JPH0646201B2 - Electronic reactive energy meter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic reactive watt-hour meter, and more particularly to correction of a frequency variation when an integrator is used as a phase shifter.

[Conventional technology]

In power trading, the unit price may change depending on the power factor. This power factor cosφ can be calculated by the following equation if the power amount P and the reactive power amount Q are measured.

Fig. 4 shows an electronic watt-hour meter (hereinafter referred to simply as watt-hour meter)
2 is a block diagram showing a schematic configuration of a signal V (hereinafter referred to as a load voltage) proportional to a load voltage of a power supply line (not shown) and a signal I (hereinafter referred to as a load current) proportional to a load current. , Where a voltage or current signal proportional to the product of load voltage V and load current I is obtained. This voltage signal or current signal is converted into the pulse converter 2
Is converted into a pulse having a frequency proportional to its magnitude. Next, this pulse is integrated by the meter 4, and the integrated value is displayed on the display 5 as the electric energy P.

Since such a watthour meter is used in large numbers, an integrated circuit element 3 has been developed in which the functions of both the multiplier 1 and the pulse converter 2 are integrated, and the load voltage V,
Only by inputting the load current I, a pulse having a frequency proportional to the product can be obtained.

On the other hand, an electronic reactive watt hour meter (hereinafter, simply referred to as a reactive watt hour meter) uses a load voltage V of 90% instead of the load voltage V described above.
By applying the phase-shifted voltage to the multiplier 1, the integrated pulse value of the meter 4 is displayed on the display 5 as the reactive power amount Q.

By the way, as a phase shifter used for measuring the reactive power, a 90 ° phase shift circuit to which three-phase balance is applied has been used conventionally, but recently, as shown in FIG.
The so-called integrating circuit, in which the input resistance R is connected to the input terminal of and the capacitor C is connected between the input terminal and the output terminal, has come to be used.

The effective value of the input voltage of the phase shifter shown in this FIG. 5 V _in,
Assuming that the effective value of the output voltage is V _out , the angular frequency is ω, and the constant is k, there is a relation of V _out = k · V _in · 1 / ω (2), and the influence of the frequency is Will receive.

Therefore, as shown in FIG. 6, a multiplication type digital-analog converter (hereinafter referred to as a D / A converter) 7 is provided at the subsequent stage of the phase shifter 6, and the counter 8 detects the cycle of the load voltage V. The detected value was given to the D / A converter 7 to correct the frequency fluctuation.

Although this method has an advantage that the integrated circuit element 3 used for the watt-hour meter can be used as it is, normally, since the reactive watt-hour meter is used in a three-phase circuit, two 90 ° phase shift correction circuits are required. Become. Therefore, as shown in FIG. 7, the load voltage V is phase-shifted by 90 ° using the phase shifter 6 and the multiplier 1 multiplies the load current I, and the multiplication output is D / A converted. Bowl 7
And the counter 8 for correction, or
As shown in the figure, when the output of the multiplier 1 is converted into the pulse frequency, the reference voltage of the pulse converter 2 is adjusted by the D / A converter 7 and the counter 8 to correct the influence of the frequency. It was

Thus, with the watt-hour meter shown in FIG. 4 and the reactive watt-hour meter shown in any of FIGS. 6 to 8, the power factor cosφ shown in equation (1) is obtained and the unit price of electric power is determined. can do.

[Problems to be solved by the invention]

Each of the above-mentioned conventional reactive energy meters uses a D / A converter, and therefore has a problem that a lot of labor and time are spent for the adjustment.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a reactive power meter capable of significantly reducing the labor and time required for adjustment until commercialization.

[Means for solving problems]

According to the present invention, as shown in FIG. 1, a load voltage V of a power supply line is phase-shifted by a phase shifter 6 including an integrator and multiplied by a load current I by a multiplier 1, and the obtained signal is obtained. The pulse converter 2 converts the pulse into a pulse having a frequency proportional to its magnitude, and the frequency fluctuation correction circuit 10 further thins this pulse by a number proportional to the difference between the cycle of the load voltage V and the reference cycle, or After the correction of whether or not to superimpose the pulse is added, it is integrated by the meter 4 and displayed on the display 5 as a reactive power amount.

