FR2895851A1 - Data signals isolating device for electrical power distribution network, has high pass filter blocking energy signal for discriminating data signal, and insulation transformer adapted to extract discriminated data signal - Google Patents

Abstract

The device has a high pass filter (420) blocking an energy signal for discriminating a data signal. A negative feedback loop cancels the discriminated data signal at a junction point of communication segments. An insulation transformer (430) is adapted to extract the discriminated data signal, and an operational amplifier (470) is used in an inverter to inverse the data signal. An independent claim is also included for a method of isolating data signals between communication segments of electrical energy distribution network.

Description

-1- METHOD OF ISOLATING DATA SIGNALS IN A NETWORK

  The invention relates to the field of communication of data signals carrying carrier current. The invention relates more particularly to a method and a device for isolating data signals in an electrical energy distribution network. Patent application US 2005/0007241 discloses a system for isolating data signals between the segments of an electrical energy distribution network serving dwellings. This system includes low-pass filters for passing electrical energy and blocking high-frequency signals carrying useful data. This type of filter generally contains an inductive circuit in series with the energy line and a capacitive circuit connecting the energy line to the neutral. The inductive circuit attenuates the high frequency signals but remains inactive in front of the energy and the low frequencies, the capacitive circuit behaves like a short circuit in high frequency but remains indifferent to the low frequencies. Other variants of this type of filter have also been envisaged, for example by increasing the order of the filter to obtain better filtering, but while keeping the same principle of one or more inductive circuits in series with the energy line. . These filters have a major disadvantage that stems from their architecture which is that the energy must pass through the inductive circuits. In the case where the filter is placed on the electrical power distribution line of a dwelling, the currents can reach several tens of amperes requiring the associated filters to withstand such intensities without damage. Such filters have accordingly large coils making their miniaturization very difficult and high energy consumption because of losses by induction. Even when the insulation system is used inside a dwelling to isolate the data signals between several segments of the electrical distribution network of the dwelling, the intensity of the current remains of the order of a few tens of amperes, which is enough to cause losses and prevent miniaturization. In view of the state of the art, in particular patent application US 2005/0007241, the technical problem that arises is that of proposing an improved device for isolating data signals between a plurality of communication segments. a power distribution network that is small and consumes very little energy, while being simple to implement. For this purpose, the subject of the invention is a device for isolating data signals between a plurality of communication segments of an electrical energy distribution network comprising: a filtering means able to discriminate a data signal; and cancellation means adapted to reverse-cancel the discriminated data signal at the junction point of the plurality of communication segments creating a virtual ground for the data signals. Thus, in order to discriminate the data signal, the filtering means must necessarily block the energy signal, which has the consequence of having a device which is traversed only by a weak current. The device can then have very small dimensions and consume very little energy. In addition, the design of this device is simplified.

  Advantageously, the cancellation means of the isolation device comprises: a first coupling means adapted to extract the discriminated data signal; means for inverting said data signal; and second coupling means adapted to inject the inverted data signal. Thus, the injection of a signal of the same amplitude but in phase opposition thanks to a feedback loop for canceling the data signal has a filtering effect on this signal. According to a first embodiment of the invention, the second coupling means comprises a single coupler disposed on a communication segment. The filtering effect is thus obtained only for the data signals present on this segment to prevent their propagation on the rest of the electrical network. This implementation is interesting when there is need to isolate only one segment.

