Non-isolated DC / DC voltage converter

Abstract

Non-isolated voltage converter. Voltage converter (10,10') comprising first (12), second (14), third (16) and fourth (18) DC terminals and at least one arm (20,30,40) comprising exactly three electrical conversion modules (22,32,42,24,34,44,26,36,46), each comprising a chain of controllable sub-modules (SMs) capable of assuming at least one first state in which a capacitor is inserted in the chain of sub-modules, the converter further comprising a first filter module (50) electrically connected between an intermediate point of the arm and said third DC terminal, and a second filter module (54) electrically connected between a second intermediate point of the arm and said second DC terminal. Figure for the abstract: Fig. 1.

Description

Title of the invention: Non-isolated DC / DC voltage converter technical field

[0001] The present invention relates to the technical field of voltage converters for converting a first direct current voltage into a second direct current voltage. These voltage converters are also called DC / DC voltage converters. This type of converter is particularly suitable for installation in high-voltage direct current (HVDC) power supply systems.

[0002] DC / DC voltage converters allow the connection of a first portion of a DC power supply network with a second portion of a DC power supply network. Previous technique

[0003] The most commonly used voltage converters in HVDC power supply installations are modular multilevel converters (MMCs). These MMCs offer excellent efficiency and numerous control options. Furthermore, their modular structure allows for the construction of converters capable of withstanding very high voltages. One drawback of these converters is their large number of components. In particular, while it is known to create a DC / DC converter from two MMCs interconnected in their AC sections via a transformer, the resulting DC / DC converter, called a "Front-to-Front" MMC, comprises a very large number of components, is particularly bulky, and has insufficient efficiency due to the two conversion stages and the transformer.

[0004] A DC / DC converter is also known as disclosed in the publication by GJ Kish and PW Lehn, “Modeling Techniques for Dynamic and Steady-State Analysis of Modular Multilevel DC-DC Converters”. This converter allows a first portion of a DC power supply network, having a bi-pole topology and comprising a first electrical pole and a second electrical pole, to be connected to a second portion of a DC power supply network having a symmetrical monopole topology.

[0005] The voltage converter described in this document comprises first, second, third, and fourth DC terminals. The first DC terminal is configured to be connected to the first pole of the first portion of a two-pole DC power supply network, while the second terminal The DC power supply is configured to be connected to the second pole of the first segment of a DC power supply network with a two-pole topology. The converter further includes an arm with first, second, third, and fourth electrical conversion modules connected in cascade between the first and second DC terminals. Each of these electrical conversion modules is equipped with chains of sub-modules.

[0006] One drawback of this converter is that it creates coupling between the first and second poles of the first portion of the two-pole DC power supply network to which it is connected, due to the currents flowing between the four electrical conversion modules. Therefore, in the event of a fault or disturbance on the first or second pole of the first portion of the DC power supply network, this prior art converter generates a disturbance on the other, otherwise healthy, pole. Consequently, in the event of a fault on only one of the two poles, all power exchanges between the first and second portions of the DC power supply network must be interrupted, for example by means of switches, and the voltage converter must be shut down.The fault behavior of this converter is unsatisfactory and does not meet the general expectations for converters connected to a two-pole network: a fault on one pole should not disrupt the other pole, and in the event of a fault, including one internal to the converter, at least half of the rated power of the first two-pole power supply network segment should be able to be transferred without interruption. In other words, this converter does not offer redundancy, which is detrimental.

[0007] Furthermore, this converter is intended for bipolar interconnection. It comprises numerous components and is particularly bulky, so it is not suitable and sized to connect a first portion of a power supply network with a monopole topology to a second portion of a power supply network also with a monopole topology. Description of the invention

[0008] One object of the present invention is to provide a voltage converter that remedies the aforementioned problems.

[0009] To this end, the invention relates to a voltage converter for converting a first DC voltage into a second DC voltage and vice versa, the voltage converter comprising: - the first and second continuous terminals configured to be electrically connected to a first portion of a continuous power supply network; - third and fourth continuous terminals configured to be electrically connected connected to a second portion of the continuous power supply network; - at least one arm comprising an upper point and a lower point between which it extends, the upper point being electrically connected to the first DC terminal while the lower point is electrically connected to the fourth DC terminal, said at least one arm comprising a first electrical conversion module electrically connected between the upper point and a first intermediate point of the arm, a second electrical conversion module electrically connected between said first intermediate point and a second intermediate point of the arm, and a third electrical conversion module electrically connected between said second intermediate point and said lower point of the arm, the first intermediate point of the arm being electrically connected to the third DC terminal while the second intermediate point of the arm is connected to the second DC terminal, each of the first,second and third electrical conversion modules comprising a chain of sub-modules individually controllable by a control element specific to each sub-module, and each sub-module comprising a capacitor, the control element of each sub-module being able to take at least a first state in which the capacitor is inserted into the chain of sub-modules and a second state in which the capacitor is not inserted into said chain of sub-modules, at least one of the electrical conversion modules comprising an inductor connected in series with the chain of sub-modules of said electrical conversion module, said at least one arm comprising exactly three electrical conversion modules; - a first filtering module electrically connected between said first intermediate point of the arm and said third DC terminal, said first filtering module being configured to limit the flow of alternating electric current to said third DC terminal; and - a second filtering module electrically connected between said second intermediate point of the arm and said second continuous terminal, said second filtering module being configured to limit the flow of an alternating electric current to said second continuous terminal.

[0010] Without departing from the scope of the invention, the first and second continuous terminals are advantageously configured to be electrically connected to a first complete continuous power supply network, while the third and fourth continuous terminals are configured to be electrically connected to a second complete continuous power supply network. These portions of the continuous power supply network may comprise one or more stations.

[0011] The first and second portions of the DC power supply network may have the same topology or different topologies. By way of non-limitation, the The first and second portions of the DC power supply network can have a symmetric monopole, asymmetric monopole, or bipole topology. In the latter case, the converter according to the invention is connected to only one of the two poles of said portion of the DC power supply network. The converter according to the invention therefore allows different network portion topologies to be connected together and is thus particularly versatile.

[0012] The first and third DC terminals are preferably configured to be electrically connected to a high-voltage conductive line, also called a conductor. A high-voltage conductive line is defined as a conductor configured to be placed at potentials relative to earth of several tens of kilovolts (kV) or even several hundred kilovolts. The second DC terminal is preferably configured to be electrically connected to a low-voltage conductive line, for example, earth or a metallic return. A low-voltage conductive line is defined in contrast to a high-voltage conductive line. In the case of a metallic return, a low-voltage line is defined as a line configured to be placed at potentials relative to earth of a few hundred volts or even a few kilovolts at most.

[0013] By way of non-limitation, the second continuous terminal may be connected to a conductor, itself connected to an earth or a metallic return, in particular at a distance from a station.

[0014] The first, second, and third electrical conversion modules are connected in cascade in said at least one arm. It is understood that exactly three chains of sub-modules are connected in said at least one arm.

[0015] The first intermediate point of the arm is electrically connected to the third DC terminal via the first filter module. In other words, an electrical connection extends between said third DC terminal and the first intermediate point of the arm, to which the first filter module is connected. The second intermediate point of the arm is electrically connected to the second DC terminal via the second filter module.

[0016] Controlling the sub-modules in the various conversion modules makes it possible to impose the voltage across the inductor or the voltages across the inductors of the arm and thus to control the shape and amplitude of the currents flowing through the three conversion modules. It is therefore possible to impose an alternating component and a direct component in these currents.

[0017] In addition to protecting the first and second portions of the direct current power supply network against the flow of alternating current that could damage them, the first and second filtering modules allow the flow of alternating currents in all the electrical conversion modules of said network. minus one arm. This allows power exchanges between each of the electrical conversion modules of the arm and ensures the energy balance of the converter.

[0018] The voltage converter according to the invention is particularly suitable for connecting a portion of a DC power supply network with an asymmetric monopole topology and a portion of a DC power supply network with a symmetric monopole topology. Indeed, this converter is a non-isolated converter and eliminates the need for a transformer. It offers reduced size, weight, and manufacturing cost compared to a front-to-front MMC converter according to the prior art.

[0019] Unlike this front-to-front MMC converter, in which all the power to be transferred from one DC network segment to the other is transformed into AC power, the converter according to the invention allows a direct transfer of part of the DC power from the first network segment to the second network segment without it being transformed into AC power. This reduces the losses associated with the transformation. Furthermore, the converter according to the invention comprises a significantly smaller number of components, and in particular one fewer electrical conversion module, and therefore one fewer chain of sub-modules, than the converter described in the publication by GJ Kish and PW Lehn, which is designed for connecting a two-pole network to a monopole network but is not intended for connecting two monopole networks, for which it is oversized and unsuitable.The converter according to the invention is therefore less bulky and suitable for connecting two portions of a DC power supply network with a monopole topology, and in particular for connecting a portion of a network with a symmetrical monopole topology to a portion of a network with an asymmetrical monopole topology.

[0020] Alternatively, the voltage converter according to the invention also allows connection between a portion of a DC power supply network with a bi-pole topology and a portion of a DC power supply network with a monopole topology. In particular, it allows connection of a first pole of a first portion of a DC power supply network with a bi-pole topology and a second portion of a DC power supply network with a monopole topology. A second converter according to the invention can further be used to connect a second pole of said first portion of a DC power supply network with a bi-pole topology and said second portion of a DC power supply network with a monopole topology. The invention therefore provides for the use of two voltage converters for connection to a portion of a network with a bi-pole topology, unlike the installation in the publication by GJ Kish and PWLehn, who plans to use a single converter to connect a bi-pole topology network and a topology network. monopole. This converter, according to the prior art, achieves a coupling between the poles of the bipole network.

[0021] Conversely, the use of two physically separate voltage converters according to the invention makes it possible to maintain a decoupling between the two poles of said first portion of the bi-pole topology network.

[0022] According to the invention, thanks to this decoupling, in the event of a disturbance on one of the poles of said first portion of the bi-pole DC power supply network, the other pole of this network portion is not affected and can continue its normal operation without interruption or disturbance. The redundancy of the bi-pole DC power supply network portion is maintained. In the event of a disturbance on one of the poles of the bi-pole network portion, it is not necessary to interrupt the operation of the converter connected to the other pole of the bi-pole network portion.

