Experimental Investigation of Control Strategies on Voltage Inconsistency for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFC) is considered the most promising alternative vehicle power in the future owing to its highly power density and zero carbon emission. However, Voltage inconsistency of PEMFC is an essential issue that influences the performance of a PEMFC. It is affected by flow-rate and relative humidity of the inlet air. It’s necessary to establish a control strategy to ensure air supplied timely. A PEMFC system bench with 30 cells (the cells are numbered 1-30 in the direction from near to far from the air intake port) assembled in series was established to investigate the control strategy of air supply system. According to fuel cell’s position of the lowest voltage and the corresponding air flow rate, there are three different operations as follows. When it appears not in the low numbered area and the air flow rate is high, it indicates that humidity of the cell is insufficient and it needs to reduce power of the blower or close the bypass-valve. While the lowest voltage occurs not in the low numbered area and the air flow rate is low, the cell is flooded, which needs to increase power of the blower and open the bypass-valve of the humidifier. Keep the operation as before in other cases. The experimental results show that the exhaust gas entering the humidifier is a main factor at high current condition, but Cv is mainly affected by air flow-rate at low current condition. The control strategy decreased Cv by 0.3% and increased the lowest voltage of cells by 0.06V when the current was greater than 120 A.