JP2012054683A - Power line carrier transmission/reception apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement favorable signal transmission/reception by detecting only a predetermined carrier frequency component despite some noise in transmission information for signal reception at a carrier reception section.SOLUTION: A low voltage cable run 1 used for signal transmission is connected to a demarcation pole 5 by an overhead or any other type of electrical line from an electrical room 6. In the electrical room 6, a transformer 7 causes a voltage drop to a predetermined level before supplying power to each load. A carrier transmission section 12 of a demand detector 11 installed on the demarcation pole transmits information by means of the low voltage cable run 1.

Description

  The present invention provides an apparatus capable of solving the problem of noise in the case of using a conventional power line communication system (hereinafter referred to as “PLC system”) when transmitting information using a power line, and reducing a transmission failure of a carrier wave. The purpose is to obtain.

  Communication via a power line performs communication using a power line such as a low-voltage distribution line as a transmission line, and has an advantage that a dedicated communication line is unnecessary because an existing power line can be used. However, when the PLC communication device is used, cases such as an increase in electric circuit noise and an increase in load make it impossible to transmit a carrier wave and make the device unusable. .

  As a means for solving problems such as noise generated when using the power line as described above, a second power line having a lot of noise is disclosed as disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-17441. Examples have been proposed that are intended to be automatically selected as candidates. In the example disclosed in the document, not only the power line but also an arbitrary electric wire such as a telephone line can be used, and in addition to the power line, an arbitrary communication line with less noise is selected and connected, Information can be sent and received.

JP 2009-17441 A

  In the communication method of the known example, line selection means such as a changeover switch is provided in the transmission unit of the transmission apparatus, and when performing communication, a transmission path is selected so that wiring other than the power line is preferentially selected. The rank is specified. Then, by selecting the medium with the fastest communication speed and using the power line as the second medium, it is possible to ensure good communication quality with little noise during communication.

  However, in a communication environment where transmission conditions are limited, that is, a communication medium other than the power line cannot be obtained, communication must be relied solely on the power line. However, even under limited conditions, it is a natural requirement to ensure good communication quality by reducing noise entering information transmitted and received.

  The present invention can drastically solve the problem of noise of the conventional PLC system even when performing communication by an information transmission method using a power line (hereinafter referred to as “the present system”), and dramatically reduces the transmission trouble of the carrier wave. An object of the present invention is to provide a communication method that can be reduced.

  For this purpose, for example, a carrier wave such as 875 Hz (50 Hz system) that does not match the harmonics of the power supply frequency is used, and digital signal transmission is performed using a modulation method such as ASK (amplitude shift keying) or PSK (phase shift keying). Therefore, it is possible to easily obtain an apparatus capable of ensuring transmission / reception with good communication quality by selectively using the above means.

The present invention performs unidirectional signal transmission from a device such as a demand monitoring device installed in a responsibility demarcation column at the end of a low piezoelectric path to an alarm indicator provided in an electrical room or the like through a distribution line. The present invention relates to a power line carrier wave transmitting / receiving device.
In the first aspect of the present invention, an information transmission device that transmits information by injecting a carrier current having a frequency that does not match the power supply frequency and the harmonics of the power supply frequency is connected to one end away from the transformer of the two-wire low piezoelectric circuit. The information receiving device is connected to the end portion on the side close to the transformer of the low piezoelectric path,
The two-wire low piezoelectric path is connected to a transformer provided in an electrical room, and flows through the transformer winding through the low piezoelectric path at the other end of the low piezoelectric path and flows into the terminal at the other end of the information transmitting device. Forming a loop circuit, and configured as a device for transmitting information to and from the information receiving device in a state where the carrier current circulates in the loop circuit;
In the information receiving apparatus, the carrier current injected into the low piezoelectric path is directly received by a carrier detection current transformer installed in the vicinity of the transformer, and the received carrier current is converted into a carrier voltage by voltage conversion. It is characterized by performing unidirectional signal transmission used as the information of

The invention of claim 2 is provided with a parallel resonance circuit that resonates at the carrier current frequency in parallel with the two-wire low piezoelectric path in a portion closer to the transformer than the carrier detection current transformer,
By passing the parallel resonant circuit, the combined impedance between the two terminals of the transformer winding is reduced, and the carrier transmission current is increased to obtain a large received signal.

