Method for configuring a high voltage direct current installation

Abstract

The invention relates to a method for configuring a high-voltage direct current installation, said installation comprising a first main terminal (A) and a second main terminal (B), a first electrical conductor (1) which comprises a first terminal (1_1) and a second terminal (1_2) which is connected to said second main terminal (B), said method comprising in particular adding a second electrical conductor (2), which comprises a first terminal (2_1) and a second terminal (2_2) which is connected to said second main terminal (B), and inserting a power converter (PC) with three terminals (X, Y, Z), so that its first terminal is connected to the first main terminal (A), its second terminal (Y) is connected to the first connection terminal (1_1) of the first electrical conductor (1) and its third terminal is connected to the first connection terminal (2_1) of the second electrical conductor (2). Figure to be published with the abstract: Figure 2

Description

Title of the invention: Method for configuring a high-voltage direct current installation Technical field of the invention

[0001] The present invention relates to a method for configuring a high voltage direct current installation and to said high voltage direct current installation, configured using said method. State of the art

[0002] It is known to transmit power between two terminals A, B of a high voltage direct current installation (also called HVDC installation) using a first electrical conductor 1, produced in the form of a cable, an overhead line or more generally a connection made up of sections of cables and overhead lines. This connection is sized to transmit a given electrical power, referenced P in [fig.lA].

[0003] An upgrade of the installation is sometimes necessary when a greater power must be transmitted between the two terminals A, B, the surplus power to be transmitted being noted AP. In this situation, a classic solution consists of adding a second electrical conductor 2 in parallel with the first electrical conductor 1, as shown in [fig.lB]. As can be seen in [fig.lB], the two conductors 1, 2 in parallel thus make it possible to transmit the total power P+AP between the two terminals A, B. However, the electrical resistance ratio between the two conductors means that the total electrical power P+AP transmitted will not necessarily be distributed so that the first electrical conductor 1 will transmit the power P and the second electrical conductor the power AP, as illustrated in [fig.lB]. In this [fig.lB], the first electrical conductor 1 will thus transmit a power PI different from P, and the second electrical conductor will transmit a power P2 different from AP. It follows that the second electrical conductor 2 added will most certainly have to be sized to transmit a power greater than AP, in order to ensure that the power P+AP is transmitted, whatever the resistance ratio between the two conductors. With such an installation, one of the two electrical conductors is required to transmit an electrical power always lower than its maximum capacity and is therefore not used optimally.

[0004] [fig.IC] illustrates this problem. In this [fig.IC], the installation transmits the total power PT. The first electrical conductor 1 transmits the power PI with the current II and the second electrical conductor 2 transmits the power P2 with current 12. The total power to be transmitted is noted PT. The [fig.lC] also shows, for each conductor 1, 2, the electrical resistance RI, R2, the thermal resistance between the conductor and the ambient Rthl, Rth2, the temperature of the electrical conductor Tl, T2 and the power losses Plossl, Ploss2.

[0005] Since the two conductors are connected in parallel, their voltage drop must be identical. We therefore have: ÆiZi = R2I2 (1)

[0006] Knowing that I\ +12 — I, starting from (1) above, we then obtain: (2)

[0007] For each conductor, the thermal losses can be expressed as follows: next: P lossl P 1^1 RiR2I2 » (R}+R2)2 1 (3) (4)

[0008] These relationships show that if R\ < R2, the first electrical conductor 1 will be led to concentrate more current and will generate more losses. It should be noted that the electrical resistance of an electrical conductor is linked to its section, its manufacturing material and the temperature of the conductor. For each electrical conductor, its temperature can be expressed in the following way with Tanih the ambient temperature P} — Rfhl?!osx} + ? amb T 2 — Pth2P loss2 + Pamb (5) (6)

[0009] By combining relation (3) with relation (5), and relation (4) with relation (6), we understand that if we consider that < R2, and that the thermal resistances are equal (Rthi=Rth2), the temperature Tj of the first electrical conductor will be higher: (7) 2 Tl = R,a . „ ' 2' + Tmb (ZV I +K2 J (8)

[0010] The sizing of an electrical conductor must be chosen by the maximum power that it can transmit at its maximum temperature.

[0011] Thus, it can be concluded that in an installation with two electrical conductors in parallel, the first electrical conductor 1, which has the lowest resistance, will be required to transmit the highest electrical power and will have a higher temperature. The maximum power that the assembly can transmit will therefore be linked to the maximum temperature of this conductor. On the other hand, the second electrical conductor 2, which has the highest resistance, will be required to transmit less electrical power than the first electrical conductor 1, at a temperature lower than its maximum temperature. This second electrical conductor 2 will therefore be used well below its maximum capacities while the first electrical conductor 1 will be used close to its maximum capacities.