  According to a second embodiment of the invention, the second coupling means comprises a plurality of couplers each arranged on a communication segment. The filtering effect is thus obtained for the data signals present on each segment. All data signals therefore remain at the local level without mixing between the segments. This implementation is interesting when there is a need to isolate several communication segments in an electrical energy distribution network. In a particular implementation, the inverting means of the isolation device comprises an inverting amplifier having an absolute value gain of greater than or equal to 1, said inverting means serving a superposition of data signals discriminated and inverted at all. couplers arranged at each segment. This implementation advantageously makes it possible to create a second virtual mass at the output of the amplification circuit which prevents the data signals present on each segment and passing through the second coupling means from coming to mix with the common point of contact formed by the different loops of against reaction. According to a preferred embodiment of the invention, the second coupling means is an inductive coupling means. The use of an inductive coupler has the effect of preventing the propagation of the inverted data signal along the entire communication segment and of avoiding canceling the data signal at any point. The coupler can be pure inductive, or mixed inductive / capacitive. According to another embodiment of the invention, the second coupling means comprises a first coupling element for the injection of the inverted data signal, a second coupling element for the injection of a data signal, and a second inductive element disposed between the two coupling elements, the first coupling element being connected to the junction point of the communication segments. The inductive element has the effect of attenuating, if not blocking, the propagation of the inverted data signal along the entire communication segment. According to a particular characteristic, the second coupling means is arranged on the phase wire of a segment and is able to inject a data signal on the opposite side to the junction point of the communication segments. This implementation is appropriate for European countries. According to another particular characteristic, the second coupling means is disposed on the phase wire and a third coupling means is arranged on the neutral wire, the second and third coupling means collaborate for the injection of a data signal. on the opposite side to the junction point of the communication segments. This implementation is appropriate for the United States. Advantageously, a high pass filter is connected in parallel with the filtering means and the first coupling means to ensure that the phase wire and the neutral wire are at a potential identical to the high frequencies if the first coupling means has a relatively high impedance. raised at these high frequencies. The invention also relates to a method of isolating data signals between a plurality of communication segments of an electric power distribution network comprising the steps of: filtering for discriminating the data signal; and feedback canceling the discriminated data signal at the junction point of the plurality of communication segments creating a virtual ground for the data signals. The features and advantages of the invention will appear more clearly by the description of a preferred embodiment of the invention, given by way of indicative and nonlimiting example, and the appended figures, in which: FIG. typical electrical installation in which the invention is implemented; FIG. 2 represents a passive low pass filter according to the prior art; Figure 3a shows a combination of a low-pass filter and a coupling circuit for isolating a communication segment according to the invention; FIG. 3b represents an alternative embodiment of the coupling circuit to the communication segment; FIG. 4 represents a combination of a low-pass filter and a coupling circuit making it possible to isolate a plurality of communication segments that can be implemented in Europe; FIG. 5 represents a combination of a low-pass filter and a coupling circuit for isolating a plurality of communication segments that can be implemented in the United States. FIG. 1 represents a typical single-phase electrical installation in which the invention is implemented. This installation distributes electrical energy at low voltage (220 or 110 volts) with a frequency of 50 or 60 Hz in a private environment (beyond the meter) such as a home or a workplace. This figure does not represent switches and lighting systems for simplification. An external source (not shown), arranged upstream of a general circuit breaker 101, supplies the entire installation through electrical power distribution lines 102. Each line - 6 - may optionally have numerous branches, here not shown. , on which electrical outlets such as 105 may be disposed. A room 106 of the dwelling or workplace may be served by a single line or by several lines.

  However, there are sometimes in old electrical installations lines serving different parts. Individual circuit breakers 104 or fuses grouped together in an electrical box 103 located generally near the general circuit breaker 101 serve to limit the intensity of the current or cut off the power supply in the lines 102. This arrangement upstream of the elements 111 and 112 described below allows also easy dimensioning of these circuits, even if a provision downstream of these elements is also possible. According to a particular embodiment, low pass filters 111 are arranged at the head of each electrical power distribution line forming a plurality of independent communication segments, and coupling circuits 112 adjacent to the filters 111 are arranged upstream of each segment for the injection / extraction of data signals. An interconnection unit 113 comprising a plurality of ports interconnects all the coupling circuits through links 114 connected to the different ports. In an alternative embodiment, the interconnection unit may contain additional ports 115 for exchanging data with other local or external networks (satellite, Internet, etc.) if a bridge or gateway function is implemented. in this unit. In the embodiment of Figure 1 and preferably a segment is superimposed on a current line. However, a segment may equally well consist of several lines or conversely several segments may be formed by different branches of the same line. This is only a compromise to establish between the desired performance and the number of filters / couplers to implement in the electrical installation. The low pass filters are designed to necessarily pass the 50 or 60 Hz power signal and cut or strongly attenuate the high frequency signals used to carry high bit rate information, typically the frequency range of 2 to 30 MHz. In a preferred embodiment of the invention, the cutoff frequency is chosen to be greater than 500 KHz to pass the low and medium frequencies used for the transport of low bit rate information (range between 10 and 450 KHz). Thus, the operation of home automation-type low-speed carrier communication equipment (X10, CEBus, LonWorks, etc.) is not disturbed by the presence of the filters and continues in a manner similar to that which occurs classic network without filters.

