COMPENSATION APPARATUS FOR HARMONIC CURRENT

PROBLEM TO BE SOLVED: To obtain a compensation apparatus which can be used at a place in which the supply direction of electric power is not definite, such as a two-system power distribution system or a loop power distribution system by arranging and installing a selection means or the like by which compensation-current command values, for an active filter device by the output of a higher-order side current detector and that of a lower-order side current detector are selected on the basis of the output of a sign discrimination circuit. SOLUTION: Signals which are obtained by sign discrimination circuits 156, 256 are input to selection circuits 306, 307, multipliers 157, 158, 257, 258 and adders 159, 160, and whether the output of a current detector 15 is to be selected or whether the output of a current detector 25 is to be selected is decided. Harmonics effective- power values, to be discriminated, and harmonics reactive-power values obtained by high-pass bites circuits 153, 154, 253 and 254 are converted into three-phase compensation command values by a P-to-Q inversion circuit 308 and two phase-to-three phase conversion circuit 309. An error signal obtained in such a way that an adder 310 as the compensation current command value to the output current, of a converter part 304, obtained by a current detector 303 is amplified by a drive circuit 311, a converter part 304 is driven, and the error signal is compensated and controlled through an active filter device.