[0012] Of course, if the two electrical conductors have identical electrical resistance, the power will be distributed equally in each electrical conductor.

[0013] [Fig.lD] illustrates the above conclusions by a numerical example.

[0014] In this example, initially, before upgrading, the installation must transmit a power of 0.7 GW and the first electrical conductor 1 transmits the power P=0.7 GW while being sized (with a section Si of 1200 mm2 of copper) to transmit the power Pf of 0.71 GW. The installation must be modified to transmit an additional power AP with AP=0.9GW. For this, a second electrical conductor 2 is mounted in parallel with the first electrical conductor 1 with a section of 2400 mm2. To transmit the total power PT (equal to P+AP=1.6 GW), the second electrical conductor 2 must be sized to transmit a power greater than AP=0.9 GW (the second electrical conductor 2 is sized in this case to transmit a power P2' of 1.05 GW).This is linked to the fact that the second electrical conductor 2 has a section S2 greater than that of the first electrical conductor 1, which gives it a lower electrical resistance than that of the first electrical conductor 1 and therefore a tendency to concentrate more electrical power than the first electrical conductor 1. It follows that when the power PT of 1.6 GW must be transmitted, the second electrical conductor 2 will be required to transmit a power P2 close to its nominal power (P2=1.04 GW) while the first electrical conductor 1 will be underutilized, transmitting only the complement, i.e. a power Pi of 0.56 GW while it is sized to transmit a power of 0.71 GW. Furthermore, it can be noted that even if the first electrical conductor 1 turns out to be underutilized, the total power of the installation cannot however be increased.Additional power would overload the second electrical conductor. 2 and not the first electrical conductor 1, the total transmitted power cannot be distributed appropriately between the two electrical conductors taking into account their respective dimensions. In this example, the maximum permissible temperature is considered to be 70°C. It can be seen that the second electrical conductor 2 is used close to this temperature, therefore close to its maximum capacity, while the first electrical conductor 1 is used at a lower temperature. Furthermore, the first electrical conductor 1 carries a current lower than its maximum capacity, and increasing the transmitted electrical power would lead to overheating of the second electrical conductor 2 and not of the first electrical conductor 1.

[0015] The aim of the invention is therefore to propose a solution making it possible to configure a high voltage direct current installation so that it is able to transmit excess power, without having to oversize it and with the aim of being able to exploit each conductor to the maximum of its capacities. Statement of the invention

[0016] This aim is achieved by a method for configuring a high voltage direct current installation, said installation comprising a first main terminal and a second main terminal between which an electrical power called input / output is transmitted, a first electrical conductor which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected to said second main terminal, said first electrical conductor being sized to transmit a first nominal electrical power, said method consisting of:

[0017] - Adding a second electrical conductor, which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected to said second main terminal, said second electrical conductor being sized to transmit a second nominal electrical power, - Adding a power converter which comprises a first terminal, a second terminal and a third terminal, said power converter being inserted into said installation so that its first terminal is connected to the first main terminal, its second terminal is connected to the first connection terminal of the first electrical conductor and its third terminal is connected to the first connection terminal of the second electrical conductor, said power converter also comprising a first voltage source and a second voltage source, and controllable means for exchanging energy between the first voltage source and the second voltage source, - Configuring a control unit of the power converter to make it capable of controlling the power converter in order to adjust the voltage supplied by said first voltage source in series with the first electrical conductor and the voltage supplied by the second voltage source in series with said second electrical conductor and distributing said input / output electrical power in the first electrical conductor and in the second electrical conductor, taking into account the first nominal electrical power that the first electrical conductor is capable of transmitting and the second nominal electrical power that the second electrical conductor is capable of transmitting.

[0018] According to a particular feature, the second electrical conductor is sized to transmit a second nominal electrical power distinct from the first nominal electrical power.

[0019] According to another feature, the method also consists in inserting a device for turning on / off the power converter, and in controlling said device for turning on / off to insert the power converter between the two main terminals or to bypass it.

