FR2727262A1 - Electrical energy transfer installation with device for elimination of harmonics in electrical lines at terminal stations - Google Patents

Abstract

The installation includes a transmission line terminal station which lowers the tension to a level suitable for electrical distribution, and has, in the output of the voltage step-down transformers, a harmonic attenuation circuit (5).A harmonic attenuation circuit performs series injection of a harmonic compensation current with the same frequency as a harmonic signal and an amplitude and phase in predetermined relation to the harmonic signal. The attenuation circuit has a generator (6) producing the compensation signal at the desired frequency and phase, a shunt (7) resonant at the frequency of the distribution line and a transformer (8) connecting the compensation signal into the low tension side of the power transformer (3).

Description

Device for blocking harionic signals in an electrical line and electrical installation thus equipped.

 The present invention relates to improvements made to electrical energy transport installations comprising a relatively high AC supply or transport line, at least one relatively medium or low AC distribution line, and a source station including voltage-reducing transformer means which is interposed between the supply line and the distribution line.

 The voltage harmonics present in the medium or low voltage distribution lines come from the sum of the voltage harmonics present at the level of the high voltage transmission line and the harmonic voltages resulting from the presence of user means, connected to the distribution network. medium or low voltage, which include non-linear loads. The most important harmonics are those of odd ranks not multiple of 3, and in particular the most annoying is that of rank 5, that is to say that having a frequency of 250 Hz for a line frequency of 50 Hz.

 Correct operation of the electrical transmission and distribution system and the need for quality electrical energy distribution for the user means connected to the distribution network under medium or low voltage requires elimination, or at least a strong attenuation of disturbing voltage harmonics present in the electrical energy transport and distribution network. But so far, no acceptable solution, both technically efficient and economically viable, has been found. In particular, it could certainly be envisaged to carry out compensation at the level of each of the user means comprising the non-linear charges disruptive: however, this compensation would be multiple, and therefore expensive, and above all it would be of uncertain effectiveness, even insufficient due to the intervention of other factors.

 The object of the invention is therefore essentially to propose a solution which makes it possible, relatively effectively and with lower cost, to eliminate or at least substantially attenuate disturbing harmonic voltage signals present in the distribution network below average or low tension.

 To this end, an electrical energy transport installation as indicated in the preamble is essentially characterized, being arranged in accordance with the invention, in that it further comprises a device for attenuation or elimination of at least least a disturbing voltage harmonic signal which is present in the distribution line under medium or low voltage, device which is arranged to, in a manner known per se, generate and carry out a series type injection in said supply line d '' a compensation signal having the same frequency as a disturbing harmonic signal and a predetermined amplitude and phase in relation to those of the disturbing harmonic signal so that the latter is attenuated or canceled and which is placed in the aforesaid source station, in the distribution line after the transformer means.

 Indeed, because, as indicated above, the voltage harmonics present in the medium or low voltage distribution lines come from the sum of the voltage harmonics present at the level of the high voltage transmission line and the harmonic voltages originating the presence of user means, connected to the medium low voltage distribution network, which include non-linear loads, the source station, which is interposed between the high voltage supply line (transmission line) and the distribution line , undergoes a concentration of disturbing voltage harmonics at the distribution line.

 It therefore seems advisable to place a device for compensating for voltage harmonics in the source station, at the output thereof.

Among others, the consequences of the presence of this line depollution means are as follows - the share of voltage harmonics present in the line
medium or low voltage distribution from
supply line voltage harmonics under
high alternating voltage can be greatly attenuated;
the high AC voltage level no longer disturbs
or significantly less disturbs the alterna voltage level
medium or low voltage; this allows to leave a
greater pollution margin in terms of resources
users with non-linear polluan charges
your connected to the high voltage level; - due to the relief of harmonic voltages from
high voltage level, it is possible to leave
a greater margin of pollution to the means used
teurs with non-linear polluting charges
connected to medium or low voltage level.

