JPH01114763A - Electronic watthour meter for reactive power - Google Patents

Abstract

PURPOSE:To simplify the constitution and to reduce the cost by varying the pulse width or the pulse amplitude of a reference pulse signal so as to be in inverse proportion to a frequency of a voltage of a load and correcting a frequency fluctuation portion of reactive power caused by phase-shifting. CONSTITUTION:A signal from a transformer 1 being in proportion to a voltage of a load is brought to phase-shifting through a phase shifter 3 and multiplied by a signal from a current transformer 2 being in proportion to a current of the load by a multiplier 4. Whenever the obtained signal coincides with the product of pulse width and pulse amplitude of a reference pulse signal, a pulse corresponding to unit reactive energy is generated. Subsequently, by a period detector 21, the pulse width or the pulse amplitude of the reference pulse signal is varied so as to be in inverse proportion to a frequency of the voltage of the load and a frequency fluctuation portion of reactive power caused by phase- shifting of an integrator in the phase shifter 3 is corrected. In such a way, a counter, a multiplier, etc. for eliminating the frequency fluctuation portion become unnecessary and the constitution is simplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronic reactive energy meter, and particularly relates to correction of frequency fluctuations when an integrator is used as a phase shifter. .

[Conventional technology]

Now, the instantaneous value and effective value of the load voltage are expressed by g and VR, respectively, and the instantaneous value and effective value of the load current are expressed by i and h, and the load current IR lags the load voltage eH by the phase angle φ. Assuming that, there is a relationship between these as shown in the following equation.

eR-J 2VR8INωt −(1)i
-J21 5IN (ω is one φ) ...(
2) RR In addition, the reactive power QR is expressed by the following formula.

QR” VRI RSINφ ・(3)
However, ω: angular frequency t: time.

Here, the phase angle of the instantaneous value eR shown in equation (1) is π/2
Shift by the following formula e R' −J 2 VRSIN (ωt yr /
2) ...(4) is obtained, and this instantaneous value eR' and (2
) by the instantaneous value IR of the equation as shown below to obtain eR'
2-φ)-(5), and thereby the reactive power charge shown in equation (3), that is, QR-VRIRSINφ can be obtained.

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 generates a voltage signal e proportional to the load voltage eH.
t, while the current transformer 2 outputs a current signal it proportional to the load current IR. Among these, the voltage signal et is a voltage signal e whose phase angle is delayed by π/2 by the phase shifter 3.
is converted to This voltage signal e and the current signal 11 output from the current transformer 2 are multiplied by a multiplier 4 to obtain a reactive power component. Note that the current signal it may be converted into voltage mode and input to the multiplier 4. Here, if an integrator is used as the phase shifter 3, it will be affected by the power supply frequency, so in order to remove this effect, a coefficient unit 5 that generates a coefficient value corresponding to the frequency and an integrator that generates a coefficient value corresponding to the frequency and the output of the multiplier 4 are used. Another multiplier 6 for multiplying the coefficients is provided. The reactive power value output from the multiplier 6 is converted into a pulse frequency by an integrator 7 and displayed on a display 8.

FIG. 8 is a circuit diagram showing a detailed configuration of the phase shifter 3, in which the non-inverting input terminal of the operational amplifier A1 is grounded, the input resistor R1 is connected to the inverting input terminal, and the inverting input terminal and output terminal A capacitor C1 is connected between them. When a voltage signal et proportional to the load voltage is input to this phase shifter, the output e.

is e −J 2V / (RICl) f SINωt
d tq t = J 2V / (Rt Ct ω) CO8ωt-4
2V / (RIC1ω) sin (ωt −π/2
) −(6), resulting in a phase shift of π/2. Here, Vt is the effective value of e.

The voltage e shown in equation (6) has a maximum amplitude of (V2v
/RIC1ω) and is subject to the constraint of 1/ω, so a coefficient unit 5 and a multiplier 6 are provided to remove this influence.

Further, FIG. 9 is a circuit diagram showing the detailed configuration of the integrator 7. Here, an integrating circuit is constituted by an operational amplifier A2, an input resistor R, and a capacitor Cp, and a level detector 11 is connected to the output terminal of this integrating circuit. Also,
A feedback pulse generator 12 is provided that discharges the charge stored in the capacitor CF based on the output of the level detector 11. 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 this integrator 7 will be briefly explained with reference to the time chart of FIG.

