Power-line carrier communication system and modem for power-line carrier communication

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a power line carrier communication system that communicates through a power line network.

【0002】

[Conventional technology]

Power line carrier is a technology for transmitting data to users such as general households and offices using power distribution lines (see Japanese Patent Application Laid-Open No. 10-145265). FIG. 7 shows an overall schematic view of the conventional power line carrier communication system. A single-phase three-wire low-voltage distribution line (hereinafter simply referred to as "distribution line") 2 is connected from the high-voltage distribution line 10 through a pole transformer 3, and a plurality of consumers 8 are connected to the end.

【0003】

A power line network composed of distribution lines 2 in units of such pole transformers is called a "transformer section network" A, B, .. (in contrast, the Internet and the like are higher-level networks). An optical / electrical converter (O / E) 5 and a PLT modem (called a parent modem) 6 are connected from the upper network through an optical fiber 4 (a coaxial cable may be used), and the transformer section networks A and B are connected from the parent modem 6. Connected to, ..

【0004】

In homes and offices that serve as terminals for each transformer section network A, B, .., information terminal devices such as personal computers and televisions are connected through a PLT modem (called a terminal modem) 9.

【0005】

[Problems to be Solved by the Invention]

The transformer section networks A, B, .. are constructed in pole transformer units, and data cannot be directly transmitted between different transformer section networks A, B, .. To transmit data between different transformer section networks A, B, .., it must go through the parent modem. In other words, the scale of the network is limited by pole transformers, and as many parent modems as there are pole transformers are required, so if you try to build a large-scale network, the number of parent modems installed will increase and the system The overall installation cost goes up.

【0006】

Therefore, the present invention realizes a power line carrier communication system and a power line carrier communication modem capable of easily and inexpensively constructing a larger scale network regardless of the pole transformer unit in the power line carrier communication system. The purpose.

【0007】

[Means for solving problems]

(1) The power line carrier communication system of the present invention is a system in which a filter device for blocking a power signal and passing a high frequency signal used for communication is connected between adjacent transformer section networks (Claim 1). According to the above configuration, the high frequency signal can be directly transmitted between the transformer section networks through the filter device. Therefore, a large-scale network can be constructed by connecting the transformer section networks in a chain through the filter device.

【0008】

As the configuration of the filter device, a capacitor for blocking the power signal may be used (claim 2), or a high-frequency transformer may be used (claim 3). Further, an amplifier (repeater) for amplifying a communication signal may be added to the filter device (claim 4). In this way, the filter function that cuts off the power signal and the repeater function can be realized by one device. The amplifier is preferably capable of bidirectional amplification (claim 5).

【0009】

(2) In the power line carrier communication system of the present invention, adjacent transformer section networks are connected by a common neutral line, and a high frequency signal used for communication is transmitted between the neutral line and the ground. Characteristic (Claim 6). Neutral lines are often commonly connected between adjacent transformer section networks. Therefore, in this system, we focused on the fact that the impedance between the neutral wire and the ground takes a finite value instead of 0 with respect to high frequencies, and communicates using only the neutral wire without using the voltage line. Do. Therefore, it is possible to construct a large-scale network by connecting the transformer section networks without using a filter device.

【0010】

The power line carrier communication modem of the present invention is used in the power line carrier communication system in which adjacent transformer section networks are connected by a common neutral line and a high frequency signal used for communication is transmitted through the neutral line. The present invention includes a terminal connected to a distribution line connected to the neutral wire, and includes a signal receiving circuit that captures a signal between the terminal and the ground potential peculiar to the modem (claim 7). When the modem is grounded to the ground and the modem's unique ground potential (potential of the modem's chassis) is equal to the ground potential, the modem is high frequency through the neutral wire, the distribution wires and terminals connected to this neutral wire. Can receive signals. When the modem is not grounded, the stray capacitance between the modem and the ground can be used to receive high frequency signals through the neutral wire, distribution lines and terminals connected to the neutral wire. Therefore, in any case, the modem can be used in a power line carrier communication system in which a high frequency signal is transmitted through a neutral line.

