JP2015146648A - power line communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in communication quality and improve reliability even in a case in which an injection part of a master modem is connected only to a neutral line.SOLUTION: A power line communication system 1 includes a master modem 10 and a slave modem 20A, connected to a low voltage power distribution line 2 of a single-phase three-wire method that is connected to a secondary side of a transformer 4. A transmission/reception circuit 11 of the master modem 10 is connected, by an inductive coupling method, only to a neutral line 2b of the low voltage power distribution line 2 by way of the injection part 12. The slave modem 20A includes an injection part 22 connected, by a capacitive coupling method, to power lines 2a and 2c and the neutral line 2b respectively, a signal synthesis part 23 which is connected to each of the power lines 2a and 2c through the injection part 22 and takes in signals from both of the power lines 2a and 2c, for synthesizing, and a transmission/reception circuit 21 which is connected to the power lines 2a and 2c through the injection part 22 and the signal synthesis part 23, and connected to the neutral line 2b through the injection part 22.

Description

  The present invention relates to a power line communication system, and more particularly to a power line communication system that performs power line communication between a parent device and a plurality of child devices.

  In recent years, attention has been focused on power line communication (PLC) that performs communication by superimposing a high-frequency signal of 10 kHz or more on a power line. Previously, only the frequency range of 10 kHz to 450 kHz (hereinafter referred to as the low frequency band) was recognized as the frequency band for power line communication, but it was limited to 2 MHz to 30 MHz although it was limited to indoors due to revision of radio wave law in October 2006. It has been observed to use a higher bandwidth of. Accompanying this, high speed communication of several tens to several hundreds Mbps has become possible, and thus attention is particularly focused on use in homes and offices.

  However, power line communication systems that use a conventional low frequency band are still widely used. Specifically, examples are used for meter reading (data collection) of power meters at each house in an apartment house and device control from a remote location.

  When a communication system is constructed using a power line drawn into a house, means for superimposing a high-frequency signal on the power line is required. As one of them, there is an injection method for inductively coupling to a neutral wire of a low-voltage distribution line (see Patent Document 1).

  FIG. 8 is a configuration diagram of a conventional power line communication system 40.

  As shown in FIG. 8, the conventional power line communication system 40 includes a PLC modem (master modem) 10 on the master unit connected to the single-phase three-wire low voltage distribution line 2 and a PLC modem (master modem) (Slave unit modem) 20A, 20B.

  The low-voltage distribution line 2 includes three power lines 2a, 2b, and 2c connected to the secondary side of the pole transformer 4 (transformer) that steps down the voltage (6600V) of the high-voltage distribution line to the commercial voltage (100V). . Of the power lines 2a, 2b, and 2c, the power lines 2a and 2c (red line and black line) connected to both ends of the secondary side of the pole transformer 4 are ungrounded lines and are connected to the middle point of the secondary side. The power line (white line) is a neutral line 2 b that is grounded to the ground via the ground line 6.

  The base unit modem 10 is connected to a neutral line 2b (white line) of the low-voltage distribution line 2 via an inductive coupling type injection unit 12. The high frequency signal transmitted from the transmission / reception circuit 11 of the base modem 10 is superimposed on the neutral line 2b from the injection unit 12. Since the neutral line 2b is a common line, a high frequency signal can be transmitted to both the handset modem 20A installed in the red and white phase and the handset modem 20B installed in the black and white phase. Therefore, data communication can be performed between the master modem 10 and the slave modems 20A and 20B.

  Since the impedance of the pole transformer 4 with respect to the high-frequency signal of power line communication is almost 0 ohm, the electric circuit length from the secondary side terminal of the pole transformer 4 to the place where the injection unit 12 of the master modem 10 is connected is short. If too much, the impedance on the pole transformer 4 side viewed from the base modem 10 becomes almost 0 ohms. Therefore, in the case of the capacitive coupling type injection unit, the high-frequency signal transmitted from the master modem 10 is sucked into the pole transformer 4 and does not reach the slave modems 20A and 20B. On the other hand, by adopting the inductive coupling type injection unit 12, the high-frequency signal from the master modem 10 is superimposed on the current flowing through the low-voltage distribution line 2, so that it is installed near the pole transformer 4. Deterioration of signal quality can be prevented.

