JPH09318678A - Alternating current measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the AC electricity quantity at a low sample frequency by sampling the commercial AC electricity quantity at every period divide with the prescribed time by a prime number of the specific value or above for measurement calculation. SOLUTION: A commercial AC input signal having the frequency of 50Hz or 60Hz is sampled at ever period divided with the minimum unit value of 100sec within the multiple times the period in common for the signals of 50Hz and 60Hz by a prime number of 7 or above (e.g. 8, 9, 11...). The number of samples in the fixed period is not changed when the input signal is 50Hz or 60Hz, and no frequency discriminating circuit is required. When sampling is made at every period uniformly dived with 100sec by a prime number of 7 or above, the apparent sampling frequency becomes five times, and the sampling frequency can be made low (about 1/5). The data read time of a micro-computer can be shortened, and the number of input signals can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the amount of alternating current such as current, voltage, and electric power of an alternating current signal of 50 Hz or 60 Hz by sampling, calculates the effective value or average value of the amount of alternating current, and outputs the measured information. Output, 50Hz and 6
The present invention relates to an AC measuring method and device that can be commonly used for 0 Hz.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional AC measuring device. In the figure, 1 is a current / voltage conversion device, 1a to 1d are current / voltage conversion circuits for converting the AC input signals from the first circuit to the fourth circuit into voltages, and 2 is an analog signal to a digital signal. A / D converter,
Reference numerals 2a to 2d are A / D conversion circuits for converting the analog output of the current / voltage conversion device 1 from the first circuit to the fourth circuit into digital signals, and 3 is a digital signal input from the first circuit to the fourth circuit. A multiplexer 4 which cyclically selects and outputs one of the four, a microcomputer 4 which stores and processes the measurement data obtained by the multiplexer 3 and converts it into output information, and 5 a speed and timing of the operation of the microcomputer 4. 6 is a clock circuit that controls the frequency of the AC input signal is 50Hz or 6
It is a frequency discriminating circuit for discriminating whether the frequency is 0 Hz.

Next, the operation of the conventional AC measuring device will be described. The AC input signal is converted into a voltage signal by the current / voltage conversion device 1 and then input into the A / D conversion device 2, where it is converted into a digital signal and input into the multiplexer 3. The multiplexer 3 samples each of the first to fourth digital signals by the sample signal sent from the microcomputer 4 and inputs them to the microcomputer 4. The microcomputer 4 operates in synchronization with the clock sent from the clock circuit 5. The microcomputer 4 reads the digital signal and stores the digital signal in synchronization with the multiplexer 3. The microcomputer 4 reads the stored digital data and executes various electric quantities such as the effective values of the currents of the first circuit to the fourth circuit as measurement outputs.

Sampling is performed for one cycle of the AC input signal. For example, the frequency of the AC input signal is 50H
In the case of z, if one cycle of input is sampled 10 times per circuit, the sampling frequency per circuit is 5
It becomes 0 × 10 = 500 Hz. The time interval of each sampling is 1/500 = 0.002 seconds = 2 ms. Since there are four input circuits, the frequency of the sample signal sent from the microcomputer 4 is 500 × 4 = 2000H.
z, the sampling time is 1/2000 = 0.5 ms.

As shown in FIG. 7, the microcomputer 4 has data (i) sampled by the multiplexer 3.
_1-1 , _i2-1 , _i3-1 , _i4-1 , _i1-2 , _i2-2 , ...
・ I _4-1 0 ...) is stored and calculation is performed.

When obtaining the effective value of the input signal, the effective value of the first circuit is The effective value of the second circuit is The effective value of the third circuit is The effective value of the fourth circuit is Becomes

Since the sampling of the input data is carried out at a frequency obtained by dividing one cycle by an integer, the number of samples per cycle is always constant (in this example, it is always 10) even if the measurement points are shifted. The measurement error between the first to fourth input circuits is small. Moreover, the measurement error decreases as the number of samplings per cycle increases.