  In an alternative embodiment, the cut-off frequency of the low-pass filters may be chosen to be less than 10 KHz so as to also cut the frequency range used for low-speed information transport. This makes it possible to extend the immunization with respect to noise and spurious signals to the frequency range from 10 to 450 KHz. However, for the installation to remain compatible with the home automation type communication systems described above, the interconnection unit must operate as a repeater for all the data signals transported in this frequency range, or at least transfer these data signals. signals to the segments where it is needed.

  In the case of data signals having a high transmission rate and therefore occupying a large bandwidth in the frequency range 2 to 30 MHz, it is very advantageous not to repeat the data signals in all communication segments of the local communication network but only in those likely to contain receiving equipment of these data signals. Therefore, the interconnect unit preferably operates as a switching unit for the broadband signals between the different communication segments. Obviously, proper addressing and configuring of the switching unit based on higher layer information is necessary for the routing of the data signals to be performed correctly. The implementation of these techniques is well known and can approach, for example, the operation of an Ethernet switch. In the latter, when the data signal enters the switch, the address contained in the Ethernet frames and the original port are stored in an internal table. Thus, the data signal is transmitted to the specified port based on the destination of the frame and the MAC address. If the MAC address is unknown, or is a broadcast address, the switch simply broadcasts the frame to all connected interfaces except the input port. If the destination MAC address is known, the frame is forwarded only to the recipient. If the destination port is the same as the original port, the frame is forgotten. Another advantage of using a switching unit between different communication segments is to isolate the collision domains for the channel access protocols. Indeed, communication media access protocols such as CSMA / Carrier Sense Multiple Access (Collision Avoidance) must be used at the access layer to share the communication medium. The separation of the local communication network into communication segments thus makes it possible to improve the access time.

  Couplers are an essential element of the physical layer of carrier currents because they allow the injection or extraction of data signals to or from the power grid. In general, they can be of the capacitive, inductive or mixed type. In the installation of FIG. 1 coupling circuits 112 are arranged at the head of each communication segment for the implementation of the invention as described above. However, each equipment must be routinely associated with a coupling circuit in order to communicate through the local communication network. Thus, the elements 107 and 108 constitute coupling circuits for the computer 109 and the adapter 110. The latter provides the usual interfaces (USB, Ethernet, etc.) for the connection of equipment that is not adapted to the carrier currents. A modulation / demodulation circuit or modem (not shown in FIG. 1) must be provided according to the case upstream of the coupling circuit. The modem makes it possible to adapt the data signal to the characteristics of the communication medium (use of carrier frequencies for example) and possibly the coding of this signal. Although the transmission of low-bit rate data signals can be done in baseband, complex modulations often have to be considered when it comes to maximizing the available frequency range and thereby achieving high theoretical rates. This is the case, for example, of Orthogonal Frequency Division Multiplexing (OFDM) modulation and spread spectrum modulation. FIG. 2 represents a passive low-pass filter according to the prior art which can be used in the installation of FIG. 1. On the left-hand part of FIG. 2, the data signal modulated with carrier currents passes through an inductor 201 which attenuates the high frequency signals but remains inactive with respect to the energy and the low frequencies, then the capacitor 203 behaves like a short circuit at high frequency and indifferent to the low frequencies. At the output of the filter (right of FIG. 2), another inductor 202 also reinforces this attenuation effect of the high frequencies and the signal contains only the energy and the low frequencies, the high frequencies having been eliminated thus ensuring a low pass filter (lets pass the low frequencies) effective to filter the data signals conveyed in carrier currents. However, such a filter has the disadvantage that the energy must pass through the inductors 201 and 202. As shown in FIG. 1, the segments can supply energy to several devices connected to the power sockets. 105, the currents can then reach several tens of amperes requiring the associated filters 111 to withstand such intensities without damage and therefore have bulky coils. Such filters used in carrier currents are difficult to miniaturize and consume more energy because of induction losses.

  FIG. 3a shows a particularly advantageous way of implementing the low-pass filter in combination with the coupling circuit according to the invention, which can be implemented in countries imposing a common electrical neutral for the entire electrical installation.