[0020] The invention also relates to a high-voltage direct current installation which comprises a first main terminal, a second main terminal between which an electrical power called input / output is transmitted, a first electrical conductor which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected to said second main terminal, said first electrical conductor being sized to transmit a first nominal electrical power, said installation being configured according to the method as defined above, by integrating:

[0021] - A second electrical conductor, which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected to said second main terminal, said second electrical conductor being sized to transmit a second nominal electrical power, - A power converter which comprises a first terminal, a second terminal and a third terminal, said power converter being inserted into said installation so that its first terminal is connected to the first main terminal, its second terminal is connected to the first connection terminal of the first electrical conductor and its third terminal is connected to the first connection terminal of the second electrical conductor, said power converter also comprising a first voltage source and a second voltage source, and controllable means for exchanging energy between the first voltage source and the second voltage source, - A control unit for said controllable means, - Said controllable means of the power converter being controlled by the control unit to adjust the voltage supplied by said first voltage source in series with the first electrical conductor and the voltage supplied by the second voltage source in series with said second electrical conductor and to distribute said input / output electrical power in the first electrical conductor and in the second electrical conductor, taking into account the first nominal electrical power that the first electrical conductor is capable of transmitting and the second nominal electrical power that the second electrical conductor is capable of transmitting.

[0022] According to a feature, the first voltage source is created between the first terminal and the second terminal of the power converter and the second voltage source is created between the first terminal and the third terminal of the power converter.

[0023] According to another feature, said controllable means comprise switching means connected between the second terminal and the third terminal of the converter and a current source connected between the first terminal of the power converter and a midpoint of said switching means.

[0024] According to a particular embodiment, the switching means are chosen to be non-reversible in current and non-reversible in voltage.

[0025] According to another particular embodiment, the switching means are chosen to be reversible in current and reversible in voltage.

[0026] According to another feature, the current source comprises an inductance.

[0027] According to another feature, the first voltage source comprises a first capacitor and in that the second voltage source comprises a second capacitor.

[0028] According to an advantageous embodiment, the installation comprises a device for switching the power converter on / off and a control unit configured to control said connection / disconnection device in order to insert the power converter between the two main terminals or to bypass it. Brief description of the figures

[0029] Other features and advantages will become apparent in the detailed description which

[0030]

[0031]

[0032]

[0033]

[0034] following is made with regard to the attached drawings in which: - Figures 1A to 1D illustrate the operating principle of a high-voltage direct current installation, according to the state of the art; - Figure 2 illustrates the architecture of the high voltage direct current installation according to the invention; - Figures 3 and 4 schematically represent the architecture of the power converter used in the high voltage direct current installation of the invention; - Figure 5 represents a first architecture of the power converter inserted in the high voltage direct current installation of the invention; - Figures 6A and 6B illustrate the operating principle of this first architecture of the power converter inserted into the high voltage direct current installation; - Figures 7 and 8 show two equivalent realizations of the architecture of Figure 5; - Figure 9 represents a second architecture of the power converter inserted in the high voltage direct current installation of the invention; - Figure 10 represents a third architecture of the power converter inserted in the high voltage direct current installation of the invention; - Figure 11 illustrates the operating principle of the high-voltage direct current installation according to the invention; - Figure 12 represents an alternative embodiment of the high voltage direct current installation according to the invention; - Figure 13 represents a diagram illustrating the operating principle of the installation of Figure 9; Detailed description of at least one embodiment The invention applies to a high voltage direct current installation (also called HVDC installation for "High voltage Direct Current"). The installation comprises a first main terminal A and a second main terminal B between which an electrical power is transmitted (from A to B or from B to A - for simplification, it is considered hereinafter that the power is transmitted from A to B). It comprises a first electrical conductor 1 comprising a first connection terminal 1_1 and a second connection terminal 1_2. Its second connection terminal 1_2 is connected to the second main terminal B. Initially, the installation, composed of only the first electrical conductor 1, is intended to transmit a nominal power equal to P.

[0035] This first electrical conductor 1 is sized sufficiently to transmit the nominal power P.

[0036] The term "dimension" means that an electrical conductor has characteristics (in particular type of material, cross-section, maximum temperature) which enable it to transmit a given nominal electrical power.

[0037] To ensure that the installation can transmit an electrical power greater than P, corresponding to a surplus power AP, a first aspect of the invention consists of upgrading the installation. For this, with reference to [fig.2], it is thus a question of adding to the installation:

[0038] - A second electrical conductor 2, and - A power converter PC.

[0039] The power converter PC has three electrical terminals, a first terminal X, a second terminal Y and a third terminal Z.

[0040] The second electrical conductor 2 comprises a first connection terminal 2_1 and a second connection terminal 2_2 connecting to the second main terminal B.

