JP2000329804A - Electronic reactive power measurement device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To measure reactive power more accurately with a smaller circuit configuration than before. SOLUTION: First A / D conversion means 1 for converting one of an AC voltage V and an AC current I into a digital value, and a second A / D converter for converting the other of the AC voltage and the AC current into a digital value.
D conversion means 2, integration means 3 (or differentiation means) for integrating the output of the second A / D conversion means, output of the integration means (or differentiation means) and the first A / D conversion means Multiplying means 4 for calculating the instantaneous reactive power by multiplying the output of

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electronic reactive power measuring device such as an electronic reactive wattmeter for measuring reactive power and an electronic reactive power meter.

2. Description of the Related Art In order to measure reactive power, one or both of a voltage and a current are moved to generate a relative phase difference of π / 2 between the two and then multiplied. There is a need to. FIG. 7 shows, for example,
It is a circuit example of a conventional reactive power meter using a digital circuit disclosed in Japanese Patent Application Laid-Open No. 7955. The AC current I is converted into a digital signal by the A / D converter 101 and input to the multiplier 102. On the other hand, the AC voltage V is similarly supplied to the A / D converter 1
After being converted into a digital signal at 03, the digital signal is input to a multi-stage register 104 as a storage element. Multistage register 104
In the register, sequentially digitized voltage values are stored in a register. The π / 2 calculator 105 detects the period of the AC voltage V and calculates a time corresponding to a phase difference of π / 2. The selector 106 reads a voltage value at a point in time corresponding to a phase difference of π / 2 from the voltage values stored in the multi-stage register 104 according to the time calculated by the π / 2 calculation unit 105. Is output to the multiplier 102. The multiplier 102 calculates the reactive power by multiplying the AC current I by the AC voltage V delayed by a time of π / 2. The result of the multiplication is input to the adder 107, and the result of the multiplication is the reactive power.

In the conventional reactive energy meter, in order to delay either the AC voltage or the AC current by a time corresponding to a phase difference of π / 2, the A / D of a signal to be delayed is set. It is necessary to store at least π / 2 conversion results. That is, a memory element having a number of bits corresponding to π / 2 of the A / D-converted signal is required, so that the circuit size is increased. Further, in order to cope with the frequency fluctuation of the input signal, it is necessary to always calculate the time corresponding to the phase difference of π / 2 of the input signal, which also becomes a factor for increasing the circuit scale. In addition, since the input signal is delayed by π / 2 equivalent to the fundamental wave, the harmonic component is not delayed by π / 2 equivalent, and the accuracy of the measured reactive power is not improved. It also had the disadvantage of being low. (Object of the Invention) An object of the present invention is to provide an electronic reactive power capable of measuring a reactive power more accurately with a smaller circuit configuration than in the past without the need to provide a storage element or a π / 2 calculator. It is to provide a measuring device.

To achieve the above object, according to the present invention, there is provided a first A / D conversion means for converting one of an AC voltage and an AC current into a digital value, Second A / D conversion means for converting the other of the AC voltage and the AC current into a digital value, integration means for integrating the output of the second A / D conversion means, output of the integration means and the first And a multiplication means for calculating the instantaneous reactive power by multiplying the output of the A / D conversion means. Similarly, to achieve the above objective,
According to a second aspect of the present invention, a first modulation means for converting one of an AC voltage and an AC current to a digital value and a second modulation means for converting the other of the AC voltage and the AC current to a digital value.
Σmodulation means, integration means for integrating the output of the second △ Σmodulation means, output from the first △ Σmodulation means inputted through a digital filter, and the second signal inputted without passing through a digital filter. (2) An electronic reactive power measuring device having a multiplying means for calculating an instantaneous reactive power by multiplying the output from the △ Σ modulation means. Similarly, in order to achieve the above-mentioned object, the present invention described in claim 3 is
The first to convert one of AC voltage and AC current to digital value
A / D conversion means, a second A / D conversion means for converting the other of the AC voltage and the AC current into a digital value, and a differentiation means for differentiating an output of the first A / D conversion means, An electronic reactive power measuring device includes a multiplying means for calculating an instantaneous reactive power by multiplying an output of the differentiating means and an output of the second A / D converting means.

