Need to add a new parameter to a dataset via Powershell

I can update existing parameters on datasets, no problem.  The documentation for that is good, and it explicitly says that "All specified parameters must exist in the dataset."

But is there a way to programatically add a new parameter, that doesn't already exist?  I know it can be done via the GUI but I need to programatically add a new parameter to datasets that already exist.  I've searched quite a bit, and while I find all sorts of references to creating new datasets and updating existing parameters, I can't find anything on adding a new parameter to an existing dataset. 

Any pointers to documentation on this would be great--I'll gladly take it from there.  Thanks in advance.