 Another advantage provided by the invention resides in the fact that the series injection device makes it possible to damp the resonance caused by the LC circuit formed by the inductive impedance of the high voltage transmission line and the compensation capacitors. reactive energy connected to the distribution line under medium / low voltage, with a resonant frequency included in the frequency band where the harmonics exist which are also sought to compensate in the context of the invention.

To equip an installation arranged according to the invention, the device for eliminating harmonic signals may comprise - a compensation signal generator having the amplitude,
the desired frequency and phase, - a shunt resonating at the frequency of the distribution line
tion and the harmonic compensation frequency, and - a transformer for connection, with adaptation to
the power line.

 It should be noted here that the installations for transporting electrical energy are currently equipped with remote control systems making it possible to remotely control receiving members, for example meters to differentiate tariff periods. These remote control systems send, by the electrical transmission line itself, pulses at determined frequencies (for example 175 or 188 Hz) emitted by a remote control transmitter which is precisely located at the output of the source station. he remote control transmitter has a structure similar (except for transmission frequencies) to that provided for the harmonic compensation device. It is therefore conceivable to provide, in a particularly advantageous embodiment of the invention, for the harmonic compensation device to be produced in integrated form with a transmitter of at least one remote control signal carried by the power line and that it is arranged to generate and transmit in the power line at least one harmonic compensation signal having at least a first frequency and at least one remote control signal having at least a second frequency.

 In a first exemplary embodiment, the device can then be made to include switching means arranged to selectively allow the online injection of at least one compensation signal having a first frequency or at least one remote control signal having a second The tuned resonant shunt usually comprising an L, C resonant circuit. at the line frequency (50 Hz for example) and, in parallel thereon, a tuning capacitor to the remote control frequency or harmonic compensation, the device according to the first embodiment of the invention can then comprise, on the one hand, at least two tuning capacitors respectively conferring an agreement on the said first frequency of at least one compensation signal and an agreement on the said second frequency of at least one remote control signal and, on the other hand, switching means able to selectively connect one of the tuning capacitors.

 In a second exemplary embodiment, provision may be made for the inductance of the tuned resonant shunt to be constituted by at least two inductors connected in series and with at least two tuning capacitors connected in parallel respectively on at least one of the above inductors and on the assembly constituted by the other inductor in series with a tuning capacitor at the line frequency (for example 50 Hz), one of the resonant circuits being tuned to a first frequency for the online injection of a signal compensation having said first frequency and the other resonant circuit being tuned to a second frequency for the online injection of a remote control signal having said second frequency, whereby the device can operate as a harmonic signal compensator and / or as a remote control transmitter.

 Advantageously also, the signal generator comprises, at output, at least two tuning circuits arranged in parallel with each other and tuned respectively on the frequencies of the first and second harmonic compensation signals and / or remote control to inject online.

 Ultimately, in accordance with the invention, we are able, with a single device, to perform two functions, namely remote control by the transmission line and the elimination or attenuation of undesirable harmonic signals, these two functions that can be performed selectively or simultaneously depending on the implementation selected.

The structure of the device is known and its operation is reliable; its adaptation for its dual function is simple and can possibly be carried out by modification on remote control devices already in place. Finally, the desired goal can be achieved, in accordance with the invention, reliably and at low cost.

The invention will be better understood on reading the following description of certain preferred embodiments, given solely by way of nonlimiting examples. In this description, reference is made to the appended drawings in which
- Figure 1 is a schematic representation of an electrical energy transport installation arranged in accordance with the invention
- Figure 2 is a block diagram of Figure 1
- Figure 3 is an electrical diagram of a device for eliminating or attenuating harmonic signals which is present in the installation of Figure 2; and
- Figures 3 and 4 respectively show a first and a second preferred embodiment of the device of Figure 3 combined with a remote control transmitter.

