JP2015133627A - power line communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely distribute a broadcast signal from a master unit PLC modem to all slave unit PLC modems while preventing a power line network from getting involved in congestion.SOLUTION: The power line communication system comprises a master unit modem 11 and a plurality of slave unit modems 13 connected to a power line network 5. The master unit modem 11 distributes a broadcast signal onto the power line network 5. The master unit modem 11 selects at least one slave unit modem from among slave unit modems 13 that have returned a response signal to the broadcast signal as a relay unit. The selected slave unit modem distributes a second broadcast signal onto the power line network 5. A slave unit modem 13 receiving the broadcast signal for the first time transmits a response signal to the broadcast signal, and a slave unit modem 13 that is a transmission source of the broadcast signal transfers the response signal to the master unit modem 11.

Description

  The present invention relates to a power line communication system, and more particularly to a power line communication system preferably used in an automatic metering system for power consumption.

  In recent years, in electric power companies, introduction of an automatic meter-reading system that collects power usage from a remote location via a power line is progressing (see, for example, Patent Document 1).

  In the automatic meter reading system, a master PLC (Power Line Communication) modem is attached to a utility pole, etc., and a slave PLC modem for transmitting meter reading data to the master PLC modem is built in the power meter at each customer's house. Is done. Since these PLC modems use a power line connecting a power pole and a power meter as a communication path, there is no need to newly lay a communication line, which is very advantageous in terms of introduction cost.

JP 2011-223063 A

  In power line communication, a master PLC modem may broadcast a test signal for route understanding, device search, and the like. In addition, a reference signal for determining the timing of communication between the parent device and the child device PLC modem may be periodically broadcast. These broadcast signals need to be reliably distributed to all the slave PLC modems under the parent device connected to the power line network.

  As a method of distributing the broadcast signal to all the slave PLC modems on the power line network, there is a method of redistributing the broadcast signal to the slave PLC modem that has received the broadcast signal. In this method, for example, the maximum number of relays is set to “5”, for example, and the number of relays is decremented every time the broadcast signal passes through the slave PLC modem. When the number of relays reaches “0”, the broadcast signal is redistributed. Terminate. That is, the broadcast signal is redistributed five times by the slave PLC modem. According to this method, it is possible to deliver a broadcast signal to a remote slave PLC modem that does not directly receive a broadcast signal from the master PLC modem.

  However, since the power line network forms a mesh topology, a broadcast signal redistributed from a slave PLC modem is received by a slave PLC modem that has already received the broadcast signal, and is further redistributed. Therefore, there is a problem that the broadcast signal reciprocates between the slave PLC modems that have already received the broadcast signal. That is, there is a problem that the broadcast signal strays on the power line network and the power line communication is congested.

  In particular, when the number of power meters is very large, such as apartment houses such as condominiums, and the number of slave PLC modems allocated to a single master PLC modem is as large as several tens to hundreds. The problem due to the redistribution of broadcast signals becomes significant. This problem increases as the maximum number of relays is increased in order to reliably deliver a broadcast signal to a remote slave PLC modem. In the worst case, the network may be down due to a so-called broadcast storm.

  Accordingly, an object of the present invention is to provide a power line communication system capable of reliably delivering a broadcast signal from a parent PLC modem to all the slave PLC modems while preventing congestion of the power line network. .

  In order to solve the above problems, a power line communication system according to the present invention includes a master PLC modem connected to a power line network and a plurality of slave PLC modems connected to the master PLC modem via the power line network. The master PLC modem distributes a first broadcast signal set not to be relayed by the slave PLC modem over the power line network, and the first broadcast signal among the plurality of slave PLC modems. The slave PLC modem that has received the signal transmits a first response signal to the first broadcast signal on the power line network, and the master PLC modem returns the first response signal. At least one slave PLC modem is selected from the PLC modems, and the slave PLC model is selected. Transmits an instruction signal instructing to distribute a second broadcast signal having the same content as the first broadcast signal, and the slave PLC modem instructed to distribute the second broadcast signal includes: The slave PLC modem that distributes the second broadcast signal set not to be relayed by the slave PLC modem to the power line network and receives the second broadcast signal among the slave PLC modems. The slave PLC modem that transmits the second response signal to the second broadcast signal on the power line network and distributes the second broadcast signal sends the second response signal to the master PLC modem. Forward.

  According to the present invention, a remote slave unit that cannot directly receive a broadcast signal from the master unit PLC modem is located near the slave unit and has been distributed from the slave unit PLC modem that has already received the broadcast signal. Since the broadcast signal is distributed, the broadcast signal can be reliably distributed to all the slave units. In addition, since many slave PLC modems that have received a broadcast signal from the master PLC modem do not redistribute the broadcast signal, the occurrence of a broadcast storm can be suppressed, and the broadcast signal can be efficiently distributed.

