JPH08233873A - Two-way watt-hour meter - Google Patents

Abstract

PURPOSE: To prevent an erroneous judgment as to whether the power is received or supplied due to errors in a circuit in a two-way watt-hour meter which measures both the receiving amount of power in a forward direction and the supplying amount of power in an opposite direction. CONSTITUTION: The meter is provided with a multiplication circuit 5 for multiplying a line voltage and a line current of a power feed line, and a frequency conversion circuit 6 for outputting a pulse proportional to the product of the line voltage and line current. Moreover, the meter is provided with pulse cycle detection circuits 10 and 11. In the detection circuits 10 and 11, the pulse output proportional to a received power is not measured when the output is smaller than a received power of a reference time, and the pulse output proportional to a supplied power is not measured when the output is smaller than a received power of the reference time, respectively. The meter also includes integration circuits 16, 17 for integrating the received power, supplied power, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when supplying electric power, measures both the received electric energy flowing in the forward direction and the transmitted electric energy flowing in the reverse direction, or both the delayed reactive energy and the advanced reactive energy. The present invention relates to a bidirectional watt hour meter that

[0002]

2. Description of the Related Art FIG. 11 shows, for example, Japanese Patent Publication No. 63-5911.
1 shows a conventional bidirectional watt-hour meter shown in Japanese Patent Publication No. 0, where 1 is a transformer for converting a line voltage of a power supply line, and 2 is a current transformer for converting a line current of a power supply line. Is. The line voltage of the power supply line is converted by the transformer 1 into a voltage ev proportional thereto. Line current is the current transformer 2
Is converted to a voltage ± ei, which is proportional to that and has the same absolute value and different polarities. The multiplication circuit 50 causes the voltage e
v is multiplied by the voltage ei, and a voltage proportional to the instantaneous power ev × ei is output as the output of the multiplication circuit 50. The instantaneous power output (A) is input to the frequency conversion circuit 51. In the frequency conversion circuit 51, the positive / negative of one cycle of the instantaneous power is discriminated, and the positive / negative is used as a polarity discrimination signal,
It also outputs a pulse output signal having a frequency proportional to the magnitude of the input instantaneous power.

Reference numeral 52 is an averaging circuit, which averages the instantaneous power based on the polarity discrimination signal and the pulse output signal and polarizes the metering pulse signal (c) having a frequency proportional to the average power and the average power. The power transmission / reception determination signal (b) that has determined is output. The signal based on the metering pulse signal and the power transmission / reception discrimination signal is used as it is or in the inverter circuit 55.
And the AND circuit 56, the output of the AND circuit (e)
As (d), the power receiving integrating circuit 53 and the power transmitting integrating circuit 5
4 is input. The metering pulse signals input to the power receiving integrating circuit 53 and the power transmitting integrating circuit 54 are displayed on the display devices 57 and 58.
Is displayed as a numerical value.

FIG. 12 shows the waveform of each part of the above circuit. (A) shows the instantaneous power waveform e output from the multiplication circuit 50.
Indicates v × ei. (B) shows a power transmission / reception determination signal for determining the extreme positive of the average power output from the difference between the positive power waveform and the negative power waveform of one cycle in the instantaneous power from the frequency conversion circuit 51. (C) is a metering pulse signal proportional to the average power obtained through the averaging circuit 52 from the pulse output signal proportional to the instantaneous power from the frequency conversion circuit 51. (D)
Is a power transmission metering pulse signal input to the power transmission integrating circuit 54 via the AND circuit 56 when the power transmission / reception determination signal is “H”. (E) is A when the power receiving discrimination signal is "L"
This is a power-reception measuring pulse signal that is input to the power-reception integrating circuit 53 via the ND circuit 56. Then, the power receiving integrating circuit 53 and the power transmitting integrating circuit 54 integrate the input pulses, measure the received power amount and the transmitted power amount, and display them on the displays 57 and 58.