 Referring first to FIG. 1, an installation for transporting electrical energy comprises a line 1 for supplying relatively high alternating voltage (HV) - for example three-phase line 90 kV - or more, a source station 2 which includes voltage-reducing transformer means 3 and a distribution line 4 with medium or relatively low AC voltage (MV / LV) - for example three-phase 20 kV line - which leads to a set of distribution bars at the output of the source station .

For the elimination or at least the attenuation of harmonic signals, for example of the harmonic of rank 5, ie 250 Hz for a network frequency of 50 Hz, there is, according to the invention, a device 5 of attenuation or elimination of harmonics - which is arranged to, according to a known technique, generate
and inject a signal into the distribution line
compensation of the same frequency as the harmonic signal at
attenuate or eliminate and having an amplitude and a phase
predetermined in relation to those of the harmonic signal
that disruptive so that it is attenuated or
canceled.

- which is designed to perform a series type injection
of said compensation signal, and - which is arranged in the source station 2, in the line of
distribution 4 between transformer and busbar
medium voltage, where its efficiency is the best.

 Figure 2 shows the block diagram of such a device 5 capable of performing a serial type injection.

This device essentially comprises: a generator 6 supplying at least one alternating signal having the same frequency as the disturbing harmonic signal (for example 250 Hz) and a predetermined amplitude and phase in relation to those of at least one disturbing harmonic signal so whether the latter is canceled or attenuated a resonant shunt 7 tuned on the line frequency (for example 50 Hz) consisting of an inductor L. and a capacitor C. in series, and a tuned capacitor This tuned on the required frequency (for example 250 Hz); and finally an injection transformer 8 which insulates and couples generator 6 with line 4.

 Of course, to the generator 6 are added means for detecting the amplitude and the phase of the harmonic signal present online and means for regulating the amplitude and the phase of the signal generated by the generator so that it is obtained the desired attenuation or elimination of the disturbing harmonic signal.

 FIG. 3 shows a detailed diagram of the device 5. The MV / LV line 4 is assumed to be a three-phase line and three devices 5 are then to be provided in relation to each phase (the equivalent single-phase diagram is shown in FIG. 3).

The generator 6 develops, from a power supply source (here three-phase 50 Hz), a voltage having the desired frequency (for example 250 Hz for the compensation of the harmonic of rank 5). It may include in particular - a straightening unit 9, for example at the Graetz bridge
with thyristors, which delivers an adjustable DC voltage,
filtered by an LC cell - an inverter 10, for example with bipolar transistors, which
transforms the rectifier output voltage 9
into a three-phase alternating voltage at the frequency
required ;; - a step-up transformer 11 which isolates the assembly
rectifier 9 / inverter 10 and which amplifies the voltage
alternative to the appropriate value for harmonic compensation - a three-phase inductor-capacitor cell 12, which
allows to adapt the generator output impedance to
that of the coupling circuit and of the network 4; the cell
12 is a series resonant filter (zero impedance at the
desired frequency (e.g. 250 Hz), so that the
transients likely to appear, due in particular
network faults (short circuits, over-voltage
sions) or load variation, are not applied
to the generator.

The resonant shunt 7 comprises a circuit (L ,, C.) Tuned to 50 Hz which forms a short circuit for this frequency. This circuit is composed of an inductor L. and a capacitor C. in series, at the terminals of which is connected in parallel a tuning capacitor C. which compensates, at the frequency of the compensation signal (for example 250 Hz) , the magnetizing current absorbed by the circuit L1, C. and the injection transformers: the circuit L., C. 7 behaves in fact like an equivalent inductance for the frequency of the signal (for example 250
Hz).

 The set of circuits constituted by the series resonant filter 12, the transformer 11 and the tuning capacity C. of the resonant shunt 7 form a filter which contributes to the smoothing of the niche voltages produced by the inverter 10 to develop the desired frequency. harmonic compensation.

