What can I do to increase power in my abs?

Typically, to develop power in any muscle you must train those muscles using fast, explosive movements. An example exercise that can be used to help increase power in the abdominals would include a rotational chest pass. You can pass the medicine ball off a wall or to a partner. Perform 2-3 sets of 8-10 repetitions. It will be important to note, however, that for one to be powerful, they must also be stable and strong. So one should first develop ample amounts of stability and strength before they begin power exercises. For example, you can begin by performing a plank as an exercise to improve stability through your core and abdominals. You can then progress to perform a strength specific abdominal exercise that is more dynamic and allows you to lift heavier weight, like resisted ball crunches. Finally, once stability and strength have been developed, you can start performing your abdominal power exercises. This will ensure you're prepared to handle the stresses that come with these power exercises and you'll get the most out of them.