[Work]

In the present invention, since the number of pulses to be accumulated in the integrator is corrected according to the cycle of the load voltage, the D / A converter used in the conventional device becomes unnecessary, and the labor of adjustment is thereby improved. And the time can be shortened.

〔Example〕

FIG. 2 shows a pulse converter 2 according to an embodiment of the present invention.
Fluctuation compensating circuit 1 inserted between the measuring instrument 4 and the measuring instrument 4
In the block diagram showing the detailed configuration of 0, when the load voltage V is input, the D-type flip-flops 11 to 13 for opening the gate G from the rising of the voltage to the next rising.
And a clock pulse CL having a frequency sufficiently higher than the voltage frequency as one input, the D-type flip-flop 1
An AND gate (hereinafter simply referred to as a gate) 14 that receives the output of 2 as the other input, an 11-bit binary counter 15 that counts the output pulse of this gate 14, and a pulse Q that is output from the pulse converter 2 Then, the gate 19 is opened until the count value reaches a predetermined value, and then the gate 19 is closed until the count value matches the counter 15.
The bit control counter 17, a matching circuit 16 that compares the count value of the load voltage for one cycle of the counter 15 with the current count value of the counter 17, and outputs a match signal when the two match, and the matching circuit 16. 16 coincidence signal and a signal indicating that the count value of the control counter 17 has exceeded a predetermined value are logically ANDed, and the outputs thereof cause the counter 15 and the control counter 17 to return to 0 and the D-type flip-flop 11 And a gate 18 for resetting the.

First, the fluctuation range of the frequency of the power supply line is 57 to 63 Hz.
Then, the D-type flip-flop 11 sets the output terminal Q to “H” at the rising of the load voltage, and when the output is “L” → “H”, the D-type flip-flop 12 sets the output to “H”. To do. When the output of the D flip-flop 12 becomes "H", the gate 14 opens and the clock pulse CL
Pass through. The D-type flip-flop 13 at the next rise of the load voltage changes from "L" to "H" and resets the D-type flip-flop 12, so that the gate 14 is gated only for one cycle from the rise to the rise of the load voltage. Open, gate 14 closes, then counter 1
The operation of closing the gate is repeated until the rising after the count value of 7 and the count value of the counter 15 match. The frequency of the clock pulse is 64.512KH
If z, the number of clock pulses counted by the counter 15 is 1024 at 63 Hz and 1075 at 60 Hz.
And 1132 at 57 Hz. Next, the control counter 17 outputs the output pulse Q of the pulse converter 2 (for example, 1
(Pulses / 3.6 seconds) is counted, the gate 19 is opened until just before the value becomes 1024, and the gate 19 is opened while the count value is 1024 or more and the most significant bit is “H”.
Keep closing. After that, when the count value of the counter 15 matches, the control counter 17 is reset to 0, thereby opening the gate 19. The coincidence circuit 16 detects the coincidence, and when the both count values coincide, the counter 1
5 and 17 are reset to 0, and the D flip-flop 11 is reset. The gate 18 is the coincidence circuit 16
Output a coincidence signal and a signal indicating that the count value of the control counter 17 is 1024 or more to obtain a logical product and prevent the signal from returning to 0 before that.

When the D-type flip-flop 11 is reset, the D-type flip-flop 11 is inverted at the next rise of the voltage frequency, which causes the D-type flip-flop 13 to be inverted and the next period measurement is started. Since the frequency of the output pulse Q of the pulse converter 2 is sufficiently lower than the frequency of the clock pulse CL, the control counter 17 is used during the period measurement.
Does not reach 1024.

In this way, 51 pulses are thinned out at 60 Hz and 108 pulses are thinned out at 57 Hz, and the output pulse Q increases as the frequency of the power feeding line decreases, but the gate Q is reduced by that amount. Since 19 thins out the pulse, the pulse whose frequency fluctuation is corrected is applied to the measuring instrument 4.