[0023] Furthermore, the symmetrical structure of the GJ Kish and PW Lehn converter only allows power exchanges between the first and second electrical conversion modules and between the third and fourth electrical conversion modules of this converter. In contrast, the asymmetrical structure of the voltage converter according to the invention, comprising three electrical conversion modules, makes it possible to generate alternating currents flowing in each of the three electrical conversion modules and enabling energy exchanges between each of these electrical conversion modules. These energy exchanges ensure the energy balance of the voltage converter.

[0024] Preferably, the submodules of the submodule chains of the first, second, and third electrical conversion modules of said at least one arm shall have a half-bridge topology or a full-bridge topology. Without departing from the scope of the invention, an electrical conversion module may comprise only half-bridge submodules, only full-bridge submodules, or a plurality of half-bridge submodules and a plurality of full-bridge submodules.

[0025] Advantageously, the first electrical conversion module of said at least one arm comprises at least one sub-module having a full-bridge topology. Such a full-bridge sub-module is capable of generating negative voltages to interrupt the flow of a fault current in said electrical conversion module.

[0026] Preferably, but not limitingly, in said at least one arm, only the first electrical conversion module comprises one or more full bridge topology sub-modules.

[0027] Advantageously, the upper point of said at least one arm is electrically connected tricement directly to the first continuous terminal.

[0028] Advantageously, the lower point of said at least one arm is electrically connected directly to the fourth continuous terminal.

[0029] In other words, no component, active or passive, is disposed between said upper point and the first DC terminal or between said lower point and said fourth DC terminal. The voltage converter advantageously does not have a switch disposed between said upper point and the first DC terminal or between said lower point and the fourth DC terminal, insofar as it eliminates the problems of coupling converters according to the prior art and therefore the need to isolate a disturbed pole.

[0030] Preferably, each of the first and third electrical conversion modules of said at least one arm comprises an inductor connected in the arm, in series with the chain of sub-modules of the corresponding electrical conversion module. It is understood that a first inductor is disposed between the upper point and the first intermediate point of the arm and that a second inductor is disposed between the second intermediate point and the lower point of the arm.

[0031] By way of non-limitation, the second electrical conversion module may include an inductor connected in the arm, in series with the chain of sub-modules of said second electrical conversion module.

[0032] Advantageously, the first filtering module comprises at least one passive component, for example an inductor. A passive component is understood to be a non-controllable component. Such a passive component does not produce energy, voltage, or current. It may also, but is not limited to, be a resistor or a capacitor.

[0033] By way of non-limitation, the first filtering module may comprise only passive components, so that it forms a passive filtering module.

[0034] Preferably, the second filtering module includes at least one passive component.

[0035] Preferably, but not limited to, the first filtering module comprises at least one active component, for example a transistor, such that the first filtering module is active. An active component is understood to be a controllable component whose change of state can be controlled, for example, the transition from a closed / blocked state to an open / conducting state. Such an active component is preferably capable of generating a controlled voltage or current. Not limited to, it may be a switch, a semiconductor such as a transistor, or a sub-module comprising at least one semiconductor.

[0036] Advantageously, the second filtering module includes at least one active component.

[0037] Preferably, the converter comprises a plurality of arms connected in parallel with respect to each other, each arm comprising an upper point and a lower point between which it extends, the upper point of each arm being electrically connected to the first DC terminal while the lower point of each arm is electrically connected to the fourth DC terminal, each arm comprising a first electrical conversion module electrically connected between the upper point and a first intermediate point of said arm, a second electrical conversion module electrically connected between said first intermediate point and a second intermediate point of said arm, and a third electrical conversion module electrically connected between said second intermediate point and said lower point of said arm,the first intermediate point of each arm being electrically connected to the third continuous terminal while the second intermediate point of each arm is connected to the second continuous terminal, said first filtering module being electrically connected between said first intermediate points of the arms and said third continuous terminal, said second filtering module being electrically connected between said second intermediate points of the arms and said second continuous terminal, each of the first, second and third electrical conversion modules of each arm comprising a chain of controllable sub-modules, each arm comprising exactly three electrical conversion modules.

[0038] The upper points of each arm are connected together and form a single electrical node. Similarly, the lower points of each arm are connected together and form a single electrical node.

[0039] The first intermediate points of each arm are electrically connected to the third continuous terminal via the first filtering module. The second intermediate points of each arm are electrically connected to the second continuous terminal via the second filtering module.

[0040] The sub-modules of the electrical conversion modules of each of the arms are individually controllable by a control element specific to each sub-module and each sub-module includes a capacitor, the control element of each sub-module being able to take at least a first state in which the capacitor is inserted into the chain of sub-modules and a second state in which the capacitor is not inserted into said chain of sub-modules.

[0041] The voltage converter preferably comprises at least three arms connected in parallel, more preferably exactly three arms.

