DIA Commander or Powered Commander is a 3rd party add on to make Henkei Convoy or Classics Prime to be more beefy and intimidating. It is created by FansProject not related with Takara nor Hasbro. Just from Fans to Fans kinda operations.
Not to forget, Henkei Convoy or Classics Optimus Prime sold seperately. You need to have either Henkei Convoy, Classics Optimus Prime or Classics Ultra Magnus to complete DIA Commander.
I got mine after deciding to make my Henkei Convoy more intimidating. Powered Commander is inspired from the City Commander, and add on to Classics Ultra Magnus to reflect its G1 roots. Other than that I do not recall any canon story line of any Transformers that include Powered Commander.