Power Surge is refreshed (duration reset to 60s) when you use Jump or a weaponskill, including reactive abilities like Feint, Disembowel and Full Thrust. Power Surge is refreshed even if the ability misses. I haven't tested Leg Sweep or Ring of Talons with no target in range. After ten refreshes, Power Surge goes up a level, to a max of three.
Power Surge I --> Use ten weaponskills/jumps --> Power Surge II --> Ten more weaponskills/jumps --> Power Surge III.
It may seem like it takes a while to get all the way to PSIII, but the buff is much more potent. The new PSI is almost as potent as the old PSIII. Plus no TP spent.