[0041] The PC power converter is inserted into the installation in the following manner

[0042] - Its first terminal X is connected to the first main terminal A; - The first connection terminal 1_1 of the first electrical conductor 1 is connected to its second Y terminal; - The first connection terminal 2_1 of the second electrical conductor is connected to its third terminal Z;

[0043] The power converter inserted in the installation is thus intended to be controlled to distribute the electrical power in the two electrical conductors.

[0044] Considering that the total power to be transmitted is P+AP, the power converter PC makes it possible to guarantee that the first electrical conductor 1 transmits the electrical power P and that the second electrical conductor 2 transmits the electrical power AP.

[0045] The insertion of the power converter PC makes it possible to use a second electrical conductor 2 sized as precisely as possible to pass the surplus power AP, without unnecessary oversizing, thus limiting additional costs.

[0046] With reference to [fig.3], the power converter PC may comprise a first voltage source V1 which, on command, can be connected in series with the first electrical conductor 1 and a second voltage source V2 which, on command, can be connected in series with the second electrical conductor 2. The power converter PC also comprises means 3 configured to ensure an exchange of electrical energy between the two voltage sources VI, V2, in view to distribute the total current IT in each electrical conductor 1, 2 and distribute the electrical power in each electrical conductor, taking into account the sizing of each electrical conductor. In [fig.3], the two dotted vertical arrows illustrate the principle of energy exchange between the two voltage sources VI, V2.

[0047] The possible insertion of a voltage in series with each electrical conductor 1, 2 makes it possible to modify the voltage at the terminals of the two electrical conductors and therefore to distribute the currents in an appropriate manner in the two electrical conductors. Thanks to the exchange of energy between the two voltage sources, the distribution of the currents is modified without generating significant losses. Indeed, the power absorbed by the source in series with the electrical conductor whose current is to be reduced is transmitted to the other voltage source.

[0048] According to an advantageous aspect of the invention, none of the terminals X, Y or Z of the power converter PC is connected to the ground. In HVDC type installations, the conductors are placed at potentials relative to the ground of several tens of kilovolts or even several hundred kilovolts (voltages between terminal A and the ground or between terminal B and the ground). In order to produce the desired effect (control of the distribution of currents between the two electrical conductors 1, 2 of the installation), the voltages between terminals X, Y and Z are of the same order of magnitude as the voltage drops across the terminals of these electrical conductors (voltage between the two main terminals A and B), i.e. of the order of a few hundred volts, or even a few kilovolts. Thus, the voltage dimensioning of this converter is reduced and its production is facilitated.

[0049] To ensure a transfer of energy between each voltage source, with reference to [fig.4], the means 3 may comprise a current source 30 and switching means 31 arranged and controlled to allow a connection of said current source 30 in parallel with the first voltage source VI or in parallel with the second voltage source V2.

[0050] It should be noted that, according to the mesh law, imposing a voltage between the terminals X and Y of the converter on the one hand and a voltage between the terminals X and Z of the converter on the other hand, amounts to imposing the voltage between the terminals Y and Z of the converter. Thus, a device imposing voltages between the terminals Y and Z on the one hand and X and Z on the other hand would produce the same effect and in reality only corresponds to another way of describing the device described above.

[0051] The switching means 31 may comprise one or more power switches. The number of power switches, their arrangement and their characteristics depend on the sign of the currents L and I2 in each electrical conductor 1, 2 and the polarity of the voltages inserted in each electrical conductor. A unit of The installation's UC control is responsible for controlling each power switch of the PC converter, in order to obtain the distribution of currents between its two terminals Y and Z.

[0052] The current source 30 may comprise at least one inductance L.

[0053] According to a particular aspect of the invention, with reference to [fig.4], the general architecture of the PC power converter can be as follows:

[0054] - The first voltage source Vi is connected between the first terminal X and the second terminal Y of the converter; - The second voltage source V2 is connected between the first terminal X and the third terminal Z of the converter; - The switching means 31 are connected between the second terminal Y and the third terminal Z of the converter; - The current source 30 is connected between the first terminal X of the converter and a midpoint M of the switching means;

[0055] Each voltage source is created using one or more capacitors (Ci, C2, C3) connected in a suitable manner between the terminals X, Y, Z of the power converter PC.

[0056] Based on the above principles, the PC power converter can be implemented according to different architectures.

[0057] Figures 5 to 10 show several possible architectures for the production of the power converter.

