for each auxiliary power source is monotonic, the co-states of different auxiliary power sources have coupling effect.
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