 The injection transformer 8 (three-phase in the example considered), of the type without air gap, has, in the absence of operation, its low voltage windings which are short-circuited by an injection switch (not shown) connecting them to the generator when a compensating signal is transmitted. This transformer functions as a current transformer for the 50 Hz frequency of network 4 and as a power transformer for the compensating signal to be injected online.

Finally, a regulation loop is provided which, on the basis of a detection carried out on the network, manages the operation of the generator 6 in order to obtain as perfect elimination as possible of the undesirable harmonic signal or signals in the network 4. At this end, a step-down transformer, here three-phase, 13 (which may preferably be, for saving purposes, the so-called "potential" transformer already existing in the source stations) supplies a measurement unit 14 which detects the component Unwanted harmonic. The measurement unit 14 is connected to an input of a control / command unit 15 which in particular - in 16 regulates the voltage of the compensating signal
tion at the desired frequency (for example 250 Hz); - in 17 the control of the inverter 10 at the desired frequency
tée (for example 250 Hz) - in 18 the regulation of the DC voltage supplying
the inverter 10 - at 19 the control of the rectifying unit 9.

 At the location provided for the installation of the compensating device 5 according to the invention at the low / medium voltage output of the source station 2, more precisely between the transformer and the MV busbar of the source station 2 there is already a remote control transmitter device which is arranged to transmit, through lines 4 of the network, remote control signals intended for remote receivers, connected to said network. In addition, the arrangement of the transmitting device is that of a signal injection device in series in the network, and it is therefore almost analogous to that provided for the injection of harmonic compensation signals.

Thus, in accordance with the invention, provision is made to set up, between the transformer and the busbar
MT of source station 2, a single device for injecting signals into the network arranged to perform the two functions, namely remote control and / or harmonic compensation.

Figure 4 shows the electrical diagram of a first preferred embodiment of such a device. This diagram is analogous to that of FIG. 3, except that the resonant shunt 7 is switchable to be tuned selectively on a remote control frequency ft (for example 175
Hz or 188 Hz depending on typical values) or on a harmonic compensation frequency fc (for example 250 Hz for the harmonic compensation of rank 5). For this purpose, there are two tuning capacitors, respectively, Ce and Cc, which are selectively connected, using a switch 20, to the terminals of the circuit L, C ..

 In addition, the series resonant filter 12, at the output of the generator 6, is split into two circuits which can be permanently connected in parallel, namely a filter 12t tuned to the remote control frequency and a filter 12C tuned to the compensation frequency d 'harmonic.

 Finally, in the regulation circuit, to the measurement unit 14 detecting the harmonic component is added a measurement unit 21 detecting the remote control component, while the control / command unit 15 is arranged to manage the operation of the generator. 6 in accordance with the type of signal injected online. It is possible to provide for a selection of the operating mode of the control unit 15 which is coupled, mechanically and / or electrically, to the switch 20 (as shown in 22).

 Of course, it is possible to multiply the resonant filters 12 and the tuning capacitors C, so that the device can operate selectively with several remote control frequencies or several harmonic compensation frequencies. However, a drawback of this arrangement is that it only allows selective operation as a remote control or as a harmonic compensator.

To overcome this limitation, the invention provides a second preferred embodiment shown diagrammatically in FIG. 5, which is capable of simultaneously providing remote control and compensation for harmonics on different frequencies. In this arrangement, the shunt inductor is subdivided, for example into three inductors L11, L.2, L13; a tuning capacitor C.1 is connected in parallel to the assembly consisting of one of the above inductors L, 1 in series with a tuning capacitor C at the line frequency (for example 50 Hz), and two other capacitors agree Ce2 and Ca3 are connected in parallel on the two other inductors L and L, 3, in on 12 13
Each LC sub-circuit is a plug circuit which has a very high impedance at the frequencies considered. In the example shown, a circuit, for example ((Lî1, Cî) Ce1J, can correspond to a tuning on the remote control frequency (by example 175 Hz, circuit L.1 C, behaving in fact like an equivalent inductance for the remote control frequency at 175 Hz), while the other two circuits correspond to a tuning on two frequencies of harmonics to be eliminated online ( for example 250 Hz for row 5 and 350 Hz for row 7) or conversely two remote control frequencies (for example 188 Hz and 175 Hz) and a harmonic frequency to be eliminated (for example 250 Hz). the generator 6 (converter 9-10 and resonant filter 12) as well as the measurement unit 14 and / or 21 of the regulation must be adapted in number and in operating characteristics in correspondence with the number and the values of the frequencies signals to inject online.