[0058] The architecture chosen for the converter will depend in particular on the degree of reversibility in current and voltage that one wishes to have.

[0059] [Fig.5] shows a first architecture, non-reversible in current and non-reversible in voltage. In this first architecture:

[0060] - The first voltage source Vi comprises a first capacitor Ci. - The second voltage source V2 includes a second capacitor C2. - The first capacitor Ci is oriented so that it can create a positive voltage in series with the first electrical conductor 1. - The second capacitor C2 is oriented so that it can create a negative voltage in series with the second electrical conductor. - The switching means 31 comprise an electronic transistor T i (for example type IGBT, IGCT, GTO, MOSFET, etc.) and a diode Db. For the transistor Tb, its gate is controlled by the control unit UC of the installation according to a determined control law (see below), its collector is connected to the midpoint and its emitter is connected to the second terminal Y of the converter. The diode Di is connected between the midpoint M and the third terminal Z of the converter and oriented conductively from the midpoint M to the third terminal of the converter. - The current source is formed by an inductance L, connected between the first terminal of the converter X and the midpoint M of the switching means.

[0061] This first architecture can be used when the total current IT enters through the first terminal X of the converter and the two currents II, I2 leave the converter PC respectively through its second terminal Y to circulate in the first electrical conductor 1 and through its third terminal Z to circulate in the second conductor 2. This architecture makes it possible to obtain a distribution of the currents different from the distribution which would be observed if the conductors were placed in parallel as in [fig.lB]. In [fig.5], the capacitors C1, C2 are connected so as to create a positive voltage in series with the first electrical conductor 1, to lower the current II and a negative voltage in series with the second electrical conductor to increase the current I2.This solution can be used when the conductor likely to be overloaded (i.e. the conductor with the lowest electrical resistance) is the first electrical conductor 1. It is of course possible to reverse the architecture to discharge the other electrical conductor.

[0062] [Fig.6A] and [Fig.6B] illustrate the operating principle of this first architecture, by presenting the path followed by the currents (represented in gray) in the different branches of the PC power converter, neglecting the current oscillations in the inductance.

[0063] - In Figure 6A, the transistor Ti is in the closed state. The total current IT (=Ii+I2) enters through the first terminal X of the converter, passes through the inductance L then the transistor Th. A part of this current IT leaves through the second terminal Y of the power converter PC, forming the current h present in the first electrical conductor 1. Another part of the current IT passes through the first capacitor Ci, then the second capacitor C2 to leave through the third terminal Z of the power converter PC, forming the current I2 in the second electrical conductor 2. - In Figure 6B, transistor Ti is in the open state. The total current IT (=Ii+I2) enters through the first terminal X of the power converter PC, passes through the inductor L and then the diode Dp. Part of this current IT leaves through the third terminal Z of the power converter PC, forming the current I2 present in the second electrical conductor 2. Another part of the current IT passes through the second capacitor C2, then the first capacitor Ci to leave through the second terminal Y of the power converter PC, forming the current L present in the first electrical conductor 1.

[0064] This first architecture is to be considered in a non-limiting manner and allows to illustrate a principle of a non-reversible realization in current and non-reversible in voltage.

[0065] Figures 7 and 8 show equivalent architectures to that of [fig.5]. In [fig.7], the capacitor C2 is connected between the first terminal X and the third terminal Z of the converter and an equivalent capacitor C3 is connected between the terminals Y and Z of the power converter PC. In the same way, in [fig.8], the capacitor C1 is connected between the terminals X and Y of the power converter and an equivalent capacitor C3 is connected between the terminals Y and Z. To create the two voltage sources VI, V2, it is thus possible to imagine different combinations of connection of two or three capacitors, between the terminals X, Y, Z of the power converter PC.

[0066] [Fig.9] shows a second architecture reversible in current and voltage.

[0067] In this second architecture:

