JP2518582B2 - Electronic electricity 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 obtaining load power on a power supply line based on a digital signal obtained by converting a signal proportional to the power of the power supply line from analog to digital. is there.

[0002]

2. Description of the Related Art With the development of electronic equipment, in the field of watt-hour meters, electronic watt-hour meters that measure digitally are about to replace conventional inductive watt-hour meters in recent years.

FIG. 3 shows the structure of this electronic watt hour meter.

In this figure, 1 is a transformer and 2 is an analog-digital (hereinafter referred to as AD) converter.
The transformer 1 has a primary side connected to a power supply line, reduces the voltage of the power supply line to a value that can be handled by the subsequent AD converter 2, and instantaneously converts the voltage of the power supply line to a voltage of the power supply line. It outputs a voltage signal whose value and effective value are proportional. AD
The converter 2 samples the instantaneous value of the secondary voltage signal of the transformer 1 and outputs voltage data.

Reference numeral 3 is a current transformer, and 4 is an AD converter. The current transformer 3 has a primary side connected to a power supply line, converts the current of the power supply line into a small current that can be handled by the subsequent AD converter 4, and supplies the power supply line to the secondary side. Output a current signal in which the instantaneous value and the effective value are proportional to the current.
The AD converter 4 samples the instantaneous value of the secondary current pressure signal of the current transformer 3 and outputs current data.

Reference numeral 5 is a multiplier, 6 is an integrator, 7 is a pulse generator, and 8 is a display. The output data of the AD converters 2 and 4 are multiplied by the multiplier 5 and converted into electric power data. The integrator 6 integrates this power data and
When the integrated value exceeds a certain value, a generation command for one pulse is output, and the operation of subtracting the power value corresponding to one pulse from the integrated value is repeated to repeat the operation every time the integrated value exceeds the certain value. An output command for one pulse is output to. The pulse generator 7 generates a pulse each time the pulse generation command is received, and gives a notification of the generation to the integrator 6, and the integrator 6 responds to the notification with the pulse 1
Subtraction of the integral value for each piece is performed. In this integrator 6, the time when the integrated value exceeds the above fixed value becomes shorter as the instantaneous power becomes larger, so that the output frequency of the pulse generation command becomes higher as the instantaneous power becomes larger, whereby the pulse train corresponding to the power value generates pulses. It is generated from the container 7. The output pulse is given to the display unit 8, and the display unit 8 adds the pulse number to the present integrated value and displays the electric energy every moment. The output pulse of the pulse generator 9 is also output to the external output terminal, and the test of the power meter can be performed using this external output terminal.

As described above, the voltage signal and the current signal proportional to the voltage and the current on the power feeding line are converted into digital signals, the two signals are multiplied and converted to obtain the power data, and the power data is integrated to determine the power amount. Now that the development of semiconductor devices is remarkable, it is taking the form of operation suitable for the times, and there is a possibility of improving the performance as the capabilities of the device improve.

Here, the instantaneous value and the effective value of the load voltage are represented by eR and VR, respectively, and the instantaneous value and the effective value of the load current are represented by iR and IR, respectively, and the load current iR is a phase angle θ rather than the load voltage eR. If it is delayed by only eR = 2 ^(1/2) VR sin ωt (1) iR = 2 ^(1/2) IR sin (ωt-θ) (2), the instantaneous power pR is pR = VR IR (cos θ−cos (2ωt−θ)) (3) (where ω is the angular frequency and t is the time).

[0009]

However, there are still unsolved problems in the above-mentioned electronic power meter.

First, the cause is that the output pulse interval from the pulse generator 7 becomes dense and sparse as the magnitude of pR becomes large, and the pulse interval largely changes due to the change of the instantaneous power. It is to be. And this is
Even if the measurement is performed for the same time, the measurement accuracy varies so that a difference occurs in the measured electric energy value for each measurement section even though the electric power is in the same usage state. In order to measure with high accuracy, such effects must be minimized.

Therefore, when theoretically considering reducing the influence of the change in the pulse interval, it is concluded that the longer the pulse measurement time is, the better.

However, if the measurement time is lengthened, it becomes more susceptible to the influence from the outside, and the problem of accuracy loss due to the external factor comes out.

In constructing an electronic watt hour meter,
Ensuring accuracy is important and indispensable, and for that purpose, it is required to simultaneously eliminate the effects of changes in instantaneous power and the effects of external factors.

An object of the present invention is to solve the above problems by providing an electronic watt-hour meter with stable measurement accuracy.

The electronic watt-hour meter of the present invention is a multiplier for generating electric power data by multiplying a digital signal obtained by converting a signal proportional to a voltage and a current on a power feeding line by an analog-digital converter. And a first integrator that integrates the value indicated by the power data and generates a pulse output command each time the integrated value exceeds a certain value, and a pulse generator that outputs pulses corresponding to the number of received pulse output commands. And a second integrator that integrates the power data for the time set in the integration time controller and outputs the integrated value data, and the pulse output interval of the pulse generator is the value indicated by the integrated value data. And a pulse output interval controller for controlling the operation of the pulse generator for shifting the pulse output interval so that the pulse output interval is adjusted according to the above.

