JPH0646200B2 - 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]

Now, assuming that the instantaneous value and the effective value of the load voltage are represented by e _R and V _R , respectively, and the load current i _R lags behind the load voltage e _R by the phase angle φ, the relation of the following equation There is.

Further, the reactive power Q _R is expressed by the following equation.

_{Q R = V R I R SIN} φ ... (3) where, ω: angular frequency t: is the time.

Here, by shifting the phase angle of the instantaneous value e _R shown in equation (1) by π / 2, the following equation Then, the instantaneous value e _R ′ and the instantaneous value I _{R of the} equation (2) are multiplied by the following equation to obtain e _R ′ × i _R = V _R I _R sinφ−V _R I _R cos (2ωt -π / 2-φ) ... give (5), thereby (3) the reactive power _{Q R} shown in the expression, i.e., it is possible to obtain a _{Q R = V R I R SIN} φ.

FIG. 7 is a block diagram showing the configuration of a conventional electronic reactive watt hour meter constructed according to this basic theory. In the figure, the transformer 1 outputs a voltage signal e proportional to the load voltage e _R.
While outputting _t , the current transformer 2 outputs a current signal i _t proportional to the load current i _R. Among them, the voltage signal e _t is the voltage signal e _q whose phase angle is delayed by π / 2 by the phase shifter 3.
Is converted to. Reactive power component is obtained and the current signal i _t that is output from the voltage signal e _q and current transformer 2 is multiplied by the multiplier 4. Incidentally, the current signal i _t sometimes input to the multiplier 4 is converted into a voltage mode. Here, if an integrator is used as the phase shifter 3, it is affected by the power supply frequency. Therefore, in order to remove this effect, the coefficient unit 5 that generates a coefficient value corresponding to the frequency and the output of the multiplier 4 Another multiplier 6 for multiplying the coefficient is provided. The reactive power value output from the multiplier 6 is converted into a pulse frequency by the integrator 7 and displayed on the display 8.

FIG. 8 is a circuit diagram showing the detailed configuration of the phase shifter 3, in which the non-inverting input terminal of the operational amplifier A ₁ is grounded, the inverting input terminal is connected to the input resistor R ₁ , and the inverting input terminal is The capacitor C ₁ is connected between the output terminals. When the voltage signal e _t proportional to the load voltage is input to this phase shifter, the output e _q becomes And a phase shift of π / 2 occurs. Here, V _t is the effective value of e _t .

The (6) voltage e _q shown in Formula maximum amplitude is Thus, the coefficient unit 5 and the multiplier 6 are provided in order to remove this effect because the constraint is 1 / ω.

FIG. 9 is a circuit diagram showing the detailed structure of the integrator 7. Here, the operational amplifier A ₂ , the input resistance R _M, and the capacitor C _F form an integrating circuit, and the level detector 11 is connected to the output terminal of this integrating circuit. Also, based on the output of the level detector 11, the capacitor C _F
A feedback pulse generator 12 is provided to discharge the electric charge charged in the. The amplitude of the feedback pulse generator 12 is determined by the output of the reference voltage (or reference current) circuit 13, and the time width is determined by the pulse width of the reference pulse generator 14.

Next, the operation of the integrator 7 will be briefly described with reference to the time chart of FIG.

Since the output voltage E _M of the multiplier 6 is applied to the input resistance R _M , it is converted into a current signal I _M = E _M / R _M. Here, when the output of the multiplier 6 is in the current mode, the input resistance R _M
Is unnecessary, and the output I _M of the multiplier 6 is directly input to the integrator. When this current I _M flows through the capacitor C _F , the output potential e _A of the operational amplifier A ₂ gradually drops. Then, when the potential drops to a value set in the level detector 11, the level detector 11 outputs a pulse e _L. Further, at this time, the feedback pulse generator 12 operates to output a feedback pulse having an amplitude I _S determined by the reference voltage circuit 13 and a time width τ _S determined by the reference pulse generator 14, and output the time of τ _S. Only the current I _S is fed back and the pulse e _F is output. As a result, Q = I
The electric charge of _S · τ _S is discharged, and the output potential of the salting amplifier A ₂ is restored during this period. At this time, the charged charge I _M
Since T _F and the discharged charge I _S · τ _S are equal, the following equation holds.

I _M · T _F = I _S · τ _S (7) F = 1 / T _F = I _M / (τ _S · I _S ) = E _M / (τ _S · I _S · R _M ) ... (8) However, T _F is the period of the pulse frequency output, and F is its frequency.

Thus, it can be seen that the integrator 7 integrates the reactive power into a proportional voltage signal or current signal and converts it into a pulse frequency.

