What makes Voting Power increase?
Great explanation from 
Power decreases with each vote. Voting frequently in a small amount of time increases the rate at which voting power decays and it recovers slowly after a period of not voting. How much the power decreases and how long it takes to build up again depends on the number of votes during a given period of time. You can view the percent of your voting power at any time at steemd.com/@yourusername