WO2022002573A1

WO2022002573A1 - Three-phase ac/dc voltage converter with only two electrical conversion modules

Info

Publication number: WO2022002573A1
Application number: PCT/EP2021/066000
Authority: WO
Inventors: Pierre-Baptiste STECKLER
Original assignee: Supergrid Institute
Priority date: 2020-06-29
Filing date: 2021-06-14
Publication date: 2022-01-06
Also published as: EP4173128A1; FR3112042B1; FR3112042A1

Abstract

The invention relates to a voltage converter (10) for converting AC voltage to DC voltage and vice versa, the voltage converter comprising first and second electrical conversion modules (22, 24) connected in series in an arm (20); an electrical power conversion device (40) having a first primary winding (41a) connected between first and second AC terminals (30, 32) and a second primary winding (42a) connected between second and third AC terminals (32, 34), as well as first and second secondary windings (41b, 42b); and a control module (100) configured to control the first and second electrical conversion modules so that a first alternating current (I₁) flowing in the first secondary winding and a second alternating current (I₂) flowing in the second secondary winding are out of phase, the voltage converter comprising only two electrical conversion modules.

Description

DESCRIPTION

THREE-PHASE AC / DC VOLTAGE CONVERTER INCLUDING ONLY TWO ELECTRIC CONVERSION MODULES

Technical area

The present invention relates to the technical field of AC voltage converters to DC voltage and vice versa, also called AC / DC voltage converters. This type of converter is particularly suitable for installation in high voltage direct current power supply installations (HVDC for "High Voltage Direct Current").

HVDC power supply installations typically consist of a continuous power supply network that allows electricity to be transported over long distances using direct current lines several hundred kilometers long. They also include an alternative electricity supply network, for example connected to an offshore wind farm. AC / DC voltage converters allow the connection of such an AC power supply network with a DC power supply network.

Prior art

Three-phase AC / DC voltage converters are known, such as the converter described in EP 2 569 858 A1. This converter comprises an arm extending between first and second DC terminals in which three electrical conversion modules are connected in series. This converter further comprises a transformer comprising three primary windings and three secondary windings. Each of the secondary windings of the transformer is electrically connected to one of the three electrical conversion modules.

A disadvantage of this three-phase converter is that it has a very large number of components and is very bulky. This is because the high voltage application imposes minimum distances between the electrical conversion modules of this converter. This converter, provided with three electrical conversion modules therefore has a large size and bulk.

Furthermore, each of the three electrical conversion modules of this converter comprises several tens of submodules connected in a phase branch. Also, this converter is very heavy, bulky and bulky. In addition, its manufacture is particularly difficult and expensive. In addition, significant resources must be used in order to control all of the control elements of this converter. Controlling the converter is therefore particularly expensive and complex.

Disclosure of the invention

An object of the present invention is to provide a voltage converter overcoming the aforementioned problems and in particular making it possible to reduce the number of components of said voltage converter.

To do this, the invention relates to a voltage converter making it possible to convert an AC voltage into a DC voltage and vice versa, the voltage converter comprising: first and second DC terminals configured to be electrically connected to a power supply network continued ; first, second and third AC terminals configured to be electrically connected to an AC power supply network; an arm extending between the first and second DC terminals and having a first electrical conversion module and a second electrical conversion module connected in series in said arm or in parallel with each other, the first and second electrical conversion modules each having a first DC terminal and a second DC terminal between which it extends, as well as a first AC terminal and a second AC terminal; a device for transforming electrical energy comprising a first primary winding connected between the first and second alternating terminals and a second primary winding connected between the second and third alternating terminals, the device for transforming electrical energy further comprising a first secondary winding connected between the first and second AC terminals of the first electrical conversion module and a second secondary winding connected between the first and second AC terminals of the second electrical conversion module, the first electrical conversion module being configured to generate a first controllable AC current flowing in the first secondary winding, the second electrical conversion module being configured to generate a second controllable alternating current flowing in the second secondary winding; a control module configured to control the first and second electrical conversion modules so that the first AC current flowing in the first secondary winding and the second AC current flowing in the second secondary winding are out of phase, the voltage converter comprising only two electrical conversion modules.

The voltage converter according to the invention can be easily connected in an HVDC electrical installation, between an AC power supply network and a DC power supply network. The voltage converter is advantageously reversible, so that it makes it possible to convert an alternating voltage into a direct voltage but also to convert a direct voltage into an alternating voltage.

It is understood that each of the electrical conversion modules is connected in the arm through its first and second continuous terminals. Each secondary winding of the electrical transformation device is associated with an electrical conversion module.

The first and second power conversion modules can be connected either in series in the arm or in parallel with each other.

When the converter is controlled to absorb or supply reactive power to the AC power supply network, the two power conversion modules absorb different active powers. When they are connected in series in the arm, the first and second electrical conversion modules are crossed by the same current. In order to control the level of energy stored in their submodules, it is appropriate either to introduce an AC component to this current or to impose different DC components for the voltages at the terminals of the electrical conversion modules.

An advantage of the parallel connection of the first and second electrical conversion modules is to facilitate the control of the energy stored in said first and second electrical conversion modules by circulating different DC components of current at the level of the first DC terminals of the electrical conversion modules. This eliminates the need to generate an alternating balancing current when reactive power appears in the alternating part of the converter, at the primary windings.

In addition, paralleling the first and second electrical conversion modules can reduce the sizing and therefore the size of the components.

Unlike the voltage converters of the prior art, in which the primary windings are coupled in a star, and each have a terminal connected to neutral, or in delta, each of the primary windings of the voltage converter according to the invention is connected between two alternative terminals, and are therefore configured to be connected directly to the AC power supply network.

The first and second electrical conversion modules make it possible to generate respectively a first inserted DC voltage and a second inserted DC voltage controllable in the arm between their respective first and second DC terminals. These first and second inserted DC voltages make it possible to control a direct current flowing in the arm.

The first and second electrical conversion modules further make it possible to generate respectively a first inserted AC voltage and a second inserted AC voltage which can be controlled between their respective first and second AC terminals.

These first and second inserted alternating voltages make it possible to generate respectively said first alternating current h circulating in the first secondary winding and said second alternating current circulating in the second secondary winding.

