What happens if the auction nominator is outbid?
Your understanding is exactly correct. From the rules:


  When the auctioning player wins the auction and gets the power plant, the next player in turn order takes his turn at offering a power plant for auction, if he has not
   already purchased a power plant this round. If he has, the next player in turn order may start an auction, and so on. When a player other than the player who started
   the auction wins the auction, the auctioning player may choose a new plant to auction from the actual market or pass.