JP2813508B2 - Electronic watt-hour meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic watt-hour meter for measuring active power and reactive power.

[0002]

2. Description of the Related Art The configuration of a conventional electronic watt-hour meter will be described with reference to FIG. FIG. 7 is a block diagram showing a conventional electronic watt-hour meter.

In FIG. 7, reference numeral 1 denotes an input terminal of a current signal proportional to an alternating current consumed by a customer, and reference numeral 2 denotes an input terminal of a voltage signal proportional to an AC voltage supplied to the customer. Reference numeral 3 denotes a phase adjustment device that adjusts a phase shift between the voltage signal and the current signal by a sensor (not shown) that detects an AC voltage and an AC current, and includes a variable resistor 4, a resistor 5, and capacitors 6 and 7. ing.

[0004] Further, a multiplier 8 multiplies a voltage signal output via the phase adjusting device 3 by a current signal input to the input terminal 1 to calculate power, and 9 adds an output of the multiplier 8. An adder 10 for calculating the power amount is a power amount indicator for displaying the power amount.

In the conventional watt-hour meter, the original voltage signal fluctuates by performing the phase adjustment because the phase adjustment device 3 uses the resistors 4 and 5 and the capacitors 6 and 7. In addition, the voltage signal fluctuates even when the frequency changes.

[0006]

In the conventional electronic watt-hour meter as described above, since the phase adjusting device 3 uses the resistors 4 and 5 and the capacitors 6 and 7, the phase is adjusted. However, there has been a problem that the original voltage signal fluctuates and the voltage signal fluctuates even when the frequency changes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to improve the accuracy of measurement by quantizing a voltage signal and a current signal and performing phase adjustment using the quantized digital signal. , IC can be realized, cost can be reduced, reliability can be improved, and
An object of the present invention is to provide an electronic watt-hour meter capable of automating phase adjustment.

Further, the present invention provides an oversampling type analog / digital converter which realizes a high conversion accuracy by performing a conversion operation at a very high frequency as compared with a signal frequency.
It is an object of the present invention to provide an electronic watt-hour meter capable of realizing an inexpensive, compact, high-precision phase adjuster and a 90-degree phase shifter using a digital converter.

[0009]

[0010]

[0011]

An electronic watt-hour meter according to a first aspect of the present invention includes the following means. [1] Current Δ for converting AC current to a quantized numerical value
ΣModulation means. [2] Voltage Δ for converting AC voltage into a quantized numerical value
ΣModulation means. [3] A first memory for storing m quantized AC currents
Shift register means. [4] Second shift register means for storing n (n> m) quantized AC voltages. [5] Sampling clock supply means for supplying a sampling clock to the current △ Σ modulation means, the voltage ΔΣ modulation means, the first shift register means and the second shift register means. [6] Phase adjusting means for selecting only one of the n outputs of the second shift register means. [7] Calculation means for calculating the electric energy based on the outputs of the first shift register means and the phase adjustment means which have passed through the digital filter.

An electronic watt-hour meter according to a second aspect of the present invention includes the following means. [1] Current Δ for converting AC current to a quantized numerical value
ΣModulation means. [2] Voltage Δ for converting AC voltage into a quantized numerical value
ΣModulation means. [3] A first memory that stores n quantized AC currents
Shift register means. [4] Second shift register means for storing m (n> m) quantized AC voltages. [5] Sampling clock supply means for supplying a sampling clock to the current △ Σ modulation means, the voltage ΔΣ modulation means, the first shift register means and the second shift register means. [6] Phase adjusting means for selecting only one of the n outputs of the first shift register means. [7] Calculation means for calculating the electric energy based on the outputs of the second shift register means and the phase adjustment means which have passed through the digital filter.

An electronic watt-hour meter according to a third aspect of the present invention includes the following means. [1] Current Δ for converting AC current to a quantized numerical value
ΣModulation means. [2] Voltage Δ for converting AC voltage into a quantized numerical value
ΣModulation means. [3] Shift register means for storing n quantized AC voltages. [4] Sampling clock supply means for supplying a sampling clock to the current △ Σ modulation means, the voltage ΔΣ modulation means and the shift register means. [5] 1 out of n outputs of the shift register means
90-degree phase shifting means for selecting only [6] Calculation means for calculating the amount of reactive power based on the outputs of the current ΔΣ modulation means and the 90-degree phase shift means passed through a digital filter.