In this embodiment, the case where the upper limit frequency of the power supply line is set has been described, but it is also possible to set the lower limit frequency of the power supply line and add a pulse when the frequency becomes high. FIG. 2A shows a configuration example of the above.

In FIG. 2A, the same reference numerals as those in FIG. 2 denote the same elements. Then, the gate 14, the coincidence circuit 16, and the gates 18 and 19 in FIG. 2 are removed, respectively, and gates 21, 22 and 23 are provided instead. Of these, the gate 21 is an AND gate which receives the reference clock signal as one input and the status signal of the most significant bit of the counter 15 as the other input and adds the output to the counter 15. The gate 22 is an AND gate having the output signal of the gate 21 as one input and the output signal of the D-type flip-flop 12 as the other input. The gate 23 receives the output of the pulse converter 2 (FIG. 2) as one input, and the gate 2
It is an OR gate having the output of 2 as the other input, and the output thereof is added to the control counter 17 and is also output as a correction signal for the frequency fluctuation.

The operation of the embodiment shown in FIG. 2A will be described, particularly focusing on the part having a different configuration from that of FIG.

First, 48.126H as the reference clock pulse CL
A pulse signal of z is applied to the gate 21. Further, it is assumed that the D-type flip-flop 11 is reset by the output of the control counter 17, and at the same time, the counter 15 and the control counter 17 are reset to 0. From this point, the output of the D-type flip-flop 12 is “H” → “L” → “H” → “L” → ... every other cycle of the load voltage.
Repeat. At this time, since the gate 21 is opened, the counter 15 counts the clock pulse CL. And
When the count value of the counter 15 reaches 1024, that is, when the most significant bit becomes "H", the gate 21 is closed. Therefore, the counter 15 holds this state until it is reset. .

The pulse signal applied to the counter 15 through the gate 21 is also applied as one input of the gate 22, but when the output of the D-type flip-flop 12 is "H", the gate 22 is closed and "L". Is opened.

Here, if the frequency of the power line is 47 Hz, until the counter 15 starts counting and counts 1024,
Since the output of the flip-flop 12 is "H",
During this time, the gate 20 is closed and does not output a pulse. However, if the frequency of the power line is 50 Hz,
When the counter 15 counts 964, the D-type flip
Since the flop 12 changes from “H” to “L”, the gate 22 is opened and the counter 15 is set to 1 from this change point.
When counting 024, the gate 21 is closed and no pulse is applied to the gate 22. That is, 60 pulses are output from the gate 22.

Next, the output Q of the pulse converter 2 (FIG. 1) is output to the gate 23.
The output of the gate 23 is output as a correction signal for the frequency fluctuation while being added to the control counter 17 via the. At this time, the control counter 17 is the counter 15 described above.
At the same time, counting is started. Then, when the value becomes 1024, the reset signal for the D-type flip-flop 11 and the 0 return signal for the counters 15 and 17 are output.

In this process, assuming that the frequency of the power line is 47 Hz, the measuring instrument 4 (FIG. 1) is adjusted,
When the frequency becomes 50 Hz, it is necessary to give the meter 4 a pulse in which the count value 1024 of the control counter 17 is corrected by a value corresponding to the frequency difference.
Therefore, in this embodiment, pulses corresponding to the frequency difference, that is, 60 pulses are output from the gate 22,
This pulse is added to the gate 23 to correct the frequency fluctuation.

In this case, since the pulse frequency of the output Q of the pulse converter 2 is much lower than the pulse frequency output from the gate 22, even if the pulses are applied to the gate 23 at the same time, the error is only one pulse. Is clear.

In this way, the output pulse Q of the pulse converter 2 is set to 1
It can be corrected every 024 pulses.

Moreover, in the embodiment shown in FIG.
While the number of pulses to be accumulated by the measuring instrument 4 is collectively thinned while counting more than 24, for example, the counter 1
When 5 counts 20 clock pulses and thins out the integrated pulse for the time corresponding to one clock pulse, the influence of variations in pulse intervals is eliminated. However, the pulse constant of the instrument is actually 1000 pulses / k.
Since it is more than Var · s, it does not matter if you thin out all at once.

