If you're looking in terms of refineries, then the Advent have none. Instead, their Trade Port can switch to increasing resource extraction rates for that gravity well, with appropriate research (research subject is Resource Focus).
Once researched, Resource Focus allows the Advent Trade Port to surrender trade capabilities (disabling the Trade Drones belonging to that port as well as denying other Drones from using the port) in order to raise resource extraction rates to all extractors in the gravity well the Trade Port is in. The Trade Port can switch between these two modes. The initial increase in extraction rate is 8%, but with further research, can be raised to 17% and finally 25%. Since the extraction bonus is based on percentage of the original extraction rate, it has the greatest impact at planets with a relatively high alleigance.
Be wary, however, of breaking your longest chain of trade ports unless you don't need to worry about credits.