【0011】

The terminal is a power plug having two electrodes, and it is preferable that the signal receiving circuit is provided with two corresponding to each of the two electrodes of the power plug (claim 8). Even if the power plug is attached to the outlet in any direction, a high frequency signal can be received from the neutral wire by either signal receiving circuit. The power line carrier communication modem of the present invention is used in a power line carrier communication system in which adjacent transformer section networks are connected by a common neutral line and high frequency signals used for communication are transmitted through the neutral line. The present invention includes a terminal connected to a distribution line connected to the neutral wire, and includes a signal transmission circuit for transmitting a signal between the terminal and the ground potential peculiar to the modem (claim 9).

【0012】

When the modem is grounded to the ground and the modem's unique ground potential (potential of the modem's chassis) is equal to the ground potential, the modem has a high frequency signal through the terminals, distribution wires leading to the neutral wire and the neutral wire. Can be sent. When the modem is not grounded, the stray capacitance between the modem and the ground can be used to transmit high frequency signals in the same way. Therefore, in any case, the modem can be used in a power line carrier communication system in which a high frequency signal is transmitted through a neutral line.

【0013】

The terminal is a power plug having two electrodes, and it is preferable that the signal transmission circuit is provided with two corresponding to each of the two electrodes of the power plug (claim 10). Even if the power plug is attached to the outlet in any direction, a high-frequency signal can be transmitted to the neutral wire by either signal transmission circuit. The two signal transmission circuits may transmit high frequency signals in opposite phases (claim 11). As a result, the generation of common mode noise can be reduced, and the leaked radiated power can be reduced.

【0014】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First embodiment FIG. 1 is an overall schematic view of a power line carrier communication system to which the present invention is applied. In the conventional power line carrier communication system (Fig. 7), a parent modem 6 is installed for each of the adjacent transformer section networks A, B, .., but this power line carrier communication system has the adjacent transformer section networks A, B. A filter device 1 that cuts off the power signal and passes the signal used for communication is connected between ,..

【0015】

FIG. 2 is an installation state diagram of the terminal modem in the customer. The distribution line 2 on the secondary side of the pole transformer is drawn to the customer 8. The terminal modem 9 is connected to the electrical outlet of the consumer 8. To elaborate on the connection form between the terminal modem 9 and the distribution line 2, if the parent modem 6 uses a single-phase three-wire voltage line L and a neutral line N for the communication line, the terminal modem 9 has the voltage line. Connect to L and neutral wire C. If a single-phase three-wire system double-voltage line L, L is used, the terminal modem 9 is connected to the double-voltage line L, L. FIG. 2 illustrates an example in which the voltage line L and the neutral line N are used for the communication line.

【0016】

In this power line carrier communication system, communication between the master station and each terminal modem 2 employs a full-duplex system using Frequency Division Duplex (FDD), which divides the frequency bands of uplink and downlink signals. , In addition to this, a method such as time division duplex may be adopted. The filter device 1 will be described. The filter device 1 may be installed anywhere between the transformer section networks A and B. For example, it may be installed on a pillar.

【0017】

The cutoff frequency fc of the filter device 1 is selected to be lower than the communication frequency band (several MHz to several tens of MHz) and higher than the commercial frequency band (50,60 Hz). The filter device 1 has a low impedance in the communication frequency band (several MHz to several tens of MHz) and a high impedance in the commercial frequency band (50,60 Hz). The filter device 1 may be inserted into the distribution line of the phase in which the communication signal is transmitted among the distribution lines of the single-phase three-wire system.

【0018】

With this filter device 1, only high-frequency signals used for communication can be passed. A specific circuit example of the filter device 1 is shown. Figures 3 (a) and 3 (b) show a circuit configuration in which a capacitor C is inserted in series as a low-frequency blocking element. The withstand voltage of capacitor C must be equal to or higher than the peak value of the power supply voltage (141V or higher is required if the effective value of the power supply voltage is 100V).