FIG. 1 is a diagram showing an electronic reactive watt-hour meter according to an embodiment of the present invention. Reference numerals 1 and 2 denote A to which the AC current I and the AC voltage V to be measured are input, respectively.
/ D converter, 3 is an integrator for integrating the output of the A / D converter 2, 4 is a multiplier for multiplying the output of the A / D converter 1 and the output of the integrator 3, 5 is the output from the multiplier 4 This is an accumulator to be accumulated. The current I is input to the A / D converter 1 and converted into a digital signal. On the other hand, the voltage V is input to the A / D converter 2 and is converted into a digital signal. The digitally converted voltage V is sent to the integrator 3 and integrated. The result of this integration is ∫SINωt dt = −COSωt = SIN (ωt−π / 2). As shown by this equation, the voltage V output from the integrator 3
Is delayed by π / 2 compared with the voltage V before integration. The voltage V output from the integrator 3 and delayed by π / 2 and the current I output from the A / D converter 1 are both input to the multiplier 4 and multiplied. Become. The output of the multiplier 4 is sent to the adder 5, where the accumulated result is the reactive power. According to the present embodiment, since the real-time π / 2 phase shift according to the input signal is realized by the integrator 3, a storage element for at least π / 2, which has been conventionally required, becomes unnecessary. Further, since the π / 2 calculating means for coping with the frequency fluctuation is not required, the circuit can be simplified and the cost can be reduced.
In addition, since the phase shift is performed not only for the fundamental wave but also for all the harmonics as in the related art, it is possible to measure the reactive power amount with higher accuracy. In the embodiment of FIG. 1, the integrator 3 is provided on the voltage V side, but may be provided on the current I side. In this case, since the current I is delayed by a phase difference of π / 2 with respect to the voltage V which is the original phase, a so-called advanced phase reactive power meter is obtained. Also, in the embodiment of FIG. 1, the current I and the voltage V
Although the digital conversion is performed by the / D conversion unit, it is also possible to configure a circuit with one A / D conversion unit. FIG. 2 is a diagram showing another embodiment of the present invention. The current I and the voltage V are first input to the sample hold circuit 6, and the current I and the voltage V at the same time are sampled and held. The sampled and held current I and voltage V are sequentially A
The signal is input to the / D conversion unit 1 and is converted into a digital signal. A / D
The output of the converter 1 is sent to a selector 7 from which further
The current I data is output to the multiplier 4 and the voltage V data is output to the integrator 3. The integrator 3 integrates the input voltage as described above to delay the phase difference by π / 2,
The result is sent to the multiplier 4. The multiplier 4 calculates the reactive power by multiplying the undelayed current I by the voltage V delayed by π / 2, and outputs the result to the adder 5. FIG.
Is a 1-bit quantizer as A / D conversion means.
FIG. 11 is a diagram illustrating another embodiment of the present invention using a modulator. In the present embodiment, the current I is the △ Σ modulator 8,
The voltage V is digitally converted by the デ ジ タ ル modulator 9. In this case, a 1-bit adder / subtractor (up / down counter) 10 is used as an integrator for integrating the output of the modulator 9.
Can be used, and the configuration of the integrator can be further simplified. The outputs of the modulator 8 and the 1-bit adder / subtracter 10 are input to the multiplier 4 via digital filters 11 and 12, respectively. Since the 1-bit adder / subtracter 10 as an integrator has the effect of a low-pass filter, as shown in FIG.
Can be deleted or simplified.
FIG. 5 is a diagram showing another embodiment of the present invention using a differentiator instead of an integrator. The current I is input to the A / D converter 1 and converted into a digital signal, and then sent to a differentiator 13 to be differentiated. The result of this differentiation is d / dt (SINωt) = COSωt = SIN (ωt + π / 2). As shown in this equation, the current I output from the differentiator 13 leads the current I before differentiation by π / 2 in phase difference. In other words, the voltage V is delayed by π / 2 relative to the current I. The current I output from the differentiator 13 and advanced by π / 2 and the voltage V output from the A / D converter 2 are both input to the multiplier 4 and multiplied, and the result becomes reactive power. The output of the multiplier 4 is sent to the adder 5, where the accumulated result is the reactive power.
According to the present embodiment, since a real-time π / 2 phase shift is realized by the differentiator 13 in accordance with the input signal, a storage element equivalent to π / 2, which has been conventionally required, becomes unnecessary. Further, since the π / 2 calculating means for coping with the frequency fluctuation is not required, the circuit can be simplified and the cost can be reduced.
Further, since the phase can be shifted not only with respect to the fundamental wave but also with respect to all harmonics as in the related art, more accurate reactive power measurement can be performed. Further, since the differentiation has the effect of a high-pass filter, the offset component included in the output signal of the A / D converter 1 can be removed. Also in the embodiment of FIG. 5, it is possible to provide the differentiator 13 on the voltage side instead of the current side, in exactly the same way as described in the embodiment of FIG. It is also possible to configure a circuit with one A / D converter. FIG. 6 is a diagram showing another embodiment of the present invention in which a △ Σ modulator, which is a 1-bit quantizer, is used as A / D conversion means. In the present embodiment, the current I is digitally converted by the △ Σ modulator 8, and the voltage V is digitally converted by the △ Σ modulator 9. In this case, △ Σ
A 1-bit adder / subtractor can be used as the differentiator 13 for differentiating the output of the modulator 8, and the configuration of the differentiator 13 can be further simplified. The outputs of the differentiator 13 and the △ Σ modulator 9 are input to the multiplier 4 via digital filters 11 and 12, respectively. Digital filter 1
1 may be connected between the △ Σ modulator 8 and the differentiator 13.