[0042] According to a particularly advantageous aspect of the invention, the converter further comprises a control module configured to control the sub-modules of the first, second, and third electrical conversion modules so as to generating first, second, and third alternating currents circulating respectively in the sub-module chains of said first, second, and third electrical conversion modules, these alternating currents generating energy exchanges between the first and second electrical conversion modules, between the first and third electrical conversion modules, and between the second and third electrical conversion modules. These exchanges are made possible by the asymmetrical structure of the converter according to the invention. These energy exchanges ensure the energy balance of the voltage converter.

[0043] The invention also relates to a high voltage direct current transmission installation comprising a first portion of a direct current power supply network, a second portion of a direct current power supply network and at least one first voltage converter as described above, said first voltage converter being configured to electrically connect said first and second portions of the direct current power supply network together.

[0044] Preferably, the first portion of the DC power supply network has a first topology, for example, an asymmetric monopole or bipole topology, while the second portion of the DC power supply network has a second topology, different from the first topology, for example, a symmetric monopole topology. The voltage converter according to the invention is therefore particularly versatile and allows for heterogeneous interconnections. Without limitation, the first portion of the DC power supply network could also have a symmetric monopole topology.

[0045] According to a particularly advantageous aspect of the invention, the first portion of the continuous power supply network comprises at least one first high-voltage conductive line electrically connected to the first continuous terminal of the first voltage converter and a low-voltage return line electrically connected to the second continuous terminal of the first converter, and the second portion of the continuous power supply network comprises a first high-voltage conductive line electrically connected to the third continuous terminal of the first voltage converter and a second high-voltage conductive line electrically connected to the fourth continuous terminal of the first voltage converter.

[0046] In this configuration, the first portion of the DC power supply network can be of asymmetric monopole or bipole topology. In the latter case, the voltage converter is connected to the first pole of the first portion of the network. The second portion of the DC power supply network is of symmetric monopole topology.

[0047] The high-voltage conductor lines of the first and second network segments are conductors. Without limitation, the return line may be a line of mass or a metallic return.

[0048] Advantageously, the first portion of the DC power supply network further comprises a second high-voltage conductor line, the installation further comprising a second voltage converter as described above, the first DC terminal of said second voltage converter being electrically connected to said second high-voltage conductor line of the first portion of the DC power supply network, the second DC terminal of the second voltage converter being electrically connected to the low-voltage return line of the first portion of the DC power supply network, the third DC terminal of the second converter being electrically connected to the second high-voltage conductor line of the second portion of the DC power supply network,and the fourth DC terminal of the second voltage converter being electrically connected to the first high-voltage conductor line of the second portion of the DC power supply network.

[0049] In this embodiment, it is understood that the first portion of the DC power supply network has a two-pole topology, the second voltage converter being connected to a second pole of said first portion of the network. The first and second voltage converters are physically separate.

[0050] The two converters operate independently of each other and maintain decoupling between the poles of the first portion of the bi-pole DC power supply network. Therefore, a disturbance on one pole does not cause a disturbance on the other pole, which can continue its normal operation. The redundancy of the bi-pole system is maintained.

[0051] The sub-modules of the second voltage converter are connected with a suitable polarity. Preferably, the sub-modules of the second converter are connected with a polarity reversed with respect to the sub-modules of the first voltage converter.

[0052] The invention also relates to a method of controlling a voltage converter as described above, in which the sub-modules of the first, second and third electrical conversion modules are controlled so as to generate first, second and third alternating currents flowing respectively in said first, second and third electrical conversion modules, these alternating currents generating energy exchanges between the first and second electrical conversion modules, between the first and third electrical conversion modules and between the second and third electrical conversion modules. Brief description of the drawings

[0053] The invention will be better understood upon reading the following description of modes of realization of the invention given by way of non-limiting examples, with reference to the attached drawings, on which:

[0054] [Fig.1] The [Fig.1] illustrates a voltage converter according to the invention;

[0055] [Fig.2] [Fig.2] illustrates a half-bridge topology submodule of the converter of tension of the [Fig.l];

[0056] [Fig.3] The [Fig.3] illustrates a full bridge topology submodule of the voltage converter of the [Fig.1];

[0057] [Fig.4] Fig.4 illustrates a first embodiment of an HVDC installation according to the invention; and

[0058] [Fig.5] The [Fig.5] illustrates a second embodiment of an HVDC installation according to the invention. Description of the implementation methods

[0059] The invention relates to a DC / DC voltage converter, in particular a voltage converter particularly suitable for installation in an HVDC system. Such a voltage converter is configured to convert a first DC voltage U1 into a second DC voltage U2 and vice versa.

[0060] Fig. 1 illustrates such a voltage converter 10 according to the invention, allowing a first portion of a DC power supply network to be connected with a second portion of a DC power supply network having the same topology or different topologies.

[0061] This voltage converter 10 comprises a first DC terminal 12, a second DC terminal 14, a third DC terminal 16, and a fourth DC terminal 18. The first and second DC terminals 12 and 14 are configured to be electrically connected to a first portion of a DC power supply, while the third and fourth DC terminals 16 and 18 are configured to be electrically connected to a second portion of a DC power supply. The first DC voltage U1 is shown between the first and second DC terminals, and the second DC voltage U2 is shown between the third and fourth DC terminals and results from the sum of the voltage +U3 shown between the third DC terminal and ground and the voltage -U4 shown between the fourth DC terminal and ground.The voltages U3 and U4 are equal in the case of a connection to a symmetrical monopole network.

