An advanced power converter topology to significantly improve the CO tolerance of the PEM fuel cell power systems

In this paper an advanced power converter topology to significantly improve the CO (carbon monoxide) tolerance of the PEM fuel cell power systems is proposed. In the proposed scheme, an additional two-stage dc/dc converter is connected to the fuel cell to draw a low frequency (0.5Hz) pulsating current of specific amplitude. This pulse current creates the sufficient anode overpotential to electro-oxidize the CO from the catalyst layer of the fuel cell. The resulting system is shown to produce increased power (up to 50%) when supplied by hydrogen fuel with 500 parts per million (ppm) CO. The amplitude, frequency and the duty cycle of the pulsating current are varied to determine optimum performance. Experimental results from a 300 W PEM fuel cell stack operating on pure hydrogen fuel as well as with 500 ppm CO are presented. The proposed method can be easily modified to adapt to different CO concentration levels. The proposed CO tolerant PEM fuel cell power system is more robust and lower in cost, thereby facilitating the usage of cheaper natural gas to hydrogen reformer technologies.