FR2811833A1 - METHOD OF RECEIVING A SIGNAL TRANSMITTED VIA THE ELECTRICAL NETWORK AND DEVICE FOR IMPLEMENTING IT - Google Patents

Abstract

The invention concerns a method for receiving a control signal transmitted via a power distribution network which consists in converting the analog signal coming from the network into a digital signal and in selectively filtering at least the frequency of the electric signal (H3, H4) closest to the main frequency of the control signal (SC). The invention also concerns a device for implementing said method.

Description

Il4 2811833

  METHOD FOR RECEIVING A SIGNAL TRANSMITTED BY

  INTERMEDIATE ELECTRICAL NETWORK AND DEVICE FOR SA

IMPLEMENTATION

  The present invention relates to a method of receiving a control signal transmitted via the network for the distribution of an electrical signal having a fundamental frequency and harmonic frequencies, the control signal having a main frequency different from the fundamental frequency and harmonic frequencies of the electrical signal, the method comprising converting the analog control signal into a digital signal and filtering said digital signal. It also relates to a device for implementing the method. The invention applies more particularly to the reception of a centralized remote control signal. For a long time, it has been known to use a centralized analog remote control signal transmitted via the electricity distribution network in order to modify the pricing of meters, trigger a switching for the connection or disconnection of electric heaters or air conditioners at users' premises or any other electrical switching. The control signal is made up of pulses whose number, frequency, duration and amplitude constitute the characteristics determining the control considered. The electrical signal distributed by the network has a fundamental frequency, for example 50 Hz, and harmonic frequencies. In order to facilitate its reception, the control signal has a main frequency generally located between two harmonic frequencies of the electrical signal. Its frequency is for example fixed at 175 Hz say 2811833 which is between the harmonics 3 and 4 of the electric signal (respectively

  Hz and 200 Hz if the fundamental frequency is equal to 50 Hz).

  It is known to use after analog to digital conversion of the signal, a digital selective bandpass filter eliminating any frequency not contained in a narrow band (for example ranging from 173 Hz to 177 Hz) centered on the

  main frequency of the control signal (for example 175 Hz).

  We thus obtain at the output of the filter, the only control signal which is then

  processed by an algorithm to determine the content of the command.

  We understand that the narrower the filter, the better the rejection of harmonics. But we know that the rise time of the filter is inversely proportional to the width of the passband. In other words, reducing the width of the pass band of the filter imposes a minimum duration of the pulses constituting the control signal. These pulses can for example have a duration of around one second for a frame having a duration of around sixty seconds (a frame comprising around forty pulses). However, the number of different devices which it is desired to switch via the increasing control signal, the number of commands contained in the control signal must also increase. This implies an increase in the number of pulses contained in a frame and therefore a reduction in their duration. However, this reduction in the duration of the pulses composing the control signal

  is limited by the use of a narrow band selective bandpass filter.

  The present invention provides a solution to the problem posed by the increase in the number of pulses within a frame of a control signal transmitted over the electrical network and therefore by the reduction in the duration of the pulses and their reception. . For this, after the conventional step of 3j 2811833 conversion of the analog signal into a digital signal, the invention recommends a selective filtering intended to eliminate at least the frequency of the electrical signal

  closest to the main frequency of the control signal.

  Selective filtering must be understood as acting only in a very narrow band of width equal to or less than 4 Hz. The width of the bands is for example measured at mid-height in a representation of the amplitude of the

  signal components as a function of their frequency.

  Advantageously, selective filtering consists in performing a filtering intended to eliminate the two frequencies of the electrical signal framing the

  main frequency of the control signal.

  The fundamental frequency (and therefore the harmonic frequencies) of the electrical signal is not fixed but varies over a range of a few Hertz. For example when the fundamental frequency is qualified as 50 Hz, it in fact varies in a frequency range going from 47 Hz to 53 Hz. This is why, according to a variant of the invention, the fundamental frequency of the electrical signal is measured in permanence and selective filtering is adapted according to

  variations in the main frequency of the electrical signal.

  According to an advantageous variant, the method according to the invention comprises a step of bandpass filtering with a wide passband centered on the

  main frequency of the control signal.

  For the purposes of this text, the expression "wide bandwidth" should be understood as opposed to "narrow bandwidth". Consequently, a

  bandwidth is considered wide if it is greater than 4 Hz.