[0068] - The first voltage source Vi comprises a first capacitor Ci. - The second voltage source V2 includes a second capacitor C2. - The first capacitor Ci is oriented so that it can create a positive or negative voltage in series with the first electrical conductor 1. - The second capacitor C2 is oriented so that it can create a positive or negative voltage in series with the second electrical conductor 2. - The switching means 31 comprise two switching arms connected in parallel between the second terminal Y and the third terminal Z of the converter. Each switching arm comprises two assemblies connected by the midpoint M and each formed for example by a transistor Ti, T2, T3, T4 (for example of the IGBT, IGCT, GTO, MOSFET type, etc.) and a diode DB D2, D3, D4 in series. Depending on the transistor technology used, it is possible to dispense with the diodes. The gate of each transistor is controlled by the control unit UC of the installation according to the adapted control law. - In the first switching arm: • The collector of each transistor TH T2 is connected to the midpoint M and their emitter is connected respectively to the second terminal Y and the third terminal Z of the converter, via the diode Dh D2. Each diode is oriented passing towards the corresponding terminal of the converter. - In the second switching arm: • The collector of the first transistor T3 is connected to the second terminal Y of the converter and its emitter to the midpoint M2, via the diode D3. The collector of the second transistor T4 is connected to the third terminal Z of the converter and its emitter is connected to the midpoint M, via diode D4. Each diode is connected conducting in the emitter to midpoint direction. - The current source is formed by an inductance L, connected between the first terminal X of the converter and the midpoint M of the switching means.

[0069] This second architecture is to be considered in a non-limiting manner and makes it possible to illustrate an embodiment with reversibility in current and voltage. It can be used regardless of the sign of the currents h and I2, provided that h and I2 are of the same sign. In all cases, the voltage V3 created by the converter between the two conductors can be positive or negative, thus making it possible to increase or decrease the current h caused to circulate in the first electrical conductor.

[0070] [Fig. 10] shows a third architecture, also reversible in current and voltage. This architecture is equivalent to that of the second architecture, but implemented in a more economical manner, using fewer electronic switches. In this architecture:

[0071] - The first voltage source Vi comprises a first capacitor Ci. - The second voltage source V2 includes a second capacitor C2. - The first capacitor Ci is oriented so as to be able to create a positive voltage in series either with the first electrical conductor 1 or with the second electrical conductor 2. - The second capacitor C2 is oriented so that it can create a negative voltage in series either with the first electrical conductor 1 or with the second electrical conductor 2. - The switching means comprise a switching arm with two switches separated by the midpoint. Each switch comprises a transistor Ti, T2 (for example of the IGBT, IGCT, GTO, MOSFET type, etc.) and a diode Di, D2 in antiparallel. They also comprise several mechanical switches (e.g., relays or contactors) arranged in a suitable manner to be able to configure the converter according to the current to be increased or decreased. These may be two groups of two switches. The first group comprises the switches Swi, Sw2 and is connected on the one hand to the first voltage source and on the other hand to each of the two electrical conductors. The second group comprises the switches Sw3, Sw4 and is connected on the one hand to the second voltage source and on the other hand to each of the two electrical conductors.Each group allows the voltage source considered to be selectively connected in series with the first electrical conductor 1 or in series with the second conductor. electric 2. - The current source is formed by an inductance L, connected between the first terminal of the converter and the midpoint M.

[0072] When the switches Swl and Sw4 are closed (Sw2 and Sw3 being open), the voltage VI is inserted in series with the first electrical conductor 1 and the voltage V2 is inserted in series with the second electrical conductor 2. As in the case of [fig.5], the converter is then used to decrease the current in conductor 1 and to increase the current in conductor 2.

[0073] When the switches Sw2 and Sw3 are closed (Swl and Sw4 being open), the voltage V1 is inserted in series with the second electrical conductor 2 and the voltage V2 is inserted in series with the first electrical conductor 1. In a dual manner to the case of [fig.5], the power converter PC is used to increase the current in the first electrical conductor 1 and to decrease the current in the second electrical conductor 2.

[0074] [Fig. 11] illustrates the advantages of inserting a converter into the installation to better distribute the currents. Apart from the converter, the installation has the same characteristics as those described above in connection with [Fig. 1D]. As a reminder, we thus have at the start:

[0075] - The total power PT to be transmitted, equal to P+AP, worth 1.6 GW. - The first electrical conductor 1 with a section of 1200 mm2 allowing it to transmit a nominal power P / of 0.71 GW.

[0076] In this case, the second electrical conductor 2 has a cross-section of 1900 mm2, allowing it to transmit a nominal power P2' of 0.92 GW. In the example of [fig.lD], the cross-section was 2400 mm2, allowing it to transmit a nominal power P2' of 1.05 GW.

[0077] The power converter PC is controlled to create a first voltage Vi in series with the first electrical conductor 1 and a second voltage V2 in series with the second electrical conductor 2, making it possible to modify the natural distribution of the current between the two electrical conductors. Thus, for the total power PT of 1.6 GW, the first electrical conductor 1 will transmit a power of 0.68 GW with a current h of 1.07 kA and the second electrical conductor 2 will transmit a power of 0.92 GW with a current I2 of 1.43 kA.