JP 2004-532562 A

  In the conventional power line communication system shown in FIG. 8, the injection unit 12 of the master modem 10 is installed near the pole transformer 4, and the high-frequency signal injected from the injection unit 12 branches into a red-white phase and a black-white phase. Therefore, both of the handset modems 20A and 20B can receive a high frequency signal. However, since the received signal level is halved, it has been difficult to communicate with a remote handset. When the power line communication system is used for meter reading of a power meter, the installation cost is reduced as the number of slave units communicating with one master unit is reduced. Therefore, it is desirable that communication with a remote unit is possible.

  The present invention has been made to solve the above problems, and an object of the present invention is to prevent deterioration in communication quality even when the injection unit of the master modem is connected only to the neutral line. It is an object of the present invention to provide a highly reliable power line communication system.

  In order to solve the above-described problems, a power line communication system according to the present invention is a power line communication system that transmits and receives signals by superimposing a high-frequency signal on a power line, and transforms the voltage of a high-voltage distribution line into a commercial voltage by stepping down the voltage. A main unit modem connected to a single-phase three-wire low-voltage distribution line connected to the secondary side of the transformer and a first slave unit modem, the low-voltage distribution line being connected to the secondary side of the transformer First and second power lines connected to both ends, and a neutral line connected to the middle point of the secondary side, and the master modem is connected to only the neutral line by an inductive coupling method A first injection unit, and a first transmission / reception circuit connected to the neutral line via the first injection unit, the first handset modem includes the first power line, the first power line, Capacitive coupling for the second power line and the neutral line Connected to each of the first and second power lines via the second injection unit connected through the second injection unit, and signals from both the first power line and the second power line A signal synthesizing unit that captures and synthesizes the signal, and is connected to the first and second power lines via the second injection unit and the signal synthesizing unit, and is connected to the neutral via the second injection unit. And a second transmission / reception circuit that is connected to a line and generates the high-frequency signal.

  When the first injection unit of the main unit modem is installed near the transformer, the high frequency signal injected from the main unit modem flows to the transformer side, and further branches to the first power line side and the second power line side As a result, the level of the received signal that the slave modem can extract from one power line is halved, but if the slave modem has a signal synthesizer, its reception characteristics can be improved, The reliability of the entire power line communication system can be improved. Furthermore, according to the present invention, it is possible to configure a very simple master unit modem composed of only one injection unit, thereby shortening the installation work time and keeping the installation cost low. be able to. Moreover, since the injection part can be reduced in size, component costs can be kept low.

  The power line communication system according to the present invention further includes a power meter for measuring the amount of power, the first handset modem is connected to the power meter, and the power amount data measured by the power meter is stored in the base unit. Preferably it is sent to the modem. According to this configuration, it is possible to monitor a power meter installed at a distance as viewed from the parent device, and to construct a highly reliable remote meter reading system.

  The power line communication system according to the present invention further includes a second slave unit modem connected to the low-voltage distribution line, and the second slave unit modem is one of the first power line and the second power line. And a third injection part connected to the neutral line by a capacitive coupling method, and between the neutral line and one of the first and second power lines via the third injection part. The second handset modem is preferably installed closer to the transformer than the first handset modem. The slave modem in the vicinity of the master modem has a basic method of receiving a signal from either the first power line or the second power line, and the slave modem far from the master modem has the first and second power lines. By adopting a highly reliable method for receiving the composite signal of the signal superimposed on the base, a single master modem can cover a large area, greatly increasing the cost of constructing a power remote meter reading system Can be suppressed.

  In this invention, it is preferable that the said 1st injection part is provided until each power line of the said low voltage distribution line extended from the secondary side terminal of the said transformer is concentrated from the state mutually isolate | separated. . In this case, it is preferable that the first injection unit is connected within a range from a secondary side terminal of the transformer to a line length of 2 m. According to this configuration, the master modem can be easily installed near the pole transformer. Therefore, the installation work time can be shortened by this, and the installation cost can be kept low.

