Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
  • H02J1/10—Parallel operation of dc sources
  • H02J1/106—Parallel operation of dc sources for load balancing, symmetrisation, or sharing
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link

Definitions

• the present invention relates to a method for configuring a direct current high voltage installation and to said direct current high voltage installation, configured using said method.
• a conventional solution consists in adding a second electrical conductor 2 in parallel with the first electrical conductor 1, as represented in FIG. 1 B.
• the two conductors 1, 2 in parallel thus make it possible to transmit the total power P+AP between the two terminals A, B.
• 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 figure 1 B.
• the first electrical conductor 1 will thus transmit a power Pi different from P, and the second conductor electric will transmit a power P2 different from AP.
• the second electrical conductor 2 added will most certainly have to be sized to transmit a greater power 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 that is always lower than its maximum capacity and is therefore not used optimally.
• FIG. 1C illustrates this problem.
• the installation transmits the total power PT.
• the first electrical conductor 1 transmits the power Pi with the current h and the second electrical conductor 2 transmits the power P2 with the current I2.
• the total power to be transmitted is denoted PT.
• FIG. 1C also shows, for each conductor 1, 2, the electrical resistance Ri, R2, the thermal resistance between the conductor and the ambient Rthi, Rth2, the temperature of the electrical conductor T1, T2 and the power losses Pi oss i , Pioss2.
• the dimensioning of an electrical conductor must be chosen by the maximum power that it can transmit at its maximum temperature.
• the first electrical conductor 1 which has the lowest resistance, will be caused 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.
• the second electrical conductor 2, which has the highest resistance will have 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 stressed close to its maximum capacities.
• Figure 1D illustrates the above findings with a numerical example.
• a second electrical conductor 2 is mounted in parallel with the first electrical conductor 1 with a section of 2400 mm 2 .
• the maximum admissible 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, whereas 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 electrical power transmitted would lead to overheating of the second electrical conductor 2 and not of the first electrical conductor 1.
• EP2670013A1 describes for its part a power flow control device between two DC networks. It has two current flow control units and three power transmission lines connected to three terminals, which can have different current draws through the three power lines.
• the object of the invention is to propose a solution making it possible to configure a high voltage direct current installation so that it is able to pass a surplus of power, without having to oversize it and with the aim of being able to exploit each driver to the maximum of his abilities.
• a method for configuring a high voltage direct current installation comprising a first main terminal and a second main terminal between which is transmitted a so-called input/output electrical power, a first electrical conductor which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected only to said second main terminal, said first electrical conductor being sized to transmit a first rated electrical power, said method comprising: - Add a second electrical conductor, which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected only 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 in 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 exchange means energy between the first voltage source and the second voltage source,
• the installation of the invention has the particularity of comprising only two power lines, both connected only to the second main terminal.
• the solution of the invention differs from the prior solution described in patent application EP2670013A1.
• each main terminal is associated with a single DC terminal and the solution of the invention makes it possible to configure this installation by allowing distribution of the currents on the two lines.
• the second electrical conductor is dimensioned to transmit a second nominal electrical power distinct from the first nominal electrical power.
• the method also consists in inserting a device for putting the power converter into service/out of service, and in controlling said device for putting into service/out of service to insert the power converter between the two main terminals or the get around.
• the invention also relates to a high voltage direct current installation which comprises a first main terminal, a second main terminal between which is transmitted a so-called input/output electrical power, a first electrical conductor which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected only 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:
• a second electrical conductor which comprises a first connection terminal and a second connection terminal, its second connection terminal being connected only to said second main terminal, said second electrical conductor being dimensioned 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 in said installation so that its first terminal is connected to the first main terminal, its second terminal is connected to the first terminal connection 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 of 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 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 able to transmit and the second power electrical rating that the second electrical conductor is capable of transmitting.
• 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.
• 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.
• the switching means are chosen to be non-reversible in current and non-reversible in voltage.
• the switching means are chosen to be reversible in current and reversible in voltage.
• the current source comprises an inductor.
• the first voltage source comprises a first capacitor and in that the second voltage source comprises a second capacitor.
