Each convention is run by a different committee unaffiliated with any national fannish body.
These votes are held at a Business Meeting organised by the convention committee, and held at the convention, in practice much of the organisation of the meeting is done by a standing committee selected by the prior meeting.
[1] The Ditmar Award has been awarded at the convention since 1969 to recognise achievement in Australian science fiction (including fantasy and horror) and science fiction fandom.
At various times in its history the award has included international categories, but this is the exception.
Categories include both professional and fan categories, focusing on fiction but also including some artistic and general achievement (as well as, since the demise of the ASFMAs, several "production" awards).