Hi Wouter,
As you've found, that transfer function can't be implemented in Simulink in a Transfer Fcn block.
Depending on the structure of your model, you may be able to incorporate that term into another block. For example, if the taud*s + 1 is in series with another transfer function, you may be able to incorporate the taud*s + 1 into that other tranfer function (depending on its relative order) and retain the same, overall, input/output behavior.
Another option would be to approximate what you want by adding a high frequency pole, i.e., (taud*s + 1) / (taup*s + 1) where taup is small enough that you're basically getting the correct repsonse for inputs of interest. However, making taup too small could eventually slow down the simulation by forcing a small simulation step size (depending on the other dynamics in the simulation), so there may be a trade-of in how small you're willing to make taup.