As described above, according to the present invention, real-time π / 2 phase shift according to an input signal is realized by an integrator or a differentiator. There is no need to provide a storage element or a π / 2 calculation unit, and the reactive power measurement device can be configured with a smaller circuit than before. Further, since π / 2 phase shift can be performed for all waveforms including harmonics as well as the fundamental wave, more accurate reactive power can be measured. According to the second aspect of the present invention, the digital filter on the side of the second △ Σ modulation means can be omitted, and the cost can be further reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electronic reactive watt-hour meter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electronic reactive watt-hour meter according to another embodiment of the present invention.

FIG. 3 is a block diagram showing an electronic reactive watt-hour meter according to another embodiment of the present invention.

FIG. 4 is a block diagram showing a modification of the circuit configuration shown in FIG. 3;

FIG. 5 is a block diagram showing an electronic reactive watt-hour meter according to another embodiment of the present invention.

FIG. 6 is a block diagram showing an electronic reactive watt-hour meter according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a circuit example of a conventional electronic reactive watt-hour meter.

[Explanation of symbols]

 1, 2 A / D conversion unit 3 Integrator 4 Multiplier 5 Adder 6 Sample hold circuit 7 Selector 8, 9 △ Σ modulator 10 1-bit adder / subtractor 11, 12 Digital filter 13 Differentiator

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[Procedure amendment]

[Submission date] June 10, 1999 (1999.6.1
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Detailed description of the invention

[Correction method] Change

[Correction contents]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electronic reactive power measuring device such as an electronic reactive wattmeter for measuring reactive power and an electronic reactive power meter.

[0002]

2. Description of the Related Art In order to measure reactive power, one or both of a voltage and a current are moved to generate a relative phase difference of π / 2 between the two and then multiplied. There is a need to. FIG. 7 shows, for example,
It is a circuit example of a conventional reactive power meter using a digital circuit disclosed in Japanese Patent Application Laid-Open No. 7955. The AC current I is converted into a digital signal by the A / D converter 101 and input to the multiplier 102. On the other hand, the AC voltage V is similarly supplied to the A / D converter 1
After being converted into a digital signal at 03, the digital signal is input to a multi-stage register 104 as a storage element. Multistage register 104
In the register, sequentially digitized voltage values are stored in a register. The π / 2 calculator 105 detects the period of the AC voltage V and calculates a time corresponding to a phase difference of π / 2. The selector 106 reads a voltage value at a point in time corresponding to a phase difference of π / 2 from the voltage values stored in the multi-stage register 104 according to the time calculated by the π / 2 calculation unit 105. Is output to the multiplier 102. The multiplier 102 calculates the reactive power by multiplying the AC current I by the AC voltage V delayed by a time of π / 2. The result of the multiplication is input to the adder 107, and the result of the multiplication is the reactive power.

[0003]

In the conventional reactive energy meter, in order to delay either the AC voltage or the AC current by a time corresponding to a phase difference of π / 2, the A / D of a signal to be delayed is set. It is necessary to store at least π / 2 conversion results. That is, a memory element having a number of bits corresponding to π / 2 of the A / D-converted signal is required, so that the circuit size is increased. Further, in order to cope with the frequency fluctuation of the input signal, it is necessary to always calculate the time corresponding to the phase difference of π / 2 of the input signal, which also becomes a factor for increasing the circuit scale.

[0004] In addition, the fundamental wave of the input signal is π /
Π / 2 for harmonic components to delay by 2
There is also a drawback that the result is not considerably delayed and the accuracy of the measured reactive power is low. (Object of the Invention) An object of the present invention is to provide an electronic reactive power capable of measuring a reactive power more accurately with a smaller circuit configuration than in the past without the need to provide a storage element or a π / 2 calculator. It is to provide a measuring device.