As described above, by configuring the signal circuit in the carrier wave receiver, even if there is some noise in the transmission information, it is possible to detect the information only by using only the predetermined carrier frequency component. Signal transmission / reception can be performed in good condition.
In addition, this method has an advantage that the carrier wave abnormality can be reduced. Since the carrier current sent by the carrier sending unit can be directly received without being attenuated, a very strong received signal exceeding several A can be obtained. It is possible to obtain a method that is less susceptible to the influence of electric circuit noise.

  In addition, the method of the present invention can be applied to large-scale electrical equipment. In other words, in the conventional system, when applied to a large-scale facility, the combined impedance between receiving terminals decreases, the carrier voltage that can be received decreases, and the number of cases in which the carrier cannot be received increases. In this system, a very strong received signal can be obtained even when the combined impedance is small, so that it can be applied to a large-scale facility.

The present invention can exhibit the feature that the transmission distance can be increased. That is, in the method of the present invention, a very strong received signal can be basically obtained, so that it is not easily influenced by the transmission impedance of the low piezoelectric path, and the transmission distance is increased (the conventional method has a limit of several hundred meters). I can do it.
Further, since the change from the conventional method to the present method is basically only the carrier wave signal input circuit, it can be easily incorporated.

It is explanatory drawing of the demand monitoring apparatus of this invention. It is explanatory drawing of the circuit structure of a carrier wave transmission part. It is explanatory drawing of the circuit structure of a carrier wave receiving part. It is explanatory drawing of the example of improvement of the demand monitoring apparatus of this invention. It is explanatory drawing of the prior art example of a demand monitoring apparatus. It is explanatory drawing of the Zab equivalent circuit integrated in the circuit of FIG. It is explanatory drawing of the relationship between the Zab circuit of the said FIG. 6, and Vs. It is explanatory drawing of the influence of the transmission line impedance with respect to the Zab circuit of FIG.

  In order to solve the problems of the current PLC system as described above, in the present invention, a transmission / reception circuit is configured as illustrated in FIG. The low piezoelectric path 1 is connected from the electrical chamber 6 to the responsibility demarcation column 5 by an electric line such as an aerial system. Further, in the electric room 6, the voltage is lowered to a predetermined voltage by the transformer 7, and electric power is supplied to each load. Then, information is transmitted from the carrier wave sending unit 12 of the demand detector 11 installed in the responsibility demarcation column 5 using the low piezoelectric path 1.

  Further, the carrier wave receiving unit 16 arranged on the power receiving side constitutes the demand monitoring device 10 that receives information sent through the low piezoelectric path 1 and displays it on the display unit of the alarm indicator 15. Further, information processed through the current / voltage conversion circuit 17 is input to the carrier wave receiver 16 of the alarm indicator 15 and an alarm is transmitted as necessary according to preset conditions.

  The carrier detector 12 of the demand detector has a circuit configuration as shown in FIG. 1, so that the carrier detector of the demand monitoring device has a demand installed on the responsibility demarcation column 5 as shown in the figure. The detector 11 is arranged to transmit a signal in one direction toward an alarm indicator 15 provided in an electrical room or an office room.

  With respect to the current / voltage conversion circuit 17 arranged on the reception side, the carrier wave transmission unit 12 is configured as a transmission circuit as shown in FIG. Then, in the carrier wave sending unit 12 of the demand detector 11, following the carrier wave sending unit CPU 21 for inputting the input value of the demand data D1, the A / D conversion circuit 22, the modulation circuit 24 for connecting the oscillation circuit 23, the driver amplifier 25 and the coupling circuit 26, and the carrier wave D 2 is output via the low piezoelectric path 1.

Each member constituting the processing circuit of FIG. 2 performs the following signal processing operation.
Carrier wave sending unit CPU21: When demand data D1 is input to the CPU, a signal corresponding to the data is sent to the A / D conversion circuit.
A / D conversion circuit 22: The A / D conversion circuit converts the signal from the carrier wave sending unit CPU 21 into a digital signal and sends it to the modulation circuit 24.