By applying the output voltage E of the multiplier 6 to the input resistor RM, it is converted into a current signal I M "" E M/RM. Here, when the output of the multiplier 6 is in the current mode, the input resistor RM is not necessary, and the output (2) of the multiplier 6 is directly input to the integrator. When this current IM flows through the capacitor C, the output potential eA of the operational amplifier A2 gradually drops. When the potential drops to a value set in the level detector 11, the level detector 11 outputs a pulse el. Also, at this time, the feedback pulse generator 12 operates to output a feedback pulse having an amplitude Is determined by the reference voltage circuit 13 and a time width τ determined by the reference pulse generator 14, and the current is While feeding back Is, a pulse e is output. As a result, the charges of Q-I8·τ8 are discharged, and during this time, the output potential of the operational amplifier A2 is restored to its original state. At this time, the charged charge I -T and the discharged charge I .tau. are equal to M, [' SS , so the following equation holds true.

■8・Tp-Is・8...(7
) F■1 / T p -■ / (τ bow) M 5S -E / (τ ・■ ・R) ... (8) M
SSM where T, is the period of the pulse frequency output, and F is its frequency.

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

[Problem that the invention seeks to solve]

In the above-mentioned conventional electronic reactive energy meter, the influence of frequency is removed by the coefficient unit 5 and the multiplier 6, but there are a relatively large number of components, which increases the complexity of the configuration and the cost. There was a problem with rising prices.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electronic reactive watt-hour meter that can simplify the configuration and reduce the cost of the device.

[Means for solving problems]

The electronic reactive energy meter according to the present invention phase-shifts one of a signal proportional to the voltage of a load and a signal proportional to the current of the load using a phase shifter including a first integrator. The second integrator integrates the resulting signal, and generates a pulse corresponding to unit reactive energy each time the integrated value matches the product of the pulse width and pulse amplitude of the reference pulse signal. In the electronic reactive energy meter, the pulse width or pulse amplitude of the reference pulse signal is changed in inverse proportion to the frequency of the voltage of the load to reduce the reactive power caused by the phase shift of the first integrator. The present invention is characterized in that it includes frequency number variation correction means for correcting frequency number variation.

[For production]

In the conventional electronic reactive energy meter shown in FIG. 7, the coefficient unit 5 and the multiplier 6 remove frequency fluctuations, but if the integrator 7 shown in FIG. If a function for compensating for numerical fluctuations could be easily added, the coefficient unit 5 and the multiplier 6 would be unnecessary. Looking at this from a different perspective, if a frequency number variation correction means corresponding to the coefficient multiplier 5 is provided and its output is applied to the feedback pulse generator 12 of the integrator 7, the coefficient multiplier 5 and the multiplier 6 can be 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 multiplier output EM (voltage mode) or 1
M (current mode) is the output It of current transformer 2 and (6)
Since it is a product of e in the equation, the following equation is obtained.

E (or IM) −, VRIR8INφ/(RIC1ω)...(9) However, K1 is a proportionality constant.

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

FM-KIVRI,, SINφ/(τsIsω)...
(10) Here, using a frequency number variation correction means, 1/τ −
K ω or 1/I − to 3ω S2
s makes it possible to simplify the configuration and reduce device costs.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 7 indicate the same elements. Then, the coefficient unit 5 and the multiplier 6 in FIG. 7 are removed, and a period detector 21 as a frequency number variation correction means is provided in their place, and the integrator in FIG. As shown in FIG. 7, the use of the integrator 7a without the reference pulse generator 14
It is different from the illustration.

Here, the period detector 21 detects a sine wave voltage e output from the output of the transformer 1, as shown in the time chart of FIG.
t is waveform-shaped to obtain a pulse signal eB', and this pulse signal is further frequency-divided by 1/2 to obtain a voltage signal eB, which is applied to the feedback pulse generator 12. As a result, 1/τ
The frequency variation can be removed by setting 2ω to S-.

