| 摘要 |
PROBLEM TO BE SOLVED: To eliminate frequency component which is twice that of a power source frequency without using a notch filter. SOLUTION: An electric power detecting device is provided with a transformer 13 and a current transformer 14 for detecting voltage V and a current I, a phase shifter 16 for generating voltage Vp with a 90 deg. delay to the detected voltage, multipliers 17, 18 for computing active power P=V.I and reactive power Q=V90 .I, and computing elements 19, 20 for computing the direct current component of active power p=P-(1/2ω)) (dQ/dt) and the direct current component of reactive power q=Q+(1/2ω) (dP/dt) on the basis of the output of the multipliers 17, 18. The computing elements 19, 20 are formed of low-pass filters 21, 22 and high-pass filters 23, 24 to which active power P and reactive power Q from the multipliers 17, 18 are inputted, and the high-pass filters 23, 24 execute approximate differential operation of the active power P and reactive power Q from the multipliers 17, 18 and add/subtract the computed result to/ from the output of the low-pass filters 21, 22. |
