METHOD FOR LIMITING OVERCURRENT OF ACTIVE FILTER

PURPOSE:To perform the compensating operation of limiting reactive power within the range of the capacity of a device without failing in the compensation for harmonics at the time of being overloaded by limiting a command for compensating for the reactive power of a fundamental wave in the case where the current of a power converter exceeds the corresponding value to a rated current. CONSTITUTION:A limiter means 65a gives instructions to limit a command for the reactive power of a fundamental wave only when a power converter is overloaded. Next, an arithmetic means 66 for a compensating current calculates out the value i*C of a command for a compensating current from the output of the limiter means 65a and the instantaneous power PAC, qAC of harmonic components calculated in an arithmetic means for instantaneous power to make the current iC, actually flowing through an active filter through a comparator means 67, a current control circuit 68 and a gate circuit 69 follow the value i*C of the command for a compensating current. Thereby, the compensating operation can be performed within the range of the capacity of a device without damaging the compensating characteristics for high frequency even at the time of being overloaded.