The electrical energy transformation device has a transformation ratio r corresponding to the ratio between the number of turns of the first secondary winding and the number of turns of the first primary winding. As a first approximation, this transformation ratio is approximately equal to the ratio between the voltage at the terminals of the first secondary winding and the voltage at the terminals of the first primary winding.

From the first and second alternating currents flowing in the first and second secondary windings, the electric power transforming device supplies first and second alternating currents flowing in the first and second primary windings, which are images, at the transformation ratio r close to said first and second alternating currents flowing in the first and second secondary windings.

From the first and second alternating currents flowing in the first and second primary windings, the voltage converter according to the invention makes it possible to construct a three-phase system of three alternating phase currents. This three-phase system comprises first, second and third alternating phase currents laJ _b c flowing respectively to the first, second and third AC terminals of the voltage converter. These alternating phase currents are controllable in phase and amplitude, so that the active power and the reactive power of the voltage converter can also be controlled.

The relationships between the first and second alternating currents I1 2 flowing in the first and second secondary windings and the first, second and third alternating phase currents B C are as follows:

[Math. 1]

[Math. 2]

[Math. 3]

The electrical energy transforming device of the voltage converter according to the invention achieves a three-phase distribution of three alternating phase currents from two alternating currents flowing in the secondary windings of the electrical energy transforming device.

These three IAJBJC alternating phase currents define a three-phase system.

The phase and amplitude of the first alternating current flowing through the first secondary winding and the phase and magnitude of the second alternating current flowing through the second secondary winding of the electrical energy transforming device form four degrees of freedom of the given three-phase system above.

By applying a Fortescue transformation to this system, also called the symmetric component method, this three-phase system can be decomposed into a sum of three three-phase systems, namely a direct balanced system, an inverse balanced system and a zero sequence system.

The direct balanced system allows the active power and the reactive power of the voltage converter to be imposed. In order for the three-phase system made up of the three alternating phase currents to be balanced, the inverse balanced system and the homopolar system must each have a real part and a zero imaginary part. In fact, this makes it possible to keep only the direct system, which is a balanced three-phase system formed by the three alternating phase currents IAJBJC, which are then phase-shifted by 120 ° and have the same amplitude. These three systems therefore impose six constraints to be satisfied, namely the control of the active power, the control of the reactive power, the cancellation of the real and imaginary parts of the inverse balanced system, the cancellation of the real and imaginary parts of the homopolar system. .

The coupling of the primary windings of the energy transforming device of the voltage converter according to the invention, in which the first primary winding is connected between the first and second alternating terminals and the second primary winding is connected between the second and third alternative terminals, allows to cancel the real part and the imaginary part of the homopolar system, by construction. In fact, the zero sequence current is defined as the sum of the three alternating phase currents. Thanks to the three equations given previously, it can be seen that the sum of the three alternating phase currents is zero. There is no zero sequence current, and the real and imaginary parts of the zero sequence system are therefore zero. Also, thanks to this coupling of the primary windings of the electrical transformation device according to the invention, only four constraints, namely the control of the active and reactive powers and the cancellation of the real and imaginary parts of the inverse system, must be satisfied by means of of the aforementioned four degrees of freedom. The resolution of the three balanced systems is therefore made possible by virtue of the particularly clever coupling of the primary windings of the voltage converter according to the invention. The control module is advantageously configured to adjust the phase shift between the first and second alternating currents flowing in the first and second secondary windings, so as to impose a phase shift of approximately 120 ° between each of the three alternating phase currents l _a , U _c

The voltage converter according to the invention therefore makes it possible to obtain a balanced three-phase distribution of three alternating phase currents UbJc from two currents passing through the secondary windings of the device for transforming electrical energy, namely the first and second alternating currents circulating in the first and second secondary windings. By balanced is meant that the first, second and third alternating phase currents U _bc have substantially the same amplitude and are phase-shifted by approximately 120 ° or 2TT / 3.

In other words, the voltage converter according to the invention makes it possible to obtain a balanced three-phase distribution of three alternating phase currents from two electrical conversion modules connected in series in the arm, or in parallel one by one. compared to each other.

Thanks to the invention, the voltage converter comprises exactly two electrical conversion modules, and therefore strictly less than three electrical conversion modules, unlike prior art voltage converters which include at least three electrical conversion modules.

Therefore, the voltage converter according to the invention comprises a reduced number of components, and in particular of electrical conversion modules, reduced. One benefit is to reduce the size and bulk of the voltage converter by reducing the number of power converter modules.

In addition, it has a reduced number of submodules, when the conversion modules are provided with them. This also makes it possible to reduce the number of electrical connections between the various components, which can prove to be costly and complex to make, and thus simplify the arrangement of the voltage converter.

In addition, each of the electrical conversion modules of the voltage converter according to the invention is able to generate AC and DC inserted voltages greater than those generated by each of the conversion modules of the voltage converters provided with three conversion modules according to l prior art. Indeed, the total voltage to be produced is distributed over two electrical conversion modules instead of three. On the other hand, each of the electrical conversion modules is required to withstand lower currents than the electrical conversion modules of the prior art. Also, the size of these electrical conversion modules can be reduced.

The voltage converter according to the invention therefore has a much smaller weight and bulk than the voltage converters of the prior art, as well as a reduced manufacturing cost.

Furthermore, the voltage converter according to the invention can be provided with only two primary windings and two secondary windings, which further reduces the size of the voltage converter.

Preferably, the control module is configured to control the first and second electrical conversion modules, so that the first AC current flowing in the first secondary winding and the second AC current flowing in the second secondary winding are of the same frequency.

Advantageously, the first primary winding is connected directly to the first and second alternating terminals. Advantageously, the second primary winding is connected directly to the second and third alternating terminals.

Preferably, the first and second primary windings each include only two terminals. Each of these terminals is then electrically connected to an AC terminal.

Advantageously, at least one of the first, second and third AC terminals is electrically connected both to a terminal of the first primary winding and to a terminal of the second primary winding.

Preferably, the first and second secondary windings include only two terminals.

Preferably, the first and second secondary windings are separate and are not electrically connected to each other.

