Ab - see this question https://forum.mendix.com/questions/3993/
That link explains that a currency field is really just a float attribute (that may be rounded to 2 decimal places, but is still a float). That means that you can add floats to it, subtract, or do comparisons in exclusive splits like
$Entity/CurrencyAttrib >= $Entity/FloatAttrib
There is no need to do any conversion. You can set the value of a float field from a currency field or vice versa.
That answer is not really suitable for my case. I need to compaire a float value against a currency value in my microflow. Does any one know how to cast these values?