| 摘要 |
PURPOSE:To detect basic wave power, reverse phase current and higher harmonic current separately and to eliminate error due to a basic wave reverse phase current from a detected value of the third higher harmonic by providing a first circuit for detecting the reverse phase component of an AC three-phase current, a second circuit for detecting effective and reactive powers and a third circuit for detecting higher harmonic components. CONSTITUTION:A reverse phase current operating circuit 50 detects a basic wave reverse phase current iN according to a method for operating instantaneous real and imaginary powers based on a voltage (v) and a current (i). The basic wave reverse phase current iN is eliminated from the current (i) through a subtracting circuit 60 and the output i-iN therefrom is employed, together with the voltage (v), in the operation of instantaneous real and imaginary powers (p), (q) through a p, q operating circuit 70. Low-pass filters 80a, 80b then extract only DC components from thus operated (p) and (q) to produce effective and reactive powers P and Q. Furthermore, high-pass filters 81a, 81b extract only AC components from the (p) and (q) and an instantaneous current operating circuit 90 detects a higher harmonic current iH. |