• the installation comprises a device for commissioning/decommissioning the power converter and a control unit configured to control said connection/disconnection device with a view to inserting the power converter between the two main terminals or circumvent it.
• Figures 1 A to 1 D illustrate the principle of operation of a high voltage direct current installation, according to the state of the art
• FIG. 2 illustrates the architecture of the high voltage direct current installation according to the invention
• FIGS. 3 and 4 schematically represent the architecture of the power converter used in the high voltage direct current installation of the invention
• FIG. 5 represents a first architecture of the power converter inserted in the high voltage direct current installation of the invention
• FIGS. 6A and 6B illustrate the principle of operation of this first architecture of the power converter inserted in the high voltage direct current installation
• FIGS 7 and 8 show two equivalent embodiments of the architecture of Figure 5;
• FIG. 9 represents a second architecture of the power converter inserted in the high voltage direct current installation of the invention.
• FIG. 10 represents a third architecture of the power converter inserted in the high voltage direct current installation of the invention.
• FIG. 11 illustrates the principle of operation of the high voltage direct current installation according to the invention
• FIG. 12 represents an alternative embodiment of the direct current high voltage installation according to the invention.
• Figure 13 represents a diagram illustrating the operating principle of the installation of Figure 9;
• 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, for example associated with a first terminal, and a second main terminal B, for example associated with a second terminal, between which electrical power is transmitted (from A to B or from B to A - for simplification, it is considered below 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 only to the second main terminal B.
• the installation composed of a single first electrical conductor 1, is intended to transmit a nominal power equal to P.
• This first electrical conductor 1 is dimensioned sufficiently to transmit the nominal power P.
• an electrical conductor has characteristics (in particular type of material, cross-section, maximum temperature) which allow it to transmit a given nominal electrical power.
• a first aspect of the invention consists in upgrading the installation. To do this, with reference to figure 2, it is thus a question of adding to the installation:
• a second electrical conductor 2 and
• the power converter PC has three electrical terminals, a first terminal X, a second terminal Y and a third terminal Z.
• the second electrical conductor 2 comprises a first connection terminal 2_1 and a second connection terminal 2_2 connecting only to the second main terminal B.
• connection only means the fact that the electrical conductor is not connected to anything other than the second main terminal B, or in other words that it does not include a branch point, or other point connection to another terminal or to another terminal than the second main terminal B.
• the two electrical conductors are therefore connected in parallel to the second main terminal B.
• the PC power converter is inserted into the installation as follows:
• 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 terminal Y;
• the first connection terminal 2_1 of the second electrical conductor is connected to its third terminal Z;
• the power converter inserted in the installation is thus intended to be controlled to distribute the electrical power in the two electrical conductors.
• 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.
• the insertion of the power converter PC makes it possible to use a second electrical conductor 2 dimensioned as accurately as possible to pass the excess power AP, without unnecessary oversizing, thus limiting the additional costs.
• the power converter PC can include a first voltage source Vi 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, with a view to distributing the total current IT in each conductor electrical 1, 2 and distribute the electrical power in each electrical conductor, taking into account the dimensioning of each electrical conductor.
• the two dotted vertical arrows illustrate the principle of energy exchange between the two voltage sources V1, V2.
• none of the terminals X, Y or Z of the power converter PC is connected to ground.
• the conductors are placed at potentials with respect to earth of several tens of kilovolts or even several hundreds of kilovolts (voltages between terminal A and earth or between terminal B and earth).
• the voltages between the terminals X, Y and Z are of the same order of magnitude as the voltage drops at the terminals of these electrical conductors (voltage between the two main terminals A and B) is of the order of a few hundred volts, or even a few kilovolts.
• the voltage dimensioning of this converter is reduced and its production is facilitated.
• the means 3 may comprise a current source 30 and switching means 31, arranged and controlled to allow connection of said current source 30 in parallel with the first voltage source Vi or in parallel with the second voltage source V2.
• the switching means 31 can include one or more power switches.
• the number of power switches, their arrangement and their characteristics depends on the sign of the currents h and I2 in each electrical conductor 1, 2 and on the polarity of the voltages inserted in each electrical conductor.
• a control unit UC of the installation is responsible for controlling each power switch of the converter PC, with a view to obtaining the distribution of the currents between its two terminals Y and Z.
• Current source 30 may include at least one inductor L.
• the general architecture of the power converter PC can be as follows:
• the first voltage source V1 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;
• Each voltage source is created using one or more capacitors (Ci, C2, C3) suitably connected between the X, Y, Z terminals of the power converter PC.
• the PC power converter can be made according to different architectures.
• FIGS 5 to 10 show several possible architectures for the realization of the power converter.
• the architecture chosen for the converter will depend in particular on the degree of current and voltage reversibility which it is desired to have.
• FIG. 5 shows a first architecture, non-reversible in current and non-reversible in voltage.
• this first architecture :
• the first voltage source Vi includes 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 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 T1 (for example of the IGBT, IGCT, GTO, MOSFET type, etc.) and a diode D1.
• transistor T1 for example of the IGBT, IGCT, GTO, MOSFET type, etc.
• diode D1 For transistor T1, its gate is controlled by the installation's control unit UC 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.
• Diode D1 is connected between the midpoint M and the third terminal Z of the converter and oriented conductive 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.
• This first architecture can be used when the total current IT enters through the first terminal X of the converter and the two currents h, 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. 1B.
• the capacitors Ci, C2 are connected so as to create a positive voltage in series with the first electrical conductor 1, to lower the current h 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 (that is to say 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.
• Figure 6A and Figure 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 power converter PC while neglecting the current oscillations in the inductor.
• transistor T1 is in the closed state.
• 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 l T passes through the first capacitor Ci, then the second capacitor C2 to exit by the third terminal Z of the power converter PC, forming the current I2 in the second electrical conductor 2.
• transistor T1 is in the open state.
• a part of this current IT leaves by the third terminal Z of the power converter PC, forming the current I2 present in the second electric conductor 2.
• Another part of the current IT crosses the second capacitor C2, then the first capacitor Ci to leave by the second terminal Y of the power converter PC, forming the current h present in the first electrical conductor 1.
• This first architecture is to be considered in a non-restrictive way and makes it possible to illustrate a principle of a non-reversible current and non-reversible voltage realization.
• Figures 7 and 8 show architectures equivalent to that of Figure 5.
• 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 PC power converter.
• capacitor Ci is connected between terminals X and Y of the power converter and an equivalent capacitor C3 is connected between terminals Y and Z.
• FIG. 9 shows a second reversible current and voltage architecture.
• the first voltage source V1 includes 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 or negative voltage in series with the first electrical conductor 1.
• the second capacitor C2 is oriented so as to be able to 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 sets connected by the midpoint M and each formed, for example, of a transistor T1, T2, T3, T4 (for example of the IGBT, IGCT, GTO, MOSFET type, etc.) and a diode D1, D2, D3, D4 in series.
• a transistor T1, T2, T3, T4 for example of the IGBT, IGCT, GTO, MOSFET type, etc.
• D1, D2, D3, D4 in series.
• the gate of each transistor is controlled by the control unit UC of the installation according to the appropriate control law.
• each transistor T1, T2 is connected to the midpoint M and their emitter is connected respectively to the second terminal Y and to the third terminal Z of the converter, via the diode Di, D2.
• Each diode is conductive oriented towards the corresponding terminal of the converter.
• 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 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 conductively connected 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.
• This second architecture is to be considered in a non-limiting way and makes it possible to illustrate an embodiment provided with current and voltage reversibility. It can be used whatever the sign of the currents h and I2, as long as h and I2 have 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 flow in the first electrical conductor.
• Figure 10 shows a third architecture, also reversible in current and in voltage. This architecture is equivalent to that of the second architecture, but carried out in a more economical way, by using fewer electronic switches.
• This structure is equivalent to that of the second architecture, but carried out in a more economical way, by using fewer electronic switches.
• the first voltage source V1 includes 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 as to be able to 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 middle point.