Oscillation circuit 23: The oscillation circuit oscillates at a carrier frequency such as 875 Hz that does not match the high frequency of the power supply frequency.
Modulation circuit 24: The modulation circuit uses a modulation method such as ASK (amplitude shift keying) or PSK (phase shift keying) from the carrier frequency signal from the oscillation circuit 23 and the digital signal from the A / D conversion circuit 22. , Perform digital signal transmission.

Driver amplifier 25: The driver amplifier amplifies the signal from the modulation circuit 24 to a required magnitude and sends it to the coupling circuit.
Coupling circuit 26: The coupling circuit is composed of a transformer, a capacitor, and the like, and is connected to the low piezoelectric path 1 to send a carrier current to the power line.

As described above, the carrier sending unit 12 provided in the detector 11 of the demand monitoring device 10 uses a carrier wave such as 875 Hz (50 Hz system) that does not match the harmonics of the power supply frequency, and uses a modulation method such as ASK or PSK. , Doing digital signal transmission.
From the carrier sending unit 12 of the demand monitoring device 10, the modulated carrier signal is sent to the transformer 7 as a carrier sending current Is.

  The carrier transmission current Is from the demand monitoring device constitutes a loop circuit that returns to the carrier transmission unit 12 of the demand detector 11 through the winding of the transformer 7 as shown in FIG. Then, the carrier wave transmission current Is mainly flows through the transformer winding, and a signal is transmitted from the detection CT 31 arranged on the path returning from the transformer 7 toward the alarm indicator 15.

  The carrier wave receiver 16 of the alarm indicator 15 is provided with a receiving circuit as shown in FIG. In the carrier wave receiving unit 30, following the detection CT 31 arranged in the low piezoelectric path 1, the current / voltage conversion circuit 32, the band pass filter (BPF) 33, the demodulation circuit 34, the carrier wave receiving unit CPU 35, and the alarm display It is provided connected to the display circuit 36.

Each component circuit member arranged in the carrier wave receiving circuit is provided to perform the following signal processing operation.
Detection CT31: A carrier current flowing through the low piezoelectric path 1 is detected and sent to the current / voltage conversion circuit 17.

Current / voltage conversion circuit 17: This circuit converts the current received by the detected CT 31 into a voltage corresponding to the magnitude thereof.
BPF33 BPF is an abbreviation for bandpass filter, and detects only a predetermined carrier frequency component from the carrier signal detected by the detection CT 31 and noise, and sends it to the demodulation circuit 34.

Demodulation circuit 34: Demodulates a modulated signal transmitted with a digital signal in accordance with a modulation method from a carrier sending unit such as ASK or PSK, and converts it into a digital signal.
Carrier wave receiving unit CPU 35: The CPU performs arithmetic processing on the received signal from the demand detecting unit 11 and determines various alarms and the like.
Alarm display 36: Various alarms determined by the carrier wave receiver CPU 35 are displayed with a buzzer, a lamp, etc. (not shown).

  In the signal processing circuit described in FIG. 1, for example, in the case of an electric facility with a very low capacity, it is considered that the combined impedance Zab on the receiving side increases, the carrier wave sending current Is decreases, and reception becomes difficult. . In addition to the detection points shown in the figure, it may be necessary to receive the carrier transmission current Is at an arbitrary point in the same electric circuit.

  As described above, in order to avoid the inconvenience that the carrier transmission current Is decreases and signal transmission / reception becomes difficult, it is required to receive the carrier as a stronger one. At that time, as described in FIG. 4, it can be solved by providing a parallel resonant circuit 18 in parallel with the electric circuit 1 on the receiving side.

The operation of the parallel resonant circuit and reception of a carrier wave will be described. In the parallel resonant circuit 18 of FIG.
The combined impedance Zab between the power lines ab is reduced by the parallel resonance circuit 18 and Is is increased, so that a large received signal can be obtained.

-Since the parallel resonant circuit is separated from the power supply frequency and the frequency band, the power supply circuit is not affected.
-Even when a carrier wave is received at an arbitrary point connected to the same electric circuit, it can be received by providing a parallel resonance circuit.
The characteristics of the operation based on the configuration as described above can be exhibited.

The carrier transmission unit 12 provided in the detector 11 of the demand monitoring apparatus 10 uses a carrier wave such as 875 Hz (50 Hz system) that does not match the harmonics of the power supply frequency, and uses a modulation method such as ASK or PSK to transmit digital signals. Is going.
From the carrier sending unit 12 of the demand monitoring device 10, the modulated carrier signal is sent to the transformer 7 as a carrier sending current Is.

