Switch options for StC_DOF_MODE

Hello everybody

I would like to simulate a wind turbine with a tuned mass damper in the nacelle using OpenFAST and have a question about the switch options for „StC_DOF_Mode".

As I understand it from the discription, there are 6 options for „StC_DOF_Mode":

0: No StC (passive TMD)

1: Up to three direction indipendent StCs (one for each direction)

2: omnidirectiopnal StC (in XY plane)


4: Prescribed force/moment time series

5: Force determined by external DLL

Possibilities 0-3 are pretty clear to me, but I am a bit confuesed about the options 4 and 5.
Are they implemented in OpenFAST 3.1.0?
What exactly is meant by options 4 and 5?

Can only passive and semi-active TMDs be simulated or is it also possible to simulate an active TMD?

Thanks for your help and best regards.