JP3100010B2 - Power factor transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor transducer for converting a power factor in a power line such as power transmission, distribution, and power reception into a DC signal corresponding to the power factor.

[0002]

2. Description of the Related Art The phase difference 電 圧 (shown in FIG. 3) between a voltage and a current in a power line can be detected with high accuracy by a relatively simple circuit. On the other hand, the power factor ± (1
−COSψ) (shown in FIG. 4)
Several methods have been proposed so far for converting the phase difference signal て in FIG. 3 using an analog linearize circuit. However, the conversion range is limited and the frequency used is also limited. The fact is that you can't get anything.

[0003]

DISCLOSURE OF THE INVENTION The present invention is directed to -90 ° to -90 °.
An object of the present invention is to realize a transducer capable of converting a power factor over a wide input range from 0 ° to + 90 ° into an accurate output proportional to the input factor and obtaining a converted output independent of an input frequency. is there.

[0004]

According to the present invention, there is provided a phase difference detecting circuit for detecting a phase difference between an input AC voltage and an AC current, an absolute value circuit for converting an output of the phase difference detecting circuit into a positive-only signal, A pulse width modulation multiplier for multiplying the output of the phase difference detection circuit and the output of the absolute value circuit; and a means for applying a bias to the output of the multiplier when the output of the absolute value circuit exceeds a predetermined voltage. It was done.

[0005]

According to the present invention, the power factor is converted into a DC signal whose power factor is proportional to the linearization circuit of (square curve) + (square curve) using the multiplier of the pulse width modulation system.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a configuration diagram showing one embodiment of a power factor transducer according to the present invention. In the figure, 11 is a transformer to which an AC voltage v is supplied in a power line, 12 is a transformer to which a current i is also supplied, and 20 is a phase difference detector for detecting a phase difference の between an input AC voltage v and a current i. Circuit. Various known circuits can be used as the phase difference detection circuit. 3
0 is an absolute value circuit that converts the output の of the phase difference detection circuit 20 into only a positive output, 40 is a comparator, 41 is a voltage V
x voltage source. Comparator 40 compares output ψ of absolute value conversion circuit 20 with voltage Vx. Reference numeral 60 denotes a known multiplier using a pulse width modulation method, multiplies inputs A and B, and outputs a multiplication result C. The phase difference detection circuit 20
Is connected to the input terminal of the absolute value conversion circuit 30 and to the A input terminal of the multiplier 60.
51 and 52 are switches, 53 to 55 are resistance elements, and 56 is a voltage source of the voltage Vy. The output terminal of the absolute value circuit 30 is connected to the input terminal of the comparator 40 as described above, and the resistance element 53, the resistance element 54 and the switch 5 are connected.
It is connected to the B input terminal of the multiplier 60 via one series circuit. The switch 52 is connected to the output terminal C of the multiplier 60 via a series circuit of the resistance element 55 and the voltage source Vy. 70 is a signal added to the signal input from the input terminal In.
An addition function for adding the signal input from the terminal Ad;
In filter circuit having a scale <br/>-ring function to output a DC signal that corresponds to the addition signal obtained by, its input terminal I
n is connected to the output terminal of the multiplier 60. Reference numeral 80 denotes an output terminal from which a DC signal corresponding to the power factor is extracted.
When the ψ output of the absolute value circuit 30 becomes larger than the reference voltage Vx, the switch 51 is switched from on to off, and conversely, the switch 52 is switched from off to on. The operation of the transducer having the above-mentioned structure and which is replaced by the present invention will be described as follows.

[0007] The AC voltage v and the current i in the power line are transmitted through transformers 11 and 12, respectively, to the phase difference detection circuit 20.
And the phase difference 両 者 between the two is detected. The detected phase difference signal ψ is applied to multiplier 60 as an A signal, and is also applied to absolute value circuit 30 so that B having a positive value only
After being converted into a signal , it is applied to a comparator 40.
The comparator 40 compares the output of the absolute value circuit 30 with the reference voltage Vx. In this case, while the ψ output of the absolute value circuit 30 is smaller than the reference voltage Vx, the switch 51 is turned on,
The switch 52 is turned off, and the signal A becomes the phase difference signal.
B signal is the absolute value of the phase difference signal ψ
Therefore, the output C of the multiplier 60 is expressed as follows: C = A × B = ψ × │ψ│ (1) in the range of −X ≦ ψ ≦ + X determined by the reference voltage Vx . On the other hand, when the ψ output of the absolute value circuit 30 becomes larger than the reference voltage Vx, the switch 51 is turned off, and the switch 5 is turned off.
2 is turned on, and the A signal becomes the same as in the case of the above equation (1).
The B signal is proportional to the phase difference signal ψ, and the B signal is
Since it is proportional to the absolute value of signal 、, it depends on the reference voltage Vx.
-90 ° ≦ [psi ≦ -X determined Te, the output C of the multiplier 60 in the range of -90 ° ≦ ψ ≦ + 90 DEG C = A × B = ψ × α | represented by ... (2) | ψ You. Here, α is a coefficient determined by the resistance elements 53 and 54 . When the switch 52 is turned on , the voltage Vy is impressed on the addition signal end Ad of the filter 70.
, The addition function of the filter 70 allows the input terminal
The voltage Vy is applied to the signal C represented by the equation (2) input to In.
Is added as a bias. Assuming that this bias is Y, D = α · ψ | ψ | + Y (3) , and the signal represented by the equation (3) is
The signal is converted into a DC signal by the scaling function , and the DC signal is extracted from the output terminal 80 as a DC signal Eo. FIG. 2 shows C and D expressed by the equations (1) and (3). FIG. 2 shows the power factor ± (1-COS
the approximate signal to [psi).

[0008]

According to the present invention, a signal proportional to the power factor is obtained by a linearization circuit based on (square curve) + (square curve). As a multiplier for obtaining the square curve, A pulse width modulation method is used. Since the pulse width modulation circuit does not depend on the input frequency, according to the present invention in which such a pulse width modulation circuit is used as a linearization circuit, a transducer that does not depend on the frequency can be obtained. The obtained power factor signal has a maximum error of 0 in the range of -90 ° to 0 ° to + 90 ° by selecting a breakpoint determined by the bias Vy and a square coefficient determined by the resistance elements 53 and 54 to appropriate values. .004 (power factor conversion)
It is possible to:

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a power factor transducer of the present invention.

FIG. 2 is a diagram showing a power factor signal obtained by the transducer of the present invention.

FIG. 3 is a diagram illustrating a phase difference signal.

FIG. 4 is a diagram showing a power factor signal.

[Explanation of symbols]

 11, 12 Transformer 20 Phase difference detection circuit 30 Absolute value circuit 40 Comparator 51, 52 Switch 53-55 Resistance element 60 Pulse width modulation circuit 70 Filter 80 Output terminal

Claims (1)

(57) [Claims] 1. A phase difference detection circuit for detecting a phase difference between an input AC voltage and an AC current, an absolute value circuit for converting an output of the phase difference detection circuit into a positive-only signal, and an output of the phase difference detection circuit. A pulse width modulation multiplier for multiplying the output of the absolute value circuit, and a means for applying a bias to the output of the multiplier when the output of the absolute value circuit exceeds a predetermined voltage, A power factor transducer configured to be removed through a filter.