Note that when the reference pulse generator 14 shown in FIG. 9 gives a pulse having a much higher frequency than the sine wave voltage e to the feedback pulse generator 12, as shown in FIG. PLL type multiplier circuit 2 converts the sine wave voltage e of frequency f into
2 to obtain a pulse frequency with a frequency of N1·f, and apply a pulse signal ep with a period of 2π/Nω to the feedback pulse generator 12.

FIG. 5 is a block diagram showing the configuration of another embodiment in which a pulse signal ep with a period of 2π/Nω is applied to the feedback pulse generator 12. Here, the sine wave voltage et is detected by the period detector 21.
A reference clock generator 24 is provided which outputs a pulse signal eB by shaping the waveform at the sine wave voltage e, and also generates a clock signal with a much higher frequency than the sine wave voltage e.The clock is divided into 1/N by a frequency divider 25. After frequency division, it is applied to the AND gate 26 together with the pulse signal eB, the output pulses are counted by the counter 27, and the count value of the counter 27 is held by the latch 28. Further, the clock from the reference clock generator 24 is counted by another counter 2, and the counted value and the value held in the latch 28 are compared by a coincidence detection circuit 30. Then, each time the two match, a pulse is generated and applied to the counter 29 as a reset pulse, and also applied to the waveform shaping circuit 31. As a result, from the waveform shaping circuit 31,
A pulse signal ep with a period of 2π/(N ω) is output.

In all of the above embodiments, the reference pulse applied to the feedback pulse generator 12 is changed depending on the frequency, but instead of this, the current value of the feedback pulse generator may be changed depending on the frequency. FIG. 6 shows an example of this, in which the output pulse eB of the period detector 21 and the clock of the reference clock generator 24 are applied to an AND gate 26, and the output pulses thereof are counted by a counter 27. Then, the count value is latched 28
The D/A converter 32 converts this into an analog current signal l or voltage signal E8. The analog signal 8 or E obtained in this way is the sine wave voltage e
is inversely proportional to the frequency of E8S
In the case of [, it is possible to perform current conversion and perform frequency correction according to 3ω to 1/■s-. This makes it possible to use an integrator 7b with a simple configuration in which the reference voltage circuit 13 is removed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the frequency variation of the reactive power due to the phase shift of the first integrator is converted into a reference pulse signal related to the pulse frequency of the second integrator. Since it is equipped with a frequency number variation correction means that corrects the pulse width or pulse amplitude by changing it in inverse proportion to the frequency of the load voltage, the configuration can be significantly simplified compared to conventional devices, and at the same time, the device cost can be reduced. This has the effect of reducing the

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
Fig. 2 is a block circuit diagram showing the detailed configuration 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 diagram of the second embodiment of the invention. FIG. 5 is a block diagram showing the configuration of the third embodiment of the present invention, FIG. 6 is a block diagram showing the configuration of the fourth embodiment of the present invention, and FIG. 7 is the conventional circuit diagram. FIGS. 8 and 9 are block diagrams showing the configuration of the electronic reactive energy meter; FIGS. 8 and 9 are block circuit diagrams showing the detailed configuration of the main elements of the device; FIGS.
The figure is a waveform diagram for explaining the operation of the device. 1...Transformer, 2...Current transformer, 3...Phase shifter, 4
... Multiplier, 7a, 7b... Integrator, 8... Display, 21... Period detector, 22... PLL type multiplier circuit, 26... Reference clock generator, 25... ...Frequency divider, 26...AND gate, 27.29...Counter, 28...Latch, 30...-number circuit, 31...
Waveform shaping circuit, 32...D/A converter. Applicant's agent Sato - Yu figure rri7) i>・u (l si', no change to 1) not Figure 1 n Figure 2 Figure 3 Figure 4 Figure 9 Procedure amendment 1986 December 7.5″ day

Claims (1)

[Claims] Either 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 a phase shifter including a first integrator and multiplied by the other, and the obtained signal is subjected to second integration. In an electronic reactive energy meter that integrates with a device and generates a pulse corresponding to unit reactive energy every time the integrated value matches the product of the pulse width and pulse amplitude of a reference pulse signal, Frequency variation correction means for correcting frequency variation of reactive power caused by phase shift of the first integrator by changing the pulse width or pulse amplitude of the pulse signal in inverse proportion to the frequency of the voltage of the load. An electronic reactive watt-hour meter characterized by comprising: