Control system design for the small proton exchange membrane fuel cell stack

Small PEM (proton exchange membrane) fuel cell systems do not require humidification and have great possibility of commercialization with simple BOS (balance of stack), but the control method for small PEM fuel cell stack is not defined clearly. In this paper, a control method with dual closed-loop with static feedforward structure is defined and realized using micro-controller in order to control small PEM fuel cell systems. In general, core element of control in fuel cell systems is divided largely into supply of air and hydrogen, water management inside the stack, and heat management of the stack. In controlling of small PEM fuel cell stack operated without a separate humidifier, fan performs a core role in air supply, heat management and water management of stack. Purge valve discharges surplus water in the stack. The proposed method controls the fan using dual closed-loop with static feedforward, thereby improving the system efficiency and operation stability. The validity of the proposed method is proved by the experiments with 150 W PEM fuel cell stack. The proposed control algorithm is expected to be widely used for controlling small PEM fuel cell stacks.