 Of course, the specific arrangements shown in FIGS. 4 and 5 can be combined to obtain a device adapted to specific needs, which is capable of injecting one or more remote control frequencies online selectively and / or simultaneously and / or one or more frequencies compensation of harmonics selectively and / or simultaneously.

 As is obvious and as already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more particularly envisaged; on the contrary, it embraces all its variants.

Claims (7)

 1. Installation for transporting electrical energy comprising a supply or transport line (1) with relatively high AC voltage, at least one distribution line (4) with relatively medium or low AC voltage, and a source station (2 ) including voltage lowering transformer means (3) which is interposed between the supply line and the distribution line, characterized in that it further comprises a device (5) for attenuation or elimination of least one disturbing voltage harmonic signal which is present in the distribution line under medium or low voltage, a device which is arranged to, in a manner known per se, generate and carry out a series type injection into said distribution line (4 ) of a compensation signal having the same frequency as a disturbing harmonic signal and a predetermined amplitude and phase in relation to those of the disturbing harmonic signal the latter is that is attenuated or canceled, and which is arranged in the aforesaid source station (2) in the distribution line (4) after the transformer means (3).  2. A device for eliminating harmonic signals for an installation for transporting electrical energy according to claim 1, characterized in that it comprises - a generator (6) of compensation signal having the amplifier.  tude, the desired frequency and phase, - a resonant shunt (7) at the frequency of the line  distribution and frequency of harmonic compensation,  and - a transformer (8) for connection, with adapta  tion, to the power line.  3. Device according to claim 2, characterized in that it is produced in integrated form with a transmitter of at least one remote control signal carried by said medium or low voltage power line and in that it is arranged to generate and transmit in said power line at least one compensation signal having at least a first frequency and at least one remote control signal having at least a second frequency.  4. Device according to claim 3, characterized in that it comprises switching means (19) arranged to selectively allow the online injection of at least one compensation signal having a first frequency or at least one signal remote control having a second frequency.  5. Device according to claim 4, in which the tuned resonant shunt comprises an L.C. resonant circuit. at the line frequency and, in parallel thereon, a tuning capacitor (C.) at the remote control or harmonic compensation frequency, characterized in that it comprises on the one hand, at least two capacitors d 'agreement (Ce, C) respectively conferring an agreement on the above first frequency of at least one compensation signal and an agreement on the said second frequency of at least one remote control signal and, on the other hand, switching means (19) able to selectively connect one of the tuning capacitors.  6. Device according to claim 3, characterized in that the inductance of the tuned resonant shunt is constituted by at least two inductors (L.1, L.2) connected in series and with at least two tuning capacitors (this, C, 2) connected in parallel respectively on at least one of the above inductors and on the assembly constituted by the other inductor in series with a tuning capacitor at the line frequency, one of the resonant circuits t (L1, C. ) Cl] being tuned to a first frequency for online injection of a compensation signal having said first frequency and the other resonant circuit (L.2, C, 2) being tuned to a second frequency for injection on-line of a remote control signal having said second frequency, whereby the device can operate as a harmonic signal compensator and / or as a remote control transmitter.  7. Device according to any one of claims 3 to 6, characterized in that the signal generator (6) comprises, at output, at least two tuning circuits (12t, 12C) arranged in parallel one on the 'other and tuned respectively to the frequencies of the first and second harmonic compensation and / or remote control signals to be injected online.