Since sampling is performed for one cycle of the AC input signal, for example, the frequency of the AC input signal is 6
In the case of 0 Hz, if one cycle of input is sampled 10 times per circuit, the sampling frequency per circuit is 60 × 10 = 600 Hz. The time interval of each sampling is 1/600 = 0.017 seconds = 1.7 milliseconds.

Since there are four input circuits, the frequency of the sample signal sent from the microcomputer 4 is 600.
× 4 = 2400Hz, sampling time is 1/2400
= 0.42 msec. If the frequency of the sampling signal sent from the microcomputer 4 is set to 2000 Hz which is the same as 50 Hz, one cycle will be divided into 8.3 equal parts, and one cycle will be divided into 8 parts by the deviation of the sampling points.
There will be cases of sampling 7 times and cases of sampling 7 times. Therefore, the measurement accuracy deteriorates due to the deviation of the measurement points, that is, the measurement error between the input circuits increases.

Therefore, the frequency discriminating circuit 6 for discriminating whether the AC signal input from the first circuit to the fourth circuit is 50 Hz or 60 Hz and transmitting the result to the microcomputer 4 is required. . The microcomputer 4 determines whether the frequency of the sample signal should be 2000 Hz or 2400 Hz based on the information of the frequency discrimination circuit.

Further, in this example, the four input circuits, that is, the first to fourth circuits, are explained. However, when the number of input circuits increases, it is necessary to increase the frequency of the sample signal. For example, if the number of input circuits is 8, 2 in the case of 4 circuits
Double frequency, that is, when the frequency of the input signal is 50 Hz, the frequency of the sample signal is set to 4 kHz, and when the frequency of the input signal is 60 Hz, the frequency of the sample signal is 4.8.
Must be set to kHz.

[0012]

Since the conventional AC measuring apparatus samples at a frequency obtained by dividing one cycle of the input signal by an integer, it is necessary to have a frequency judging circuit for judging the frequency of the input signal. There was a problem.

Further, in the measurement by the sampling method, the sampling frequency needs to be set sufficiently higher than the frequency of the input signal to be measured, for example, it is necessary to set it at least about 10 times the frequency of the input signal. Therefore, in the conventional AC measurement device, it is necessary to perform sampling about 10 times for all input circuits in one cycle. When the number of input circuits is large, the multiplexer is operated at high speed to read the data at high speed. It is necessary for the microcomputer to read the input data frequently, and other operations such as calculation cannot be performed.
There is a problem that the number of input circuits that can be measured is limited.

The present invention has been made in order to solve such a problem, and can measure both 50 Hz and 60 Hz of an input signal without error without a frequency discriminating circuit, and moreover, even with a multi-circuit input signal at a low sampling frequency. It is an object of the present invention to obtain an alternating current measuring method and device capable of measuring accurately.

[0015]

According to an AC measuring method of the present invention, commercial AC electricity is measured and calculated for sampling data in units of a predetermined time, and sampling is performed with a prime number n of 7 or more for a predetermined time. The effective value of the alternating-current electricity amount is output as the measurement information by performing the operation in the cycle divided by.

The predetermined time for measuring and calculating the sampling data is in the unit of 100 msec. When the measured commercial AC electricity quantity is plural, the sampling clock frequency is set to 10 × n × the measured quantity, and the sampling data of the measurement calculation object of each measured AC electricity quantity is taken out every 1 / measured quantity. It was done.

Further, in sampling, the latest sampling value is sequentially adopted for the number of data of the division prime number n minus 1 to be measured and the oldest sampling value is discarded, and the sampling data is measured and calculated. is there.

An AC measuring device according to the present invention is a voltage converting device for converting a commercial AC electric quantity into a voltage signal, an A / D converting device for converting a voltage signal converted by the voltage converting device into a digital signal, A multiplexer for sampling the output of the A / D conversion device, and a microcomputer for computing the output of the multiplexer and outputting the effective value of the AC electric quantity as measurement information, and determining the sampling period of the multiplexer.
The microcomputer is configured to perform measurement calculation of sampling data in units of 100 msec and to perform sampling in the multiplexer at a cycle in which 100 msec is divided by a prime number n of 7 or more.