【0019】

When a signal is transmitted between the voltage line La and the neutral line N among the single-phase three-wire distribution lines, the capacitor C is inserted into the voltage line La as shown in FIG. 3 (a). When a signal is transmitted between the voltage line La and the neutral line N and between the voltage line Lb and the neutral line N, two capacitors C1 and C2 are used as shown in Fig. 3 (b). Insert into the voltage lines La and Lb of. When a signal is transmitted between the voltage line La and the voltage line Lb, the capacitors C1 and C2 are inserted into the two voltage lines La and Lb, respectively, as shown in FIG. 3 (b).

【0020】

In addition, in FIG. 3A and 3B, the capacitor may be inserted in series not only in the voltage lines La and Lb but also in the neutral line N. If the neutral wires are not connected between the adjacent transformer section networks A, B, .. from the beginning, the neutral wires may be connected by a capacitor or directly by a conductor. FIG. 3 (c) shows a circuit configuration using a capacitor C and a transformer T as a low-frequency blocking element. The voltage line La and the neutral line N are separated by a capacitor C and a transformer T, and only a high frequency signal is passed through. This transformer T uses a transformer for communication through which high-frequency signals can pass.

【0021】

A repeater function for amplifying a communication signal may be added to the filter device 1. FIG. 4A shows a circuit that realizes a low frequency cutoff function and a repeater function by using a capacitor C, an amplifier A, and a hybrid circuit H. As shown in FIG. 4A, the hybrid circuit H has three terminals a, b, and c, and outputs an input signal input from the a terminal to the b terminal and an input signal input from the c terminal to the a terminal. .. Hybrid circuits with such a configuration are known, as used in two-wire telephones.

【0022】

In the filter device 1 of FIG. 4A, when the wraparound attenuation of the hybrid circuit in the closed loop w (the amount of attenuation of the signal wrapping from the c terminal to the b terminal) is smaller than the amplification degree of the amplifier, the gain of the closed loop w is Since it exceeds 1 (0 dB), it oscillates. Therefore, in order to prevent oscillation, it is necessary to use a hybrid circuit H having a wraparound attenuation larger than that of the amplifier A. In the description of FIG. 4A, transmission / reception separation is performed using a hybrid circuit. For example, when the frequency band of the transmission signal from the parent modem and the frequency band of the transmission signal from the terminal modem are different, a bandpass filter is used. You can also separate transmission and reception using.

【0023】

Figure 4 (b) shows a circuit that realizes a low frequency cutoff function and a repeater function using bandpass filters BPF1 and BPF2 and amplifiers A1 and A2. A bandpass filter BPF1 that passes the frequency band of the transmission signal of the parent modem and attenuates the frequency band of the transmission signal of the terminal modem is inserted on the output side (may be the input side) of the amplifier A1 and is inserted into the output side of the amplifier B (may be the input side). A bandpass filter BPF2 is inserted on the input side) to pass the frequency band of the transmission signal of the terminal modem and attenuate the frequency band of the transmission signal of the parent modem. The out-of-band attenuation of the bandpass filter needs to be equal to or greater than the amplification degree of the amplifier.

【0024】

With this circuit, transmission / reception can be separated by frequency without using a hybrid circuit. -Second embodiment- In the embodiments of the present invention, any two of the single-phase three-wire distribution lines have been used as communication lines. However, using the stray capacitance with the ground, communication can be relayed even by using one neutral line connected between adjacent transformer section networks A, B, ..

【0025】

FIG. 5 is a line configuration diagram for downlink communication from the parent modem 6 to the terminal modem 9. The high-frequency signal transmitted from the modem body of the parent modem 6 is amplified by the final stage amplifier 61 and transmitted to the neutral line N of the distribution line 2. C6 represents the stray capacitance between chassis 60 of the parent modem 6 and the ground. The neutral wire N is grounded to the ground at any point via the draw wire 2a. Therefore, the potential of the neutral line N becomes 0 in the low frequency commercial frequency band. However, in the high frequency communication frequency band, the draw wire 2a acts as an inductance LN, and there is also a stray capacitance CN between the neutral line N and the ground. Therefore, the neutral wire N has an impedance with the ground and can pass a signal.