The carrier transmission current Is from the demand monitoring device constitutes a loop circuit that returns to the carrier transmission unit 12 of the demand detector 11 through the winding of the transformer 7. Then, the carrier wave sending current Is mainly flows through the transformer winding, and a carrier voltage signal (hereinafter referred to as “Zab”) is generated by a voltage drop caused by a combined impedance (hereinafter referred to as “Zab”) between the terminals a and b of the transformer 7 and the like. "Vs") occurs at the transformer terminal.
The receiver 16 of the demand monitoring device is configured to detect the carrier voltage signal Vs generated by the circuit, demodulate the carrier signal, and issue various alarms.

(Problems of the conventional method)
Next, the communication principle and problems of the current PLC system will be described again using the conventional example shown in FIG.
In the apparatus of the current PLC system (hereinafter referred to as “current PLC system”), as shown in the figure, the demand detector 11 installed in the responsibility demarcation column 5 or the like is provided in an electric room or office room. It is arranged to perform signal transmission in one direction toward the alarm indicator 15.

  Equivalent circuit of Zab; The equivalent circuit of the combined impedance Zab between the terminals a and b of the transformer 7 and the like is represented by the RLC parallel circuit 13 of FIG. 6, and R varies depending on the size of the load. As the resistance value decreases.

  The symbol L in the circuit diagram is an inductance of a transformer or the like, which mainly changes depending on the capacity of the transformer, and becomes smaller as the capacity increases, and the inductive reactance also decreases. Furthermore, the symbol C is based on low-voltage conversion by a low-load filter and a transformer of a power capacitor (high-voltage capacitor). The larger the electric equipment, the larger the value, and the larger the C reactance, the smaller the capacitive reactance. The capacitive reactance decreases.

  Correlation between Synthetic Impedance Zab and Carrier Voltage Signal Vs: When current Is flows through synthetic impedance Zab as shown in FIG. 7, voltage drop Vs is generated due to the impedance of Zab. The voltage drop Vs is expressed by Vs = Is × Zab, and the current Is is maintained at a substantially constant current, so that Vs is proportional to the magnitude of Zab.

To further explain the relationship between the Zab constant and the received voltage Vs,
-The capacity of the transformer and the power capacitor is large. As the load increases, the Zab decreases. When the capacity of the transformer, the power capacitor, etc. is small, the capacity increases.
-Since the carrier current transmitted from the transmitter often has constant current characteristics, even if the combined impedance changes, the change in the current value is small.
From the above conditions, the carrier voltage Vs received by the receiving unit is proportional to the combined impedance, so that there is a characteristic that Vs is smaller for larger capacity electrical equipment and Vs is larger for smaller capacity electrical equipment. .

However, many problems remain in the current PLC system as listed below.
・ When the electrical equipment becomes large-scale, the capacitive reactance due to the inductive reactance of the transformer and the power capacitor decreases, and the combined impedance Zab between the terminals a and b to which the carrier wave receiver is connected also decreases, so Vs also decreases. However, it is difficult to receive the carrier wave.
-When the number of loads using the filter capacitors of the low-voltage load equipment increases, the synthesized capacitance increases, Zab decreases, and reception of the carrier wave becomes difficult.

-Since the transmission unit and the reception unit use power lines, if the distance between both increases, the transmission unit is affected by transmission line impedance (hereinafter referred to as "Zlin"). Since the transmission line impedance Zlin is inserted in series between transmission and reception as shown in FIG. 8, when the distance between both increases, the value of Zlin increases, the transmission side cannot maintain constant current characteristics, and the current ls decreases. Since the carrier voltage Vs is small, it is difficult to receive the carrier.
・ Due to the increase in semiconductor devices such as inverters in recent years, electric circuit noise has increased, and the number of cases in which a carrier wave cannot be received is affected by noise in a band close to the carrier frequency.
As described above, there are many obstacles in the signal transmission system based on the current PLC system.