  In the present invention, the master unit PLC modem returns the first response signal until it receives the first or second response signal from all the slave unit PLC modems on the power line network. It is preferable to repeat the process of instructing the slave PLC modem selected from the PLC modems to distribute the second broadcast signal. In this case, the slave PLC modem that transmits the second response signal is preferably a slave PLC modem that has not received the first broadcast signal and that has received the second broadcast signal for the first time. According to this, it is possible to prevent unnecessary response signals from being transmitted on the power line network, and to reduce signal collisions on the power line network as much as possible.

  In the present invention, it is preferable that the master PLC modem selects the at least one slave modem based on the reception level of the first response signal. According to this, it is possible to select a remote slave modem as viewed from the master by a very simple method.

  The power line communication system according to the present invention further includes a plurality of power meters provided corresponding to the plurality of slave PLC modems and connected to the power lines constituting the power line network, each of the plurality of power meters measuring The meter reading data is preferably transmitted from the corresponding slave PLC modem to the master PLC modem via the power line network. In the so-called automatic meter reading system, a large number of slave PLC modems are provided for one master PLC modem, so that a broadcast signal can be reliably transmitted to each slave PLC modem. It is remarkable.

  ADVANTAGE OF THE INVENTION According to this invention, the power line communication system which can deliver reliably the broadcast signal from a main | base station PLC modem to all the subunit | mobile_unit PLC modems can be provided, preventing the congestion of a power line network.

FIG. 1 is a schematic diagram showing an example of the configuration of an automatic meter reading system to which a power line communication system according to the present invention is applied. FIG. 2 is a block diagram functionally showing the configuration of the PLC modem. FIG. 3 is a schematic block diagram showing an example of the configuration of a power line communication system realized by the remote meter reading system of FIG. FIG. 4 is a diagram showing the topology of the power line network in the power line communication system 10 shown in FIG. FIG. 5 is a flowchart for explaining the communication operation between the parent device and the child device modem.

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

  FIG. 1 is a schematic diagram showing an example of the configuration of an automatic meter reading system to which a power line communication system according to the present invention is applied.

  As shown in FIG. 1, this automatic meter reading system 1 is used for metering the amount of power used in each of the doors 9a to 9d of the apartment house 9, for example. , Simply referred to as “master modem”) and slave PLC modems 13a to 13d (hereinafter simply referred to as “slave modem”) built in the power meters 12a to 12d of the respective houses. And remote meter-reading of electric power consumption is implement | achieved by the power line communication between the main | base station modem 11 and several subunit | mobile_unit modems 13a-13d.

  The electric power supplied from the substation 3 is supplied to the consumer electronics devices 8a to 8d of the respective consumers a to d via the pole transformer 4, the power lead-in wire 5a, the power meters 12a to 12d, and the breakers 16a to 16d. . One communication terminal of the base modem 11 is connected to the meter-reading server 7 (first server) via, for example, the optical network 6, and the other communication terminal is connected to the power lead-in line 5a.

  One communication terminal of the slave modems 13a to 13d is connected to the controllers 15a to 15d of the corresponding power meters 12a to 12d, respectively, and the other communication terminal is connected to the power lead-in line 5a. In addition, when each subunit | mobile_unit modem 13a-13d is incorporated in the electric power meter 12a-12d, the controllers 15a-15b are positioned as a power meter of the narrow sense with respect to those subunit | mobile_unit modem.

  FIG. 2 is a block diagram functionally showing the configuration of the PLC modem. The PLC modem 20 is a general-purpose one that can be used in common for both the master modem 11 and the slave modems 13a to 13d.

  As shown in FIG. 2, the PLC modem 20 includes a control unit 21, a memory 22, an interface (I / F) 23, a communication unit 24, a modulation unit 25, a transmission unit 26, a demodulation unit 27, a reception unit 28, and a multiplexer 29. Have.

  The control unit 21 acquires various types of information from the host device and controls each unit of the PLC modem 20 based on the acquired information. The host device referred to here is the meter reading server 7 if the master modem 11 and the controller 15a of the power meter 12a if the slave modem 13a.

  The memory 22 is a storage unit that stores data input from the host device in accordance with an instruction from the control unit 21. Various information including setting information is recorded in the memory 22.

  The interface unit 23 is an interface with a higher-level device, receives higher-layer data from the higher-level device, and outputs it to the communication unit 24. Also, the upper layer data is received from the communication unit 24 and is output to the upper device.

