I thought of an interesting idea. Yosef had two dreams, the first that that eleven bundles of wheat were bowing down to his bundle. He then had another dream that 11 stars and the moon were bowing down to him.
There is a fundamental difference between the two dreams. In the first dream, Yosef himself doesn't appear. He is represented by his bundle, but in the second dream, the stars and moon didn't bow down to his star but rather to him himself.
The way to understand the difference, is that each dream refers to different time periods. The first dream describes the brothers' first trip to Mitzrayim when they had no reason to fear Yosef, and bowed down to him merely as a way to receive food. Hence, their need for 'a bundle' of wheat paid homage to Yosef's ability to provide it. During the subsequest trips, they did have reason to fear Yosef, as Yosef treated them as spies, when they bowed down, they therefore bowed down to Yosef himself, as the ruler who had the power of life and death over them.
According to this idea, that each of the two dreams depicts one of the two stages in the relationship between Yosef and his brothers as king, we can understand the two dreams of Pharoh in the same light. The first dream of the thin stalks swallowing up the plump stalks depicts the first stage of hunger where the population were losing the ability to provide food for themselves. The second dream of the thin cows swallowing up the healthy cows reflects the second stage, where the population were no longer able to afford to buy food and Yosef (as related in the pesukim) demanded that they barter their animals in exchange for food, hence the hunger went from swallowing up their food supply to swallowing up their animal supply.
