JP2012103073A - Electric energy measurement device and calibration method of watt-hour meter using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric energy measurement device which can reduce a frequency error of pulse output to an electric energy measurement value without raising a frequency of a clock and a calibration method of a watt-hour meter using the same.SOLUTION: In an electric energy measurement device which outputs a pulse having a frequency proportional to an electric energy measurement value, there is provided the electric energy measurement device provided with: a counter which outputs the pulse having a predetermined bit length and the frequency; a plurality of registers in which the bit length of data for setting the frequency to the bit length of the counter is extended and which are provided according to the number of pieces of the extended bit length; a register control circuit in which data for the bit length of the counter is taken out from a high order of the data for setting the frequency to be set in the plurality of registers, and which adds 1 for registers for a numerical value of the extended bit length from a low order of the data for setting the frequency among the plurality of registers; and a selector which selectively inputs data on the plurality of registers as the data on the counter, and a calibration method of the watt-hour meter using the same.

Description

  The present invention relates to a watt-hour measuring device and a method for calibrating a watt-hour meter using the watt-hour measuring device, and more particularly to improvement in accuracy of a watt-hour measuring device used for calibration and verification of a watt-hour meter to be measured.

  The watt-hour meter (integrated watt-hour meter) is a meter for measuring the amount of power used in the circuit system to be measured, and based on the measurement results, payment of electricity charges and energy management are performed. .

  In general, inductive energy meters that have a function to measure the active power of AC power are the mainstream as watt-hour meters for general households, and digitized static energy meters are often used in commercial facilities. Yes.

  The inductive watt hour meter utilizes the rotation of an Arago disk, and is configured to integrate and digitize electric power based on the number of rotations of the disk that rotates by the flow of electricity.

  By the way, watt-hour meters installed in general households are used as the basis for payment of electricity charges to electric power companies. Used.

  When inspecting such an inductive watt-hour meter, a reference power signal is input in parallel to the measured watt-hour meter and the master watt-hour meter calibrated for verification, and the measured watt-hour meter rotates a predetermined number of times. The number of pulses output within the same time is compared with the number of pulses output from the master watt hour meter within the same time.

  FIG. 4 is a block diagram showing an example of a conventional master watt-hour meter. In FIG. 4, the voltage input unit 10 includes a series circuit of resistors 11 and 12 constituting a voltage dividing circuit that divides an input voltage, an amplifier 13 that normalizes the output voltage of the voltage dividing circuit, and a normalized amplifier 13. A / D converter 14 that converts the output signal of the signal into a digital signal, and an isolation element that galvanically isolates the output data of the A / D converter 14 and inputs it to one input terminal of a DSP (Digital Signal Processor) 30 15.

  The current input unit 20 includes a resistor 21 that forms a shunt circuit that shunts an input current, an amplifier 22 that normalizes the shunt output of the shunt circuit, and an A / A that converts the output signal of the normalized amplifier 22 into a digital signal. The D converter 23 and the insulating element 24 that galvanically isolates the output data of the A / D converter 23 and inputs the data to the other input terminal of the DSP 30.

  The DSP 30 constitutes a calculation unit, a voltage calculation function for calculating an instantaneous value of the voltage value based on the output of the A / D converter 14, and an instantaneous value of the current value based on the output of the A / D converter 23. And a power calculation function for calculating an instantaneous value of the power value based on the outputs of the A / D converters 14 and 23. Note that these calculations are performed in real time.

  The CPU 40 calculates the frequency of the pulse output from the counter 60 based on the power value calculated by the DSP 30 and the clock frequency output from the clock circuit 70, and inputs the calculation result to the register 50.

For example, if the relationship between the measured electric energy and the frequency of the pulse output from the counter 60 is 5 Hz / W, the clock frequency is 66 MHz, and the measured electric energy is P (W), the set value PFREG of the register 50 is , Is calculated as in equation (1).
PFREG = 66000000 / (5 * P) (1)

  The counter 60 adds a count value every time a clock is input from the clock circuit 70. When the count value becomes equal to the set value of the register 50, the counter 60 outputs a pulse to the output terminal 80 and clears the count value. Repeat the operation. The frequency of the pulse output to the output terminal 80 is a value obtained by dividing the clock frequency output from the clock circuit 70 by the set value of the register 50.

  FIG. 5 is a timing chart for explaining the operation of FIG. 4, showing the operation when the set value of the register 50 is 3 (decimal number), (a) showing the clock, (b) showing the counter 60. The count value is shown, and (c) shows the frequency of the pulse output from the counter 60.

  In the example of FIG. 5, the counter 60 adds a count value every time a clock is input from the clock circuit 70, and outputs a pulse to the output terminal 80 when the count value becomes equal to the set value “3” of the register 50. The count value is cleared, and thereafter the same operation is repeated. Thereby, the frequency of the pulse output to the output terminal 80 becomes a value obtained by dividing the clock frequency output from the clock circuit 70 by the set value “3” of the register 50.

  Patent Document 1 calculates and displays the error of the coefficient value of the measurement pulse with respect to the coefficient value of the reference pulse, based on the measurement pulse and the reference pulse proportional to the power output by measuring the power with the measured meter and the master meter. The technology to do is described.