Preferably, the control module is configured to control the first and second electrical conversion modules so that the first current AC flowing in the first secondary winding and the second AC current flowing in the second secondary winding are phase-shifted by an angle between 55 ° and 65 °, preferably by an angle substantially equal to 60 °.

One interest is to improve the balance of the three-phase system formed by the first, second and third phase AC currents, built from the first and second AC currents flowing in the first and second secondary windings. This allows for a phase shift of approximately 120 ° between the first and second AC phase currents, as well as between the second and third AC phase currents and between the third and first AC phase currents.

Preferably, the control module controls the first and second electrical conversion modules so as to regulate the first and second AC voltages inserted between the first and second AC terminals of the first and second electrical conversion modules, which makes it possible to adjust the voltage. phase and amplitude of the first and second alternating currents flowing in the secondary windings of the device for transforming electrical energy.

The first alternating current flowing in the first secondary winding is advantageously in phase with the first alternating phase current.

Advantageously, the first and second electrical conversion modules each comprise a main branch extending between the first and second continuous terminals of the corresponding electrical conversion module and in which is connected a chain of sub-modules, each of the sub-chains. -modules comprising a plurality of individually controllable submodules by a control member specific to each submodule and each submodule comprising a capacitor, the control member of each submodule being able to take at least a first state in which the capacitor is inserted into the main branch and a second state in which the capacitor is not inserted into said main branch.

The control module advantageously controls the control members of the first and second electrical conversion modules.

In a non-limiting manner, the control members of the sub-modules can comprise controllable switching elements of the IGBT switch type and an antiparallel diode. In a nonlimiting manner, the control members can be placed in the first state and in the second state in response to a control command, originating for example from the control module, or even according to the sign of the current flowing in the arm.

The submodules can be ordered in a sequence chosen to gradually vary the number of capacitors that are connected in series in the main branch of the corresponding electrical conversion module and therefore in the arm of the voltage converter, so as to provide several voltage levels.

Advantageously, the control module is configured to control the control members of the sub-modules of the chains of sub-modules of the first and second electrical conversion modules, so as to regulate the voltages at the terminals of said chains of sub-modules. The control of the submodules of the electrical conversion modules makes it possible to adjust the direct voltages inserted in the arm but also the alternating voltages inserted between the alternating terminals of the electrical conversion modules, and therefore to regulate, in phase and in amplitude, the alternating currents flowing in the primary and secondary windings of the device for transforming electrical energy. This makes it possible to regulate, in phase and in amplitude, the three alternating phase currents flowing to the alternating terminals of the voltage converter.

Preferably, at least one of the first and second electrical conversion modules comprises an upper electrical connection, electrically connecting the first DC terminal and the first AC terminal of said electrical conversion module, and a lower electrical connection, electrically connecting the second DC terminal and the second alternating terminal of said electrical conversion module, said electrical conversion module comprising at least one capacitor connected in said upper electrical link and / or in said lower electrical link. One advantage is to block the flow of a direct current in the secondary windings of the electrical transformation device while allowing the flow of an alternating current.

Advantageously, the first electrical conversion module and the second electrical conversion module each comprise at least one capacitor connected in its upper electrical connection and / or in its lower electrical connection.

The first and / or the second electrical conversion module can comprise a single capacitor connected in its upper electrical connection or in its lower electrical connection. Alternatively, the first and / or the second electrical conversion module may include a first capacitor connected in the upper electrical link and a second capacitor connected in the lower electrical link.

Advantageously, at least one of the first and second electrical conversion modules comprises a secondary branch, extending between the first and second continuous terminals of said electrical conversion module, and in which are connected in series a chain of sub-modules comprising a plurality of controllable submodules, and an H-shaped bridge comprising a first sub-branch in which are connected two switches and a second sub-branch, connected in parallel with the first sub-branch, and in which are connected two switches, the first and second alternating terminals of said electrical conversion module being electrically connected respectively to the first sub-branch and to the second sub-branch.

The secondary branch is connected in parallel with the main branch of said electrical conversion module. The first sub-branch is connected to a first terminal of the corresponding secondary winding, while the second sub-branch is connected to a second terminal of said corresponding secondary winding.

Advantageously, the two switches of the first sub-branch are connected to each other at a first intermediate point, the first alternating terminal of said electrical conversion module being electrically connected to said first intermediate point. Advantageously, the two switches of the second sub-branch are connected to each other at a second intermediate point, the second alternating terminal of said electrical conversion module being electrically connected to said second intermediate point.

The switches of the H-bridge are advantageously controlled by the control module. The switches of the H-bridge are advantageously high-voltage switches. The H-bridge adjusts the direction of flow of the first or second alternating current flowing in the corresponding secondary winding of the electrical energy transformation device.

Preferably, the submodules of the submodule chains of the first and second electrical conversion modules have a half-bridge topology or a full-bridge topology. Without departing from the scope of the invention, other topologies of submodules can be envisaged. Each of the electrical conversion modules may include a combination of half-bridge submodules and full-bridge submodules.

The controller of a half-bridge submodule comprises a first electronic switching element connected in series with the energy storage device and a second electronic switching element coupled between the input and output terminals of the submodule.

The control unit of a full bridge sub-module has four switching elements. In these two topologies, the control unit advantageously comprises an antiparallel diode connected in parallel with each of the switching elements.

Preferably, the voltage converter further comprises a starting module configured to charge the capacitors of the submodules of the first and second electrical conversion modules, when it is placed in a first state.

When charging said capacitors, the voltage across the chains of submodules gradually increases until it reaches a nominal value.

The starter module is preferably connected between the AC terminals of the voltage converter and an AC power supply network to which said voltage converter is connected. Alternatively, the starter module can be connected between the DC terminals of the voltage converter and a DC power supply network to which said voltage converter is connected.

Preferably, the starting module comprises at least a first switch connected to one of the AC or DC terminals of the voltage converter and a limiting resistor connected in parallel with said switch, said switch being open when the starting module is placed in the first. state.

Also, in the first state, an uncontrolled current appears in the arm. This uncontrolled current is limited by the limiting resistor and gradually charges the capacitors of the submodules of the first and second electrical conversion modules, up to a predefined pre-charge value.

This predefined pre-charge value is in particular chosen so as to allow power to the control module.

