JP2004053455A - Electronic watthour meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic watthour meter which can measure electric power pulses accurately. <P>SOLUTION: An electric energy frequency changing circuit 3 multiplies an input voltage and an input current together, and outputs power pulses proportional to electric energy. Pulse intervals are measures by using a time measuring means 4d. A shunt running judgement part 4f decides whether the pulse interval is longer than a prescribed time T. When the pulse interval is shorter than the prescribed time T, one electric power pulse is measured. When last pulse interval is longer than T and this time pulse interval is shorter than T, two electric power pulses are measured. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in the accuracy of power metering in an electronic watt-hour meter.
[0002]
[Prior art]
FIG. 4 is a block diagram of a conventional electronic watt-hour meter disclosed in, for example, JP-A-6-102298, and FIGS. 5 and 6 are waveform diagrams for explaining the operation of the conventional electronic watt-hour meter.
In the figure, reference numeral 1 denotes a voltage input terminal, 2 denotes a current input terminal, and 3 denotes an electric energy frequency conversion circuit for A / D converting and multiplying the voltage input and the current input to output an electric pulse proportional to the electric energy. Reference numeral 4 denotes a microcomputer for controlling the electronic watt-hour meter, which is an interrupt input terminal 4a to which a power pulse from the power amount frequency conversion circuit 3 is input, a latent control signal output terminal 4b, and a power pulse count input terminal 4c. It has. Reference numeral 5 denotes an AND gate which inputs a logical sum of the power pulse and the output of the latent control signal output terminal 4b to the power pulse count input terminal 4c. Reference numeral 6 denotes a display circuit for numerically displaying the measured electric energy.
[0003]
The power amount frequency conversion circuit 3 includes an A / D converter of digital processing, a multiplication circuit, and the like. An offset pulse similar to a power pulse is output even if the current input is zero due to the offset output of the circuit element. Since the offset pulse output interval when the current input is zero is longer than the power pulse interval when the minimum metered power is detected, the normal pulse and the latent pulse due to the offset are identified by the pulse interval determination, and the offset pulse is output. Prevent weighing. The following set values and reference values are set so that the predetermined time T serving as a criterion for the pulse interval is longer than the power pulse interval at the time of detection of the minimum metered power amount.
[0004]
The microcomputer 4 has an internal counter connected to the interrupt input terminal 4a. The internal counter is set to a predetermined value at the time of the input rising of the power pulse, and is set to a predetermined value until the next power pulse is input. Count down the number of clocks. The decrement of the internal counter corresponds to the time interval until the next power pulse input. If the remaining value of the internal counter is smaller than a predetermined reference value (set value> reference value), the power pulse interval is longer than the predetermined time T.
[0005]
Next, a specific operation will be described with reference to FIG. When the power pulse input enters the interrupt input terminal 4a, the microcomputer 4 causes the internal counter to perform an interrupt operation. Then, an interval until the next power pulse is input is determined. When the pulse interval Tp (time until the next power pulse input) is within the predetermined time T, the output of the latent control signal output terminal 4b is set to the high-level (“H”) power amount measurement period. As a result, if there is a next power pulse input, the AND gate 5 outputs a pulse to the power pulse count input terminal 4c to measure the amount of power.
When the pulse interval Tp exceeds the predetermined time T, the output of the diving control signal output terminal 4b becomes low level ("L"), and the diving measurement suspension period starts. During the dive weighing stop period, one of the inputs of the AND gate 5 is in the state of “L”. Therefore, even if the next power pulse is input, the pulse is not output to the power pulse count input terminal 4c, and the offset is not applied. The diving pulse is blocked from weighing.
[0006]
[Problems to be solved by the invention]
The conventional electronic watt-hour meter operates as described above, and when the pulse interval Tp exceeds the predetermined time T as shown in FIG. However, after the start of use of the power load, the power pulse whose pulse interval Tp is within the predetermined time T is a continuous input, so that the first pulse when returning from the latent measurement stop period to the power amount measurement period is measured. There was a problem that the power meter was not counted and became inaccurate.
The present invention has been made to solve the above-described problem, and has as its object to provide an electronic watt-hour meter capable of accurately measuring a power pulse.
[0007]
[Means for Solving the Problems]
An electronic watt-hour meter according to the present invention is a power amount frequency conversion circuit that multiplies an input voltage and an input current to convert the input voltage and an input current into a power pulse proportional to the power amount, and a timing unit that counts a pulse interval of the power pulse, A descent determination unit that determines whether the pulse interval of the power pulse is longer or shorter than a predetermined time; if the pulse interval of the power pulse is shorter than the predetermined time, one power pulse is measured; When the time interval is longer than the time and the current pulse interval is shorter than the predetermined time, two power pulses are measured.