[0078] Compared to the example of [fig.1D], it can be seen that the section of the second electrical conductor 2 could be reduced while maintaining the temperature of the conductors at a value lower than or equal to the maximum admissible temperature (70°C in this example). The cost of the second electrical conductor 2 is therefore reduced for the same total power P+AP transmitted.

[0079] According to a particular aspect of the invention, it turns out that the power converter can be especially useful when a fine distribution of the current must be carried out, in particular when the power to be transmitted is close to the maximum value (P+AP) for which the installation is sized. Apart from this, it may be relevant not to use the PC converter by letting the total current be distributed naturally, according to the sizing of each of the two electrical conductors 1, 2. For this, with reference to [fig. 12], the installation can integrate a device for switching the PC power converter on / off.This device may comprise a first switch Sw5 connected between the first main terminal A and the first connection terminal 1_1 of the first electrical conductor 1, in parallel with the first voltage source V1 formed between the first terminal X and the second terminal Y of the converter PC, and a second switch Sw6 connected between the first main terminal A and the first connection terminal 2_1 of the second electrical conductor 2, in parallel with the second voltage source V2 formed between the first terminal X and the third terminal Z of the converter PC. When the two switches Sw5, Sw6 are closed, the converter PC is out of service, therefore inoperative by being bypassed, allowing the current to be distributed naturally in the two conductors 1, 2, according to their respective resistance. In this embodiment of [fig. 12], the converter PC is by default bypassed, therefore not used.It can be put into service and therefore inserted into the installation when the power transmitted by one of the two conductors reaches its nominal power (PI1 for the first electrical conductor 1, P2' for the second electrical conductor 2). If the total power continues to increase, the PC converter is commanded to insert the adapted voltages in series with each of the conductors 1, 2 and distribute the current between the two conductors to rebalance the powers.

[0080] [Fig. 13] shows an example of a control algorithm for the installation as shown in [Fig. 12], O corresponds to the "Yes" branch and N corresponds to the "No" branch). The steps are as follows:

[0081] - E0: Algorithm start step. - El: The converter is by default out of service in the installation, the inter breakers Sw5, Sw6 being in the closed state to bypass it. The control unit UC is responsible for measuring / estimating one or more physical parameters of the two electrical conductors 1, 2, among the temperature, the current, the electrical power... - E2: The UC control unit performs tests on each of the measured / estimated parameters against threshold values. • As long as none of these parameters exceeds the threshold value, the control unit executes step EL • In the event that at least one of the monitored parameters takes a value higher than a threshold value or if an operator decides so, the control unit puts the PC power converter into service and inserts it into the installation by opening the two switches Sw5, Sw6. - E3: The control unit thus inserts the power converter PC between the two main terminals A, B. In its operating mode, the switching means 31 of the power converter PC are thus controlled by the control unit UC to fulfill one or more of the following objectives: • Maintain between the two conductors, for a given parameter, a constant ratio (for example a constant electric current ratio); • Maintain a given difference on a parameter, between the two conductors; • Control one or more of the parameters to maintain it at a reference level. This action can be implemented using a control loop responsible for determining the commands to be applied to the converter to maintain the measured or estimated parameter at the reference value; - E4 When the PC power converter is no longer required (the monitored parameter falls below the threshold value) or upon decision of an operator, the PC power converter can be taken out of service again.

[0082] Alternatively, the power converter could be inserted by default in the installation (switches Sw5, Sw6 open) with the switching means 31 controlled by UC so as not to add any voltage in series with the two electrical conductors.

[0083] It is understood from the above that the solution of the invention makes it possible to upgrade a high voltage direct current installation, in a simple and reliable manner, providing the most accurate sizing, thus limiting costs.