Further, the voltage conversion device and the A / D conversion device include a plurality of voltage conversion circuits corresponding to respective input signals and a plurality of A / D conversion devices when there are a plurality of AC electric quantities to be measured.
A D conversion circuit is provided, the sampling clock frequency in the microcomputer is set to 10 × n × the number to be measured, and the clock position of 1 / number to be measured is sequentially set as data to be calculated by the multiplexer.

Further, in the sampling, the microcomputer sequentially adopts the latest sampling value for the number of data of the division prime number n minus 1 to be measured and calculated,
The oldest sampling value is discarded and the sampling data is measured and calculated.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. FIG. 1 is a block diagram showing Embodiment 1 of the present invention. In the figure, 1 to 5 are the same as those explained in the conventional device.

Next, the operation of the alternating-current measuring device having the above structure will be described. The first to fourth input signals are current /
After being converted into voltage signals in the voltage conversion circuits 1a, 1b, 1c, 1d, the A / D conversion circuits 2a, 2b, 2c, 2
It is converted into a digital signal (quantity) by d, sampled at a constant cycle by the multiplexer 3, and input to the microcomputer 4. The microcomputer 4 stores the sampled input signal, calculates the input signal for each circuit, for example, calculates the effective value, and outputs the measured information. The sampling of the multiplexer 3 is performed according to the cycle determined by the microcomputer 4.

The frequency of the commercial power source as the input signal is 50H.
Being limited to z or 60 Hz, the sampling period is determined as follows. 50Hz signal and 60Hz
When the time for which the signals in common have an integral multiple cycle is obtained,
100 msec, 200 msec, 300 msec, ...
The smallest value, 100 msec, can be considered as one unit. If sampling is performed by dividing 100 msec by an integer, the number of samples within a fixed cycle (5 cycles for 50 Hz and 6 cycles for 60 Hz) does not change regardless of whether the input signal is 50 Hz or 60 Hz. Therefore, when 50HZ is used as the input signal,
There is no difference in the calculation result of the microcomputer 4 when z is an input signal. Therefore, the input signal is 5
Sampling can be performed without having to determine whether it is 0 Hz or 60 Hz.

Next, how many divisions of 100 msec will be described. As shown in FIG. 2, when the input signal is 50 Hz, there are 5 cycles of the input signal in 100 msec.
When sampling is performed at a time that is 00 msec divided into five equal parts, it is equivalent to always sampling at the same position for one cycle, and only one point is sampled for one cycle. When sampling is performed by dividing 100 msec into six equal parts, it is equivalent to sampling six points in one cycle, and the apparent sampling frequency is 5
Double. When sampling is performed by dividing 100 msec into seven equal parts, it is equivalent to sampling seven points in one cycle, and the apparent sampling frequency is five times. Similarly, 8 equal parts, 9 equal parts, 11 equal parts, 12 equal parts,
The apparent sampling frequency when divided into 13 equal parts and 14 equal parts is 5 times the actual sampling frequency.

It is assumed that the division is started from the zero-cross point (rising zero-cross) of the first cycle of the input signal. When 5 cycles of 100 ms are divided into 7 equal parts, they are divided as shown in FIG. Find out how far each split point is from the rising zero-cross point. If the number of divisions is divided by the number of cycles, then 7/5 = 1 + 2/5. If the length of the division point is 1, the length of one cycle is 1 and 2/5. Therefore, the point has a length of 1 from the rising zero-cross point. The length of the point is 1-2 / 5 = 3/5 from the rising zero-cross point. Two
The length of the cycle is 7/5 × 2 = 2 + 4/5. Therefore, the point of is 1-4 / 5 = 1 / from the zero cross point.
The length is 5. The length of 3 cycles is 7/5 × 3 = 4 + 1
It becomes / 5, and the point becomes ⅕ from the rising zero cross point. Therefore, the point becomes a length of 1-1 / 5 = 4/5 from the rising zero-cross point. The length of four cycles is 7/5 × 4 = 5 + 3/5. Therefore, the point of becomes 1-3 / 5 = 2/5 from the rising zero-cross point.