[0008]
Further, when the pulse interval of the power pulse is longer than a predetermined time, a low-level dive control signal is output when the pulse interval is shorter than the predetermined time, and the OR of the dive control signal and the power pulse is established. It is equipped with an AND gate that sometimes measures power pulses.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram of an electronic watt-hour meter showing a first embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the present invention, and FIG. 3 is a flowchart for explaining the operation of the present invention. In the figure, reference numerals 1 to 6 are the same as those in the description of the conventional apparatus. 4d is a time measuring means in the microcomputer 4, 4e is a weighing unit, and 4f is a descent determination unit.
[0010]
The operation will be described. First, when the electronic watt-hour meter is connected to the distribution line and the microcomputer 4 starts operating, the dive control signal (the sign of the dive control signal output terminal 4b) is set to “H” as part of the initial processing ( S1). The input time interval of the power pulse from the power frequency conversion circuit 3 is measured by the timer 4d (S2). When the input interval of the power pulse is longer than the preset time T, the diving determination section 4f sets the output terminal 4b of the diving control signal to "L" and shifts to timing of the next input interval of the power pulse (S3 to S4). ). If the input interval of the power pulse is shorter than the predetermined time T, the sign of the latent control signal output terminal 4b is determined, and if "H", one power pulse is measured to the measuring unit 4e. (S3 to S6). If the sign of the latent control signal is "L", two power pulses are measured by the measuring unit 4e (S5, S7). Then, the latent control signal is set to “H” from the total of the power pulses, and the process shifts to timing of the next power pulse input interval (S8, S9).
[0011]
In the processing of the present invention, the first power pulse when returning from the latent measurement stop period to the power amount measurement period is counted as two pulses, and the measurement of the power pulse is corrected. Can be counted.
Although the configuration including the AND gate 5 has been described for the sake of easy understanding similarly to the conventional apparatus, it is obvious that the same effect can be obtained even if this part is processed by a computer.
[0012]
【The invention's effect】
As described above, the pulse interval of the power pulse is measured by the timing unit 4d, and whether the pulse interval is longer or shorter than the predetermined time T is determined by the descent determination unit 4f. If the pulse interval is shorter than the predetermined time T, When one power pulse is measured and the immediately preceding pulse interval is longer than the predetermined time T and the current pulse interval is shorter than the predetermined time T, two power pulses are measured. , The power metering becomes accurate by compensating for the omission of the count of the first one pulse when returning to the power metering period at the start of using the power load.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic watt-hour meter of the present invention.
FIG. 2 is a waveform diagram illustrating the operation of the present invention.
FIG. 3 is a flowchart illustrating the operation of the present invention.
FIG. 4 is a block diagram of a conventional electronic watt-hour meter.
FIG. 5 is a waveform diagram illustrating the operation of a conventional electronic watt-hour meter.
FIG. 6 is a waveform diagram illustrating an operation of a conventional electronic watt-hour meter.
[Explanation of symbols]
3 electric energy frequency conversion circuit, 4 microcomputer,
4a interrupt input terminal, 4b dive control signal output terminal,
4c dive control signal output terminal, 4d timing means,
4e weighing section, 4f dive judging section, 5 AND gate,
6 display circuit, T predetermined time,

Claims (2)

A power frequency conversion circuit for converting an input voltage and current into a power pulse proportional to the power by multiplying the voltage and current after A / D conversion, and a clock for measuring a pulse interval of the power pulse from the power frequency conversion circuit Means, comprising a descent determination unit that determines whether the pulse interval of the power pulse is longer or shorter than a predetermined time,
When the pulse interval of the power pulse is shorter than a predetermined time, one power pulse from the power amount frequency conversion circuit is measured, and when the immediately preceding pulse interval is longer than the predetermined time and the current pulse interval is shorter than the predetermined time, the power is measured. An electronic watt-hour meter characterized in that two pulses are measured. The diving determination section outputs a low level diving control signal when the pulse interval of the power pulse is longer than a predetermined time, and outputs a high level diving control signal when the pulse interval is longer than the predetermined time. The electronic watt-hour meter according to claim 1, further comprising an AND gate that measures a power pulse when the sum is established.

Images