Improve hydrogen economy for vehicular fuel cell system via investigation and control of optimal operating oxygen excess ratio

Abstract

This study investigates and controls the optimal operating oxygen excess ratio (OER) for PEMFC, which effectively prevents oxygen starvation and improves the hydrogen economy of proton exchange membrane fuel cells (PEMFC). Firstly, the PEMFC output characteristic model and the five-order nonlinear air supply system model are established. Moreover, an adaptive algebraic observer was developed to observe the partial pressure of gas in PEMFC and further reconstruct OER. Secondly, to achieve the minimum hydrogen consumption under the required power, the reference OER is determined by analyzing the PEMFC system output power with its minimum current. Finally, the super-twisting algorithm is adopted to track reference OER. Simulation results show that the average absolute observation errors of oxygen, nitrogen, and cathode pressures under the Highway Fuel Economy Test are 1351.1 Pa (5.1%), 1724.2 Pa (0.9%), and 409.9 Pa (1.6%), respectively. The OER adjust average absolute error is 0.03. Compared with the commonly used fixed OER (e.g., OER of 1.5 and 2.3), the optimal OER strategy can reduce the hydrogen consumption of the PEMFC system by 5.2% and 1.8%, respectively. Besides, a DSP hardware in loop test is conducted to show the real-time performance of the proposed optimal method.