[0062] According to the invention, the voltage converter 10 further comprises a first arm 20 including an upper point 20a and a lower point 20b between which it extends. Without limitation, the voltage converter further comprises a second arm 30 including an upper point 30a and a lower point 30b between which it extends and a third arm 40 comprising an upper point 40a and a lower point 40b between which it extends.

[0063] The upper points 20a, 30a, 40a of the three arms 20, 30, 40 are connected to each other and form a single electrical node. Each of the upper points is electrically connected directly to the first DC terminal 12. Similarly, the lower points 20b, 30b, 40b of the three arms 20, 30, 40 are connected together and form a single electrical node. Each of the lower points is electrically connected directly to the fourth DC terminal 18. The three arms 20, 30, 40 are therefore connected in parallel with each other between the first DC terminal 12 and the fourth DC terminal 18.

[0064] According to the invention, each of the arms 20, 30, 40 of the voltage converter comprises exactly three electrical conversion modules. The first arm comprises a first electrical conversion module 22 electrically connected between the upper point 20a and a first intermediate point 20c of the first arm. It also comprises a second electrical conversion module 24 electrically connected between said first intermediate point 20c and a second intermediate point 20d of the first arm 20, and a third electrical conversion module 26 electrically connected between said second intermediate point 20d and said lower point 20b of the first arm.

[0065] Similarly, the second and third arms 30,40 each include a first electrical conversion module 32,42 electrically connected between the upper point 30a,40a and a first intermediate point 30c,40c of the corresponding arm 30,40. They also each include a second electrical conversion module 34,44 electrically connected between said first intermediate point 30c,40c and a second intermediate point 30d,40d of the corresponding arm 30,40, and a third electrical conversion module 36,46 electrically connected between said second intermediate point 30d,40d and said lower point 30b,40b of the corresponding arm 30,40.

[0066] Each of the first, second, and third electrical conversion modules 22, 24, 26, 32, 34, 36, 42, 44, 46 of each of the arms 20, 30, 40 comprises a chain of SM sub-modules. These SM sub-modules are connected in series with each other in the corresponding arm. The SM sub-modules can be individually controlled according to a desired sequence in order to modify the voltage across each of the chains of sub-modules. Each chain of SM sub-modules can be modeled by a controllable voltage source capable of generating a voltage across its terminals that depends on the number of capacitors inserted and connected in series in said chain of sub-modules.

[0067] In this non-limiting example, the second and third electrical conversion modules of the first, second and third arms 20, 30, 40 comprise only submodules of half-bridge topology, or "Half-bridge" in English.

[0068] Figure 2 illustrates a sub-module SM having a half-bridge topology. This sub-module SM comprises a capacitor CSm and a control element T1,T2 for individually controlling the sub-module SM. By way of exception, the control element T1,T2 includes a first electronic switching element T1 such as an insulated-gate bipolar transistor (IGBT) connected in series with the capacitor CSm. This first switching element T1 and this capacitor CSm are connected in parallel with a second electronic switching element T2, also an insulated-gate bipolar transistor (IGBT). This second electronic switching element T2 is connected between the input and output terminals of the sub-module SM. Both the first and second switching elements T1 and T2 are associated with an antiparallel diode D shown in Figure 2.Without limitation, the switching elements could be of the IGBT, MOSFET or IGCT type.

[0069] The control element T1,T2 of each sub-module SM can take a first state in which the capacitor CSm is inserted into the corresponding chain of sub-modules and a second state in which the capacitor is not inserted into said chain of sub-modules. Notwithstanding, the control element T1,T2 can also take an uncontrolled state in which the first and second switching elements T1,T2 are open such that the insertion of the capacitor CSm depends on the sign of the current flowing in the corresponding half-arm, taking into account the anti-parallel diodes.

[0070] In this non-limiting example, the first electrical conversion modules 22, 32, 42 of the first, second, and third arms 20, 30, 40 each comprise a plurality of full-bridge topology submodules. Figure 3 illustrates such a full-bridge topology submodule. In this topology, the submodule comprises four switching elements T'1, T'2, T'3, T'4, each associated in parallel with an antiparallel diode D.

[0071] Without departing from the scope of the invention, each of the electrical conversion modules of the voltage converter 10 could comprise one or more SM sub-modules of full bridge topology.

[0072] Each of the electrical conversion modules 22, 24, 26, 32, 34, 36, 42, 44, 46 further comprises an inductor 27 connected in series with the SM sub-module chain of the corresponding electrical conversion module. Controlling the voltages generated by the SM sub-module chains allows the voltages across the inductors 27 to be imposed and thus the currents flowing in the arms 20, 30, 40 of the voltage converter 10 to be controlled. By way of exception, the second electrical conversion modules 24, 34, 44 of the first, second, and third arms 20, 30, 40 could be devoid of such inductance 27.

