Design, construction, and control of a stand-alone energy-conditioning system for PEM-type fuel cells

This paper presents the development of an energy-conditioning system for a proton exchange membrane (PEM) type fuel cell (FC). The developed system provides 230 V ac rms at 50 Hz, with a nominal output power of 1 kVA, and is able to handle sporadic high-power demands up to 5 kVA. An auxiliary power unit (APU), using a bank of supercapacitors as energy-storing device, provides this extra power during a certain amount of time. The output current ripple and step response constraints of the FC unit are considered in the design. A frequency-decoupling scheme is used, in which the FC provides only the low-frequency requirements, while the fast/high-frequency demands are supplied by the APU. A detailed description is given for its different constructive modules, their control design, and implementation.