  In the present invention, the first injection portion includes a toroidal core formed by combining two semi-annular cores and a signal wire wound around the toroidal core, and the neutral wire is formed of the toroidal core. It is preferable to penetrate the hollow portion. According to this, magnetic saturation can be prevented by forming a magnetic gap in the middle of the magnetic path, and installation on a power line can be easily performed.

  According to the present invention, even when the inductive coupling method injection unit of the main unit modem is connected only to the neutral line, it is possible to communicate with a distant sub unit modem without lowering the communication quality, A highly reliable power line communication system can be provided.

FIG. 1 is a configuration diagram of a power line communication system 1 according to the first embodiment of the present invention. FIG. 2 is a configuration diagram of the master modem 10. FIG. 3 is a schematic perspective view showing the configuration of the injection unit 12 of the base modem 10. FIG. 4 is a schematic diagram illustrating an installation example of the pole transformer 4 and the power lines 2a to 2c. FIG. 5 is a configuration diagram of the slave modem 20A. FIG. 6 is a configuration diagram of the slave modem 20C. FIG. 7 is a graph showing signal reception characteristics of the power line communication system according to the present invention. FIG. 8 is a configuration diagram of a conventional power line communication system 40.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a power line communication system 1 according to the first embodiment of the present invention.

  As shown in FIG. 1, a power line communication system 1 includes a PLC modem (master modem) 10 on a master unit connected to a single-phase three-wire low voltage distribution line 2 and a PLC modem (slave unit) on a slave unit side. Modem) 20A, 20B, 20C.

  The low voltage distribution line 2 includes three power lines 2a connected to the secondary side (low voltage side) of the pole transformer (transformer) 5 that steps down the voltage (6600V) of the high voltage distribution line 3 to the commercial voltage (100V). 2b, 2c. Among these power lines, the power lines 2a and 2c (red line and black line) connected to one end and the other end on the secondary side of the pole transformer 4 are ungrounded lines, but connected to the midpoint of the secondary side. The power line (white line) is a neutral line 2 b that is grounded to the ground via the ground line 5. Therefore, the voltage at both ends (red and black phase) of the secondary transformer 4 is 200V, and between the power line 2a or 2c and the neutral line 2b (red and white phase, black and white phase) is 100V.

  Generally, the low-voltage distribution line 2 extending from the pole transformer 4 is connected to each home appliance 7 via a power meter 6 in a power consumer. The base modem 10 is mounted together with the pole transformer 4 and is connected to the low-voltage distribution line 2 and is also connected to the server 9 via an optical fiber line 8 installed near the pole transformer 4. The handset modems 20A, 20B, and 20C are connected to the low-voltage distribution line 2 drawn into each electric power consumer and are connected to the power meter 6 and used for metering the amount of power.

  FIG. 2 is a configuration diagram of the master modem 10.

  As shown in FIG. 2, the base modem 10 includes a transmission / reception circuit 11 and an inductive coupling type injection unit 12, and the transmission / reception circuit 11 is connected to the low-voltage distribution line 2 via the injection unit 12. The injection unit 12 is connected only to the neutral line 2b (white line) among the three power lines. In detail, the injection part 11 has the toroidal core 13 and the signal wire | line 14, and the neutral wire 2b has penetrated the hollow part of the toroidal core 13. As shown in FIG. The transmission / reception circuit 11 of the master modem 10 is connected to the primary side of the transformer T1, one end on the secondary side of the transformer T1 is connected to one end of the signal line 14, and the other end on the secondary side of the transformer T1 is connected to the signal line 14. Is connected to the other end.

  The high frequency signal transmitted by the base modem 10 is superimposed on the neutral line 2b from the injection unit 12. Since the neutral line 2b is a common line, not only the handset modem 20C connected to both the red white phase and the black white phase, but also the handset modem 20A connected to the red white phase and the handset connected to the black white phase. A high frequency signal can also be transmitted to the modem 20B. Therefore, data communication can be performed between the master modem 10 and the slave modems 20A, 20B, and 20C.