  The L and N wires are respectively the phase and neutral wires of the energy network. The wires L and N form a power distribution line such as the lines 102 of the installation of FIG. 1. The points a and b are connected to the main arrival of the electrical energy, that is to say say on the counter. This arrival is noted V- in the figure. A filter unit 310 is connected to the points a and b, and is constituted by a first high pass filter 320, an inverting transformer 330 and a second optional high pass filter 340. The first filter 320 discriminates the low and medium frequency signals corresponding to the energy and to the low speed data signals of home automation type. The transformer 330 provides the necessary isolation between the electrical power network and the switching network while conveying an inverse version (phase shift 180) of the data signal to the switching network. Optionally a high pass filter 340 may be added between the points a and b to ensure that the point b is at the same potential for the data signals as the point a. The insertion of the unit 310 does not require the opening of the energy network to be put in place, which is an advantage over conventional filtering methods. The transmission and reception of the data signal takes place through the points X and Y which connect the coupling circuit 350 to one of the ports of the interconnection unit 115. According to techniques known to those skilled in the art In the art, the reception of the signal of the communication segment can be carried out by differential amplification between the points X and Y, and the injection emission at the point X only. The coupling circuit 350 is connected on the other hand to the point c. This coupling circuit may be a transformer or more advantageously an inductive coupling system. Inductive coupling has the advantage of not requiring the opening of a circuit to be implemented, but also of avoiding the superposition of an inverted data signal across the entire communication segment. FIG. 3b gives a different representation of the coupling circuit 350 in which the inductive effect is introduced by the element 353. On either side of this inductive element, a first coupling element 352 is used for the injection of the inverted data signal, and a second coupling element 351 is used for the injection of data signals through the communication segment, the element 352 being disposed on the side of the point c. The coupling elements 352 and 351 can then be inductive, capacitive or mixed. The device works as follows. The high-pass filter 320 discriminates the communication currents (data signals) that could develop between the points a and b of the energy circuit, during transmission by a generator which would be downstream on the L and N wires. The currents are then inverted and injected at point c, and would then be reinjected back onto the energy network by the coupling element 350 at point a. The currents at point a would then be of equal intensities and opposite directions. So we have a feedback loop. It is known to those skilled in the art that the use of a feedback loop requires the point a to be a virtual ground for the data signals. The device of Figure 3a thus operates globally as a low pass filter. Filters 320 and 340 are conventional and known to those skilled in the art. It is recalled that the communication systems covered by this invention use frequencies beyond 1.6 MHz while home automation systems use systems less than 500 KHz. A sixth order Butterworth filter is enough to separate the domains and is economical to achieve using capacitances and inductances. An active filter can also be realized, by feeding the circuit using the energy network. A 50 Hz or 60 Hz rejection circuit can be added in series. In these architectures, the filters are advantageously not traversed by the energy current 50 or 60 Hz and can therefore be made using small elements. These data are provided as an example, but are not limiting in nature. Figure 4 illustrates an optimized way of utilizing the association between filtering and coupling circuits of Figure 3a to create a plurality of communication segments.

