Is this just an expansion of the former MDG Achievement Fund?

No. The MDG Achievement Fund closed its operations in 2013. Even if the new facility shares with the MDG-F its inspiring principles (national ownership, multisectoriality, joint programmes implemented by multiple UN Agencies) and builds on its results, the SDG-F goes beyond the MDG-F in that it adapts to the new context of development aid, especially by placing a greater focus on sustainable development.