  The communication unit 24 is a functional unit that processes transmission / reception signals including a header, and is configured by, for example, a DSP (Digital Signal Processor). Specifically, the upper layer data to be transmitted is received from the interface unit 23, a header including pilot data, a destination MAC address, and the like, and redundant data for error correction are added, and the modulation unit is transmitted as transmission data. 25. In particular, when a broadcast signal is transmitted, a flag indicating the broadcast signal and the maximum number of relays (relay number data) are included in the header. In addition, receiving data including a header and higher layer data is input from the demodulator 27, and processing and error correction processing corresponding to the header in the received data are performed, and higher layer data is output to the interface unit 23.

  The modulation unit 25 selects one modulation method from the OFDM modulation method and the phase modulation method in accordance with an instruction from the control unit 21. Then, using one selected modulation method, the carrier signal is modulated based on the transmission data, a predetermined preamble including a known synchronization signal corresponding to the modulation method is added, and the radio wave law enforcement regulations (carrier output) ), The amplitude of the signal is controlled in accordance with the communication method used for the modulation process, and then output to the transmitter 26.

  The transmission unit 26 has a function of converting the signal input from the modulation unit 25 into a signal that can be transmitted to the power line, and then transmitting the signal to the power line. Specifically, the digital signal input from the modulation unit 25 is converted into an analog signal, an unnecessary frequency band component is removed using a bandpass filter, and the multiplexer 29 is further amplified by a predetermined amplification factor. To the power line.

  The control unit 21 of the PLC modem 20 that has received the output level setting information from the host device stores the output level setting information in the memory 22. The transmission unit 26 amplifies the transmission signal in accordance with the output level setting information stored in the memory 22 and sends it to the power line.

  The receiving unit 28 has a function of receiving a signal arriving on the power line, converting it to a digital signal, and outputting the digital signal to the demodulating unit 27. Specifically, unnecessary high and low frequency components are removed from the signal received through the multiplexer 29 using a band pass filter, further amplified with a predetermined amplification factor, sampled and converted into a digital signal, and demodulator 27.

  The demodulator 27 has a function of demodulating the digital signal input from the receiver 28 using an OFDM modulation scheme and a phase modulation scheme. The demodulator 27 outputs a signal obtained by demodulation to the communication unit 24. The demodulator 27 has a synchronization detection function for detecting a known synchronization signal from the signal input from the receiver 28. The synchronization signal detected here is an OFDM modulation system synchronization signal or a phase modulation system synchronization signal, and the demodulation unit 27 determines a modulation system to be used for demodulation from the detected synchronization signal.

  The PLC modem according to the present embodiment has a function of generating and distributing a broadcast signal. Further, the PLC modem has a function of redistributing the broadcast signal based on the relay number data included in the header of the received broadcast signal.

  FIG. 3 is a schematic block diagram showing an example of the configuration of a power line communication system realized by the remote meter reading system of FIG. FIG. 4 is a diagram showing the topology of the power line network in the power line communication system 10 shown in FIG.

  As shown in FIGS. 3 and 4, the power line communication system 10 according to the present embodiment includes a master modem 11 and a plurality of slave modems 13. A general residential power line network 5 has a mesh topology, and the master modem 11 is connected to the slave modem 13 in each power meter via the power line network 5. A broadcast signal from the parent device modem 11 is delivered to each child device modem 13 via the power line network 5.

  The signal transmission characteristic of the power line communication is good, and signals can be delivered to a large number (for example, 70 to 80%) of the slave modems by the first broadcast delivery from the master modem 11. On the other hand, broadcast distribution via a specific slave unit modem 13 functioning as a relay unit is performed for a remote slave unit modem 13 that cannot directly deliver a broadcast signal.

  The slave modems 13 on the power line network 5 are divided into a plurality of groups according to the distance from the master modem 11. In the present embodiment, the remote modems T1 to T12 and T19 to T26 of the first group G1 provided within a certain range within which the signal from the master modem 11 can reach, and farther than the slave modems of the first group G1 The second group G2 slave modems T13 to T18, T27 to T32 provided within a certain range of the second group G2, and the third group G3 child provided within a certain range farther than the second group G2 slave modems. It is divided into machine modems T33 to T36. Since such a power line network 5 has a larger number of slave modems that can be directly accessed from the master modem 11 than a low-power wireless network such as Zigbee (registered trademark), for example, the number of stages in the tree structure is small. There are only 3 stages.