[0073] Furthermore, the voltage converter 10 includes a first filtering module 50 connected between the first intermediate points 20c, 30c, 40c of the first, second and third arms 20, 30, 40 and the third DC terminal 16. In other words, the first intermediate points 20c, 30c, 40c of the first, second and third arms 20, 30, 40 are connected to the third DC terminal 16 via said first filtering module 50. The first filtering module 50 is configured to limit the flow of alternating current to said third DC terminal 16.

[0074] In this non-limiting example, the first filter module 50 comprises three inductors 52, which are passive components, each connected between the first intermediate point 20c, 30c, 40c of one of the arms and the third DC terminal. The first filter module is therefore passive.

[0075] The voltage converter 10 also includes a second filtering module 54 connected between the second intermediate points 20d, 30d, 40d of the first, second, and third arms 20, 30, 40 and the second DC terminal 14. In other words, the second intermediate points 20d, 30d, 40d of the first, second, and third arms 20, 30, 40 are connected to the second DC terminal 14 via said second filtering module 54. The second filtering module 54 is configured to limit the flow of alternating current to said second DC terminal 14.

[0076] In this non-limiting example, the second filtering module 54 comprises three inductors 56, which are passive components, each being connected between the second intermediate point 20d,30d,40d of one of the arms and the second continuous terminal 14. The second filtering module is therefore passive.

[0077] The voltage converter 10 according to the invention also has an asymmetrical structure in which each arm 20, 30, 40 comprises three electrical conversion modules. This makes it possible to generate alternating currents flowing in each of the three electrical conversion modules of each arm. These currents generate energy exchanges between each of the three electrical conversion modules.

[0078] In particular, in each of the arms 20, 30, 40, the sub-modules can be controlled so as to generate first, second, and third alternating currents flowing respectively in said first 22, 32, 42, second 24, 34, 44, and third 26, 36, 46 electrical conversion modules of each of the arms. These alternating currents generate, in each of the arms, energy exchanges between all the electrical conversion modules and more precisely between the first 22, 32, 42 and second 24, 34, 44 electrical conversion modules, between the first 22, 32, 42 and third 26, 36, 46 electrical conversion modules, as well as between the second 24, 34, 44 and third 26, 36, 46 electrical conversion modules. These energy exchanges ensure the energy balance of the voltage converter.

[0079] In [Fig. 1], it can be seen that the voltage converter 10 includes a control module 80 configured to control the SM sub-modules of the first 22, 32, 42, second 24, 34, 44, and third 26, 36, 46 electrical conversion modules, in particular to generate said first, second, and third alternating currents. This control module also allows the generation of direct currents enabling power exchanges between the converter and the portions of the DC power supply network.

[0080] Fig. 4 illustrates a first embodiment of an installation 8 according to the invention, in this case a high-voltage direct current (HVDC) transmission installation, comprising a voltage converter 10 connecting a first portion of a direct current power supply network 60 of asymmetric monopole topology and a second portion of a direct current power supply network 70 of symmetric monopole topology.

[0081] The first portion of the DC power supply network 60 comprises a first station 62 consisting of an AC / DC voltage converter, and a second station 64 consisting of a second AC / DC voltage converter. These first and second stations 62 and 64 are electrically connected to each other by a first high-voltage conductor line 66, also called a conductor, and by a low-voltage return line 68, here a metallic return. The first DC terminal 12 of the DC / DC voltage converter 10 is connected to the first high-voltage conductor line 66, while the second DC terminal 14 is connected to the first low-voltage return line 68.

[0082] The second portion of the DC power supply network 70 comprises a first station 73 consisting of an AC / DC voltage converter, and a second station 74 consisting of a second AC / DC voltage converter. These first and second stations 73 and 74 are electrically connected by a first high-voltage conductor line 76, forming a conductor, and by a second high-voltage conductor line 78, also forming a conductor. The third DC terminal 16 of the DC / DC voltage converter 10 is connected to the first high-voltage conductor line 76 of this second portion of the network 70, while the fourth DC terminal 18 is connected to the second high-voltage conductor line 78.

[0083] As illustrated in [Fig. 4], the voltage converter 10 according to the invention is particularly suitable for connecting two portions of a DC power supply network with a monopole topology, and in particular a portion of a network with an asymmetric monopole topology and a portion of a network with a symmetric monopole topology. Indeed, this voltage converter 10 is a non-isolated converter and eliminates the need for a transformer. It therefore offers reduced size, weight and manufacturing cost compared to a prior art "Front To Front" MMC converter, while ensuring optimal electrical conversion.

[0084] In [Fig.4], the square-shaped elements connected to the AC part of the stations represent AC circuit breakers.

[0085] As illustrated in [Fig.5], the voltage converter 10 according to the invention is also adapted to connect a portion of a power supply network with a bi-pole topology and a portion of a power supply network with a monopole topology, here a symmetric monopole.

