Fuzzy Logic Based Energy Management for Fuel Cell=Battery Hybrid Systems

The aim of energy management of the fuel cell battery hybrid system is to minimize the energy consumption while satisfying load demands. This paper proposes an energy management method for a hybrid energy system which consists of a proton exchange membrance fuel cell, two boost converters and a lithium-ion battery pack. The goal is to guarantee a proper current of the fuel cell so that the consumption of hydrogen is minimized with constraints on power and the state of charge. The necessary conditions for the minimal hydrogen consumption is derived by using Pontryagin's maximum principle. According to this optimization method, the optimal current reference of the fuel cell can be computed analytically by iteration. Compared with solving partial differential equations with the traditional variational method, the proposed method is computationally more efficient. Moreover, by adjusting the state of charge and the load demand, we guarantee that the actual battery current can keep up with the reference value. Simulation results validate the effectiveness of the proposed energy management algorithm.