An observer-based controller of anode pressure and nitrogen concentration for fuel cell system

Maintaining an appropriate permeated nitrogen concentration and stable anode pressure are crucial for fuel cell performance. However, direct detection of nitrogen concentration encounters challenges due to measurement limitations, and an abrupt pressure drop occurs during purging. In this paper, an extended Kalman filter observer is devised based on the lumped model and utilized for the anode side to filter the pressure signal, estimate the nitrogen fraction, and calculate the purge flow. The filtered pressure is utilized as feedback for a linear active disturbance rejection controller (LADRC) to achieve precise anode inlet pressure control. The estimated purge flow serves as the variable feedforward (VF) to compensate pressure fluctuation during purging, triggered by the nitrogen fraction threshold. Analysis between the traditional feedforward proportional-integral controller and the LADRC-VF underscores better performance of the latter, showcasing substantial reduction in anode inlet pressure. Finally, the LADRC-VF is validated on a 60 kW fuel cell system, demonstrating an average pressure fluctuation maintained within ±2 kPa and a 13% decrease in root mean square error. Meanwhile, the observer-based purge strategy proves advantageous over traditional fixed interval purging, showcasing efficiency in total purge time savings while ensuring a low nitrogen concentration under dynamic load conditions.