High voltage ratio non-isolated DC-DC converter for fuel cell power source applications

In this paper, a non-isolated DC-DC converter with high voltage ratio is proposed for power source like fuel cell. To take into account the low voltage - high density characteristics of power sources, a cascaded structure composed by two sub-converters in cascade has been chosen and allows obtaining a high voltage ratio. The choices of each sub-converter are based on the requirements of the source and its performances. Consequently, we have chosen a two-interleaved boost converter as the 1stsub-converter whereas the 2ndsub-converter is a two-level boost converter. The control of the whole system is realized thanks to energetic trajectories planning based on flatness properties of the system. The control of both the currents and the balance of voltage across the output serial capacitors of the two-level boost converter is ensured by nonlinear controllers based on a new nonlinear model. Experimental results allow validating the proposed power architecture and its associated control.