An electronic watt-hour meter according to a fourth aspect of the present invention includes the following means. [1] Current Δ for converting AC current to a quantized numerical value
ΣModulation means. [2] Voltage Δ for converting AC voltage into a quantized numerical value
ΣModulation means. [3] Shift register means for storing n quantized alternating currents. [4] Sampling clock supply means for supplying a sampling clock to the current △ Σ modulation means, the voltage ΔΣ modulation means and the shift register means. [5] 1 out of n outputs of the shift register means
90-degree phase shifting means for selecting only [6] Calculation means for calculating the reactive power based on the outputs of the voltage ΔΣ modulation means and the 90-degree phase shift means which have passed through the digital filter.

[0015]

In the present invention, the phase shift between the voltage and the current is adjusted by selecting only one of the n outputs of the shift register means.

Further, in the present invention, the phase shift between the voltage and the current can be reduced by using a ΔΣ type oversampling A / D converter and installing the shift register means between the ΔΣ modulation means and the digital filter. Is adjusted with high precision.

Further, according to the present invention, a Δ 微小 oversampling A
By using a / D converter and installing a shift register means between the Δ を modulation means and the digital filter, the phase fluctuation is adjusted with high precision.

[0018]

【Example】

Embodiment 1 FIG. The configuration of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a first embodiment of the present invention, in which input terminals 1, 2 and a multiplier 8 to a power amount display 10 are the same as those of the above-described conventional instrument. In addition,
In the respective drawings, the same reference numerals indicate the same or corresponding parts.

In FIG. 1, reference numeral 11 denotes an A / D converter which receives an AC current and converts it into a binary value, 12 denotes an A / D converter which receives an AC voltage and converts it into a binary value, and 13 Is a shift register that stores m binarized values of the AC current and outputs the m-th previous value.
A shift register that stores n evolved values (n> m) and outputs each of the n values. Reference numeral 15 designates the start of operation of the A / D converters 11 and 12 and the shift timing of the shift registers 13 and 14. A sampling clock circuit 3A for supplying a sampling clock is a phase adjustment device having a data selector function of supplying one of n outputs of the shift register 14 to the multiplier 8.

Next, the operation of the first embodiment will be described with reference to FIG. FIG. 2 is a timing chart showing the operation of the first embodiment of the present invention.

The voltage waveform v shown in FIG. 2A is a waveform input to the input terminal 2 of the voltage signal, and the current waveform i shown in FIG. This is the input waveform. In this example, the current lags behind the voltage by the phase difference φ.

Therefore, as shown in FIG. 2C, the A / D converter 12 outputs a binary value v ₁ by the sampling clock from the sampling clock circuit 15. On the other hand, A / D converter 11 outputs a binary value i _1. Since then
For each pulse of the sampling clock, the A / D converter 12 outputs binary values v ₂ , v ₃ ,..., And the A / D converter 11 outputs i as shown in FIGS. ₂ ,
i ₃ , ... are output.

The output of the binarized A / D converter 11 is input to, for example, a one-stage (m = 1) shift register 13. On the other hand, the output of the binarized A / D converter 12 is input to, for example, a three-stage (n = 3) shift register 14.

The phase adjusting device 3A includes a shift register 14
The most time-old (e.g., the output of the time t ₀ in v ₂₎ of the output by selecting the output phase shift φ is next zero phase is adjusted.

As a result, the phase difference between the voltage data and the current data input to the multiplier 8 becomes zero, and by multiplying the voltage and the current in the multiplier 8, instantaneous power without a phase error is output. The electric energy is obtained by successively adding by the adder 9. And the electric energy indicator 10
Displays the amount of power.

Embodiment 1 of the present invention, as described above,
Since the current signal and the voltage signal are digitized by the A / D converters 11 and 12 and the digital signal is phase-adjusted by the shift register 14 and the phase adjusting device 3A, the IC
This brings about an effect that downsizing, downsizing, and automation of adjustment can be easily realized.

In the first embodiment, the shift register 13 is provided on the current side, and the shift register 14 and the phase adjusting device 3A are provided on the voltage side. However, as shown in FIG. The same operation and effect can be expected by providing the adjusting device 3A and providing the shift register 13 on the voltage side.