  The present invention also relates to a device for implementing the method. The device comprises an analog / digital converter capable of delivering a digital signal and comprises at least one digital selective filter intended to eliminate the frequency of the electrical signal closest to the

  main frequency of the control signal.

  Advantageously, the device according to the invention comprises two digital selective filters intended to eliminate the harmonic frequencies of the electrical signal framing the main frequency of the control signal. Preferably, the device according to the invention further comprises means for determining the fundamental frequency of the electrical signal; in addition, the selective filter (s) adapt the frequency to be filtered selected by

  function of variations in the fundamental frequency of the electrical signal.

  According to a particular embodiment, the selective filter or filters are filters

notch.

  In an advantageous embodiment, the device further comprises a digital filter having a wide passband centered on the main frequency of the control signal. According to a particular embodiment, the bandpass filter comprises one or more recursive response filters

infinite impulse.

  Other characteristics and advantages of the invention will emerge from the

  description given below, for information only and in no way limitative

  reference to the accompanying drawings, in which: FIG. 1 is a diagram of an electricity meter capable of receiving a centralized remote control signal; - Figure 2 schematically shows the frequency distribution of the electrical signal and the control signal which is superimposed on it; - Figure 3 schematically shows the bands of the various filters applied to the electrical and control signals according to the invention.

2811833

  Centralized remote control signals are superimposed on electrical signals and generally emitted by high / medium voltage substations in the electricity distribution network. They spread on this network and are received

  at the end of the network by the electricity meters distributed among the users.

  Figure 1 schematically shows an electricity meter 1 adapted to receive a centralized remote control signal. The signal from the network is directed on the one hand to metrological means 10 making it possible, among other things, to determine the electrical consumption and on the other hand, to the

  centralized remote control signal receiver 12.

  The receiver 12 comprises an analog / digital converter 14 which converts the input signal constituted by the superposition of the electrical signal and

  of the control signal into a digital signal.

  FIG. 2 schematically represents the distribution in amplitude of the input signal as a function of the frequency. A main component Hl of the electrical signal at a fundamental frequency, for example 50 Hz, and harmonic components H2, H3, H4, ... (at 100 Hz, 150 Hz, 200 Hz, ...) are superimposed on the component SC of the control signal located in this

  example between harmonics 3 and 4 of the electrical signal, at 175 Hz.

  The digital signal is delivered by the converter 14 on the input of a filter 16 intended to eliminate the components of the electrical signal without affecting the

component of the control signal.

  FIG. 3 schematically represents the action of the digital filter 16 on the frequency distribution of the digital signal. A digital bandpass filter having a large passband LB eliminates the fundamental component of the electrical signal, its harmonic 2 and the harmonics of order greater than 4. The passband in this example is approximately 50 Hz to mid -height. Such a filter can be achieved by adding a few recursive filters with infinite impulse response. These filters have the advantage of being simple to implement and requiring little computation time. Indeed, these filters are of the type: Yn = aoXn + a1 y ,, 1 + a2Yn-2 oy, designates the output signal of the filter during the nth iteration, xn the input signal, a., A1, a2 parameters to adjust. We see that each filter requires only three multiplications per iteration. These filters being known per se

  there is no need to give a more detailed description here. We can

  find more information on this subject in the work "Digital Signal Processing", Maurice Bellanger, Chapter VI, page 200 - MASSON (4th edition) To obtain the desired filtering, ie the elimination of the components having frequencies outside the interval between the frequency of harmonic 3 and that of harmonic 4, five recursive filters can be used with

  infinite cascade impulse response.

  However, as can be seen in FIG. 3, such a broadband filter has a passband LB whose sides have a slope such that part

  of the components of harmonics 3 and 4 is not eliminated.

  The harmonics surrounding the control signal are eliminated using two digital selective filters, for example notch filters. The frequency response of a notch filter is close to zero over a range of

  very narrow frequency (for example less than 1 Hz), and equal to one elsewhere.

  Such filters are known per se and do not require a detailed description.

  More information on them can be found in the book "Treatment

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  Digital signal ", Maurice Bellanger, Chapter VI, page 211- MASSON (4th edition) In order to adapt the selective filtering to the frequency variations of the harmonic components, the receiver 12 includes means for measuring the fundamental frequency of the electrical signal. means can be achieved using a notch filter in a manner known per se.Moreover, some electricity meters include in their metrological elements means for measuring the main frequency of the signal

  electric and it is then enough to transmit this information to the filter 16.