[0086] Figure 5 illustrates a second embodiment of an HVDC installation 8' according to the invention. In this embodiment, the first portion of the DC power supply network 60' comprises a first station 62', a second station 64', a third station 63', and a fourth station 65', each consisting of an AC / DC converter. The first and second stations 62', 64' are connected to each other by a first high-voltage conductor line 66' and a low-voltage return line 68', in this case a metallic return line. The third and fourth stations 63', 65' are connected to each other by a second high-voltage conductor line 72' and the aforementioned low-voltage return line 68'. The second portion of the DC power supply network 70 is similar to that of the embodiment in Figure 4.

[0087] In this non-limiting embodiment, the installation 8' comprises a first DC / DC voltage converter 10, such as that illustrated in [Fig. 1], and further comprising first, second, third, and fourth DC terminals 12, 14, 16, 18. The installation 8' also comprises a second voltage converter 10', such as that illustrated in [Fig. 1] and substantially similar to the first voltage converter 10. This second voltage converter 10' also comprises first, second, third, and fourth DC terminals 12', 14', 16', 18'. The sub-modules of the second voltage converter 10' are, however, connected with the opposite polarity to the sub-modules of the first voltage converter 10.

[0088] The first DC terminal 12 of the first voltage converter 10 is connected to the first high-voltage conductor line 66' of the first portion of the DC power supply network 60', while the second DC terminal 14 is connected to the low-voltage return line 68' of this first portion of the network. The third DC terminal 16 of the first DC / DC voltage converter 10 is connected to the first high-voltage conductor line 76 of the second portion of the network 70, while the fourth DC terminal 18 is connected to the second high-voltage conductor line 78 of this second portion of the network 70.

[0089] The first 12' DC terminal of the second 10' voltage converter is connected to The second high-voltage conductor line 72' of the first section of the DC power supply network 60' is connected to the second DC terminal 14' of this second converter 10', while the third DC terminal 16' of the second DC / DC voltage converter 10' is connected to the second high-voltage conductor line 78 of the second section of the network 70, while the fourth DC terminal 18' of the second converter 10' is connected to the first high-voltage conductor line 78 of this second section of the network 70.

[0090] In other words, the first voltage converter 10 is electrically connected to a first pole of the first portion of the bi-pole topology continuous power supply network 60', while the second voltage converter 10' is electrically connected to the second pole of this first portion of the network.

[0091] In this installation 8' according to the invention, the two voltage converters 10, 10' are physically separate and independent of each other. One advantage is maintaining the decoupling between the two poles of the first portion of the DC power supply network 60' so that a disturbance on one of these poles does not affect the other pole. In this situation, the operation of the converter connected to the faulty pole can be interrupted while the converter connected to the healthy pole continues its normal operation. Thanks to the invention, the redundancy of the bipolar system is therefore preserved, unlike the installation in the publication by GJ Kish and PW Lehn, which, although it uses only one converter, generates coupling between the poles of the bipolar network to which it is connected, resulting in the complete shutdown of the converter and therefore of power conversion as soon as a single pole is disturbed.

Claims

1. Demands Voltage converter (10,10') allowing the conversion of a first DC voltage (U1) into a second DC voltage (U2) and vice versa, the voltage converter comprising: - of the first (12) and second (14) continuous terminals configured to be electrically connected to a first portion of continuous power supply network (60,60'); - of the third (16) and fourth (18) continuous terminals configured to be electrically connected to a second portion of continuous power supply network (70); - at least one arm (20, 30, 40) comprising an upper point (20a, 30a, 40a) and a lower point (20b, 30b, 40b) between which it extends, the upper point being electrically connected to the first continuous terminal while the lower point is electrically connected to the fourth continuous terminal, said at least one arm comprising a first electrical conversion module (22, 32, 42) electrically connected between the upper point and a first intermediate point (20c, 30c, 40c) of the arm, a second electrical conversion module (24, 34, 44) electrically connected between said first intermediate point and a second intermediate point (20d, 30d, 40d) of the arm, and a third electrical conversion module (26, 36, 46) electrically connected between said second intermediate point and said lower point of the arm,the first intermediate point of the arm being electrically connected to the third continuous terminal while the second intermediate point of the arm is connected to the second continuous terminal, each of the first, second and third electrical conversion modules comprising a chain of sub-modules (SM) individually controllable by a control element (T1,T2) specific to each sub-module and each sub-module comprising a capacitor (CSm), the control element of each sub-module being able to take at least a first state in which the capacitor is inserted into the chain of sub-modules and a second state in which the capacitor is not inserted into said chain of sub-modules, at least one of the electrical conversion modules comprising an inductor (27) connected in series with the chain of sub-modules of said electrical conversion module, said at least one arm comprising exactly three electrical conversion modules, exactly three chains of, sub-modules being connected in said at least one arm; - a first filtering module (50) electrically connected between said first intermediate point of the arm and said third continuous terminal, said first filtering module being configured to limit the flow of an alternating electric current to said third continuous terminal; and - a second filtering module (54) electrically connected between said second intermediate point of the arm and said second continuous terminal, said second filtering module being configured to limit the flow of an alternating electric current to said second continuous terminal.

2. Voltage converter according to claim 1, wherein the submodules (SM) of the submodule chains of the first (22,32,42), second (24,34,44) and third (26,36,46) electrical conversion modules of said at least one arm have a half-bridge topology or a full-bridge topology.