Embodiment 2 FIG. Second Embodiment A configuration of a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram showing a second embodiment of the present invention.
The multiplier 8 to the electric energy display 10, the shift register 13 to the sampling clock circuit 15, and the phase adjusting device 3A are the same as those in the first embodiment. In the drawings, the same reference numerals indicate the same or corresponding parts.

In FIG. 4, reference numeral 11A denotes a ΔΣ modulation circuit which receives an AC current as an input, integrates a difference between the feedback signal and a feedback signal, and 12A inputs an AC voltage and integrates a difference between the feedback signal and the feedback signal. .DELTA..SIGMA. Modulation circuits for converting into digital signals, and 16 and 17 are digital filters having a low-pass filter function.

FIG. 5 is a block diagram showing the ΔΣ modulation circuits 11A and 12A according to the second embodiment of the present invention. The ΔΣ modulation circuit outputs the difference between the analog input and the feedback signal from the D / A conversion circuit 21 through the integrator 18 and outputs a 1-bit digital signal by the comparator 19. The digital output signal is fed back from the D / A conversion circuit 21 via the delay circuit 20 as an analog signal corresponding to digital “0” and “1”.

By setting a plurality of reference voltages of the comparator 19, a digital output of a plurality of bits can be obtained.

This ΔΣ modulation circuit is a circuit having a configuration capable of realizing high-precision A / D conversion as the sampling clock is made faster. It is a part of the circuit configuration of the so-called oversampling type A / D converter.
A high-precision A / D conversion can be performed by a combination of a ΔΣ modulation circuit and a digital filter having a low-pass function.

The operation of the second embodiment of the present invention is the same as that of the first embodiment if the ΔΣ modulation circuits 11A and 12A are regarded as A / D converters 11 and 12.

Here, the power factor of voltage and current is 0.5 (co
(sθ = 0.5, θ = 60 degrees), the error ε when the phase shift φ is 1 degree, for example, is as follows.

Ε = (cos59 ° -cos60 °) / c
os60 ° × 100 ≒ 3 (%)

Therefore, in order to accurately adjust the phase shift, it is necessary to increase the frequency of the sampling clock described above. For example, a clock frequency sampling 360 times in one cycle causes a 3% error.

The second embodiment of the present invention, as described above,
An oversampling type A / D converter composed of a ΔΣ modulation circuit and a digital filter is employed.
By installing a phase adjuster comprising a shift register between the modulation circuit and the digital filter, it is possible to increase the sampling clock frequency on a relatively small scale, to improve the accuracy of A / D conversion, and to adjust the phase. Accuracy can be improved. Furthermore, since the output of the ΔΣ modulation circuit is 1 bit, there is an effect that a phase adjustment device including a shift register can be easily configured.

Embodiment 3 FIG. The configuration of the third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing a third embodiment of the present invention. The input terminals 1 and 2, the multiplier 8, the adder 9, the shift register 14 to the digital filter 17, and the ΔΣ modulation circuits 11A and 12A are the same as those in the above embodiment. Same as in Example 2. In the drawings, the same reference numerals indicate the same or corresponding parts.

In FIG. 6, 3B is a shift register 14
90-degree phase shifter having a data selector function of supplying one of the n outputs of
0A is a reactive power indicator. The ΔΣ modulation circuit 1
1A and 12A have the configuration shown in FIG.

The operation of the third embodiment of the present invention is the same as that of the second embodiment, but differs in the following parts. That is, the output of the binarized ΔΣ modulation circuit 12A is output to the shift register 14
And the digital signal of the n-th stage delayed by 90 degrees is output.

Here, the power factor of the voltage and the current is 0.5 (co
(sθ = 0.5, θ = 60 degrees), the error ε when the frequency variation φ of the input signal is, for example, 1 degree is as follows.

Ε = (cos59 ° -cos60 °) / c
os60 ° × 100 ≒ 3 (%)

Therefore, in order to accurately shift the phase by 90 degrees, it is necessary to increase the frequency of the sampling clock and select n outputs of the shift register 14. For example, the clock frequency for sampling 360 times in one cycle is required. When n outputs of the shift register 14 are selected, an error of 3% or less occurs at the maximum.

