Modeling Study of a Combined Fuel-Cell Stack/Switch Mode DC-DC Converter

Abstract

A fuel-cell stack produces a low and unregulated dc voltage; therefore, a dc-dc converter is required to step up and regulate the output voltage. A major drawback is that the output voltage of the fuel-cell stack exhibits a nonlinear behavior since the output voltage drops when more current is drawn. This output voltage will be later connected to a switch-mode dc-dc converter to step up its value; therefore, it is very important to consider the dynamic behavior of fuel-cell stack as input to a switching converter. In this work, a model is proposed for a combined fuel-cell stack/boost converter system. The interest of this model is clearly motivated by the need to have a model compatible with the standard techniques for controller design as current-mode control. The model is tested using a power module and a boost converter delivering an output power of 740 W. The power module uses polymer electrolyte membrane fuel cells (PEMFCs) and delivers a variable output dc voltage between 24 V to 42 V. Experimental results verify the theoretical results given within.