Preferably, the starter module can be placed in a second state, in which said at least one switch is closed, so as to short-circuit said limiting resistor.

The limiting module is first kept in the first state until the capacitors of the submodules of the electrical conversion modules reach the preset pre-charge value. The chains of submodules are then controllable and can be ordered to progressively increase the energy stored in their capacitors. When the voltage at the terminals of each string of submodules reaches a final value substantially equal to the voltage of the DC power supply network, the starting module is placed in the second state. All of the capacitors of the submodules of the first and second electrical conversion modules are then charged to a final charge value and the voltage converter then operates normally.

Preferably, said voltage converter comprises only two primary windings and two secondary windings. Here again, it is of interest to reduce the number of components of the converter and in particular the number of terminations called "bushings" forming external connections of said electrical energy transformation device. This further reduces the weight, bulk and cost of manufacturing the voltage converter, compared to prior art converters which include at least three primary windings and three secondary windings. It will be understood that the converter comprises exactly two primary windings and two secondary windings, each being associated with a single electrical conversion module.

In addition, voltage converter transformers are generally fitted with particularly bulky terminations called “bushings”. By reducing the number of primary and secondary windings, and therefore the number of transformers used, the voltage converter according to the invention also makes it possible to reduce the number of these terminations, which further reduces the size of the voltage converter.

Advantageously, the voltage converter according to the invention comprises only a device for transforming electrical energy.

Advantageously, the voltage converter according to the invention comprises only two primary windings and two secondary windings.

According to a first advantageous variant, the electrical energy transformation device comprises a single transformer comprising said first and second primary windings as well as said first and second secondary windings. One advantage is to reduce the cost and size of the voltage converter by limiting the number of components it includes.

According to a second advantageous variant, the device for transforming electrical energy comprises: a first transformer comprising the first primary winding and the first secondary winding; and a second transformer comprising the second primary winding and the second secondary winding. These first and second transformers are single phase transformers. One advantage is to allow better galvanic isolation between the windings of the first and second transformers. Additionally, for very high power applications, the size of a transformer with multiple primary and secondary windings may be such that it will be difficult to manufacture and transport. The use of several single-phase transformers facilitates the manufacture and transport of the device for transforming electrical energy and therefore of the voltage converter.

The first and second transformers are preferably substantially identical. They advantageously have the same number of terminals at the level of the secondary windings and at the level of the secondary windings.

Preferably, the voltage converter comprises at least one filter module connected in series with the arm and configured to limit the AC component of a current flowing in said arm. The voltage resulting from the sum of the voltages inserted into the arm, generated by the first and second power converter modules, has a residual AC component so that an alternating current remains in the arm.

One advantage of the filtering module is to filter and therefore to reduce, preferably eliminate, this AC component of the total voltage in the arm so as to favor the circulation in the arm of a direct current. This makes it possible to have no AC component in the current flowing in the DC power supply network and therefore to protect this network.

Advantageously, the filtering module comprises at least one passive component and / or one active component. By passive component is meant a component whose condition and / or behavior cannot be controlled. Such a passive component makes it possible to store or conserve energy. Without limitation, it can be a resistance or an inductance.

The filter module may only include passive components so that it forms a passive filter module. The passive components are then advantageously dimensioned so that the filtering module has a high impedance at its resonant frequency, in order to effectively filter the AC component of the current in the arm.

By active component is meant a controllable component whose condition and / or behavior can be monitored. In a nonlimiting manner, it may be a switch, a semiconductor, such as a transistor, or even a submodule comprising at least one semiconductor.

The filter module can include at least one active component, so that it forms an active filter module.

Preferably, the filter module comprises an inductor and a capacitor connected in parallel with each other. More preferably, the filter module consists of an inductor and a capacitor connected in parallel with each other.

The filter module then forms a filter preventing the flow of alternating current in the arm. Said inductance and said capacitance so that the resonant frequency of the filter module coincides with that of the AC power supply network.

Preferably, the filtering module comprises an additional chain of sub-modules comprising a plurality of individually controllable sub-modules by a control member specific to each sub-module and each sub-module of said chain of additional sub-modules comprising at least a capacitor connectable in series with the arm when the control member of the submodule is in a first state.

The invention also relates to a high voltage direct current transmission installation comprising a direct electric power supply network, an alternating electric power supply network and a voltage converter as described above, said voltage converter being configured to electrically connect said AC and DC power supply networks between them.

The DC power supply network is electrically connected to the first and second DC terminals. The AC power supply network is electrically connected to the first, second and third AC terminals of the voltage converter.

The invention further relates to a method of controlling a voltage converter making it possible to convert an alternating voltage into a direct voltage and vice versa, the voltage converter comprising: first and second DC terminals configured to be electrically connected to a network continuous power supply; first, second and third AC terminals configured to be electrically connected to an AC power supply network; an arm extending between the first and second DC terminals and having a first electrical conversion module and a second electrical conversion module connected in series in said arm or in parallel with each other, the first and second electrical conversion modules each having a first DC terminal and a second DC terminal between which it extends, as well as a first AC terminal and a second AC terminal; a device for transforming electrical energy comprising a first primary winding connected between the first and second alternating terminals and a second primary winding connected between the second and third alternating terminals, the device for transforming electrical energy further comprising a first secondary winding connected between the first and second AC terminals of the first electrical conversion module and a second secondary winding connected between the first and second AC terminals of the second electrical conversion module, the voltage converter comprising only two electrical conversion modules, the method comprising the steps of: generating a first controllable alternating current flowing in the first secondary winding, using the first module electrical conversion; generating a second controllable alternating current flowing in the second secondary winding, using the second electrical conversion module; the first and second electrical conversion modules are controlled so that the first alternating current flowing in the first secondary winding and the second alternating current flowing in the second secondary winding are out of phase.

Preferably, the first and second electrical conversion modules are controlled so that the first alternating current flowing in the first secondary winding and the second alternating current flowing in the second secondary winding are phase-shifted by an angle between 55 ° and 65 ° , preferably at an angle substantially equal to 60 °.