JP-A-7-27842

  However, according to the configuration of FIG. 4, according to the equation (1), when the power measurement value P increases, the value of PFREG decreases and the resolution of the pulse frequency output deteriorates. The frequency output error increases.

  For example, when P = 1000 W, PFREG = 13200, and the error is 0 ppm, but when P = 999.93 W, PFREG = 13200.924. If the decimal point is rounded down and PFREG = 13200, the frequency of the pulse output is 5000 Hz, but since the true value of the frequency of the pulse output is 4999.65 Hz, the error is 70 ppm. Here, the calculation is performed with the decimal part rounded down, but even when the decimal part is rounded off, the error is only improved to about ½.

  Further, when P = 1500 W, PFREG = 8800 and the error is 0 ppm, but when P = 1499.83 W, PFREG = 8800.997. If PFREG = 8800 is rounded down after the decimal point, the frequency of the pulse output is 7500 Hz, but since the true value of the frequency of the pulse output is 7499.15 Hz, the error is 113 ppm.

  In order to improve such an error, it is conceivable to increase the frequency of the clock output from the clock circuit 70. However, if the clock frequency is increased, an expensive component corresponding to a high frequency must be used as a circuit component. I must.

  The present invention pays attention to such a conventional problem, and an object of the present invention is to provide an energy measuring device capable of reducing the frequency error of the pulse output with respect to the energy measuring value without increasing the clock frequency, and the same. It is in providing the calibration method of the watt-hour meter using this.

The invention of claim 1 which achieves such a problem,
In the energy measurement device configured to output a pulse having a frequency proportional to the energy measurement value,
A counter having a predetermined bit length and outputting a pulse having the frequency;
The bit length of the data for setting the frequency with respect to the bit length of the counter is expanded, and a plurality of registers provided according to the number of the extended bit lengths;
Data corresponding to the bit length of the counter is extracted from the upper part of the data for setting the frequency and set in the plurality of registers, and the numerical value of the extended bit length from the lower part of the data for setting the frequency among the plurality of registers. A register control circuit for adding 1 to the registers;
A selector that selectively inputs data of the plurality of registers as the counter data;
Is provided.

The invention of claim 2
The watt-hour measuring device according to claim 1 is used as a master watt-hour meter, and a reference power signal is input in parallel to the measured watt-hour meter and the calibrated master watt-hour meter. A watt-hour calibration method characterized by comparing and collating the number of pulses output within a time period with the number of pulses output from a master watt-hour meter within the same time period.

The invention of claim 3 is the watt-hour meter calibration method of claim 2,
The watt-hour meter to be measured is an inductive watt-hour meter using rotation of an Arago disk.

  As a result, it is possible to realize a power amount measuring apparatus capable of reducing the frequency error of the pulse output with respect to the power amount measurement value without increasing the clock frequency and performing high-precision measurement, and a method for calibrating the watt hour meter using the power amount measuring device.

It is a block diagram which shows one Example of this invention. It is explanatory drawing of the data in the register | resistor of FIG. 2 is a timing chart illustrating the operation of FIG. 1. It is a block diagram which shows an example of the conventional master electric energy meter. 5 is a timing chart for explaining the operation of FIG. 4.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and the same reference numerals are given to portions common to FIG. The difference between FIG. 1 and FIG. 4 is that the register 50 is increased by 3 bits to 32 bits in FIG. 1, and a register control circuit 90, registers 101 to 108, and a selector 110 are added.

  In FIG. 1, 29-bit registers 101 to 108 are connected in parallel to a 32-bit register 50 via a register control circuit 90, and output terminals of these registers 101 to 108 are connected to a counter 60 via a selector 110. ing.

The CPU 40 of FIG. 1 calculates the set value PFREG of the register 50 obtained from the power amount measurement value P in correspondence with the increment of the register 50 by 3 bits as follows.
PFREG = 8 * 66000000 / (5 * P) (2)

  The register control circuit 90 divides the 32 bits set in the register 50 into upper 29 bits and lower 3 bits, and sets the upper 29 bits in the registers 101 to 108. Among these eight registers 101 to 108, the register relating to the numerical value of the lower 3 bits is set by adding 1 to the data. The data set in these registers 101 to 108 is selected by the selector 110 and input to the counter 60.

  The selector 110 switches the registers 101 to 108 in order each time the counter 60 outputs a pulse once, so that the data in the registers 101 to 108 are input to the counter 60 in order.

  FIG. 2 is an explanatory diagram of data in the register 50 and the registers 101 to 108 in FIG. It is assumed that 18 (decimal number) “0000_0000_0000_0000_0000_0000_0001_0010b” is set in the register 50. The upper 29 bits “0_0000_0000_0000_0000_0000_0001_0010b” of the register 50 are set in the registers 101 to 108, but since the lower 3 bits of the register 50 are “010”, the data obtained by adding 1 to the two registers 107 and 108 Set “0_0000_0000_0000_0000_0000_0001_0011b”.