[0005]

To achieve the above object, according to the present invention, there is provided a first A / D conversion means for converting one of an AC voltage and an AC current into a digital value, Second A / D conversion means for converting the other of the AC voltage and the AC current into a digital value, integration means for integrating the output of the second A / D conversion means, output of the integration means and the first And a multiplication means for calculating the instantaneous reactive power by multiplying the output of the A / D conversion means.

[0006] Similarly, in order to achieve the above object,
According to a second aspect of the present invention, a first modulation means for converting one of an AC voltage and an AC current to a digital value and a second modulation means for converting the other of the AC voltage and the AC current to a digital value.
Σmodulation means, integration means for integrating the output of the second △ Σmodulation means, output from the first △ Σmodulation means inputted through a digital filter, and the second signal inputted without passing through a digital filter. (2) An electronic reactive power measuring device having a multiplying means for calculating an instantaneous reactive power by multiplying the output from the △ Σ modulation means.

[0007] Similarly, in order to achieve the above object,
According to a third aspect of the present invention, there is provided a first A / D converter for converting one of an AC voltage and an AC current into a digital value, and a second A / D converter for converting the other of the AC voltage and the AC current into a digital value. / D conversion means, differentiation means for differentiating the output of the first A / D conversion means, and output of the differentiation means and the second A / D conversion means.
And a multiplying means for calculating the instantaneous reactive power by multiplying the output from the / D conversion means.

[0008]

FIG. 1 is a diagram showing an electronic reactive watt-hour meter according to an embodiment of the present invention.

Reference numerals 1 and 2 denote A / D converters to which an AC current I and an AC voltage V to be measured are respectively input, 3 an integrator for integrating the output of the A / D converter 2, and 4 an A / D converter. A multiplier 5 for multiplying the output of the unit 1 and the output of the integrator 3 is an adder for accumulating the output from the multiplier 4.

The current I is input to the A / D converter 1 and is converted into a digital signal. On the other hand, the voltage V is input to the A / D converter 2 and is converted into a digital signal. The digitally converted voltage V is sent to the integrator 3 and integrated.
The result of this integration is ∫SINωt dt = −COSω
t = SIN (ωt−π / 2). As shown in this equation, the voltage V output from the integrator 3 is delayed by π / 2 in phase difference from the voltage V before integration.

The voltage V output from the integrator 3 and delayed by π / 2 and the current I output from the A / D converter 1
Are input to the multiplier 4 and multiplied, and the result becomes reactive power. The output of the multiplier 4 is sent to the adder 5, where the accumulated result is the reactive power.

According to the present embodiment, in order to realize the real-time [pi / 2 phase shift in response to the input signal by the integrator 3, at least [pi / 2 equivalent of storage elements which is conventionally necessary becomes unnecessary. Further, since the π / 2 calculating means for coping with the frequency fluctuation is not required, the circuit can be simplified and the cost can be reduced. In addition, since the phase shift is performed not only for the fundamental wave but also for all the harmonics as in the related art, it is possible to measure the reactive power amount with higher accuracy.

In the embodiment of FIG . 1, the integrator 3 is provided on the voltage V side, but may be provided on the current I side. In this case, since the current I is delayed by a phase difference of π / 2 with respect to the voltage V which is the original phase, a so-called advanced phase reactive power meter is obtained.

In the embodiment shown in FIG. 1, the current I and the voltage V are digitally converted by different A / D converters. However, a circuit may be constituted by one A / D converter. It is possible. FIG. 2 is a diagram showing another embodiment of the present invention. The current I and the voltage V are first input to the sample hold circuit 6, and the current I and the voltage V at the same time are sampled and held. Sample-held current I
And the voltage V are sequentially input to the A / D conversion unit 1 and are digitally converted. The output of the A / D conversion unit 1 is sent to the selector 7, from which the data of the current I is further input to the multiplier 4.
If the data is voltage V, it is output to the integrator 3. The integrator 3 integrates the input voltage as described above to obtain π /
Then, the result is sent to the multiplier 4. The multiplier 4 calculates the reactive power by multiplying the undelayed current I by the voltage V delayed by π / 2, and outputs the result to the adder 5.

FIG . 3 is a diagram showing another embodiment of the present invention using a △ Σ modulator which is a 1-bit quantizer as A / D conversion means. In the present embodiment, the current I is digitally converted by the Δ modulator 8 and the voltage V is digitally converted by the Δ modulator 9. In this case, a 1-bit adder / subtractor (up / down counter) 10 can be used as an integrator for integrating the output of the △ Σ modulator 9, and the configuration of the integrator can be further simplified. △ Σ modulator 8
And the output of the 1-bit adder / subtracter 10 are input to the multiplier 4 via digital filters 11 and 12, respectively. Since the 1-bit adder / subtracter 10 as an integrator has the effect of a low-pass filter, the digital filter 12 on the voltage side can be deleted or simplified as shown in FIG.