[0005]

Since the conventional bidirectional watt-hour meter is constructed as described above, the measured average power value is represented by W = VIcos θ + ε (where V is the input voltage, I is the input current, θ is the phase angle between current and voltage, ε
Is an error due to offset in the circuit, etc.), and when the value of W is positive, it is the power receiving side when the value of W is positive, and when the value of W is negative, it is the power transmitting side. Therefore, the level of the theoretical average power (VIcos θ) When is small, the influence of an error due to an offset or the like in the circuit of ε becomes large, and this has a drawback that an error occurs in power transmission / reception determination.

The present invention has been made to solve the above-mentioned problems. When the average power level is low, no measurement is performed, and an error such as an offset in the circuit causes power transmission, It is an object of the present invention to provide a bidirectional watt-hour meter that does not cause an error in power reception determination.

[0007]

A bidirectional watt-hour meter according to the present invention comprises a multiplication means for extracting the instantaneous power of a line from a line voltage and a line current and a magnitude and polarity of an output of the multiplication means. A converting means for outputting a pulse proportional to the magnitude for each polarity, and a pulse cycle detecting means for detecting the pulse cycle of the pulse for each polarity output from the converting means and outputting only a pulse having a predetermined cycle or less And two integrating means for integrating the pulses from the pulse period detecting means for each of the polarities.

In the above structure, the multiplication means includes a pulse width modulation circuit for obtaining a pulse width proportional to the line voltage,
The output voltage of the pulse width modulation circuit controls a voltage proportional to the line current.

The multiplying means includes an A / D conversion circuit for converting the line voltage into digital data, an A / D conversion circuit for converting the line current into digital data, and both of the A / D circuits.
And a multiplier that multiplies the output of the conversion circuit.

Further, in the above structure, the converting means outputs the pulse when the value of the adding circuit for counting the output of the multiplying means and the value of the adding circuit is equal to or more than the positive predetermined value or less than the negative predetermined value. It consists of a positive and negative magnitude comparator that resets the adder circuit at the output.

The pulse period detecting means is driven by the output of the converting means, and a one-shot circuit for maintaining a pulse for a predetermined time, and an AND circuit for obtaining a logical product of the output of the one-shot circuit and the output of the converting means. It consists of and.

Further, the pulse period detecting means is a counter which counts down the value loaded by the output of the oscillator by loading the set value written in the memory by the output of the rewritable memory, the oscillator and the converting means. And an AND circuit that obtains the logical product of the output of this counter and the output of the conversion means.

In any of the above constructions, the multiplying means is provided with a 90-degree phase shift circuit at the line voltage input terminal, and the integrating means measures the reactive power.

[0014]

In the bidirectional watt-hour meter according to the present invention, the pulse cycle detecting means detects the pulse cycle of the pulse output which is obtained through the multiplying means and the converting means and is proportional to the received power of the power supply line. When the power is less than the corresponding received power, the power is not metered, and similarly, the pulse cycle of the pulse output proportional to the transmitted power is detected by the pulse cycle detection means. When this is less than the transmitted power corresponding to the reference time, the power is reduced. By not measuring, it is possible to prevent an error such as an offset in the circuit from affecting the determination of power reception and power transmission when the average power level is low.

Further, by providing a 90-degree phase shift circuit at the line voltage input terminal of the multiplying means, it becomes possible to measure the reactive power in the integrating means.

[0016]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a block circuit diagram of a bidirectional energy meter according to a first embodiment of the present invention, in which 1 is a transformer for converting a line voltage of a power supply line, and 2 is a line current of a power supply line. It is a current transformer. The converted voltage ev is input to the pulse width modulation circuit 3 in which the duty of the pulse changes in proportion to the voltage. The voltage ± ei corresponding to the current converted by the current transformer 2 is input to the changeover switch 4. The changeover switch 4 is controlled by the pulse width modulation circuit 3. That is, the pulse width modulation circuit 3 and the changeover switch 4 form a multiplication circuit 5, and the output W of the changeover switch 4 becomes a signal of a level proportional to ev × ei. The output of the multiplication circuit 5 is input to the frequency conversion circuit 6 based on the integration circuit. In the frequency conversion circuit 6,
The instantaneous power signal of the multiplication circuit 5 is converted to the resistor 61 and the capacitor 6
2 and is integrated by the operational amplifier 64.

