I recommend that you listen to your teacher. His (or her) opinions on the structure and usage of the English language are more important in your life than anything we say here. Many of the "rules" of English that we teach aren't really rules at all, and that's why we teachers can disagree so often.

If your teacher says that "You have been commanded to go," is a passive-voice form of the imperative sentence, "Go," then that's exactly what it is.