Online

Bacher-Chong, Eli

Mechanical Engineering

2022

M.S.

Fuel cell technology offers the potential for clean, efficient, robust energy production for both stationary and mobile applications. But without fast and robust control systems, fuel cells cannot hope to maintain real-life efficiencies near enough to their theoretical potential. This work studies control and constraint management techniques to regulate a nonlinear multivariable air-path system for a proton exchange membrane fuel cell (PEMFC). The control objectives are to avoid oxygen starvation, run at the maximum net efficiency, achieve fast tracking of air flow and pressure set-points, and be easy to calibrate. To operate at maximum efficiency, a set-point map is generated for air pressure at the cathode inlet. Considering that the conventional PEMFC system cannot independently control the inlet pressure using only the compressor motor, a new multivariable analysis and control scheme is formulated by considering an electronic throttle body (ETB) valve downstream of the cathode as a new degree of freedom in the control problem. Based on this new configuration of the fuel cell model, an internal model control (IMC) controller is designed with intuitive tuning parameters to simultaneously control airflow and pressure, and achieves a fast and smooth response despite strongly coupled plant dynamics. Further, a reference governor (RG) using a computationally tractable linear prediction model is included with IMC-based Multi-Input Multi-Output (MIMO) controller to satisfy the constraint on oxygen level. Compared with a Single-Input Single-Output (SISO) air-flow control approach, the proposed MIMO control approach demonstrated up to 7.36 percent lower hydrogen fuel consumption.