The output of the frequency conversion circuit 6 is the comparator 7
And to the comparator 8. Comparator 7
Performs level comparison with a reference voltage + VR, and the comparator 8 performs level comparison with a reference voltage -VR. The output of the comparator 7 becomes a pulse output signal and is connected to the pulse period detection circuit 10 and the AND circuit 14 therein.
The output of the comparator 8 becomes a pulse output signal, which is connected to the pulse cycle detection circuit 11 and the AND circuit 15 therein. The output sides of the comparators 7 and 8 are connected to the OR circuit 9, and the output of the OR circuit 9 controls the switch 63 connected to both ends of the capacitor 62 of the frequency conversion circuit 6 to reset the integrated voltage. ing.

The pulse cycle detection circuit 10 and the pulse cycle detection circuit 11 are circuits that perform the same operation, and are composed of inverter circuits 10a and 11a, retriggerable one-shot circuits 10b and 11b, and AND circuits 14 and 15. An "H" level signal is output for a certain period of time in synchronization with the falling edges of the pulse signals from the comparator 7 and the comparator 8. The AND circuit 14 is connected to the power receiving integrating circuit 16, and the AND circuit 15 is connected to the power transmitting integrating circuit 17. The integrating circuit 16 counts the input pulses, measures the integrated amount of received power, and adds the integrated circuit 17
Counts the input pulses and measures the integrated amount of transmitted power.

FIG. 2 shows the waveform of each part of the circuit of FIG. 1, and (a) shows the instantaneous power waveform ev × ei which is the output of the multiplication circuit 5 for multiplying the voltage ev and the current ei.
(B) shows the output waveform of the frequency conversion circuit 6, and when the instantaneous power output is positive, that is, when the power is received, integration is performed in the positive direction, and when the instantaneous power output is negative, that is, when the power is transmitted, the integration is performed in the negative direction. It is carried out. (C) shows the output of the comparator 7, and the output of the frequency conversion circuit 6 is +
When it reaches VR, the output of the comparator 7 becomes "H",
The capacitor 62 is discharged through the OR circuit 9 and the switch 63, and the integrated voltage is reset to zero. (D) shows the output of the comparator 8, and when the output of the frequency conversion circuit 6 reaches −VR, the output of the comparator 8 becomes “H”, and the capacitor 6 via the OR circuit 9 and the switch 63.
2 is discharged and the integrated voltage is reset to zero. Therefore, the output of the comparator 7 is a pulse output proportional to the received power, and the output of the comparator 8 is a pulse output proportional to the transmitted power.

(E) shows the output of the one-shot circuit 10b. The pulse cycle detection circuit 10 including the inverter circuit 10a and the one-shot circuit 10b capable of retriggering is
In synchronization with the falling edge of the input pulse, the reference time T0
The one-shot output of is output. (F) shows the output of the one-shot circuit 11b. The pulse cycle detection circuit 11 including the inverter circuit 11a and the re-triggerable one-shot circuit 11b outputs a one-shot output for the reference time T0 in synchronization with the falling edge of the input pulse. Output (e) of pulse cycle detection circuit 10 and pulse cycle detection circuit 1
The output of 1 (f) maintains "H" while a pulse is input in a cycle shorter than the reference time T0, and becomes "L" in a pulse longer than the reference time T0. (To) is AND
It shows the output of the circuit 14, and as is clear from the figure,
The pulse is output from the AND circuit 14 only when the received power is larger than the received power corresponding to the reference time T0, that is, when the cycle of the output pulse of the comparator 7 is shorter than T0, and this is integrated by the integrating circuit 16 as the received power amount. .
(H) shows the output of the AND circuit 15, and similarly,
Only when the transmitted power is larger than the transmitted power corresponding to the reference time T0, the AND circuit 15 outputs a pulse, and the integrated circuit 17 integrates the pulse as the transmitted power amount. In other words, the pulse period of the comparators 7 and 8 is detected by the pulse period detection circuits 10 and 11, and the pulse period is the reference time T.
A small amount of electric power that exceeds 0 is not integrated.

Therefore, the measured average power value is W = V
Icos θ + ε (where V is an input voltage, I is an input current, θ is a phase angle between current and voltage, and ε is an error due to an offset in the circuit). The value of the error component due to the offset or the like is calculated by the pulse cycle detection circuit 10 as ε = reference time T0 and by the pulse cycle detection circuit 11 ε = reference time T0.
By setting the transmission power equivalent to, it is possible to set a non-measurement range in which neither the reception power nor the transmission power is measured within the range of ± ε. Therefore, when the theoretical value (VIcos θ) of the average power is small, the influence of ε becomes relatively large in the determination of power transmission and power reception, but according to the above configuration of the present invention, the pulse cycle detection circuits 10 and 11 are provided.
By this function, it is possible to measure electricity without erroneous power transmission or power reception.

Example 2. 3 and 4 are a block circuit diagram and an operation waveform diagram showing a second embodiment of the present invention. In the figure, 1 to 9, 14 to 17 and 61 to 63 are the same as those in the first embodiment. In the first embodiment, the pulse cycle detection circuits 10 and 11 are composed of the inverter circuit, the one-shot circuit and the AND circuit which can be re-triggered, but in the second embodiment, the pulse cycle detection circuits 70 and 71.
Is composed of rewritable memories 70a and 71a, counters 70b and 71b, and an oscillator 70c. Counters 70b and 7 of the pulse period detection circuits 70 and 71
1b includes memories 70a, 7 at the falling edge of the input pulse.
The value held in 1a is loaded. On the other hand, the counters 70b and 71b perform subtraction with the clock signal from the oscillator 70c, and output "L" when the values of the counters 70b and 71b become zero. Therefore, the memories 70a, 7
If the value held in 1a corresponds to the reference time T0, for example, when the power is smaller than the received power corresponding to the reference time T0, no output pulse is output from the AND circuit 14 and the received power amount is integrated. The integration circuit 16 does not. Similarly, the pulse period detection circuit 71 and the AND circuit 15
Therefore, when the power is smaller than the transmission power corresponding to the reference time T1, no output pulse is output from the AND circuit 15, and the integration circuit 17 does not integrate the transmission power amount. This is shown by the operation waveforms (a) to (h) in FIG.

In the second embodiment, the reference time is held in the rewritable memories 70a and 71a, so that the reference time can be made variable. That is, Example 1
However, in the range of ± ε, the non-measurement range is set, but in the present embodiment, + ε0 (power received corresponding to the reference time T0) to −.
The range of ε1 (transmitted power corresponding to the reference time T1) is a non-measurement range, and + ε0 and −ε1 are variable. In general, error components such as offsets are different for each circuit. Therefore, by making + ε0 and −ε1 variable, a more accurate non-measurement range can be set, and power transmission will not be mistaken for power reception or power reception will be mistaken for power transmission.

Example 3. FIG. 5 is a block circuit diagram of the third embodiment of the present invention. In the figure, 1, 2, 10, 1
1, 14 to 17 are the same as those in the first embodiment. In the third embodiment, an A / D conversion circuit 20 that converts the output ev of the transformer 1 into digital data is used instead of the multiplication circuit 5 that includes the pulse width modulation circuit 3 and the changeover switch 4 in the first embodiment. A multiplier 22 for multiplying the output ei of the current transformer 2 by an A / D conversion circuit 21 for converting it into digital data is used.

In the first embodiment, the frequency conversion circuit 6 composed of the capacitor 62, the resistor 61 and the operational amplifier 64, the reference voltages + VR and -VR and the comparators 7 and 8 are used to output a pulse proportional to the received power. Although the pulse output proportional to the transmission power is obtained, in the present embodiment, the digital output data w of the multiplier 22 indicating the instantaneous power is integrated by the addition circuit 23, and the reference value 1 in the register 26 and the addition circuit 23. The magnitude comparator 24, which compares the magnitude with the output value of, the pulse proportional to the received power, and the magnitude comparator 25, which compares the magnitude between the reference value 2 in the register 27 and the output value of the adder circuit 23, transmits the power. You get a pulse proportional to the power. The adder circuit 23 is reset to zero every time the magnitude comparator 24 or the magnitude comparator 25 outputs a pulse. Since the operations after the outputs of the magnitude comparator 24 and the magnitude comparator 25 are the same as those in the first embodiment, the description thereof will be omitted. In the third embodiment, since the A / D conversion circuits 20 and 21 and the subsequent steps are digital processing, the circuit forming the watt hour meter can be easily integrated into an LSI, which is effective for downsizing the watt hour meter.