Thus, the value obtained by dividing the number of divisions by the number of cycles is obtained as a fraction, multiplied by 1, doubled, tripled, and multiplied by 4 to find the value excluding the integer part. , 1/5, 3/5, and it is understood that each division point is at a different distance from the rising zero-cross point. In the same way, when the fraction is calculated, in the case of 8 equal parts, 3/5, 1/5, 4/5, 2/5
And each division point is at a different distance from the rising zero-cross point.

FIG. 3 shows the case where the input signal is 60 Hz.
Since there are 6 cycles of input signal at 100 msec, 100
When sampling is done by dividing msec into 6 equal parts, it is always 1
It is equivalent to sampling at the same position in the cycle,
Only one point in one cycle is sampled. When sampling is performed by dividing 100 msec into seven equal parts, it is equivalent to sampling seven points in one cycle, and the apparent sampling frequency is six times. When sampling is performed by dividing 100 msec into eight equal parts, it is equivalent to sampling four points in one cycle, and the apparent sampling frequency is tripled.

Similar to the case of 50 Hz, a fraction obtained by dividing the number of divisions by the number of cycles is obtained, and the value obtained by multiplying by 1, 2, 3, 4, 5 times the integer part is divided into 7 equal parts. In case of, 1/6,
It is 2/6, 3/6, 4/6, 5/6, and it can be seen that each division point is at a different distance from the rising zero cross point. For 8 equal parts, 2/6, 4/6, 0 /
It becomes 6, 2/6, and 4/6, and it can be seen that among the divided points, some are at the same distance from the rising zero-cross point.

When the division points of 50 Hz and 60 Hz are at different distances from the rising zero-cross point, the apparent sampling frequency is 5 times at 50 Hz and 6 times at 60 Hz. 5 times when apparent sampling frequency is 50 Hz and 6 when it is 60 Hz
If we ask for a division that doubles, 7, 11, 13, 1,
It turns out that it is 5, 17, 19, 23, 27, ... (Prime number).

Embodiment 2 FIG. The microcomputer 4 preliminarily selects an appropriate value from among the prime numbers, selects 7 as the prime number, and divides 100 msec by the selected prime number 7. That is, for one measurement sampling, the input signal may be sampled at a sampling frequency of 70 Hz.
Therefore, when there are a plurality of measured signals, for example, when the measured signal is input from four circuits, the sampling clock from the clock circuit 5 is set to 70 × 4 = 280 Hz at a minimum, and the multiplexer 3 divides each into 1/4. By sequentially setting the clock position as the data to be calculated, it is possible to simultaneously measure four circuits. That is, a plurality of measured circuits can be sampled at a sampling frequency of the number of measured circuits multiplied by 10 times the prime number n.

The microcomputer 4 receives 1 of the input signal.
The following electric quantity calculation is performed in units of 00 msec. As shown in FIG. 4, when n = 7 when 100 ms is divided into seven, the effective value of the first circuit is The effective value of the second circuit is The effective value of the third circuit is The effective value of the fourth circuit is Becomes

Embodiment 3. FIG. 5 is a diagram for explaining a situation in which measurement calculation of sampling values is performed in the third embodiment of the present invention. In this figure, 100 ms is divided into 7 parts. Of the sampling timings divided into seven, the seven data from the back are targeted for calculation. These seven pieces of data are sampling data of each part corresponding to one cycle regardless of whether the measured commercial alternating current is 50 Hz or 60 Hz, and the measurement value D1 for the first 100 msec (sampling timing) is obtained by arithmetic processing. To be In the next sampling, the measurement value D is calculated for the seven data from sampling timing
Get 2. As described above, by discarding the data of the oldest sampling timing and adopting the data of the latest sampling timing as the target of the arithmetic processing, it is possible to quickly follow the fluctuation of the measured value of the measured commercial AC.