(Features of the present invention)
As described above, the conventional signal transmission system still has problems that require various solutions. In the present invention, as described with reference to FIG. 1, the demand detector 11 is provided at the end of the low piezoelectric path. The detection information is transmitted through the low piezoelectric path 1 from the carrier wave transmission unit 12 provided in FIG. The carrier wave receiving unit 16 arranged on the power receiving side constitutes the demand monitoring device 10 that receives information transmitted through the low piezoelectric path 1 and displays it on the display unit of the alarm indicator 15.

  Since the carrier transmission unit 12 of the demand detector is configured by a signal processing circuit as illustrated in FIG. 2, the carrier transmission unit of the demand monitoring device has a responsibility demarcation column 5 or the like. It is possible to perform unidirectional signal transmission from the demand detector 11 installed in to the alarm indicator 15 provided in the electric room or office.

  And, as shown in FIG. 3, by configuring the signal circuit in the carrier wave receiver, even if there is some noise in the transmission information, only the predetermined carrier frequency component can be detected, and signal transmission and reception is good. It can be done in the state.

  As a feature of this method, first, there is an advantage that carrier wave abnormality can be reduced. In other words, in the conventional system, the receivable carrier voltage is as low as about several hundred mV, so that it is easily affected by noise close to the carrier frequency. On the other hand, in this method, the carrier current sent by the carrier sending unit can be directly received without being attenuated, so that a very strong received signal exceeding several A can be obtained and affected by electric circuit noise. It is a difficult system.

  The method of the present invention can be applied to large-scale electrical equipment. That is, in the conventional system, when applied to a large-scale facility, the combined impedance Zab between the receiving terminals decreases, the receivable carrier voltage decreases, and the number of cases where the carrier cannot be received increases. On the other hand, this system can be applied to a large-scale facility because a very strong received signal can be obtained even when Zab is small.

The present invention can exhibit the feature that the transmission distance can be increased. That is, in the system of the present invention, a very strong received signal can be basically obtained, so that it is not easily affected by the transmission line impedance Zlin and the transmission distance is increased (the conventional system has a limit of several hundred meters). I can do it.
Further, since the change from the conventional method to the present method is basically only the carrier wave signal input circuit, the change of the method is easy.
The above characteristics can be exhibited.

1 Low piezoelectric path, 5 Responsible demarcation column, 6 Electrical room, 7 Transformer,
10 demand monitoring device, 11 demand detector, 12 carrier wave transmission unit,
15 alarm indicator, 16 carrier wave receiver, 17 current / voltage conversion circuit,
18 parallel resonance circuit, 21 carrier wave transmission part CPU, 22 A / D conversion circuit,
23 oscillation circuit, 24 modulation circuit, 25 driver amplifier,
26 coupling circuit, 30 carrier wave receiver, 31 detection CT,
33 BPF, 34 demodulation circuit, 35 carrier wave receiver CPU,
36 Alarm display device.

Claims (2)

Power line carrier transmission / reception device that transmits signals in one direction from a device such as a demand monitoring device installed at a demarcation pillar at the end of a low piezoelectric path to an alarm indicator installed in an electrical room or the like through a distribution line In
An information transmission device for transmitting information by injecting a carrier current having a frequency that does not match the power supply frequency and the harmonics of the power supply frequency is connected to one end away from the transformer of the two-wire type low piezoelectric circuit. An information receiving device is connected to the end on the side close to
The two-wire low piezoelectric path is connected to a transformer provided in an electrical room, and flows through the transformer winding through the low piezoelectric path at the other end of the low piezoelectric path and flows into the terminal at the other end of the information transmitting device. Forming a loop circuit, and configured as a device for transmitting information to and from the information receiving device in a state where the carrier current circulates in the loop circuit;
In the information receiving apparatus, the carrier current injected into the low piezoelectric path is directly received by a carrier detection current transformer installed in the vicinity of the transformer, and the received carrier current is converted into a carrier voltage by voltage conversion. A power line carrier wave communication device that performs unidirectional signal transmission used as information of A portion closer to the transformer than the current transformer for carrier wave detection is provided with a parallel resonance circuit that resonates with the carrier current frequency in parallel with the two-wire low piezoelectric path,
The configuration is such that a large received signal can be obtained by reducing the combined impedance between both terminals of the transformer winding and increasing the carrier wave sending current by passing the parallel resonant circuit. Item 4. A power line carrier transmission and communication device according to Item 1.

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