Brief description of the drawings

The invention will be better understood on reading the following description of embodiments of the invention given by way of non-limiting examples, with reference to the accompanying drawings, in which:

[Fig. 1] Figure 1 illustrates an HVDC installation comprising a voltage converter according to the invention;

[Fig. 2] FIG. 2 illustrates a first embodiment of the voltage converter of FIG. 1;

[Fig. 3] Figure 3 illustrates a half-bridge topology submodule;

[Fig. 4] Figure 4 illustrates a full bridge topology submodule;

[Fig. 5] Figure 5 illustrates a reconstruction of the three-phase distribution of the three AC phase currents flowing to the AC terminals of the converter of Figure 2;

[Fig. 6] Figure 6 illustrates a first variant of a filter module of the voltage converter of Figure 2;

[Fig. 7] Figure 7 illustrates a second variant of a filter module of the voltage converter of Figure 2;

[Fig. 8] Figure 8 illustrates a second embodiment of the voltage converter of Figure 1; [Fig. 9] FIG. 9 illustrates a first variant of the voltage converter of FIG. 2; and

[Fig. 10] FIG. 10 illustrates a second variant of the voltage converter of FIG. 2.

Description of the embodiments

The invention relates to a voltage converter for converting an alternating voltage to a direct voltage and vice versa and comprising only two electrical conversion modules.

FIG. 1 illustrates an HVDC installation 8 comprising a first embodiment of a voltage converter 10 according to the invention, connecting between them a DC power supply network 12 and an AC power supply network 14 of the installation . The AC power supply network 14 is a three-phase network comprising three phases.

As can be seen in Figure 1, the voltage converter 10 comprises a first DC terminal 16 and a second DC terminal 18 configured to be electrically connected to the DC power supply network 12. The voltage VDC of the DC power supply network 12 is shown between the first continuous terminal 16 and the second continuous terminal 18.

The converter includes an arm 20 extending between the first DC terminal 16 and the second DC terminal 18. The arm 20 includes a first electrical conversion module 22 and a second electrical conversion module 24 connected in series with one of the two. another in the arm 20, between the first and second continuous terminals 16,18.

The first electrical conversion module 22 includes a first continuous terminal 22a and a second continuous terminal 22b between which it extends. It is connected in the arm 20 through said first and second continuous terminals 22a, 22b. Likewise, the second electrical conversion module 24 includes a first continuous terminal 24a and a second continuous terminal 24b between which it extends. It is connected in the arm 20 through said first and second continuous terminals 24a, 24b.

Furthermore, the first electrical conversion module 22 comprises a first AC terminal 23a and a second AC terminal 23b. The second electrical conversion module 24 includes a first AC terminal 25a and a second AC terminal 25b.

According to the invention, the voltage converter 10 comprises only and exactly two conversion modules 22, 24, unlike converters prior art voltage which comprises at least three electrical conversion modules.

In Figure 1, it can be seen that the voltage converter 10 also includes a first AC terminal 30, a second AC terminal 32 and a third AC terminal 34. Each of the first, second and third AC terminals 30,32,34 is configured to be electrically connected to one of the three phases of the AC power supply network 14.

The voltage converter 10 further comprises an electrical energy transformation device 40 comprising, in this non-limiting example, a single two-phase transformer comprising first 41a and second 42a primary windings associated respectively with first 41b and second 42b secondary windings. The electrical energy transformation device 40 comprises only and exactly two primary windings 41a, 42a and only and exactly two secondary windings 41b, 42b. The voltage converter 10 comprises only and exactly two primary windings 41a, 42a and only and exactly two secondary windings 41b, 42b

As can be seen in Figure 1, the first secondary winding 41b is connected between the first and second alternating terminals 23a, 23b of the first electrical conversion module 22. The second secondary winding 42b is connected between the first and second alternating terminals 25a, 25b of the second electrical conversion module 24.

According to the invention, the first primary winding 41a is connected between the first and second alternating terminals 30, 32 of the voltage converter 10. In other words, the first primary winding 41a comprises a first terminal 43 electrically connected to the first alternating terminal. 30 and a second terminal 45 electrically connected to the second AC terminal 32. The first primary winding is connected directly to the first and second AC terminals. The second primary winding 42a is connected between the second and third AC terminals 32,34 of the voltage converter 10. In other words, the second primary winding 42a comprises a first terminal 47 electrically connected to the second AC terminal 32 and a second terminal 49 electrically connected to the third AC terminal 34. The second primary winding 42a is connected directly to the second and third AC terminals.

The first and second primary windings 41a, 42a each include only two terminals. Likewise, the first and second secondary windings 41b, 42b each comprise only two terminals. The second AC terminal is electrically connected to both the second terminal 45 of the first primary winding and the first terminal 47 of the second primary winding.

Figure 2 illustrates a first embodiment of the voltage converter of Figure 1 provided with a first variant of the electrical conversion modules. In this embodiment, the first electrical conversion module 22 and the second electrical conversion module 24 are substantially identical. The first electrical conversion module 22 comprises a main branch 46 connected between the first and second continuous terminals 22a, 22b of the first electrical conversion module 22. The first electrical conversion module 22 comprises a chain of SM submodules connected in said branch. main 46. Likewise, the second electrical conversion module 24 comprises a main branch 48 connected between the first and second continuous terminals 24a, 24b of the second electrical conversion module 24 and in which is also connected a chain of submodules SM.

Each of the chains of submodules comprises a plurality of submodules SM connected in series with each other in the corresponding main branch and which can be controlled in a desired sequence. In FIG. 2, only two submodules per chain are shown. However, each chain of submodules can comprise from two to several dozen SM submodules.

As illustrated in FIGS. 3 and 4, each submodule SM comprises an energy storage device comprising in this example a capacitor CSM, and a control member for selectively connecting this capacitor in series between the terminals of the submodule SM or to bypass it.

FIG. 3 illustrates a submodule having a half-bridge topology. In this half-bridge submodule, the control unit comprises a first electronic switching element T1 such as an insulated gate bipolar transistor (“IGBT: Insulated Gâte Bipolar Transistor”) 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 coupled between the input and output terminals of the SM submodule. The first and second switching elements T1 and T2 are both associated with an antiparallel diode D shown in Figures 3 and 4.

