DC/DC Invertor

Development of an electrical power converter for fuel cell applications

Fuel cells supply, with the increase of power, a lower voltage. This means, that the electrical behavior is strongly dependant on the operating conditions. When fuel cells are used as a power source in vehicles, this is unwanted behavior. Therefore, a solid voltage has to be offered to the electro engine to, for example, realise an independant speed regulation.

Also, the fuel cell has to operate in the optimal workpoint of the cell. For this, an electronic power converter is realised, which, at the entrance, fuel cell side, lets an automatic adjustment of the electrical load at the voltage- and power graphic of the cell take place towards the optimal work point. At the same time, at the exit, engine side, the converter adjusts to the to be transported power within the allowed voltage tolerance of, for example, the electro engine.

Because this converter with a high yield (> 95%) has to be compact, mechanical robust and low cost producable, there has been chosen for a few savingstransformers which are actived when when shifted in relation to one another. The energy that is stored in the transformer is being regulated as well on the absorption side as the dispatch side by a high frequent circuit. With this, at the cell side, an optimal workpoint can be set while this 'powersource' can behave as a constant power or a constant powersource at the exit.