[Problems to be solved by the invention]

In the above-mentioned conventional electronic reactive watt-hour meter, the influence of the frequency is removed by the coefficient unit 5 and the multiplier 6, but the number of components is relatively large, and the configuration is complicated by that amount, and at the same time, the cost is increased. There was a problem of rising prices.

The present invention has been made to solve the above problems, and an object thereof is to provide an electronic reactive watt-hour meter capable of simplifying the configuration and reducing the device cost.

[Means for solving problems]

In the electronic reactive watt hour meter according to the present invention, one of the signal proportional to the voltage of the load and the signal proportional to the current of the load is phase-shifted by the phase shifter including the first integrator to be the other. The signal obtained by multiplication is integrated by the second integrator, and a pulse corresponding to the unit reactive energy is generated each time the integrated value matches the product of the pulse width and pulse amplitude of the reference pulse signal. In the electronic reactive wattmeter, the pulse width or pulse amplitude of the reference pulse signal is changed so as to be inversely proportional to the frequency of the voltage of the load, and the reactive power caused by the phase shift of the first integrator is changed. It is characterized in that a frequency fluctuation compensating means for compensating the frequency fluctuation is provided.

[Work]

In the conventional electronic reactive energy meter shown in FIG. 7, the frequency fluctuation component was removed by the coefficient unit 5 and the multiplier 6, but the frequency fluctuation was eliminated by the integrator 7 shown in FIG. If the function of compensating for the minute can be easily added, the coefficient unit 5 and the multiplier 6 become unnecessary. From a different point of view, if a frequency fluctuation correction unit corresponding to the coefficient unit 5 is provided and its output is added to the feedback pulse generator 12 of the integrator 7, the coefficient unit 5 and the multiplier 6 are made unnecessary. At the same time, either the reference voltage circuit 13 or the reference pulse generator 14 can be removed. The present invention has been made in accordance with this idea.

That is, the output of the multiplier E _M (voltage mode) or I
_M (current mode), (6) the _{e q} output i of the current transformer 2
_Since it is calculated from the average value of the product of _t , (However, _{I t} is the effective value of the current signal _{i t)} as _{a, e q × i t = (} 2V t I t / R 1 C 1 ω) × sin (ωt-π / 2) sin (ωt-φ _{) = (V t I t /} R 1 C 1 ω) sin φ - (V t I t / R 1 C 1 ω) × cos (2ωtπ / 2-φ) is obtained, the table the average value of the following formula To be done.

E _M (or I _M ) = (V _t I _t / R ₁ C ₁ ω) sin φ = K ₁ (V _R I _R / R ₁ C ₁ ω) sin φ ... (9) However, K ₁ is a proportional constant Is.

The following equation is obtained from this equation (9) and the above equation (8).

F = E _M / (τ _s I _s R _M ) = K ₁ (V _R I _R / R ₁ C ₁ ω) × (1 / τ _s I _s R _M ) × sin φ = K ₂ (V _R I _{R sin φ) / (τ s I} s ω) ... (10) However, _{K 2} is a proportionality constant.

Here, τ _s or I _s and ω have the following relationship.

1 / τ _s = K ₃ ω or 1 / I ₃ = K ₄ ω where K ₃ and K ₄ are proportional constants.

Thus, the angular frequency ω of the load voltage can be removed from the equation (10) to obtain the pulse frequency F that is not affected by the frequency of the load voltage, and the configuration can be simplified and the device cost can be reduced.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the drawing, the same reference numerals as those in FIG. 7 denote the same elements. Then, the coefficient unit 5 and the multiplier 6 in FIG. 7 are removed, and instead of this, a period detector 21 is provided as a frequency fluctuation correction unit, and
As shown in FIG. 2, an integrator 7a from which the reference pulse generator 14 is removed is used instead of the integrator shown in FIG.

Here, as shown in the time chart of FIG. 3, the period detector 21 uses the sine wave voltage e output from the output of the transformer 1.
_The waveform of _t is shaped to obtain a pulse signal e _B ′, and the voltage signal e _B obtained by dividing the pulse signal by ½ is applied to the feedback pulse generator 12. This gives 1 / τ
_The frequency variation can be removed by setting _S = K ₃ ω.

Note that the pulse e _F shown in FIG. 2 may be required to have a frequency higher than the frequency of the load voltage e _R.
At this time, it is necessary for the reference pulse generator 14 shown in FIG. 9 to give a pulse having a frequency higher than the load voltage e _R to the feedback pulse generator 12. In this case, as shown in FIG. 4, the voltage signal e _t of the frequency f is fed to the PLL.
A pulse signal e _p having a frequency of N ₁ · f is input to a (phase-locked loop) type multiplication circuit 22 and divided by ½ to obtain a pulse width of 2π / (N ₁ ω). It suffices that the pulse signal of 1 is applied to the feedback pulse generator 12.