FIG . 5 shows the use of a differentiator instead of an integrator.
It is a figure showing other embodiments of the present invention. The current I is A /
After being input to the D conversion unit 1 and converted into a digital signal,
It is sent to the differentiator 13 and differentiated. The result of this differentiation is d / dt (SINωt) = COSωt = SIN (ωt + π / 2). As shown by this equation, the current I output from the differentiator 13 is advanced by π / 2 in phase difference from the current I before the differentiation. In other words, the voltage V is delayed by π / 2 relative to the current I.

The current I output from the differentiator 13 and advanced by π / 2 and the voltage V output from the A / D converter 2 are both input to the multiplier 4 and multiplied. Becomes The output of the multiplier 4 is sent to the adder 5, where the accumulated result is the reactive power.

According to the present embodiment, in order to realize the real-time [pi / 2 phase shift in response to an input signal by a differentiator 13, conventionally required it was [pi / 2 equivalent of the memory element is not required. Further, since the π / 2 calculating means for coping with the frequency fluctuation is not required, the circuit can be simplified and the cost can be reduced. Further, since the phase can be shifted not only with respect to the fundamental wave but also with respect to all the harmonics as in the prior art, it is possible to measure the reactive power amount with higher accuracy. Further, since the differentiation has the effect of a high-pass filter, the offset component included in the output signal of the A / D converter 1 can be removed.

In the embodiment of FIG . 5, the differentiator 13 can be provided not on the current side but on the voltage side, in exactly the same way as described in the embodiment of FIG. Also,
It is also possible to configure a circuit with one A / D converter.

Furthermore, FIG. 6, 1 as the A / D conversion means
FIG. 11 is a diagram illustrating another embodiment of the present invention using a △ Σ modulator that is a bit quantizer. In this embodiment, the current I is at the △ Σ modulator 8 and the voltage V is at the △ Σ modulator 9,
Each is digitally converted. In this case, △ Σ modulator 8
Can be used as the differentiator 13 for differentiating the output of the above, and the configuration of the differentiator 13 can be further simplified. Outputs of the differentiator 13 and the △ Σ modulator 9 are input to the multiplier 4 via digital filters 11 and 12, respectively. Digital filter 11
It may be connected between the modulator 8 and the differentiator 13.

[0021]

As described above, according to the present invention, real-time π / 2 phase shift according to an input signal is realized by an integrator or a differentiator. There is no need to provide a storage element or a π / 2 calculation unit, and the reactive power measurement device can be configured with a smaller circuit than before. Further, since π / 2 phase shift can be performed for all waveforms including harmonics as well as the fundamental wave, more accurate reactive power can be measured.

Further , according to the present invention, the digital filter on the side of the second .SIGMA. Modulation means can be omitted, and the cost can be further reduced.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiro Fujiwara 1-29-1-10-102 Ikegami, Ota-ku, Tokyo (72) Inventor Kazuhiro Shimozawa 1-43-19-1-101 Takatahigashi, Kohoku-ku, Yokohama-shi, Kanagawa (72) Inventor Takeo Ohira 4-8-27-501 F-term (reference) 5H420 BB16 EB25 FF03 FF04 FF07

Claims (3)

[Claims] A first A / D converter for converting one of an AC voltage and an AC current into a digital value; and a second A / D converter for converting the other of the AC voltage and the AC current into a digital value. Integration means for integrating the output of the second A / D conversion means, and multiplication means for calculating the instantaneous reactive power by multiplying the output of the integration means by the output of the first A / D conversion means An electronic reactive power measuring device having: 2. A first △ Σ modulation means for converting one of the AC voltage and the AC current into a digital value, a second △ Σ modulation means for converting the other of the AC voltage and the AC current into a digital value, Integrating means for integrating the output of the second modulating means, and the first す る input through a digital filter;
An electronic reactive power measuring device, comprising: a multiplying unit that calculates an instantaneous reactive power by multiplying an output from a modulating unit and an output from the second modulating unit that is input without passing through a digital filter. 3. A first A / D converter for converting one of an AC voltage and an AC current to a digital value, and a second A / D converter for converting the other of the AC voltage and the AC current to a digital value. A differentiating means for differentiating an output of the first A / D converting means; and a multiplying means for calculating an instantaneous reactive power by multiplying an output of the differentiating means by an output of the second A / D converting means. An electronic reactive power measuring device having: