JP2531470B2 - Electronic electricity meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic watt-hour meter for determining load power on a power supply line based on a digital signal obtained by analog-digital conversion of a signal proportional to the power of the power supply line. is there.

[0002]

2. Description of the Related Art With the development of electronic equipment, in the field of watt-hour meters, electronic watt-hour meters that measure digitally are about to replace conventional inductive watt-hour meters in recent years.

This electronic watt-hour meter converts a voltage signal and a current signal proportional to a voltage and a current on a power supply line into a digital signal and multiplies and converts them to obtain power data.
The amount of power is calculated by integrating this power data, and the semiconductor device is developing at a remarkable pace, and the operation format suitable for the times has been taken, and the performance can be improved with the improvement of the device capacity Have a secret.

The instantaneous value and the effective value of the load voltage are represented by eR and VR, respectively, and the instantaneous value and the effective value of the load current are represented by iR and IR, respectively, and the load current iR is smaller than the load voltage eR by the phase angle θ. If it is delayed, eR = 2 ^(1/2) VR sin ωt (1) iR = 2 ^(1/2) IR sin (ωt-θ) (2), and the instantaneous power pR is pR = VR IR (cos θ−cos (2ωt−θ)) (3) (where ω is the angular frequency and t is the time).

[0005]

By the way, conventionally, the supply of electric power has been in the direction from the electric power company to the customer (hereinafter referred to as the positive direction), but in recent years overseas, the electric power generated by the customer himself / herself. Is being supplied to the electric power company in the opposite direction. It is expected that it will be implemented in Japan soon, and implementation requires a watt-hour meter that can handle both the forward and reverse directions of supply and demand.However, current watt-hour meters are designed to supply self-generated power to electric power companies. In reality, it does not have the ability to measure electric energy.

There is no doubt that the electronic watt hour meter as described above will be required to have such capability.

[0007] Incidentally, since electric power is supplied and demanded through the same electric power supply line in both the forward and reverse directions, the ability to identify the supply and demand direction of the electric power is indispensable in making a watt-hour meter capable of handling both the forward and reverse directions.

An object of the present invention is to solve such problems and to provide an electronic watt-hour meter capable of coping with the supply and demand of electricity in both forward and reverse directions.

[0009]

The electronic watt hour meter of the present invention comprises a digital voltage signal generating means for generating a digital voltage signal proportional to the voltage on the power feed line and a digital voltage signal proportional to the current on the power feed line. Digital current signal generating means for generating a current signal, power data generating means for generating power data having a value determined by the digital voltage signal and the digital current signal, and integrating the value indicated by the power data, And the result is obtained as the electric power in the electric power feeding direction on the electric power feeding line, the first integrating means for outputting the value and the value indicated by the electric power data are integrated, and the result is received on the electric power feeding line. The power is calculated as the electric power in the direction opposite to the direction, and the value is output to the second integrator, or the data is selected to one of the first and second integrators. A signal transmission path switching means for applying to,
On the power feeding line based on a third integrating means for integrating the power data for a set time corresponding to an integral multiple of a half cycle of a signal flowing on the power feeding line, and a sign of an output value of the third integrating means. Of the electric power in the electric power receiving direction or in the opposite direction, and discriminating means for controlling the switching of the signal transmission path switching means in accordance with the result.

[0010]

[0011]

According to the present invention, if the power data when the signal flowing on the power feeding line is in the positive direction is integrated for a set time (for example, half period) corresponding to an integral multiple of a half period of the signal flowing on the power feeding line, The sign of the integrated value becomes "+", and the sign of the integrated value becomes "-" if the power data when the signal flowing on the power feeding line is in the opposite direction is integrated for the same time. By looking at the sign of the integrated value, the power supply direction is determined, and the power data is switched and supplied to the integrating means corresponding to each of the forward and reverse directions according to the determination result. It becomes possible to correspond to the payment form. Also, it generates digital power data proportional to the power on the power feed line, integrates this digital power data for a set time corresponding to an integral multiple of a half cycle of the signal flowing on the power feed line, and based on the sign of the integration result. It determines whether the power on the power feed line is in the power receiving direction or in the opposite direction, so the power fluctuation cycle, which is the minimum time to determine the polarity of the power, that is, the voltage Since the digital value itself, which is proportional to the electric power during the half cycle of the current cycle or the current cycle, is integrated and determined, the polarity can be accurately determined in a short time.

[0012]

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of an electronic watt-hour meter for a single-phase two-wire type power feed line according to a first embodiment of the present invention.

In this figure, 1 is a transformer, and 2 is an analog-digital (hereinafter referred to as AD) converter.
The primary side of the transformer 1 is connected to the power supply line, and the voltage of the power supply line is stepped down to a value that can be handled by the AD converter 2 in the subsequent stage, and the voltage of the power supply line is instantaneously supplied to the secondary side. It outputs a voltage signal whose value and effective value are proportional. AD
The converter 2 samples the instantaneous value of the secondary voltage signal of the transformer 1 and outputs code data indicating each sampled value.

Reference numeral 3 is a current transformer, and 4 is an AD converter. The current transformer 3 has a primary side connected to a power supply line, converts the current of the power supply line into a small current that can be handled by the AD converter 4 in the subsequent stage, and supplies the power supply line to the secondary side. It outputs a current signal whose instantaneous value and effective value are proportional to the current.
The AD converter 4 samples the instantaneous value of the secondary current pressure signal of the current transformer 3 and outputs code data indicating each sampled value.

Reference numeral 5 denotes a multiplier, which multiplies the voltage data and current data of the AD converters 2 and 4 to generate electric power data.

Reference numeral 6 denotes a signal transmission path switching unit, which is a multiplier 5
The power data of 1 is selectively transmitted to the forward measurement system and the reverse measurement system.

The forward measurement system is composed of an integrator 7, a pulse generator 8 and a display 9. The integrator 7 integrates the power data, generates an output command for one pulse when the integrated value exceeds a certain value, and simultaneously subtracts the power value corresponding to the one pulse from the integrated value. Repeat the operation. The pulse generator 8 generates a pulse each time it receives a pulse output command from the integrator 7. Each time the display device 9 receives an output pulse from the pulse generator 8, the power per pulse is integrated and the integrated value is displayed.

The backward measurement system is composed of an integrator 10, a pulse generator 11 and a display 12. Integrator 1
0 is an operation of integrating power data, generating an output command for one pulse when the integrated value exceeds a certain value, and at the same time subtracting the power value corresponding to one pulse from the integrated value. Repeat. The pulse generator 11 is the integrator 1
A pulse is generated each time a pulse output command from 0 is received. Each time the display device 12 receives an output pulse from the pulse generator 11, the display device 12 integrates the electric power per pulse and displays the integrated value.

13 is an integrator, 14 is an integration time controller, 1
Reference numeral 5 is a current direction discriminator. The integrator 13 integrates the power data from the multiplier 5 every set time corresponding to an integral multiple of a half cycle of the signal flowing on the power feed line, and the integration time controller 14 calculates the integration time by the integration time. To instruct. The current direction discriminator 15 determines the direction of the current on the power feed line based on the sign of the integrated data of the integrator 13,
In other words, it is determined whether the power supply and demand direction is normal or reverse,
According to the determination result, the switching unit 6 is set to either the normal or reverse measurement system. As a result, the switching unit 6 is reset every time corresponding to the integration time, and the measurement is performed in each measurement system in the integration time unit.

FIG. 3 exemplifies the signal waveforms of the instantaneous voltage, the instantaneous current, the instantaneous power, the sign waveform of the instantaneous power, and the integral waveform in the forward and reverse directions on the single-phase two-wire type power feed line.

T is an integration time, and it is assumed that the supply and demand direction from time t0 to time t1 is positive and the supply and demand direction from time t1 to time t2 is opposite.

Then, the sign of the instantaneous power from the time t0 to the time t1 is shown by the solid line in FIG. 3B, and the sign of the instantaneous power is "-" from the time t0 to the time t3. As shown in FIG. 3 (c), the sign of the integrated waveform by the integrator 13 is "-", and the sign of the instantaneous power is "+" from time t3 to time t1, so the sign of the integrated waveform is at time t3. It turns back in the "+" direction, and finally becomes "+" at time t1. Therefore, this sign “+” indicates that the power supply and demand direction is the positive direction.

Similarly, from time t1 to time t2, the sign of the instantaneous power is as shown by the alternate long and short dash line in FIG. 3 (b), and from time t1 to time t4 the sign of the instantaneous power is " 3 (c), the sign of the waveform integrated by the integrator 13 is "+" and the sign of the instantaneous power is "-" from time t4 to time t2.
The sign of the integrated waveform turns back in the "-" direction at time t4, and finally becomes "-" at time t2. Therefore, the sign "-" indicates that the power supply and demand direction is the opposite direction.

According to the present embodiment, the electric power data is switched and supplied to the measurement system corresponding to each of the forward and reverse directions according to the result of the determination, so that it is possible to correspond to the supply and demand form of the forward and reverse directions of the electric power. Becomes

FIG. 2 shows a circuit configuration of an electronic watt-hour meter for a single-phase two-wire power feed line according to a second embodiment of the present invention. The components of the watt hour meter shown in this figure that are the same as those shown in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted, and only the different portions will be explained.

In this figure, 16 is an instantaneous power code discriminator, 17 is a code time measuring device, 18 is a measurement time controller,
Reference numeral 19 is a code ratio discriminator. The instantaneous power code discriminator 16 discriminates the code of the power data from the multiplier 5, and outputs a code display signal as shown in FIG.
The code-based time measuring device 17 measures ± the occupied time of each code in the unit measurement time T. The measurement time controller 18 indicates the unit measurement time T to the code time measuring device 17. The code ratio discriminator 19 is a time meter for each code 1
Based on the time occupancy ratio of ± each sign in the measurement result of 7, it is determined whether the power supply / demand direction is forward or reverse, and the switching unit 6 is set according to the determination result. Therefore, the switching unit 6 is reset every time corresponding to the measurement time T, and the measurement is performed in each measurement system in the measurement time unit.

According to this embodiment, the sign of the electric power data when the signal flowing on the single-phase two-wire type electric power supply line is in the positive direction is monitored for a set time T corresponding to an integral multiple of a half cycle, and T +
(Time when sign is "+")> T- (Time when sign is "-")
Therefore, if the sign of the power data when the signal flowing on the power supply line is in the opposite direction is monitored for a set time (for example, half cycle) corresponding to an integral multiple of half cycle, then T-> T + is used. , T +, T-, the power supply / demand direction is discriminated based on the occupancy ratio, and the electric power data is switched and supplied to the integrating means corresponding to each of the forward and reverse directions according to the discrimination result. It is possible to support both supply and demand patterns in both forward and reverse directions.

Although the current signal is converted into the digital data in the current mode in the above embodiment, it may be converted into the voltage mode.

[0031]

According to the present invention, the power data when the signal flowing on the power feeding line is in the positive direction is integrated for a set time (for example, half period) corresponding to an integral multiple of a half period of the signal flowing on the power feeding line. Then, the sign of the integrated value will be "+", and if the power data when the signal flowing on the power feeder line is in the opposite direction is integrated for the same time, the sign of the integrated value will be "-". It is designed to determine the power supply direction by looking at the sign of the integrated value and switch the power data to the integrating means corresponding to each of the forward and reverse directions according to the result of the determination, so that the positive power It becomes possible to cope with the receiving form in both directions. Also, it generates digital power data proportional to the power on the power feed line, integrates this digital power data for a set time corresponding to an integral multiple of a half cycle of the signal flowing on the power feed line, and based on the sign of the integration result. It determines whether the power on the power feed line is in the power receiving direction or in the opposite direction, so the power fluctuation cycle, which is the minimum time to determine the polarity of the power, that is, the voltage Since the digital value itself, which is proportional to the electric power during the half cycle of the current cycle or the current cycle, is integrated and determined, the polarity can be accurately determined in a short time.

[0032]

[Brief description of drawings]

FIG. 1 is a block diagram of an electronic watthour meter according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an electronic watt hour meter according to a second embodiment of the present invention.

FIG. 3 is a waveform diagram illustrating an instantaneous voltage, an instantaneous current, a signal waveform of an instantaneous power, a sign waveform of the instantaneous power, and an integral waveform in each of the forward and reverse directions on the single-phase two-wire power feed line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transformer 2 Voltage signal analog-digital converter 3 Current transformer 4 Current signal analog-digital converter 5 Multiplier 6 Signal transmission path switching unit 7 Positive direction measurement system integrator 8 Positive direction measurement system pulse generator 9 Forward direction measurement system indicator 10 Reverse direction measurement system integrator 11 Reverse direction measurement system pulse generator 12 Reverse direction measurement system indicator 13 Forward / backward judgment integrator 14 Forward / backward judgment integration time controller 15 Positive Reverse determination current direction discriminator 16 Forward / reverse determination instantaneous power sign discriminator 17 Forward / reverse determination code-dependent time measuring device 18 Forward / reverse determination measurement time controller 19 Forward / reverse determination code ratio discriminator

Claims (1)

(57) [Claims] 1. A digital voltage signal generating means for generating a digital voltage signal proportional to a voltage on a power feeding line, a digital current signal generating means for generating a digital current signal proportional to a current on the power feeding line, and the digital signal. Power data generating means for generating power data having a value determined by the voltage signal and the digital current signal, integrating the value indicated by the power data, and calculating the result as the power in the power receiving direction on the power feeder line. As a power in the direction opposite to the power receiving direction on the power feed line, and outputs the value. Second integration means for performing the above, and a signal transmission path switching means for selectively applying the data to one of the first and second integration means, Third integrating means for integrating the power data for a set time corresponding to an integral multiple of a half cycle of a signal flowing on the power feeding line; and on the power feeding line based on the sign of the output value of the third integrating means. An electronic watt-hour meter, comprising: a determining unit that determines whether the power is in the power receiving direction or the reverse direction and that controls switching of the signal transmission path switching unit according to the result.