In operation, the submodule can be placed in two distinct states. In a first state called “on” or inserted state, the first switching element T1 and the second switching element T2 are configured so as to insert the capacitor CSM into the main branch 46,48, in series with the other submodules. of the submodule chain. In a second state called the “off” or non-inserted state, the first switching element T1 and the second switching element T2 are configured so as to bypass the capacitor CSM and not to insert it into the main branch 46,48.

The submodules are controlled according to a sequence chosen to gradually vary the number of energy storage elements, and therefore the number of capacitors, which are connected in series in the corresponding chain of submodules and therefore in the arm. 20 of the voltage converter 10, so as to provide several voltage levels.

FIG. 4 illustrates a variant of the submodule of FIG. 3, in which the submodule has a full bridge topology (“Full-bridge” in English). 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.

Referring again to Figure 2, it can be seen that the first electrical conversion module 22 comprises an upper electrical connection 50, electrically connecting the first DC terminal 22a and the first AC terminal 23a of said first electrical conversion module 22. The first electrical conversion module 22 also comprises a lower electrical connection 52, electrically connecting the second DC terminal 22b and the second AC terminal 23b of said first electrical conversion module 22. In this non-limiting example, the upper electrical connection 50 is provided with a first capacitor 54. The capacitor makes it possible to block the flow of a direct current in said upper electrical connection 50 and in the first secondary winding 41b.

Likewise, the second electrical conversion module 24 comprises an upper electrical connection 56, electrically connecting the first DC terminal 24a and the first AC terminal 25a of said second electrical conversion module. The second electrical conversion module 24 also comprises a lower electrical connection 58, electrically connecting the second DC terminal 24b and the second AC terminal 25b of said second electrical conversion module 24. In this non-limiting example, the upper electrical connection 56 is provided with 'a second capacitor 60. The capacitor 60 makes it possible to block the flow of a direct current in said upper electrical connection 56 and in the second secondary winding 42b. The chain of submodules SM of the first electrical conversion module 22 makes it possible to generate a first DC voltage Vci controllable inserted in the arm between the first and second DC terminals 22a, 22b of the first electrical conversion module 22. The chain of sub- SM modules of the second electrical conversion module 24 makes it possible to generate a second DC voltage inserted Vc _{2 which can be} controlled in the arm between the first and second DC terminals 24a, 24b of the second electrical conversion module 24. A total voltage V _SU m appears in the arm 20, between the first continuous terminal 22a of the first electrical conversion module 22 and the second continuous terminal 24b of the second electrical conversion module 24.

Said first and second inserted direct voltages Vci, Vc ₂ make it possible to control a direct current IDC flowing in the arm.

The chain of submodules SM of the first electrical conversion module 22 also makes it possible to generate a first inserted AC voltage Vi controllable between the first and second AC terminals 23a, 23b of the first electrical conversion module 22. The chain of submodules SM of the second electrical conversion module 24 makes it possible to generate a second inserted AC voltage V _{2 which can be} controlled between the first and second AC terminals 25a, 25b of the second electrical conversion module 24.

Said first inserted alternating voltage Vi makes it possible to generate a first alternating current flowing in the upper electrical connection 50 and therefore in the capacitor 54 and in the first secondary winding 41b. Said second inserted alternating voltage V _{2 also} makes it possible to generate a second alternating current I ₂ flowing in the upper electrical connection 56 and therefore in the capacitor 60 and in the first secondary winding 42b.

From the first and second alternating currents h, l ₂ circulating in the first and second secondary windings 41 b, 42b, the device for transforming electrical energy 40 supplies first and second alternating currents l _pi , l _p2 circulating in the first and second primary windings 41a, 42a. From these two alternating currents, the voltage converter according to the invention makes it possible to reconstruct from the first IA, second IB and third the alternating phase currents flowing to the alternating terminals 30,32,34 of the voltage converter, and therefore to the AC power supply network 14.

More precisely, the first AC phase current IA flows from the first terminal 43 of the first primary winding 41a to the first AC terminal 30. The third AC phase current flows from the second terminal 49 of the second primary winding 42a to the third terminal alternating 34. The second alternating phase current IB is a current resulting from the difference between the second alternating current l _p2 flowing in the second primary winding 42a and the first alternating current l _pi flowing in the first primary winding 41a. The second AC phase current IB flows from an electrical node 51 to the second AC terminal 32. The electrical node extends between the second terminal 45 of the first primary winding and the first terminal 47 of the second primary winding 42a.

The relationships between the first and second alternating currents flowing in the first and second primary windings 41a, 42a are as follows:

[Math. 4]

[Math. 5] h = I _P 2 ^~ pi

[Math. 6]

Said first and second alternating currents li, l ₂ , and therefore the first, second and third alternating phase currents IA BC are controllable in phase and in amplitude.

The voltage converter 10 comprises a control module 100 configured in particular to control the first and second conversion modules 22, 24, and more precisely the switching elements of the control members of the submodules SM of said conversion modules in order to adjust the first and second inserted direct voltages V _c -i, V _C2 , said first and second inserted alternating voltages V ₁ V ₂ and consequently the first and second alternating currents, l ₂ , as well as the first, second and third phase currents alternatives IA B C-

The relationships between the first and second AC currents, l ₂ flowing in the first and second secondary windings and the first, second and third AC phase currents IA BC are as follows:

[Math. 7]

In these relations, r is the transformation ratio of the device for transforming electrical energy.

The three alternating phase currents IA B C are used to define a three-phase system. Applying a Fortescue transformation to this system, also known as the symmetric component method, decomposes this system into a sum of three three-phase systems, namely a direct balanced system, an inverse balanced system, and a zero sequence system.

The coupling of the first and second primary windings 41a, 42a of the electrical energy transformation device 40 to the alternating terminals 30,32,34 of the voltage converter according to the invention, in which the first primary winding 41a is connected between the first and second AC terminals 30,32 and the second primary winding 42a is connected between the second and third AC terminals 32,34, allows to cancel the real part and the imaginary part of the homopolar system.

The phase and the amplitude of the first alternating current and of the second alternating current h flowing in the secondary windings 41b, 42b form four degrees of freedom of the three-phase system. To provide a balanced three-phase system, these degrees of freedom must satisfy four system constraints, which are the control of active and reactive power and the cancellation of the real and imaginary parts of the reverse system.