  The wires (L1, N1) and (L2, N2) represent the phase and neutral wires corresponding, respectively, to a first and a second communication segment. N1 and N2 cables are equipotential, according to the regulations of some countries. Only two segments are described with reference to FIG. 4, however any number of additional segments can be added by grafting to points a and b of the energy input. The energy network symbolized by points a and b is superimposed on an interconnection network at points c and d. A single filtering unit 410 per facility is sufficient to form the plurality of communication segments. The coupling circuits 450 and 455 have a function similar to the circuit 350 of Figure 3a. The high pass filters 420 and 440 are the same as the filters 320 and 340 of FIG. 3a. In this device an operational amplifier 470 is used in an inverter, the isolation transformer 430 thus performing a phase coupling unlike that of the device of FIG. 3a. In an alternative embodiment, it is the isolation transformer which operates in an inverter, the amplifier being in direct mode. The output of the operational amplifier creates a second virtual ground at point c which advantageously makes it possible to connect the different output ports of the interconnection unit while avoiding the mixing of the data signals. Thus, the signal transmitted through X1 does not reach the coupling element 455, nor does the signal transmitted through X2 reach the coupling element 450. The same would be true for all the additional coupling elements connected. at point c, and serving other segments of communication. Thus, there is dynamic filtering that prohibits the X1 data signals from propagating on the local network segments other than the first segment, and the X2 data signals propagating over the local network segments other than the first segment. only on the second segment, and so on. Since the amplifier operates as an inverter as indicated above, the counter-reaction effect makes it possible to use an absolute value gain of greater than or equal to 1. FIG. 5 represents a device combining the filtering and coupling circuits to create a plurality of communication segments applicable in countries allowing a separate electrical neutral in the electrical installation. The coupling elements 550a and 550b are used to couple the data signal from X1. They are connected in series. One of the accesses of 550a is then connected to point c. Coupling elements 555a and 555b are used to couple the data signal from X2. They are connected in series. One of the 555a accesses is then connected to point c. The injection of the data signals is therefore done through the points X1 and X2. The reception is preferably carried out between the points X1 and Y1 for the first segment and X2 and Y2 for the second segment, but it is also possible to receive the signal between the points Z1 and Y1 or Z1 and X1 for the first segment. and between the points Z2 and Y2 or Z2 and X2 for the second segment. As in FIG. 4, the points a and b are equipotential for the data signals by the action of the high-pass filter 540. The feedback loop imposes on the point a to be a virtual mass, therefore a and b are virtual masses for data signals. There is no propagation of data signals transmitted on the first segment to the second segment and vice versa. The point c is a virtual mass by the presence of the output of the operational amplifier, and there is no propagation of the currents intended for the first segment on the second segment via the distribution circuit, and conversely by symmetry . The son N1 and N2 are really distinct for their electric potential.

Claims (12)

  A device for isolating data signals between a plurality of communication segments of an electrical energy distribution network, characterized in that it comprises: a filtering means (320, 420, 520) capable of discriminating a data signal; and cancellation means adapted to reverse-cancel the discriminated data signal at the junction point of the plurality of communication segments.   2. Isolation device according to claim 1, characterized in that the cancellation means comprises: a first coupling means (330, 430, 530) adapted to extract the discriminated data signal; inverting means (330, 470, 570) of said data signal; and a second coupling means adapted to inject the inverted data signal.   3. Isolation device according to claim 2, characterized in that the second coupling means comprises a single coupler (350) disposed on a communication segment.   4. Isolation device according to claim 2, characterized in that the second coupling means comprises a plurality of couplers (450, 455, 550a, 555a) each disposed on a communication segment.   5. Isolation device according to claim 4, characterized in that the inverting means comprises an amplifier (470, 570) operating in an inverter having an absolute value gain greater than or equal to 1, said inversion means serving a superposition of discriminated and inverted data signals to all couplers (450, 455, 550a, 555a) disposed at each segment.   6. Insulation device according to one of claims 2 to 5, characterized in that the second coupling means is an inductive coupling means.   Insulation device according to one of claims 2 to 5, characterized in that the second coupling means comprises a first coupling element for the injection of the inverted data signal (352), a second coupling element for the injection of the data signal (351), and an inductive element (353) disposed between the two coupling elements, the first coupling element being connected to the junction point of the communication segments.   8. Insulation device according to one of claims 2 to 7, characterized in that the second coupling means (350, 450, 455) is disposed on the phase wire of a segment and is adapted to inject a signal data opposite the junction point of the communication segments.   9. Isolation device according to one of claims 2 to 7, characterized in that the second coupling means (550a, 555a) is disposed on the phase wire and a third coupling means (550b, 555b) is disposed on the neutral wire, the second and third coupling means collaborate for the injection of a data signal on the opposite side to the junction point of the communication segments.   10. Isolation device according to any one of claims 2 to 9, characterized in that a high-pass filter (340, 440, 540) is connected in parallel with the filter means (320, 420, 520) and the first coupling means (330, 430, 530).   11. Insulating device according to any one of claims 2 to 10, characterized in that the first coupling means (330, 430, 530) is an isolation transformer.   12. A method of isolating data signals between a plurality of communication segments of an electrical power distribution network characterized in that it comprises the steps of: filtering for discriminating a data signal; and reversibly canceling the discriminated data signal at the junction point of the plurality of communication segments creating a virtual mass for the data signals.