[0033]

As described above, according to the present invention, 50
Since the input signal of Hz or 60 Hz is divided into prime numbers in units of 100 ms, sampling is performed at 50 Hz and 60 Hz.
A circuit for discriminating the HZ is unnecessary, and a product can be constructed with a simple circuit configuration. Moreover, since the sampling frequency can be lowered (⅕ of the conventional method), the time required for the microcomputer to read the data can be shortened, and the number of input signals that can be input by the microcomputer can be increased. When the number of input circuits of the microcomputer does not have to be increased, the processing speed of the microcomputer can be slowed down, so that there is an effect that an inexpensive low speed microcomputer can be used and an inexpensive measuring device can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an AC measuring device according to a first embodiment of the present invention.

FIG. 2 is a waveform chart illustrating an operation of the first embodiment of the present invention.

FIG. 3 is a waveform diagram illustrating the operation of the first embodiment of the present invention.

FIG. 4 is a waveform diagram illustrating the operation of the second embodiment of the present invention.

FIG. 5 is a waveform diagram illustrating the operation of the third embodiment of the present invention.

FIG. 6 is a block circuit diagram showing a conventional AC measuring device.

FIG. 7 is a waveform diagram illustrating an operation of a conventional AC measuring device.

[Explanation of symbols]

1 current / voltage converters 1a, 1b, 1c, 1d current / voltage converters, 2 A / D converters 2a, 2b,
2c, 2d A / D conversion circuit, 3 multiplexer, 4
Microcomputer, 5 clock circuits.

Claims (7)

[Claims] 1. An alternating current electric quantity is obtained by measuring and calculating sampling data for a commercial alternating current electric quantity in units of a predetermined time, and sampling is performed in a cycle in which the predetermined time is divided by a prime number n of 7 or more. The alternating current measurement method is characterized in that the effective value of is output as measurement information. 2. The alternating current measuring method according to claim 1, wherein the predetermined time for measuring and calculating the sampling data is 100 msec. 3. When a plurality of commercial alternating-current electricity quantities are measured, the sampling clock frequency is set to 10 × n × the number to be measured, and the sampling data of the measurement calculation target of each measured alternating-current electricity quantity is calculated every 1 / number of the measured objects. The AC measuring method according to claim 1 or 2, characterized in that the AC measuring method is used. 4. In sampling, the latest sampling value is sequentially adopted with respect to the number of division primes n−1 of the measurement calculation target, and the oldest sampling value is discarded, and the measurement calculation of sampling data is performed. The alternating current measuring method according to claim 1, wherein the alternating current measuring method is performed. 5. A voltage converter for converting a commercial AC electricity quantity into a voltage signal, an A / D converter for converting a voltage signal converted by the voltage converter into a digital signal, and this A / D
A multiplexer that samples the output of the conversion device, and a microcomputer that performs arithmetic processing on the output of this multiplexer and outputs the effective value of the alternating-current electricity amount as measurement information, and also determines the sampling period of the multiplexer, wherein the microcomputer is , 100
The sampling data is measured and calculated in the unit of msec, and the sampling by the multiplexer is performed at 10
An alternating current measuring device, characterized in that 0 msec is divided by a prime number n of 7 or more. 6. The voltage conversion device and the A / D conversion device are provided with a plurality of voltage conversion circuits and a plurality of A / D conversion circuits corresponding to respective input signals when a plurality of measured AC electric quantities are included, 6. The AC measuring apparatus according to claim 5, wherein the sampling clock frequency in the computer is 10 * n * the number to be measured, and the clock position of 1 / the number to be measured is sequentially used as data to be calculated by the multiplexer. 7. A sampling arithmetic operation for sampling data, wherein the microcomputer sequentially adopts the latest sampling value with respect to the number of divided prime numbers n minus 1 in the sampling operation, discarding the oldest sampling value. The alternating current measuring device according to claim 5 or 6, wherein