The electrical energy transforming device 40 of the voltage converter 10 according to the invention enables a three-phase distribution of three alternating phase currents to be obtained from two alternating currents flowing in the secondary windings. The coupling of the primary windings 41a, 42a of the voltage converter 10 according to the invention makes it possible to obtain a balanced three-phase distribution of three alternating phase currents IA B C-

The control module 100 is configured to control the control member of the sub-modules of the first and second electrical conversion modules 20, 24 so as to impose a phase shift chosen between the first and second alternating currents li 2- In a non-limiting manner , this phase shift is preferably an angle of between 55 ° and 65 °, preferably an angle substantially equal to 60 °. This makes it possible to obtain a phase shift of approximately 120 ° between the first, second and third AC phase currents IA B C and thus to obtain a balanced three-phase current system.

The alternating phase currents advantageously have the same frequency.

The reconstruction of the three-phase distribution of the three AC phase currents IA BC from the first and second AC currents I1 2 is shown in FIG. 5. It can be seen in this FIG. 5 that a phase shift of approximately 60 ° between the first and second alternating currents I1 2 improves the balance of the three-phase system obtained and makes it possible to obtain a phase shift of approximately 120 ° between the first and second alternating phase currents IA, IB, between the second and third alternating phase currents IB C and between the third and first alternating phase currents IC, IA- In a non-limiting manner, the control module controls the control modules electrical conversion so that the first AC current flowing in the first secondary winding 41b is in phase with the first AC phase current IA.

In Figure 2, we note that the voltage converter 10 further comprises a filter module 80 connected in series with the arm 20, between the first and second DC terminals 16,18, and more precisely between the first DC terminal 16 and the first DC terminal 22a of the first electrical conversion module 22. The filter module 80 is configured to filter the AC component of the first and second DC voltages inserted Vci, Vc2 in the arm 20, so as to prevent the flow of a current alternating current in the arm and to guarantee the circulation in the arm of a single direct current IDC-

A first variant of a filter module is illustrated in FIG. 6. In this example, the filter module 80 comprises an inductor 82 and a capacitor 84 connected in parallel with each other. These two components are passive so that the filter module 80 is also passive.

Said inductor 82 and said capacitor 84 form a filter making it possible to reduce, preferably eliminate, the AC component circulating in the arm 20. They are dimensioned so that the resonant frequency of the filter module 80 coincides with that of the supply network. AC electric 14 and so that the filter module 80 has a high impedance at said resonant frequency.

FIG. 7 illustrates a second variant of a filtering module 80. In this example, the filtering module 80 comprises an additional chain of submodules comprising a plurality of submodules SM which can be individually controlled by a control member specific to each. submodule. Each submodule of said chain of additional submodules comprises at least one capacitor connectable in series with the arm 20 when the controller of the submodule is in a first state.

The chain of additional submodules makes it possible to generate an alternating voltage v _SUpp at its terminals having an amplitude equal to that of the alternating component of the total voltage at the terminals of all the chains of submodules of the arm 20, and having an opposite phase. The sub-modules of this chain of additional submodules are advantageously of the full bridge type.

It can be seen in FIG. 2 that the voltage converter 10 further comprises a starting module 90. In this non-limiting example, the starting module 90 comprises a switch 92 connected to the second DC terminal 18 of the voltage converter and a resistor of limitation 94 connected in parallel with said switch 92. The starting module 90 is configured to charge the capacitors of the SM submodules of the first and second electrical conversion modules 22,24 in order to allow the starting of the voltage converter 10 and the control of the direct and alternating currents flowing through the voltage converter.

When the starter module is placed in a first state, said switch 92 is opened so that an uncontrolled current appears and flows in the arm 20.

The CSM capacitors of the arm submodules charge and the voltage across the first and second power converter modules 22,24 gradually increases until it reaches its nominal value. The submodules are then controlled to gradually increase the energy stored in their capacitors. When the voltage at the terminals of each string of submodules reaches a predetermined final value, the switch 92 is then closed so as to bypass and thus bypass said limiting resistor 94. The starting module is then placed in a second state.

Control of the direct current flowing in the arm and of the alternating currents flowing in the windings of the electrical energy transformation device 40 is then re-established and the voltage converter then operates normally.

Alternatively, the starter module 90 could be connected between the AC power supply network and the AC terminals of the converter.

FIG. 8 illustrates a second embodiment of the voltage converter of FIG. 1 comprising a second variant of the electrical conversion modules 22, 24. In this embodiment, the first and second electrical conversion modules 22,24 also each comprise a main branch 46,48 in which is connected a chain of submodules SM.

The first electrical conversion module 22 further comprises a secondary branch 62, connected between the first and second continuous terminals 22a, 23a, in parallel with the main branch 46. The second electrical conversion module 24 also comprises a secondary branch 64, connected. between the first and second continuous terminals 22a, 23a, in parallel with the main branch 46. In the secondary branch 62 of the first electrical conversion module 22, a chain of submodules SM and an H-bridge 66 are connected in series. Likewise, in the secondary branch 64 of the second electrical conversion module 24 are connected in series. a chain of SM submodules and an H-bridge 68. Said H-bridges 66,68 each comprise a first sub-branch 66a, 68a and a second sub-branch 66b, 68b, connected in parallel with one of the other. Said sub-branches 66a, 66b, 68a, 68b each comprise two switches 70 electrically connected to one another in said sub-branches.

The two switches 70 of the first sub-branch 66a of the first electrical conversion module 22 are connected to one another at a first intermediate point 72. The two switches 70 of the second sub-branch 66b of the first electrical conversion module 22 are connected between them at a second intermediate point 74. The first intermediate point 72 is electrically connected to the first alternating terminal 23a of the first electrical conversion module 22 and to a first terminal of the first secondary winding 41b. The second intermediate point 74 is electrically connected to the second alternating terminal 23b of the first electrical conversion module 22, and to a second terminal of the first secondary winding 41b.

