| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for measuring the power P<SB>k</SB>, Q<SB>k</SB>of the k-th harmonic component of a power line accurately, without changing a measuring time T. SOLUTION: The problem can be solved by a method or the like described as follows: function values showing a sine function and a cosine function stored beforehand in a storage means 140, and a digital current value V<SB>D</SB>and a digital voltage value I<SB>D</SB>converted by an A/D converter 120 are subjected to product sum operation over the k-th harmonic one period of a power supply line; the approximate power P<SB>kapp</SB>, Q<SB>kapp</SB>is determined from a product sum value; further, the power P<SB>kave</SB>, Q<SB>kave</SB>is determined by averaging a plurality of approximate powers P<SB>kapp</SB>, Q<SB>kapp</SB>; and the power P<SB>k</SB>, Q<SB>k</SB>is determined by correcting the power P<SB>kave</SB>, Q<SB>kave</SB>of the k-th harmonic component by correction values E<SB>P</SB>, E<SB>Q</SB>determined from the measuring time T and an actual period T<SB>P</SB>of the power line. COPYRIGHT: (C)2009,JPO&INPIT
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