Thus, according to the embodiment shown in FIG. 2 and FIG. 2A, the D / A converter is not necessary, and the labor and time for adjustment can be shortened. Further, compared with the conventional reactive energy meter shown in FIGS. 7 and 8, it is advantageous in that the integrated circuit element 3 used in the energy meter can be used as it is.

In addition, in a multi-fee system in which a time zone meter, maximum demand power meter, etc. are contained in one box, a microcomputer (hereinafter referred to as CPU) for time measurement is built in, and Even if the control circuit is not provided, the measurement value of the counter can be easily added or subtracted every time measurement of 10 bits is performed.

Further, in the above-described embodiment, the configuration in which the pulse is thinned out by using the counter and the gate and the one in which the pulse is added have been described, but the present invention is not limited to this, and an electronic device including a CPU is used. With a reactive watt hour meter, it is possible to provide the same function as described above simply by adding a program. The processing procedure in this case is the third
A description will be given according to the flowchart in the figure.

First, the period of the power supply line is measured by counting the reference clock pulses, the count value is t ₀ , the number of pulses corresponding to the reference period is t, and if t = t ₀ , the pulse converter 2 The pulse is output as it is (step 101-).
104).

Next, in the case of t ≠ t ₀ , the correction pulse n is calculated, and the pulse number N _i indicating how many pulses one pulse is to be corrected is calculated. A rising edge is detected, and a pulse is output at the rising edge until N = N _i with respect to the value N of the counter which is incremented by 1 in sequence (steps 105 to 111).

Next, when N = N _i , the above-mentioned t and t ₀ are compared to determine whether the pulse is thinned out or added,
When adding a pulse, after outputting the pulse corresponding to the received pulse, the falling edge of the pulse of the converter 2 is detected, and at this point, one additional pulse is output (step 1
12 to 115), in the case of thinning out, the process proceeds without outputting a pulse, and increments the counter value I by 1 by 1 until N = n ₀ is added by 1 (steps 116 to 117). Then, when N = n ₀ , the process proceeds to step 101 and the subsequent steps.

If the reference frequency is set to the highest frequency to be used, it is only necessary to thin out the pulses, and the program will be simplified.

Thus, the CPU can also correct the frequency variation.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the integrated pulse applied to the measuring instrument is corrected according to the surroundings of the load voltage, so that the D / A converter used in the conventional device is used. Is unnecessary, which has the effect of reducing the labor and time for adjustment.

[Brief description of drawings]

1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2A is a block diagram showing the configuration of another embodiment of the present invention, and FIG. FIG. 4 is a flow chart showing a concrete processing procedure when a microcomputer is used as another embodiment, FIG. 4 is a block diagram showing a schematic configuration of a general electronic watt-hour meter, and FIG. 5 is electronic reactive power. A circuit diagram showing the configuration of a general phase shifter used in a meter, and FIGS. 6 to 8 are block diagrams showing the configuration of a conventional electronic reactive power meter, respectively. 1 ... Multiplier, 2 ... Pulse converter, 3 ... Integrated circuit element, 4 ... Measuring instrument, 5 ... Display, 6 ... Phase shifter, 10
...... Frequency fluctuation correction circuit, 11 to 13 ...... D-type flip-flop, 14, 18, 19 ...... AND gate, 1
5 ... Counter, 16 ... Matching circuit, 17 ... Control circuit.

Claims (1)

[Claims] 1. A phase shift of either one of a signal proportional to the voltage of a load and a signal proportional to the current of the load and multiplication with the other, and the obtained signal is converted into a pulse having a frequency proportional to its magnitude. In an electronic reactive watt-hour meter that converts and integrates this pulse with an integrator to obtain reactive energy, the number of accumulated pulses of the integrator is equal to the number proportional to the difference between the cycle of the load voltage and the reference cycle. An electronic reactive watt-hour meter, which is provided with a frequency fluctuation correction unit that increases or decreases.