Design and development of a fuel cell power supply unit

Abstract

Fuel cell (FC) technology is one of the most sought-after renewable energy technology. However, the output voltage of FC stacks is inherently unstable; as such, it is of little or no use for most power supply applications. In addition to the unstable output voltage, FC stacks are susceptible to high current ripple, which can reduce the system’s life expectancy. The work carried out in order to stabilise the output voltage, and to reduce the current ripple of FC stacks involves a review of some existing converter topologies used for power conditioning units (PCUs), modelling, design, control and simulation of different converter topologies and the experiment of the prototype circuit for the interleaved boost voltage multiplier (IBVM) converter topology. In the process to stabilise the stack output voltage and to reduce the stack output current ripple, it is also required to improve the system response to load changes. This work presents results that show that system works, with the voltage stabilised, the stack output current ripple reduced and the response time reduced.

A relative evaluation of the dynamic behaviour of four converter topologies in power conditioning units is carried out, and these are the isolated current-fed full-bridge (ICFFB) converter, the boost converter, the sepic converter and the IBVM converter. The simulation results of the four topologies show that the output voltage of a PEMFC stack was stabilised, and that the IBVM topology is a better topology compared to the others, especially when it comes to reducing the stack current ripple.