  The frequency bands FS1 and FS2 eliminated by the notch filters are therefore adapted as a function of variations in the fundamental frequency of the electrical signal. For this, the fundamental frequency measured continuously, for example at a frequency of a few kHz, is multiplied by the coefficients 3 and 4 to give the frequency of the harmonics 3 and 4. The frequencies of these harmonics are used by the notch filters as

  parameters indicating the centers of the selective bands FS1 and FS2 to be eliminated.

  The control signal isolated from the components of the electrical signal is delivered at the input of processing means 18 carrying out the conventional operations of smoothing, rectification, envelope detection, measurement of the duration of the pulses and their amplitude, and finally acceptance of the pulse considered as part of the control or rejection signal, if this pulse is

considered noise.

  At the output of the processing means 18, the shaped control signal is directed to control means MC, for example relays which

  switch or not according to the content of the command.

8 2811833

  The various conversion, filtering and processing operations can advantageously be carried out by the microprocessor which controls the metrological means of the counter and requires only additional programming without the need to integrate other components into the counter. The present invention therefore makes it possible to significantly reduce the duration of the pulses composing a control signal while taking into account the fluctuations of the fundamental frequency of the electrical signal, by using only simple and inexpensive means to implement. In addition, no analog filtering of the incoming signal is necessary. The example given here for an electrical signal frequency equal to 50 Hz and for a signal frequency at 175 Hz can be transposed to other frequencies without departing from the scope of the present invention. Furthermore, still remaining within the scope of the present invention, it can be provided in certain configurations for eliminating using a selective filter only the frequency of the electrical signal closest to the frequency of the control signal, the other components of the electrical signal being eliminated using the broadband filter. According to another variant, on the contrary, many harmonic frequencies of the electrical signal, for example the fundamental frequency and the following nine harmonics, can be eliminated by the use of an adequate number of selective filters, with or without broadband filtering. bandwidth.

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Claims (10)

  1. Method for receiving a control signal transmitted via the network for the distribution of an electrical signal having a fundamental frequency (H1) and harmonic frequencies (H2, H3, ...), the signal of control having a main frequency (SC) different from the fundamental frequency and the harmonic frequencies (H2, H3, ...) of the electrical signal, the method consisting in converting said analog control signal into a digital signal and in filtering said digital signal , characterized in that the filtering comprises a selective filtering (FS1, FS2) intended to eliminate at least the frequency of the closest electrical signal   of the main frequency of the control signal (SC).   2. Method according to claim 1 consisting in carrying out a selective filtering (FS1, FS2) intended to eliminate the two frequencies (H3, H4) from the signal   electric framing the main frequency (SC) of the control signal.   3. Method according to any one of claims 1 and 2 wherein the   fundamental frequency (H1) of the electrical signal is continuously measured and the selective filtering (FS1, FS2) is adapted according to the   variations in the fundamental frequency (H1) of the electrical signal.   4. Method according to any one of claims 1 to 3, wherein the   filtering further includes bandpass filtering with a wide band   bandwidth centered on the main frequency of the control signal (SC).   5. Device for implementing a method according to any one of   Claims 1 to 4 comprising an analog / digital converter   (14) capable of delivering a digital signal and characterized in that it comprises at least one digital selective filter (16) intended to eliminate a frequency 2811833   harmonic of the electrical signal close to the main frequency of the signal (SC).   6. Device according to claim 5 comprising two digital selective filters intended to eliminate the harmonic frequencies (H3, H4) of the electrical signal framing the main frequency (SC) of the control signal.   7. Device according to any one of claims 5 and 6 comprising in   in addition to means for determining the fundamental frequency (H1) of the electrical signal and in which the selective filter or filters adapt the selected frequency to be filtered as a function of variations in the fundamental frequency of the electrical signal.   8. Device according to claim 7 wherein the selective filter or filters   digital are notch filters.   9. Device according to any one of claims 5 to 8 comprising in   in addition to a digital bandpass filter (16) having a wide band-   bandwidth centered on the main frequency of the control signal (SC).   10. Device according to claim 9 wherein the band pass filter   digital includes one or more infinite impulse response filters.