You can not increase your Voting Power once you voted many times you become less powerful, but it regenerates over time.
If you increase your SP (as @deanlogic said) you can have greater influence on the network. Your upvote will worth more to the author and your curator rewards also going to increase. But you will still run out of power after many votes!
The only way to keep your power is to stay above 80% with Voting Power. You can see your actual level at steemd.com/@kings-empire.
Very informative reply. Hope you will post such topics again...appreciated