Preheat oven to 400°F. Line muffin pan with paper liners.
Grate carrot and set aside.
Poke sweet potatoes with a fork a few times each and microwave on high for 5 minutes or until soft.
Cut open cooked potatoes, scoop out the flesh into a large bowl, mash, and set aside.
In a medium bowl, mix together flour, baking powder, baking soda, and spices.
Add brown sugar, egg whites, orange juice, carrot, and vanilla to mashed potatoes and mix well.
Add dry ingredients to sweet potato mixture and stir just until combined.
Fill muffin cups 3/4 full with batter and bake for 15-20 minutes or until tops are brown.
Cool slightly before removing from pan, then transfer to a wire rack to cool completely before serving.