Calling sopc_builder from the Quartus Tcl console

I recommend skipping straight to qsys which should handle this better - there are executables like sb-generate.exe which you can call to generate a component.

sb-generate (and friends) should set up a lot of the environment for you so you just need to have the exe on the path. I don't have an install to hand, but I think sopc_builder/model/bin is the directory you need.