  The value of the current flowing through the neutral wire 2b is the difference between the red and white phase and the black and white phase. For example, when a current of 400 A flows in the red-white phase and a current of 300 A flows in the black-white phase, the current value of the neutral line 2 b is 100 A, which is the difference between the two. For this reason, the saturation current value of the toroidal core of the injection part 12 which is a problem in the inductive coupling method can be made relatively small, and the size of the toroidal core in the diameter direction can be made small.

  The base modem 10 is connected to the neutral line 2b by an inductive coupling method. Since the impedance of the pole transformer 4 with respect to the high-frequency signal of power line communication is almost 0 ohms, the electric circuit length from the secondary side terminal of the pole transformer 4 to the position where the injection unit 12 of the master modem 10 is connected is short. If it is too large, the impedance on the pole transformer 4 side as seen from the base modem 10 becomes approximately 0 ohm. Therefore, in the case of the capacitive coupling method, the high frequency signal transmitted from the parent modem 10 is sucked into the pole transformer 4 and does not reach the child modems 20A to 20C. On the other hand, when the inductive coupling type injection unit 12 is adopted, the high frequency signal is superimposed on the current flowing through the low voltage distribution line 2, so that the adverse effect caused by installing the base unit modem 10 near the pole transformer 4 is adversely affected. It can be avoided.

  FIG. 3 is a schematic perspective view showing the configuration of the injection unit 12 of the base modem 10.

  As shown in FIG. 3, the injection unit 12 includes a toroidal core 13 formed by combining two semi-annular cores 13 a and 13 b and a single signal line 14 wound around the toroidal core 13. Are connected to a pair of external terminals of the base modem 10. Neutral wire 2b passes through the hollow portion of toroidal core 13, whereby base modem 10 is connected to neutral wire 2b by an inductive coupling method. The number of turns of the signal line 14 wound around the toroidal core 13 is preferably 3 to 4 turns.

  As the material of the toroidal core 13, it is preferable to use nickel-based ferrite when the communication frequency is 2 MHz to 30 MHz, and when the communication frequency is 10 kHz to 450 kHz, manganese-based ferrite, amorphous material, Alternatively, it is preferable to use a nanocrystal material.

  FIG. 4 is a schematic diagram illustrating an installation example of the pole transformer 4 and the power lines 2a to 2c.

  As shown in FIG. 4, a pole transformer 4 is installed on an H pole base 33 bridged between two power poles 31 and 32, and a power line 2 a extending from a secondary side external terminal of the pole transformer 4. ˜2c extends downward and is concentrated by a sheath (collecting pipe) 34 from the middle. The line length L of the power line from the pole transformer 4 to the insertion into the sheath 34 is relatively short and within 2 m.

  The base unit modem 10 is attached to a position near the pole transformer 4 on the power pole 32, and takes in power from the pole transformer 4 via the power cable 35. In addition, the toroidal core 13 of the injection part 12 is installed on the neutral wire 2b until it is inserted from the pole transformer 4 into the sheath 34. In the range from the pole transformer 4 to the sheath 34, the toroidal core 13 can be easily attached to each power line.

  Since the power lines 2a to 2c in the vicinity of the pole transformer 4 are thick due to the current capacity and are often close to each other due to workability, it is very difficult to install the large toroidal core 13. However, according to this embodiment, since the size of the toroidal core 13 in the diameter direction can be reduced, the installation property can be improved. Therefore, the installation time can be shortened and the installation cost can be reduced.

  Each of the handset modems 20A, 20B, and 20C includes a transmission / reception circuit 21 and a capacitive coupling type injection unit 22, and the transmission / reception circuit 21 is connected to the low-voltage distribution line 2 via the injection unit 22.

  FIG. 5 is a configuration diagram of the slave modem 20A.