  FIG. 3 is a timing chart for explaining the operation of FIG. 1, showing the operation when the set value of the register 50 is 18 (decimal number) based on the data configuration of FIG. 2, and (a) shows the clock. (B) shows the registers 101 to 108 that are sequentially selected by the selector 110, (c) shows the count value of the counter 60, and (d) shows the frequency of the pulse output from the counter 60.

  In FIG. 3, the counter 60 adds a count value every time a clock is input from the clock circuit 70, and the data values “2” or “2” of the registers 101 to 108 in which the count value is sequentially selected by the selector 110. When equal to “3”, a pulse is output to the output terminal 80 and the count value is cleared, and thereafter the same operation is repeated.

  Thereby, the frequency of the pulse output to the output terminal 80 becomes an average value of values obtained by dividing the clock frequency output from the clock circuit 70 by the data value “2” or “3” of the registers 101 to 108.

  This will be described in comparison with the operation of the conventional example. In the configuration of FIG. 1, as described above, the set value PFREG of the register 50 is calculated based on the equation (2). For example, when the measured electric energy P is 999.93 W, PFREG = 105607.925 is calculated. However, the register 50 is set to PFREG = 105607 by rounding down the decimal point. In this case, the upper 29 bits of PFREG are 13200, and the lower 3 bits are 7.

  The register control circuit 90 sets 13200 to one of the registers 101 to 108 and sets 13201 obtained by adding 1 to the remaining seven related to the numerical value of the lower 3 bits.

  Since the data of the registers 101 to 108 are sequentially input to the counter 60 via the selector 110, the data relating to the frequency of the pulses output from the counter 60 to the output terminal 80 is 13200 once and 13201 is 7 Times. When the data related to the frequency of the pulse output from the counter 60 to the output terminal 80 is 13200, the frequency output of the pulse is 5000 Hz, and when the data is 13201, the frequency of the pulse output is 4999.621241 Hz.

  Thus, since 5000 Hz is repeated once and 4999.621241 Hz is repeated seven times, the average value of the pulse frequency output is 499.668586 Hz, and the error is 3.7 ppm with respect to the true value of 499.65 Hz. Therefore, it is greatly improved compared to the conventional case.

  The bit length of the register 50 is expanded with respect to the bit length of the counter 60, the register control circuit 90, the registers 101 to 108 corresponding to the expanded bit length (eight for 3 bits), and these registers 101 to 108 Are added in order. In the register control circuit 90, data having a bit length equal to the bit length of the counter 60 from the most significant bit of the register 50 is set in the registers 101 to 108 corresponding to the extended bit length (eight for 3 bits). . At this time, 1 is added to the numerical value of the bit length data extended from the least significant bit of the register 50 (7 if the extended bit length data is “111b”).

  With this configuration, the resolution of the average value of the pulse frequency output from the counter 60 is improved by an amount corresponding to the bit length extended with respect to the bit length of the counter 60, and the pulse frequency output for the power measurement value is improved. The error can be reduced.

  Then, using the power measuring device configured as described above as a master watt hour meter, a reference power signal is input in parallel to the measured watt hour meter and the calibrated master watt hour meter. By comparing and collating the number of pulses output within a predetermined time with the number of pulses output from the master watt-hour meter within the same time, the watt-hour meter can be calibrated and verified with high accuracy.

  In the above embodiment, the bit length of the counter 60 is 29 bits and the bit length to be extended is 3 bits. However, the bit length of the counter 60 and the bit length to be extended are not limited to this.

  As described above, according to the present invention, the power amount measuring apparatus capable of reducing the frequency error of the pulse output with respect to the power amount measurement value without increasing the clock frequency and performing high-precision measurement, and the power amount using the same. A calibration method for the meter can be realized.

10 Voltage Input Unit 20 Current Input Unit 30 DSP (Digital Signal Processor)
40 CPU
50, 100 Register 60 Counter 70 Clock circuit 80 Output terminal 90 Register control circuit 110 Selector

Claims (3)

In the energy measurement device configured to output a pulse having a frequency proportional to the energy measurement value,
A counter having a predetermined bit length and outputting a pulse having the frequency;
The bit length of the data for setting the frequency with respect to the bit length of the counter is expanded, and a plurality of registers provided according to the number of the extended bit lengths;
Data corresponding to the bit length of the counter is extracted from the upper part of the data for setting the frequency and set in the plurality of registers, and the numerical value of the extended bit length from the lower part of the data for setting the frequency among the plurality of registers. A register control circuit for adding 1 to the registers;
A selector that selectively inputs data of the plurality of registers as the counter data;
An electric energy measuring apparatus characterized by comprising:   The watt-hour measuring device according to claim 1 is used as a master watt-hour meter, and a reference power signal is input in parallel to the measured watt-hour meter and the calibrated master watt-hour meter. A method for calibrating a watt hour meter, comprising comparing and collating the number of pulses output within a time period with the number of pulses output from a master watt hour meter within the same time period.   The watt-hour calibration method according to claim 2, wherein the measured watt-hour meter is an inductive watt-hour meter using rotation of an Arago disk.

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