FIG. 5 shows that when the pulse e _F shown in FIG. 2 is required to have a frequency higher than the frequency of the load voltage e _R , a pulse signal having a pulse width of 2π / (N ₂ ω) is added to the feedback pulse generator 12. FIG. 9 is a block diagram showing the configuration of another embodiment for Here, the sine wave voltage e _t is waveform-shaped by the period detector 21 and the pulse signal e _B is output, while the sine wave voltage e _{t is}
A reference clock generator 24 that generates a clock signal having a frequency significantly higher than that of the reference clock generator 24
After dividing by 1 / N ₂ with AND, AND with pulse signal e _B
In addition to the gate 26, the output pulse thereof is counted by the counter 27, and the count value of the counter 27 is held by the latch 28.
Further, the clock of the reference clock generator 24 is counted by another counter 29, and the coefficient value and the value held in the latch 28 are compared by the coincidence detection circuit 30. And
A pulse is generated each time they match and is applied to the counter 29 as a reset pulse and also applied to the waveform shaping circuit 31. As a result, the waveform shaping circuit 31 outputs a period of 2π.
A pulse signal e _{p of} / (N ₂ ω) is output.

In all of the above embodiments, the reference pulse applied to the feedback pulse generator 12 is changed by the frequency, but the current value of the feedback pulse generator may be changed by the frequency instead. FIG. 6 shows an example thereof. The output pulse e _B of the period detector 21 and the clock of the reference clock generator 24 are added to the AND gate 26, and the output pulse is counted by the counter 27. Then, the coefficient value is held by the latch 28, and this is converted into the analog current signal I _S or the voltage signal E _S by the D / A converter 32. The analog signal I _S or E _S obtained in this way is a sinusoidal voltage e _t
Of inversely proportional to the frequency, in the case of E _S and current conversion 1 / I
Frequency correction according to _S = K ₄ ω becomes possible. As a result, the integrator 7b having a simple structure without the reference voltage circuit 13 is formed.
Can be used.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the frequency fluctuation of the reactive power due to the phase shift of the first integrator is used as the reference pulse signal related to the pulse frequency of the second integrator. Since a frequency fluctuation compensating means for compensating by changing the pulse width or the pulse amplitude so as to be inversely proportional to the frequency of the load voltage is provided, the configuration can be remarkably simplified as compared with the conventional device, and at the same time the device cost can be reduced. The effect is that you can.

The present invention can also simplify the configuration of the integrator itself. That is, an integrator that integrates the values obtained by multiplying two signals generally includes a reference voltage circuit having an accurate amplitude and a reference pulse generator having an accurate time width. In the present invention, since the pulse amplitude or the pulse width of the reference pulse signal is changed so as to be inversely proportional to the frequency of the voltage of the load, substantially either the reference voltage circuit or the reference pulse generator is removed. Therefore, the integrator itself can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention,
2 is a block circuit diagram showing the detailed construction of the main elements of the embodiment, FIG. 3 is a waveform diagram for explaining the operation of the embodiment, and FIG. 4 is a waveform diagram of the second embodiment of the present invention. FIG. 5 is a block diagram showing the configuration, FIG. 5 is a block diagram showing the configuration of the third embodiment of the present invention, FIG. 6 is a block circuit diagram showing the configuration of the fourth embodiment of the present invention, and FIG. FIG. 8 is a block diagram showing the configuration of the electronic reactive watt hour meter of FIG. 10, FIG. 8 is a block circuit diagram showing the detailed configuration of the main elements of the same device, and FIG.
The figure is a waveform diagram for explaining the operation of the apparatus. 1 ... Transformer, 2 ... Current transformer, 3 ... Phase shifter, 4 ... Multiplier, 7a, 7b ... Integrator, 8 ... Indicator, 21 ...
Cycle detector, 22 ... PLL type multiplying circuit, 24 ... Reference clock generator, 25 ... Divider, 26 ... AND gate, 27, 29 ... Counter, 28 ... Latch, 30 ...
... coincidence circuit, 31 ... waveform shaping circuit, 32 ... D / A converter.

Claims (1)

[Claims] 1. A signal obtained by phase-shifting one of a signal proportional to a voltage of a load and a signal proportional to a current of the load by a phase shifter including a first integrator and multiplying the other by the phase-shifter. Is integrated by a second integrator, and an electronic reactive energy meter that generates a pulse corresponding to the unit reactive energy every time the integrated value matches the product of the pulse width and the pulse amplitude of the reference pulse signal At a frequency for correcting the frequency variation of the reactive power caused by the phase shift of the first integrator by changing the pulse width or the pulse amplitude of the reference pulse signal so as to be inversely proportional to the frequency of the voltage of the load. An electronic reactive watt-hour meter characterized by having a fluctuation compensating means.