Hydrogen rate manipulation of proton exchange membrane fuel cell (PEMFC) stack using feedback control system

Control system design of PEMFC systems has been focused mostly on the electrical power side, where auxiliary battery or supercapacitor are connected either by direct parallel integration or with single, multiple or multi-input single output DC-DC converters, with the PEMFC left running at constant predetermined hydrogen flow rates. The control strategy is simply adapted to balance the voltage and power between the PEMFC stack and auxiliary power during start-ups and sudden power demands and the PEMFC stack is effectively left out of the control loop or in open loop. Peak power above the rated PEMFC power cannot be supplied on demand because of the inherent inability to supply more hydrogen fuel to the PEMFC stack. This paper presents a study on the design of the control system of an open cathode PEMFC stack that closes the loop of the feedback process control of the PEMFC by manipulating hydrogen flow rate to produce the required peak power and to reduce fuel wastage during low power demand. The Proportional Integral Derivative (PID) feedback control systems are implemented using National Instrument (NI) Data Acquisition (DAQ) devices powered by Laboratory Virtual Instrument Engineering Workbench (LabVIEW) because of their simplicity and customization flexibility for measuring, processing and recording of data. Test results on the control of a small PEMFC system show that the new control system performs better and reduce wastage compare to the previous open loop system.