Fuel Cell Power Control Based on a Master-Slave Structure: A Proton Exchange Membrane Fuel Cell Case Study

Fuel cells generally become promising candidates for the electrical power supply in automotive and stationary applications. The power control of the fuel cell is one of the essential problems. In this paper, a power control concept with a master-slave structure for fuel cell systems is suggested. Within that concept, a DC/DC converter, several slave controllers, and a master controller are combined to achieve the control objectives. The DC/DC converter conditions the power and transfers it from the fuel cell to the load. The task of the slave controller is to maintain the controlled variables at their set points. The master controller has to select the set points for the slave controllers and limits the fuel cell output power, if the requested power exceeds the maximum power, which can be instantaneously produced by the controlled fuel cell system. The proposed control concept is demonstrated by simulations of a proton exchange membrane (PEM) fuel cell system taken from the literature. For that purpose, different controllers are designed based on model-free methods. For the master controller design, two alternative options are discussed: high efficiency tracking and fast power tracking. As shown in the simulation results, high efficiency tracking leads to higher system efficiency, however, an additional energy buffer is required. In contrast, no energy buffer is needed for the option of fast power tracking. However, the system efficiency is lower. The presented control concept is meaningful for systems with dynamic load requirements and can be easily applied to different fuel cell systems due to the model-free design approach.