  As shown in FIG. 5, the handset modem 20 </ b> A is connected between the power line 2 a (red line) and the neutral line 2 b (white line) of the low-voltage distribution line 2. Specifically, the transmitting / receiving circuit 21 of the slave modem 20A is connected to the primary side of the transformer T2, and one end of the secondary side of the transformer T2 is connected to the power line 2a via the capacitor C1, and the secondary side of the transformer T2 is connected to the secondary side. The other end is connected to the neutral wire 2b via the capacitor C2.

  The configuration of the slave unit modem 20B is the same as that of the slave unit modem 20A, and only the connection to the low voltage distribution line 2 is different. The slave modem 20B is connected between the power line 2c (black line) and the neutral line 2b (white line) of the low-voltage distribution line 2. Specifically, the transmission / reception circuit 21 of the slave modem 20B is connected to the primary side terminal of the transformer T2, and one end of the secondary side of the transformer T2 is connected to the power line 2c via the capacitor C1, and the secondary side of the transformer T2 The other end of is connected to the neutral wire 2b via the capacitor C2.

  FIG. 6 is a configuration diagram of the slave modem 20C.

  As shown in FIG. 6, the slave modem 20 </ b> C further includes a signal synthesis unit 23. A pair of output terminals of the transmission / reception circuit 21 of the slave modem 20C is connected to the primary side of the transformer T2. One end of the secondary side of the transformer T2 is connected to the combining side terminal of the signal combining unit 23, and the other end of the secondary side is connected to the neutral line 2b via the capacitor C5. One terminal on the branch side of the signal synthesizer 23 is connected to the power line 2a which is one non-ground line via the capacitor C3, and the other terminal on the branch side is connected to the other non-ground via the capacitor C4. It is connected to the power line 2c which is a line. With the above configuration, the signal synthesizing unit 23 of the slave modem 20C has both the high frequency signal component superimposed on one power line 2a (red line) and the high frequency signal component superimposed on the other power line 2c (black line). Is taken in and synthesized.

  When the injection unit 12 of the base modem 10 is installed near the pole transformer 4, the high-frequency signal injected from the injection unit 12 branches and flows into a red-white phase and a black-white phase. In either case, the handset modems 20A and 20B can receive a high-frequency signal, but the received signal level is halved, making it difficult to communicate with a remote handset.

  Therefore, as in the present embodiment, the transmission / reception circuit 21 of the slave modem 20C takes in signals from both the red line and the black line and synthesizes them to synthesize a high-frequency signal branched into a red-white phase and a black-white phase. be able to. Therefore, when installed at the same position, the reception level can be made higher than that of the conventional handset modems 20A and 20B without the signal synthesizing unit 23, thereby improving the transmission performance.

  FIG. 7 is a graph showing signal reception characteristics of the power line communication system according to the present invention, where the horizontal axis represents frequency (kHz) and the vertical axis represents gain (dB). FIG. 7 shows the reception characteristics (graph G1) when using the slave unit modem 20C having the signal synthesis unit 23 and the slave unit modems (slave unit modems 20A and 20B) not having the signal synthesis unit 23. The reception characteristics (graph G2) are shown. In addition, in order to evaluate both on the same conditions, the connection position of the injection part to a low voltage distribution line is the same. As is apparent from this graph, the gain of the received signal when the signal injected from the parent device modem 10 to the neutral line 2b is received by the child device modem 20C is received by the child device modem 20C having the signal synthesis unit 23. It can be seen that the case is larger, and the case where the signal is received by the slave modem not having the signal synthesis unit 23 is smaller.

  As described above, in the power line communication system 1 according to the present embodiment, the slave modem 20C includes the signal combining unit 23, and the signal components of the two power lines 2a and 2c that are non-ground lines are combined and captured. The reception characteristics of the slave modem can be improved, and the reliability of the entire power line communication system can be improved. Actually, a slave unit in the vicinity of the master unit receives a signal only from either the red-white phase or the black-white phase, and a remote slave unit receives a combination of red and black so that one master unit is received. Because it can cover a wide area, it is possible to greatly reduce the cost for constructing a power remote meter reading system.