【0026】

Here, a numerical example is given. If the radius of the draw line is a [m] and the length is d [m], the inductance L [H] is L = 2d [log (2d / a) -1] × 10^-7Is. The impedance Z [Ω] for the signal of frequency f is Z = 2πfL It is represented by. Generally, the characteristic impedance of the distribution line is about 100 to 400Ω, so if the impedance of the draw-down line is also 100Ω, a sufficient potential can be secured with respect to the ground. Assuming that a = 0.001m and d = 5m, f = 5.3MHz or more is sufficient for Z to be 100Ω or more. Therefore, if the signal has a frequency band of about 5 MHz or more, communication is possible through the neutral line N.

【0027】

The terminal modem 9 receives the signal through the power outlet. Since the user may not know or make a mistake in the direction in which the power plug P is inserted into the power outlet CON, in the terminal modem 9, the preamplifiers 91 and 92 are used for the two wires of the power plug P, respectively. Is provided. C9 represents the stray capacitance between chassis 90 of the terminal modem 9 and the ground. With the above configuration, the terminal modem 9 can receive the high frequency signal transmitted from the parent modem 6 between the neutral line N and the ground. Further, the terminal modem 9 can receive the signal regardless of the direction in which the power plug P is inserted into the power outlet CON.

【0028】

Next, a line configuration for uplink communication from the terminal modem 9 to the parent modem 6 will be described with reference to FIG. In this case as well, as in FIG. 5, a high frequency signal is transmitted by using the impedance between the neutral line N and the ground. The terminal modem 9 supplies a high frequency signal to each terminal of the power plug P through the final stage amplifiers 93 and 94. The high frequency signal is input to the power outlet CON and transmits the neutral line N and the voltage line L. Of these, the signal that enters the adjacent transformer section network B is the signal that transmits the neutral line N.

【0029】

As mentioned above, the high frequency signal is supplied to each terminal of the power plug P through the two final stage amplifiers 93 and 94, so that the user does not know or makes a mistake in the direction of inserting the power plug P into the power outlet CON. However, one of the signals transmits the neutral line N, and no problem occurs. The parent modem 6 can receive the signal from the terminal modem 9 through the neutral line N.

【0030】

In the terminal modem 9 of FIG. 6, the two final stage amplifiers 93 and 94 supply high-frequency signals of opposite phase to each terminal of the power plug P. This effect is that (1) the generation of common mode noise can be reduced and (2) the leaked radiated power can be reduced by supplying high-frequency signals having opposite phases. Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

【0031】

[Effect of the invention]

As described above, according to the present invention, it is possible to easily and inexpensively construct a larger-scale network regardless of the pole transformer unit.

[Simple explanation of drawings]

[Figure 1]

It is a schematic diagram which shows the power line carrier communication system of this invention.

[Figure 2]

It is an installation state diagram of a terminal modem in a customer.

[Fig. 3]

(a) and (b) are diagrams showing the circuit configuration of a filter device in which a capacitor is inserted in series as a low-frequency blocking element, and (c) is a diagram using a capacitor and a transformer as a low-frequency blocking element. It is a figure which shows the circuit structure.

[Fig. 4]

(a) shows a circuit that realizes a low frequency cutoff function and a repeater function using a capacitor, an amplifier, and a hybrid circuit, and (b) shows a low frequency cutoff function and a repeater using an amplifier A and a bandpass filter. The circuit that realized the function is shown.

[Fig. 5]

It is a line block diagram in the case of downlink communication from a parent modem 6 to a terminal modem 9 using a neutral line.

[Fig. 6]

It is a line block diagram in the case of uplink communication from a terminal modem 9 to a parent modem 6 using a neutral line.

[Fig. 7]

It is an overall schematic diagram of the conventional power line carrier communication system.

[Explanation of symbols]

1 Filter device 2a Draw line 2 Low voltage distribution line 3 pole transformer 4 optical fiber 5 Optical / electrical converter 6 Parent modem 8 consumers 9 Terminal modem 10 High-voltage distribution line 60 chassis 61 Final stage amplifier 90 chassis 91,92 Preamplifier 93,94 Final stage amplifier A, B transformer section network H hybrid circuit