  The base modem 11 can arbitrarily set the maximum number of relays of the broadcast signal, and each of the handset modems T1 to T36 has a function of redistributing the broadcast signal based on the relay number data included in the broadcast signal. Yes. However, in this embodiment, the maximum number of relays is set to “0”. This setting is a setting in which each slave modem does not redistribute the broadcast signal even if the broadcast signal is directly received from the master modem 11. Instead, the base unit modem 11 selects a remote handset modem from the handset modems that have received the broadcast signal, and instructs the handset modem to redistribute the broadcast signal. This step is repeated until a broadcast signal reaches all the handset modems T1 to T36. Hereinafter, it will be described in detail with reference to a flowchart.

  FIG. 5 is a flowchart for explaining the communication operation between the parent device and the child device modem.

  As shown in FIG. 5, the base modem 11 first distributes a broadcast signal (first broadcast signal) over the power line network 5 (step S11). The master modem 11 can set the maximum number of relays in the broadcast signal, but here the maximum number of relays is set to “0” so that the slave modem does not function as a repeater.

  The slave modems T1 to T12 and T19 to T26 of the first group G1 that have received the broadcast signal transmit a response signal (first response signal) to the broadcast signal on the power line network 5 (step S12). . As described above, since the number of broadcast signal relays is set to “0”, the slave modems T1 to T12 and T19 to T26 do not redistribute the broadcast signal. By limiting the relay of broadcast signals in this way, stray broadcast signals on the power line network 5 can be suppressed.

  Next, base unit modem 11 checks whether or not response signals have been sent from all the handset modems (step S13), and if so, broadcast signal distribution ends (step S13Y). If it has not been sent, the broadcast signal is redistributed via the slave modem (steps S13N, S14 to S16).

  In the redistribution of the broadcast signal, the base unit modem 11 selects at least one handset modem from the plurality of handset modems T1 to T12 and T19 to T26 that have sent the response signal (step S14). An instruction signal for instructing the slave modem to deliver a broadcast signal is transmitted (step S15). The slave modem selected at this time is preferably located as far as possible from the master modem 11. For example, the response signal having the lowest level is transmitted by comparing the signal levels of the response signals. Select the handset modem. 3 and 4, the two slave modems T11 and T26 in the group G1 are selected as relay devices (proxy master devices).

  Next, the specific handset modems T11 and T26 that have been selected as the relay device and received the instruction signal distribute the second broadcast signal (second broadcast signal) to the power line network 5 (step S16). Of the handset modems that can receive the second broadcast signal, the handset modems T13 to T18, T27 to T32 that are unable to receive the first broadcast signal from the base modem 11 (broadcast) The slave modem that has received the signal for the first time transmits a response signal (second response signal) to the second broadcast signal on the power line network 5 (step S17). On the other hand, a slave modem (for example, T7 to T11, T12, T21 to T25) that has already received the broadcast signal from the master modem 11 ignores the second broadcast signal and does not transmit a response signal.

  Next, handset modems T11 and T26 as relay devices that have delivered the second broadcast signal receive response signals sent from surrounding handset modems, and direct the received response signals to the base modem. The data is transmitted or the received response signals are collected and transmitted to the parent modem (step S18).

  When the second broadcast signal distribution is completed, the base modem has not yet received response signals from all the handset modems (step S13N). In FIG. 3, the handset modems T33 to T36 of the group G3 are handset modems that have not yet received a broadcast signal and have not transmitted a response signal. Therefore, base unit modem 11 repeats redistribution of the broadcast signal via the slave unit modems until response signals from all the slave unit modems on power line network 5 are received (steps S13N, S14 to S17).

  In the third broadcast signal distribution, the master modem 11 selects at least one slave modem from the slaves that have transmitted the response signal (step S14), and broadcasts to the slave modem. An instruction signal instructing to distribute the signal is transmitted (step S15). As described above, it is desirable that the handset modem selected at this time is installed as far as possible from the handset modems T11 and T26 which are repeaters. For example, the signal level of the response signal is compared. Then, the slave modem that has sent the response signal having the lowest level to the repeaters T11 and T26 is selected. Further, the signal level of the response signal used when selecting the slave modem is acquired by each of the slave modems T11 and T26, and is sent to the master modem 11 together with the response signal or the total result thereof. 3 and 4, the slave modems T17 and T31 in the group G2 are selected as relay devices (proxy master devices). The instruction signal is sent to each of the handset modems T17 and T31 via the handset modems T11 and T26 that are selected as the repeaters when the second broadcast signal is distributed.