  Moreover, since the power line communication system 1 according to the present embodiment is configured such that the injection unit 12 of the parent modem 10 is connected only to the neutral line 2b by the inductive coupling method, the power line communication system 1 can have a very simple configuration. As a result, it is possible to reduce the installation time of the master unit and to reduce the installation cost. Further, since the size of the injection portion in the diameter direction can be reduced, the material cost can be suppressed, and the injection component price can be reduced.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above embodiment, the case where the injection unit 12 of the base modem 10 is installed near the pole transformer 4 is described as an example. However, it can be installed at a position away from the pole transformer 4. It is. That is, the injection unit 12 of the base modem 10 may be installed at a position where the pole transformer 4 does not appear to be substantially short-circuited. Such a distance is at least 10 m or more, and on average several tens of m.

  Moreover, in the said embodiment, although the case where the injection part 12 of the main | base station modem 10 was installed in the vicinity of the pole top transformer 4 was mentioned as an example, it is not limited to a pole top transformer, The electric power of an apartment The present invention can be applied to various transformers connected to a low voltage distribution line such as a transformer installed indoors.

  The configuration of the power line communication system 1 shown in FIG. 1 is an example, and the layout of the low-voltage distribution line 2 and the number and arrangement of the slave modems are not particularly limited.

1 Power Line Communication System 2 Low Voltage Distribution Line 2a Power Line 2b Power Line (Neutral Line)
2c Power line 3 High voltage distribution line 4 Pillar transformer (transformer)
DESCRIPTION OF SYMBOLS 5 Ground line 6 Electric power meter 7 Household appliances 8 Optical fiber line 9 Server 10 Parent machine modem 11 Transmission / reception circuit 12 Injection part 13 Toroidal core 13a, 13b Core 14 Signal line 20A, 20B, 20C Child machine modem 21 Transmission / reception circuit 22 Injection part 23 Signal synthesizers 31 and 32 Utility pole 33 Pillar base 34 Sheath 35 Power cable 40 Power line communication system

Claims (6)

A power line communication system for transmitting and receiving signals by superimposing a high frequency signal on a power line,
A main unit modem and a first sub unit modem connected to a single-phase three-wire low-voltage distribution line connected to the secondary side of a transformer that steps down the voltage of the high-voltage distribution line and converts it to a commercial voltage ,
The low-voltage distribution line includes first and second power lines connected to both ends of the secondary side of the transformer, and a neutral line connected to a midpoint of the secondary side,
The master modem is
A first injection unit connected to only the neutral wire by inductive coupling;
A first transmission / reception circuit connected to the neutral line via the first injection unit,
The first handset modem is:
A second injection unit connected to each of the first power line, the second power line, and the neutral line by a capacitive coupling method;
A signal combining unit that is connected to each of the first and second power lines via the second injection unit, and that takes in and combines signals from both the first power line and the second power line;
The high-frequency signal is generated by being connected to the first and second power lines through the second injection unit and the signal synthesis unit and to the neutral line through the second injection unit. And a second transmission / reception circuit. A power meter for measuring the amount of power;
2. The power line communication system according to claim 1, wherein the first handset modem is connected to the power meter and transmits power amount data measured by the power meter to the base modem. A second handset modem connected to the low-voltage distribution line;
The second handset modem is:
A third injection unit connected to any one of the first power line and the second power line and the neutral line by a capacitive coupling method;
3. A third transmission / reception circuit connected between one of the first and second power lines and the neutral line via the third injection unit. 2. The power line communication system according to 2.   The first injection unit is provided between the time when the power lines of the low-voltage distribution line extending from the secondary terminal of the transformer are separated from each other and concentrated. The power line communication system according to any one of claims 1 to 3.   5. The power line communication system according to claim 1, wherein the first injection unit is connected within a range from a secondary side terminal of the transformer to a line length of 2 m. 6. . The first injection portion includes a toroidal core formed by combining two semi-annular cores, and a signal line wound around the toroidal core,
The power line communication system according to claim 1, wherein the neutral wire passes through a hollow portion of the toroidal core.

Images