• Each switch comprises a transistor T1, T2 (for example of the IGBT, IGCT, GTO, MOSFET type, etc.) and an antiparallel diode D1, D2. They also include several switches of the mechanical type (relay or contactor for example) arranged in a suitable manner to be able to configure the converter according to the current which is to be increased or decreased. It can be two groups of two switches.
• the first group comprises 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 switches SW3, SW4 and is connected by a hand to the second voltage source and secondly to each of the two electrical conductors. Each group makes it possible to selectively connect the considered voltage source in series with the first electrical conductor 1 or in series with the second electrical conductor 2.
• the current source is formed by an inductance L, connected between the first terminal of the converter and the midpoint M.
• 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.
• 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.
• Figure 11 illustrates the advantages of inserting a converter in the installation to better distribute the currents. Apart from the converter, the installation has the same characteristics as those described above in connection with figure 1 D. As a reminder, we thus have at the start:
• the total power PT to be transmitted equal to P+AP, being worth 1.6 GW.
• the first electrical conductor 1 with a section of 1200 mm 2 enabling it to transmit a nominal power P/ of 0.71 GW.
• the second electrical conductor 2 has a section of 1900 mm 2 , allowing it to transmit a nominal power P 2 'of 0.92 GW.
• the section was 2400 mm 2 , enabling it to transmit a nominal power P 2 'of 1.05 GW.
• the power converter PC is controlled to create a first voltage V1 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.
• 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.
• the section of the second electrical conductor 2 could be reduced while maintaining the temperature of the conductors at a value less 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.
• the power converter can be especially useful when a fine distribution of the current must be operated, in particular when the power to be transmitted is close to the maximum value (P+AP) for which the installation is sized. Apart from that, it may be relevant not to use the PC converter, leaving the total current to be distributed naturally, according to the dimensioning of each of the two electrical conductors 1, 2. For this, with reference to the figure 12, the installation can incorporate a PC power converter commissioning/decommissioning device.
• This device may comprise a first switch Sws 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 second terminal Y of the converter PC , and a second switch Swe 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 .
• the two switches Sws, Swe are closed, the converter PC is out of service, therefore inoperative by being bypassed (“bypass” in English), allowing the current to be distributed naturally in the two conductors 1, 2, according to their resistance. respectively.
• bypass in English
• 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 (P/ for the first electrical conductor 1, P 2 'for the second electrical conductor 2). If the total power continues to increase, the converter PC is controlled to insert the appropriate voltages in series with each of the conductors 1, 2 and distribute the current between the two conductors to rebalance the powers.
• FIG. 13 shows an example of an algorithm for controlling the installation as represented in FIG. 12, O corresponds to the “Yes” branch and N corresponds to the “No” branch). The steps are as follows:
• the converter is by default out of service in the installation, the switches Sws, Swe 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 temperature, current, electrical power, etc.
• control unit UC performs tests on each of the measured/estimated parameters with respect to threshold values. o As long as none of these parameters exceeds the threshold value, the control unit executes step E1. o In the event that at least one of the monitored parameters takes a value greater than a threshold value or if an operator so decides, the control unit places the PC power converter in service and inserts it into the installation in opening the two switches Sws, Swe.
• the control unit thus inserts the power converter PC between the two main terminals A, B.
• 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: o maintain between the two conductors, for a given parameter, a constant ratio (for example a constant electric current ratio); o Maintain a difference given on a parameter, between the two conductors; o 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;
• the power converter could be inserted into the installation by default (the switches Sws, Swe open) with the switching means 31 controlled by the CPU so as not to add any voltage in series with the two electrical conductors.

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• Power Engineering (AREA)
• Direct Current Feeding And Distribution (AREA)

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• 2021
  • 2021-01-27 FR FR2100744A patent/FR3119274A1/fr active Pending
• 2022
  • 2022-01-26 EP EP22704875.8A patent/EP4285453A1/de active Pending
  • 2022-01-26 WO PCT/EP2022/051682 patent/WO2022161973A1/fr active Application Filing

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