  Next, the specific handset modems T17 and T31 that have been selected as the relay device and received the instruction signal distribute the third broadcast signal (second broadcast signal) to the power line network 5 (step S16). Of the slave modems that could receive the third broadcast signal, the slave that could not receive the first broadcast signal from the master modem or the second broadcast signal from the slave modem T11 The machine modem (the slave modem that has received the broadcast signal for the first time) transmits a response signal to the broadcast signal on the power line network 5 (step S17). On the other hand, the slave modem that has already received the broadcast signal from the master modem or the slave modem ignores the third broadcast signal and does not transmit a response signal. In FIG. 3, it is the group G3 of the slave unit modems in which the slave unit modems within the range indicated by the broken line G3 have received the broadcast signal for the first time. There is no handset modem in which the first broadcast signal is received from the handset modem T17.

  Next, the slave unit modem T31 as a relay device that has delivered the third broadcast signal receives the response signal sent from the surrounding slave unit modems and transfers the received response signal to the master unit modem 11. Or, the received response signals are totaled and then transmitted to the parent modem 11 (step S17). At that time, the response signal or the total result from the slave modem T31 is sent to the master modem 11 via the slave modem T26 as a relay device. The base unit modem 11 that has received the response signals from all the handset modems T1 to T36 thus ends the broadcast signal redistribution operation (step S13Y).

  As described above, the power line communication has a feature that the width of the first stage of the network topology (the range in which the signal from the master modem 11 directly reaches) is wider and the number of stages is shallower than that of the low power wireless communication. For this reason, the above method is very effective, and it is possible to deliver a broadcast signal to all the handset modems 11 usually by redistribution 1 to 4 times.

  As described above, in this embodiment, since the broadcast signal is distributed via the specific slave modem that can receive the broadcast signal to the slave modem that cannot receive the broadcast signal from the master modem. Thus, it is possible to reliably distribute the broadcast signal to all the handset modems. Further, according to the present embodiment, since the maximum number of relays of the broadcast signal transmitted by the master modem or the slave modem as the repeater is set to “0”, so-called broadcast storm can be prevented and broadcast The signal can be efficiently distributed to all the handset modems.

  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 power line communication system applied in the remote meter reading system is taken as an example. However, the present invention is not limited to such a power line communication system, and can be applied to various power line communication systems. It is. Further, the configuration of the power line network and the connection form of the slave PLC modem are not particularly limited, and can take various forms.

1 Automatic meter reading system 2 Power pole 3 Substation 4 Pillar transformer 5 Power line (power line network)
5a Electric power lead-in line 6 Optical network 7 Meter-reading server 8a-8d Household appliance 9 Apartment house 9a-9d Each door 11 of apartment house Master PLC modem 12a-12d Electricity meter 13a-13d Slave PLC modem 15a-15d Controller 16a-16d Breaker 20 PLC modem 21 Control unit 22 Memory 23 Interface unit 24 Communication unit 25 Modulation unit 26 Transmission unit 27 Demodulation unit 28 Reception unit 29 Multiplexer T1 to T36 Slave unit PLC modem

Claims (5)

A master PLC modem connected to the power line network;
A plurality of slave PLC modems that communicate with the master PLC modem via the power line network;
The master PLC modem distributes a first broadcast signal set not to be relayed by the slave PLC modem over the power line network,
The slave PLC modem that has received the first broadcast signal among the plurality of slave PLC modems transmits a first response signal to the first broadcast signal on the power line network,
The master PLC modem selects at least one slave PLC modem from the slave PLC modems that returned the first response signal, and the slave PLC modem is the same as the first broadcast signal. Sending an instruction signal instructing to deliver a second broadcast signal of content;
The slave PLC modem instructed to distribute the second broadcast signal distributes the second broadcast signal set not to be relayed by the slave PLC modem to the power line network.
The slave PLC modem that has received the second broadcast signal among the plurality of slave PLC modems transmits a second response signal to the second broadcast signal on the power line network,
The power station communication system, wherein the slave PLC modem that has distributed the second broadcast signal transfers the second response signal to the master PLC modem.   The master PLC modem has returned the first response signal until it has received the first or second response signal from all the slave PLC modems on the power line network. 2. The power line communication system according to claim 1, wherein a process of instructing the slave PLC modem selected from 1 to distribute the second broadcast signal is repeated.   3. The slave PLC modem that transmits the second response signal is a slave PLC modem that has not received the first broadcast signal and that has received the second broadcast signal for the first time. 4. Power line communication system.   4. The power line communication system according to claim 1, wherein the master PLC modem selects the at least one slave modem based on a reception level of the first response signal. 5. A plurality of power meters connected to the power lines constituting the power line network;
Meter reading data measured by each of the plurality of power meters is transmitted from the slave PLC modem connected to the plurality of power meters to the master PLC modem via a power line network. The power line communication system according to any one of claims.

Images