The third embodiment of the present invention, as described above,
An oversampling type A / D converter composed of a ΔΣ modulation circuit and a digital filter is employed.
By installing a 90-degree phase shifter composed of a shift register between the modulation circuit and the digital filter, the sampling clock frequency can be increased on a relatively small scale, and the accuracy of A / D conversion can be improved. The accuracy of the phase difference can be improved. Further, since the output of the ΔΣ modulation circuit is 1 bit, a 90
There is an effect that the phase shift device can be simply configured.

In the second and third embodiments, as described in the first embodiment, the same operation and effect can be obtained even if the circuit devices on the voltage side and the current side are replaced.

[0046]

According to the present invention, as described above, the voltage signal and the current signal are quantized, and the phase is adjusted using the quantized digital signal, whereby the accuracy of the measurement can be improved and the IC can be implemented. Costs can be reduced,
There is an effect that the reliability can be improved and the phase adjustment can be automated.

Further, the present invention provides an oversampling type analog / digital converter which realizes a high conversion accuracy by performing a conversion operation at a very high frequency as compared with a signal frequency.
It is possible to realize an inexpensive, compact and high-precision phase adjustment device using a digital converter.

Further, as described above, the present invention has an effect that a 90-degree phase shifter including a shift register can be simply configured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the first embodiment of the present invention.

FIG. 3 is a block diagram showing another example of Embodiment 1 of the present invention.

FIG. 4 is a block diagram showing Embodiment 2 of the present invention.

FIG. 5 is a block diagram showing a ΔΣ modulation circuit according to Embodiment 2 of the present invention.

FIG. 6 is a block diagram showing a third embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional electronic watt-hour meter.

[Explanation of symbols]

 1, 2 input terminal 3A phase adjuster 3B 90-degree phase shifter 8 multiplier 9 adder 10 electric energy indicator 11, 12 A / D converter 13, 14 shift register 15 sampling clock circuit 11A, 12A ΔΣ modulation circuit 16 , 17 Digital filter

Claims (4)

(57) [Claims] An AC current is converted into a quantized numerical value.
Current ΔΣ modulation means converts AC voltage to quantized numerical value
Voltage ΔΣ modulating means, and the quantized alternating current
First shift register means for storing the quantized
Shift register for storing n (n> m) AC voltages
Means, the current △ Σ modulation means, and the voltage ΔΣ modulation means.
Stage, the first shift register means and the second shift register.
Sampler that supplies a sampling clock to
Pulling clock supply means, the second shift register
Phase adjuster for selecting only one of the n outputs of the means
Stage and said first shift through a digital filter
Based on the outputs of the register means and the phase adjusting means,
An electronic watt-hour meter equipped with a calculating means for calculating a power. 2. Converting an alternating current into a quantized numerical value.
Current ΔΣ modulation means converts AC voltage to quantized numerical value
Voltage ΔΣ modulating means for converting the quantized AC current to n
First shift register means for storing the quantized
Shift register for storing m (n> m) AC voltages
Means, the current △ Σ modulation means, and the voltage ΔΣ modulation means.
Stage, the first shift register means and the second shift register.
Sampler that supplies a sampling clock to
Pulling clock supply means, the first shift register
Phase adjuster for selecting only one of the n outputs of the means
Stage and said second shift through a digital filter
Based on the outputs of the register means and the phase adjusting means,
An electronic watt-hour meter equipped with a calculating means for calculating a power. 3. Converting an alternating current into a quantized numerical value.
Current ΔΣ modulation means converts AC voltage to quantized numerical value
Modulating means, which converts the quantized AC voltage to n
Shift register means for storing the current
Stage, the voltage ΔΣ modulation means and the shift register means
Clock that supplies the sampling clock to the
Clock supply means and n output signals of the shift register means.
90 degree phase shift means for selecting only one and a digital
The current ΔΣ modulating means having passed through the
A calculator that calculates the amount of reactive power based on the output of the phase shifter
Electronic watt-hour meter with steps . 4. Converting an alternating current into a quantized numerical value.
Current ΔΣ modulation means converts AC voltage to quantized numerical value
Voltage ΔΣ modulating means for converting the quantized AC current to n
Shift register means for storing the current
Stage, the voltage ΔΣ modulation means and the shift register means
Clock that supplies the sampling clock to the
Clock supply means and n output signals of the shift register means.
90 degree phase shift means for selecting only one and a digital
The voltage ΔΣ modulating means and the 90 °
A calculator that calculates the amount of reactive power based on the output of the phase shifter
Electronic watt-hour meter with steps .