PROBLEM TO BE SOLVED: To provide a power tidal current controller capable of suppressing frequent control even if the state of a grid after automatic control by control center control becomes an overload again and possible to cause hunting.SOLUTION: A process logic 400 of a phase adjuster 8 includes an AC overcurrent relay 9, power relays 10 and 11, a control center control circuit 12, an abnormality occurrence condition block 13, a frequent control suppression condition block 16 which calculates, according to the amount of tidal current, how much a tidal current amount changes under automatic control, and locks control center control until the change of tidal current amount exceeds a specified value (dead zone) which is calculated in advance, control center operation circuits 310 and 311, AND gates 320, 321, 322, and 323, OR gates 330, 331, 340, and 341, and tap control circuits 14 and 15.