Claims

1. Claims Method for configuring a high voltage direct current installation, said installation comprising a first main terminal (A) and a second main terminal (B) between which an electrical power called input / output is transmitted, a first electrical conductor (1) which comprises a first connection terminal (1_1) and a second connection terminal (1_2), its second connection terminal (1_2) being connected to said second main terminal (B), said first electrical conductor (1) being sized to transmit a first nominal electrical power (P / ), said method being characterized in that it consists of: - Adding a second electrical conductor (2), which comprises a first connection terminal (2_1) and a second connection terminal (2_2), its second connection terminal (2_2) being connected to said second main terminal (B), said second electrical conductor (2) being sized to transmit a second nominal electrical power (P2'), - Adding a power converter (PC) which comprises a first terminal (X), a second terminal (Y) and a third terminal (Z), said power converter being inserted into said installation so that its first terminal is connected to the first main terminal (A), its second terminal (Y) is connected to the first connection terminal (1_1) of the first electrical conductor (1) and its third terminal is connected to the first connection terminal (2_1) of the second electrical conductor (2), said power converter also comprising a first voltage source (Vi) and a second voltage source (V2), and controllable means (3) for exchanging energy between the first voltage source (Vi) and the second voltage source (V2), - Configuring a control unit (UC) of the power converter (PC) to make it capable of controlling the power converter (PC) in order to adjust the voltage supplied by said first voltage source (Vi) in series with the first electrical conductor (1) and the voltage supplied by the second voltage source (V2) in series with said second electrical conductor and distributing said electrical power input / output in the first electrical conductor (1) and in the second electrical conductor (2), taking into account the first nominal electrical power (P / ) that the first electrical conductor (1) is capable of transmitting and the second nominal electrical power (P2') that the second electrical conductor is capable of transmitting.

2. Method according to claim 1, characterized in that the second electrical conductor is sized to transmit a second nominal electrical power (P2') distinct from the first nominal electrical power (P / ).

3. A method according to claim 1 or 2, characterized in that it consists of inserting a device for switching on / off the power converter, and controlling said switching on / off device to insert the power converter between the two main terminals or to bypass it.

4. High voltage direct current installation which comprises a first main terminal (A) a second main terminal (B) between which an electrical power called input / output is transmitted, a first electrical conductor (1) which comprises a first connection terminal (1_1) and a second connection terminal (1_2), its second connection terminal (1_2) being connected to said second main terminal (B), said first electrical conductor (1) being dimensioned to transmit a first nominal electrical power (Pf), said installation being characterized in that it is configured according to the method as defined in one of claims 1 to 3, by integrating: - A second electrical conductor (2), which comprises a first connection terminal (2_1) and a second connection terminal (2_2), its second connection terminal (2_2) being connected to said second main terminal (B),said second electrical conductor (2) being sized to transmit a second nominal electrical power (P2'), - A power converter (PC) which comprises a first terminal (X), a second terminal (Y) and a third terminal (Z), said power converter being inserted into said installation so that its first terminal is connected, to the first main terminal (A), its second terminal (Y) is connected to the first connection terminal (1_1) of the first electrical conductor (1) and its third terminal is connected to the first connection terminal (2_1) of the second electrical conductor (2), said power converter also comprising a first voltage source (Vi) and a second voltage source (V2), and controllable means (3) for exchanging energy between the first voltage source (VJ and the second voltage source (V2), - A control unit (UC) of said controllable means (3),- Said controllable means (3) of the power converter (PC) being controlled by the control unit (UC) to adjust the voltage supplied by said first voltage source (VJ in series with the first electrical conductor (1) and the voltage supplied by the second voltage source (V2) in series with said second electrical conductor and to distribute said input / output electrical power in the first electrical conductor (1) and in the second electrical conductor (2), taking into account the first nominal electrical power (Pf) that the first electrical conductor (1) is capable of transmitting and the second nominal electrical power (P2') that the second electrical conductor is capable of transmitting.,

5. Installation according to claim 4, characterized in that the first voltage source (VJ is created between the first terminal (X) and the second terminal (Y) of the power converter (PC) and the second voltage source (V2) is created between the first terminal (X) and the third terminal (Z) of the power converter (PC).

6. Installation according to claim 5, characterized in that said controllable means (3) comprise switching means (31) connected between the second terminal (Y) and the third terminal (Z) of the converter and a current source (30) connected between the first terminal (X) of the converter and a midpoint (M) of said switching means (31).

7. Installation according to claim 6, characterized in that the means switching (31) are chosen to be non-reversible in current and non-reversible in voltage.

8. Installation according to claim 6, characterized in that the switching means (31) are chosen to be reversible in current and reversible in voltage.

9. Installation according to one of claims 6 to 8, characterized in that the current source (30) comprises an inductance (L).

10. Installation according to one of claims 4 to 9, characterized in that the first voltage source (Vi) comprises a first capacitor (Ci) and in that the second voltage source (V2) comprises a second capacitor (C2).

11. Installation according to one of claims 4 to 10, characterized in that it comprises a device for switching the power converter on / off and a control unit (UC) configured to control said connection / disconnection device in order to insert the power converter between the two main terminals or to bypass it.

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