Example 4. 6 is a block circuit diagram showing a fourth embodiment of the present invention. In this embodiment, the pulse period detection circuits 10 and 11 of the third embodiment are the same as the rewritable memories 70a and 71a and the counter 70b shown in the second embodiment. , 71
b and an oscillator 70c, a pulse period detection circuit 70,
It is replaced by 71. The operation is the same as that described above, and will be omitted.

Example 5. FIG. 7 is a block circuit diagram showing a fifth embodiment of the present invention, showing a bidirectional reactive energy meter. In the figure, 1 to 9, 14 to 17 and 61 to 63 are the same as those in the first embodiment. In this embodiment, a 90-degree phase shift circuit 40 that delays the phase angle of the voltage by 90 degrees is inserted between the transformer 1 and the pulse width modulation circuit 3 of the first embodiment, and other configurations are the same as those of the first embodiment. Is the same as. Therefore,
By inserting the 90-degree phase shift circuit 40, the integration circuit 1
6, the delayed reactive power amount is integrated, and the integrating circuit 17 integrates the advanced reactive power amount to enable reactive power measurement.
By the same operation as above, the delayed reactive power advances and the reactive power advances,
Alternatively, the advanced reactive power is not mistaken for the delayed reactive power.

Example 6. FIG. 8 is a block circuit diagram showing a sixth embodiment of the present invention and shows a bidirectional reactive energy meter. In the present embodiment, a 90-degree phase shift circuit 40 for delaying the voltage phase by 90 degrees is inserted between the transformer 1 and the pulse width modulation circuit 3 of the second embodiment, and other configurations are the same as those of the second embodiment. Is. According to the present embodiment, as in the fifth embodiment, it is possible to obtain a highly accurate bidirectional reactive energy meter.

Example 7. FIG. 9 is a block circuit diagram showing a seventh embodiment of the present invention, showing a bidirectional reactive watt hour meter. In the present embodiment, a 90-degree phase shift circuit 40 for delaying the voltage phase by 90 degrees is inserted between the transformer 1 and the A / D conversion circuit 20 of the third embodiment, and other configurations are the same as those of the third embodiment. Is the same. According to this embodiment, as in the fifth and sixth embodiments, it is possible to obtain a highly accurate bidirectional reactive energy meter.

Example 8. Embodiment 8 FIG. 10 is a block circuit diagram showing Embodiment 8 of the invention and shows a bidirectional reactive energy meter. In this embodiment, a 90-degree phase shift circuit 40 for delaying the voltage phase by 90 degrees is inserted between the transformer 1 and the A / D conversion circuit 20 of the fourth embodiment, and other configurations are the same as those of the third embodiment. Is the same. According to the present embodiment, a highly accurate bidirectional reactive energy meter can be obtained as in the fifth, sixth and seventh embodiments.

[0031]

As described above, according to the present invention, in the bidirectional watt-hour meter, when the average power level is small, both the power reception and the power transmission are not measured, so that an error such as an offset in the circuit is eliminated. Does not affect the determination of power reception and power transmission.

Further, in the case where the multiplication means is provided with the A / D conversion circuit, the portion occupied by the digital circuit becomes large,
LSI can be easily realized.

Further, by configuring the pulse period detection circuit with a rewritable memory, an oscillator and a counter, the level at which no power is received and power is transmitted can be easily varied, and the error in the circuit can be reduced. Can absorb variations.

Furthermore, in the case where the 90 ° phase shift circuit is provided at the line voltage input terminal of the multiplying means, the reactive power can be measured, so that the bidirectional operation is not affected by an error such as an offset in the circuit. A reactive energy meter is obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a bidirectional energy meter according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 3 is a block circuit diagram showing a bidirectional energy meter according to a second embodiment of the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the second embodiment.

