| 摘要 |
PROBLEM TO BE SOLVED: To provide a device which detects frequencies without using phase detectors and counters. SOLUTION: In the device, values of voltage V<SB>R</SB>, V<SB>S</SB>and V<SB>T</SB>of a three-phase AC power source are converted into values of voltage Vd, Vq on d-q axes rotation coordinates rotating at a reference angular rateω<SB>0</SB>(101), and an angular rateω' of the voltage vector is calculated (103, 104 and 105), and then the angular rateω' of the voltage vector is added to the reference angular rateω<SB>0</SB>(106) and thereby calculating the frequency f of the three-phase AC power source (107). COPYRIGHT: (C)2004,JPO
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