[0016]

According to the present invention, the measured electric power is captured by the average value of the instantaneous values, the pulse interval for measuring the electric energy is determined according to the integrated value of the electric power data, and the pulse is generated within the time corresponding to the integration time. The output intervals become uniform, and uniform accuracy is maintained within the time corresponding to the integration time regardless of the length of the pulse measurement time. Therefore, it is possible to shorten the pulse measurement time, eliminate the influence of the change of the instantaneous value of the electric power and the influence of the external precision loss factor, and achieve high-precision measurement.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of an electronic watt hour meter according to an embodiment of the present invention. The same components of the watt-hour meter shown in this figure as those of the watt-hour meter shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

In FIG. 1, 9 is a pulse generator,
The pulse generator 9 can store a large number of pulse generation commands from the integrator 6, generates one pulse at a specified interval, and clears the pulse generation command at each pulse generation. It has a function. The pulse generator 9 also gives the integrator 6 a notification of the generation of one pulse, as in the conventional case. The integrator 6 subtracts the integrated value of one pulse in response to the notification.

Reference numeral 10 is an integration time controller, 11 is an integrator, and 1
2 is a pulse interval calculator, which is a pulse generator 9
It constitutes means for controlling the pulse output interval of.

That is, the integrator 11 integrates the output data of the multiplier 5 at each time designated by the integration time controller 10 and outputs the integrated value data. The pulse interval calculator 12 determines a pulse output interval according to the output data of the integrator 11, and outputs pulse interval control data indicating the pulse output interval.
The pulse interval control data is supplied to the pulse generator 9, and the pulse generator 9 generates pulses at the intervals designated by the pulse interval control data by the amount of the pulse generation command that is in stock. ing. As a result, pulses are output at even intervals during the period corresponding to the integration time set by the integration time controller 10, and the accuracy of the pulses is determined by the integration time set by the integration time controller 10. Retained. Therefore, the accuracy does not change regardless of the length of the measurement time. Therefore, by shortening the measurement time and setting the integration time in the integration time controller 10 so that the required accuracy can be secured, high accuracy can be achieved in a short time. Can be measured.

FIG. 2 shows an example of load voltage, load current, and load power on the power supply line, an output pulse whose pulse interval is not compensated, and an output pulse whose pulse interval is compensated. .

As shown in FIG. 2A, the load power periodically changes at a frequency twice the load voltage and load current.

When a pulse is output at high speed,
As shown in FIG. 2B, the pulse interval is not constant due to increase / decrease in power. Therefore, for example, when comparing the pulse trains of the times t1 to t2 and the times t2 to t3 at the same time T, it is found that there is a difference in the measured electric energy even though the loads are the same. It is obvious. That is,
In the case of time t1 to t2, the pulse group ends from the time when it is relatively dense to the time when it is also dense, whereas the time t2 to t3.
In the case of, the pulse group ends from the time when the pulse group is relatively sparse to the time when the pulse group is also sparse, and the measured electric energy is W (t1 to t2)>
W (t2 to t3). T2, which is a shorter time T / n
Looking at the period from t21 to the period from t21 to t22, one has the pulse number "2", while the other has the pulse number "10".
Therefore, the fluctuation of the pulse interval (the fluctuation of the instantaneous value) has a great influence.

According to the present invention, as shown in FIG. 2 (c), the pulse intervals are made uniform. 2 above
The accuracy is kept constant without comparing the periods of the seed time T. The same is true during the shorter time period T / 2.

As described above, according to this embodiment, the integrator 11
Since the pulse output intervals are uniform within the time corresponding to the integration time in, the uniform accuracy is maintained within the time corresponding to the integration time regardless of the length of the pulse measurement time. Therefore, it is possible to shorten the pulse measurement time, eliminate the influence of the change of the instantaneous value of the electric power and the influence of the external precision loss factor, and achieve high-precision measurement.

Although the current signal is converted into digital data in the current mode in the above embodiment, it may be converted into the voltage mode.

[0028]

As described above, according to the present invention, the measured electric power is captured by the average value of the instantaneous values, the pulse interval for measuring the electric energy is determined according to the integrated value of the electric power data, and the integration time is set. Within the corresponding time, the pulse output intervals become uniform, and within the time corresponding to the integration time, uniform accuracy is maintained regardless of the length of the pulse measurement time.
Therefore, it is possible to shorten the pulse measurement time, eliminate the influence of the change of the instantaneous value of the electric power and the influence of the external precision loss factor, and achieve high-precision measurement.

[Brief description of drawings]

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

FIG. 2 is a timing waveform diagram illustrating load voltage, load current, and load power on a power supply line, an output pulse whose pulse interval is not compensated, and an output pulse whose pulse interval is compensated.

FIG. 3 is a block diagram showing a circuit configuration of a conventional electronic watt-hour meter.

[Explanation of symbols]

 1 Transformer 2 Analog-digital converter for voltage signal 3 Current transformer 4 Analog-digital converter for current signal 5 Multiplier 6 Integrator for issuing pulse output command 8 Display 9 Pulse generator 10 Integration time for pulse interval setting Controller 11 Pulse interval setting integrator 12 Pulse interval calculator

Claims (1)

(57) [Claims] 1. A multiplier for generating power data by multiplying a digital signal obtained by converting a signal proportional to a voltage and a current on a power feed line by an analog-digital converter, and a value indicated by the power data. A first integrator that generates a pulse output command each time the integrated value exceeds a certain value, a pulse generator that outputs pulses corresponding to the number of received pulse output commands, and the power data is integrated. A second integrator that integrates for a time set in the time controller and outputs the integrated value data, and a pulse output interval of the pulse generator becomes an interval according to the value indicated by the integrated value data. And a pulse output interval controller for controlling the operation of the pulse generator for shifting the pulse output interval.