3. Voltage converter according to claim 2, wherein the first electrical conversion module (22,32,42) of said at least one arm (20,30,40) comprises at least one sub-module (SM) having a full bridge topology.

4. Voltage converter according to any one of claims 1 to 3, wherein the upper point (20a,30a,40a) of said at least one arm (20,30,40) is electrically connected directly to the first DC terminal (12).

5. Voltage converter according to any one of claims 1 to 4, wherein the lower point (20b,30b,40b) of said at least one arm (20,30,40) is electrically connected directly to the fourth DC terminal (18).

6. Voltage converter according to any one of claims 1 to 5, wherein each of the first (22,32,42) and third (26,36,46) electrical conversion modules of said at least one arm comprises an inductor (27) connected in the arm (20,30,40), in series with the chain of sub-modules (SM) of the corresponding electrical conversion module.

7. Voltage converter according to any one of claims 1 to 6, wherein the first filtering module (50) comprises at least one passive component, for example an inductor (52).

8. Voltage converter according to any one of claims 1 to 7, dans lequel le premier module de filtrage (50) comprend au moins un composant actif, par exemple un transistor.

9. A voltage converter according to any one of claims 1 to 8, comprising a plurality of arms (20, 30, 40) connected in parallel with respect to each other, each arm comprising an upper point (20a, 30a, 40a) and a lower point (20b, 30b, 40b) between which it extends, the upper point of each arm being electrically connected to the first DC terminal (12) while the lower point of each arm is electrically connected to the fourth DC terminal (18), each arm comprising a first electrical conversion module (22, 32, 42) electrically connected between the upper point and a first intermediate point (20c, 30c, 40c) of said arm, a second electrical conversion module (24, 34, 44) electrically connected between said first intermediate point and a second intermediate point (20d, 30d, 40d) of said arm, and a third electrical conversion module (26, 36,46) electrically connected between said second intermediate point and said lower point of said arm, the first intermediate point of each arm being electrically connected to the third continuous terminal (16) while the second intermediate point of each arm is connected to the second continuous terminal (14), said first filtering module being electrically connected between said first intermediate points of the arms and said third continuous terminal (16), said second filtering module being electrically connected between said second intermediate points of the arms and said second continuous terminal (14), each of the first, second and third electrical conversion modules of each arm comprising a chain of controllable sub-modules (SM), each arm comprising exactly three electrical conversion modules.

10. A voltage converter according to any one of claims 1 to 9, further comprising a control module (80) configured to control the sub-modules of the first (22, 32, 42), second (24, 34, 44), and third (26, 36, 46) electrical conversion modules so as to generate first, second, and third alternating currents flowing respectively in the sub-module chains of said first, second, and third electrical conversion modules, these alternating currents generating energy exchanges between the first and second electrical conversion modules, between the first and third electrical conversion modules as well as between the second and third electrical conversion modules.

11. High voltage direct current transmission installation (8,8') comprising a first portion of a direct current power supply network (60,60'), a second portion of a direct current power supply network (70) and at least one first voltage converter (10,10') according to any one of claims 1 to 10, said first voltage converter being configured to electrically connect said first and second portions of the direct current power supply network together.

12. Installation according to claim 11, wherein the first portion of the DC power supply network (60,60') has a first topology, for example an asymmetric monopole or bipole type topology, while the second portion of the DC power supply network (70) has a second topology, different from the first topology, for example a symmetric monopole type topology.

13. Installation according to claim 12, wherein the first portion of the DC power supply network (60,60') comprises at least one first high-voltage conductive line (66,66') electrically connected to the first DC terminal (12) of the first voltage converter (10) and a low-voltage return line (68,68') electrically connected to the second DC terminal (14) of the first converter, and wherein the second portion of the DC power supply network (70) comprises a first high-voltage conductive line (76) electrically connected to the third DC terminal (16) of the first voltage converter and a second high-voltage conductive line (78) electrically connected to the fourth DC terminal (18) of the first voltage converter.

14. Installation (8') according to claim 13, wherein the first portion of the DC power supply network (60') further comprises a second high-voltage conductor line (72'), the installation further comprising a second voltage converter (10') according to any one of claims 1 to 10, the first DC terminal (12') of said second voltage converter being electrically connected to said second high-voltage conductor line of the first portion of the DC power supply network, the second DC terminal (14') of the second voltage converter being electrically connected connected electrically to the low voltage return line (68') of the first portion of the DC power supply network, the third DC terminal (16') of the second converter being electrically connected to the second high voltage conductor line (78) of the second portion of the DC power supply network (70), and the fourth DC terminal (18') of the second voltage converter being electrically connected to the first high voltage conductor line (76) of the second portion of the DC power supply network.

15. A method for controlling a voltage converter (10,10') according to any one of claims 1 to 10, wherein the sub-modules (SM) of the first (22,32,42), second (24,34,44) and third (26,36,46) electrical conversion modules are controlled so as to generate first, second and third alternating currents flowing respectively in said first, second and third electrical conversion modules, these alternating currents generating energy exchanges between the first and second electrical conversion modules, between the first and third electrical conversion modules and between the second and third electrical conversion modules.

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