FIG. 5 is a block circuit diagram showing a bidirectional energy meter according to a third embodiment of the present invention.

FIG. 6 is a block circuit diagram showing a bidirectional energy meter according to Embodiment 4 of the present invention.

FIG. 7 is a block circuit diagram showing a bidirectional energy meter according to Embodiment 5 of the present invention.

FIG. 8 is a block circuit diagram showing a bidirectional energy meter according to Embodiment 6 of the present invention.

FIG. 9 is a block circuit diagram showing a bidirectional energy meter according to Embodiment 7 of the present invention.

FIG. 10 is a block circuit diagram showing a bidirectional energy meter according to Embodiment 8 of the present invention.

FIG. 11 is a block circuit diagram showing a conventional bidirectional energy meter.

FIG. 12 is a waveform diagram for explaining the operation of the conventional bidirectional watt-hour meter.

[Explanation of reference numerals] 1 transformer, 2 current transformer, 3 pulse width modulator, 4 changeover switch, 5 multiplication circuit, 6 frequency conversion circuit,
7, 8 Comparator, 9 OR circuit, 10, 11
Pulse period detection circuit, 10a, 11a inverter, 1
0b, 11b One-shot circuit, 14, 15 AND
Circuit, 16 power receiving integrating circuit, 17 power transmitting integrating circuit,
20, 21 A / D conversion circuit, 22 multiplier, 23 adder circuit, 24, 25 magnitude comparator, 2
6, 27 register, 40 90 degree phase shift circuit, 41 delayed reactive power integration circuit, 42 advanced reactive power integration circuit, 70, 71 pulse cycle detection circuit, 70c oscillator, 70a, 71a memory, 70b, 71b counter.

Claims (7)

[Claims] 1. A multiplication means for extracting an instantaneous power of a line from a line voltage and a line current, and a conversion means for outputting a pulse proportional to the magnitude according to the magnitude and polarity of the output of the multiplication means according to the polarity. A pulse cycle detecting means for detecting the pulse cycle of each pulse for each polarity output from the converting means and outputting only a pulse having a predetermined cycle or less, and a pulse from this pulse cycle detecting means is integrated for each polarity. A bidirectional watt-hour meter provided with two integrating means. 2. The multiplication means comprises a pulse width modulation circuit for obtaining a pulse width proportional to the line voltage and a switch for controlling a voltage proportional to the line current by the output of the pulse width modulation circuit. The bidirectional watt-hour meter according to claim 1, which is characterized in that. 3. The multiplying means multiplies an A / D conversion circuit for converting a line voltage into digital data, an A / D conversion circuit for converting a line current into digital data, and outputs of both the A / D conversion circuits. 2. The bidirectional watt-hour meter according to claim 1, wherein the bidirectional watt-hour meter is configured by a multiplier that operates. 4. The converting means outputs a pulse when the output of the multiplying means is counted, and a pulse is output when the value of the adding circuit is equal to or more than a positive predetermined value or less than a negative predetermined value, and the pulse output outputs the addition. The bidirectional watt-hour meter according to claim 5, wherein the bidirectional watt-hour meter comprises a positive and negative magnitude comparator that resets the circuit. 5. The pulse period detecting means is driven by the output of the converting means, and a one-shot circuit for maintaining a pulse for a predetermined time, and an AND circuit for obtaining a logical product of the output of the one-shot circuit and the output of the converting means. The bidirectional watt-hour meter according to any one of claims 1 to 4, characterized in that: 6. The pulse period detection means is a counter that counts down the value loaded by the output of the oscillator by loading a rewritable memory, an oscillator, and a set value written in the memory by the output of the conversion means. And an AND circuit that obtains a logical product of the output of this counter and the output of the conversion means, and the bidirectional watt-hour meter according to any one of claims 1 to 4. . 7. The multiplying means has a line voltage input terminal at which 90 is provided.
The bidirectional watt-hour meter according to any one of claims 1 to 6, wherein a degree phase shift circuit is provided, and reactive power is measured by integrating means.