Stalled Active Auction Plants in a 2- person Power Grid game?
I haven't played a great number of 2 player games of Power Grid, but I haven't seen the problem you are noting.  Perhaps you are missing out a few of the key rules?

Rule changes with 2 players

Check the table on page 7 of the rule book on how to change things up for different numbers of players.  When playing with 2 players:


Each player may keep 4 power plants
Remove 8 power plants from the deck after preparing the market.


If nothing is sold

From page 3:


  If, in later rounds, no power plant is sold in a round, the players remove the lowest numbered power plant from the market, placing it back in the box, and replace it by
           drawing a power plant from the draw stack. They then rearrange the market according to the rules


Remove small plants

From page 5: 


  If, at any time during the game, there is a power plant in the actual market with a number equal to or lower than the number of cities any player has, players 
          immediately remove it from the game and replace it with a new card from the draw stack. This rule does not affect power plants owned by players.


This should increase the turnover of the smallest, most worthless plants.

At the start of Step 2


  To start step 2, remove ONCE the lowest numbered power plant from the game and replace it with a new one from the draw stack, rearranging the market as always.


If you are using all these rules, please let me know by comment and I'll see if I can adjust my answer.