Likewise, the two switches 70 of the first sub-branch 68a of the second electrical conversion module 24 are connected to one another at a first intermediate point 72. The two switches 70 of the second sub-branch 68b of the second electrical conversion module 24 are connected to each other at a second intermediate point 74. The first intermediate point 72 is electrically connected to the first AC terminal 25a of the second electrical conversion module 24 and to a first terminal of the second secondary winding 42b. The second intermediate point 74 is electrically connected to the second AC terminal 25b of the second electrical conversion module 22 and to a second terminal of the second secondary winding 42b.

The switches of the two H-bridges 66.68 are controlled by the control module 100. Said H-bridges 66.68 make it possible to adjust the direction of flow of the first or second alternating current flowing in the corresponding secondary winding of the device. transformation of electrical energy.

Figure 9 illustrates a first variant of the voltage converter of Figure 2. In this first variant, the first and second electrical conversion modules 22, 24 are connected in parallel with respect to each other, between the first and second continuous terminals. The first continuous terminals 22a, 24a of the first and second electrical conversion modules are interconnected in a upper point 76. The second continuous terminals 22b, 24b of the first and second electrical conversion modules are interconnected at a lower point 78.

In this non-limiting example, the first electrical conversion module 22 further comprises a first electrical adaptation element 75 connected upstream of the main branch 46, between said main branch and the first continuous terminal 22a of the first electrical conversion module. Furthermore, the second electrical conversion module 24 comprises a second electrical adaptation element 77 connected upstream of the main branch 48, between said main branch and the first continuous terminal 24a of the second electrical conversion module. The first and second electrical adaptation elements can be an inductor or an active filter.

Figure 10 illustrates a second variant of the voltage converter of Figure 2. In this second variant, the first and second electrical conversion modules 22,24 are also connected in parallel with each other. Further, the converter includes a coupling element 79 of the first and second electrical conversion modules. This coupling element 79 is connected between the filter module 80, the first continuous terminal 22a of the first electrical conversion module 22 and the first continuous terminal 24a of the second electrical conversion module 24.

Claims

1. Voltage converter (10) for converting an alternating voltage into a direct voltage and vice versa, the voltage converter comprising: first and second direct current terminals (16,18) configured to be electrically connected to a power supply network continuous (12); first, second and third AC terminals (30,32,34) configured to be electrically connected to an AC power supply network; an arm (20) extending between the first and second DC terminals and having a first electrical conversion module (22) and a second electrical conversion module (24) connected in series in said arm or in parallel with each other to the other, the first and second electrical conversion modules each having a first DC terminal (22a, 24a) and a second DC terminal (22b, 24b) between which it extends, as well as a first AC terminal (23a , 25a) and a second alternating terminal (23b, 25b); an electrical energy transforming device (40) comprising a first primary winding (41a) connected between the first and second AC terminals and a second primary winding (42a) connected between the second and third AC terminals, the device for transforming electrical energy further comprising a first secondary winding (41b) connected between the first and second AC terminals of the first electrical conversion module and a second secondary winding (42b) connected between the first and second AC terminals of the second electrical conversion module, the first electrical conversion module configured to generate a first controllable alternating current (h) flowing in the first secondary winding, the second electrical conversion module being configured to generate a second controllable alternating current (h) flowing in the second secondary winding; a control module (100) configured to control the first and second electrical conversion modules so that the first AC current flowing in the first secondary winding and the second AC current flowing in the second secondary winding are out of phase, the voltage converter comprising only two electrical conversion modules.

2. Voltage converter according to claim 1, wherein the control module (100) is configured to control the first and second electrical conversion modules (22,24) so that the first alternating current (h) flowing in the first secondary winding (41b) and the second alternating current (I2) flowing in the second secondary winding (42b) are phase-shifted by an angle between 55 ° and 65 °, preferably by an angle substantially equal to 60 °.

3. Voltage converter according to claim 1 or 2, wherein the first and second electrical conversion modules (22,24) each comprise a main branch (46,48) extending between the first (22a, 24a) and second. (22b, 24b) continuous terminals of the corresponding electrical conversion module and in which is connected a chain of submodules (SM), each of the chains of submodules comprising a plurality of submodules individually controllable by a control member ( T1, T2) specific to each submodule and each submodule comprising a capacitor (CSM), the control unit of each submodule being able to take at least a first state in which the capacitor is inserted into the main branch and a second state in which the capacitor is not inserted into said main branch.

4. Voltage converter according to claim 3, wherein the control module (100) is configured to control the control members (T1, T2) of the submodules (SM) of the chains of submodules of the first and second modules. of electrical conversion (22,24), so as to regulate the voltages at the terminals of said chains of submodules.

5. Voltage converter according to any one of claims 1 to 4, wherein at least one of the first and second electrical conversion modules (22,24) comprises an upper electrical connection (50), electrically connecting the first continuous terminal ( 22a, 24a) and the first AC terminal (23a, 25a) of said electrical conversion module, and a lower electrical link (52), electrically connecting the second DC terminal (22b, 24b) and the second AC terminal (23b, 25b) of said electrical conversion module, said electrical conversion module comprising at least one capacitor (54,60) connected in said upper electrical link or in said lower electrical link.

6. Voltage converter according to any one of claims 1 to 4, wherein at least one of the first and second electrical conversion modules (22,24) comprises a secondary branch (62,64), extending between the first (22a, 24a) and second (22b, 24b) continuous terminals of said electrical conversion module, and in which are connected in series a chain of submodules (SM) comprising a plurality of controllable submodules, and an H-bridge (66,68) comprising a first sub-branch (66a, 68a) in which are connected two switches (70) and a second sub-branch (66b, 68b), connected in parallel with the first sub-branch, and in which two switches (70) are connected, the first (23a, 25a) and second (23b, 25b) alternating terminals of said electrical conversion module being electrically connected respectively to the first sub-branch and to the second sub-branch.

7. Voltage converter according to any one of claims 1 to 6, wherein the submodules (SM) of the submodule strings of the first and second electrical conversion modules (22,24) have a topology in half. bridge or a full bridge topology.

8. A voltage converter according to any one of claims 3 to 7, further comprising a starter module (90) configured to charge the capacitors (CSM) of the submodules (SM) of the first and second electrical conversion modules ( 22,24), when it is placed in a first state.

9. A voltage converter according to any one of claims 1 to 8, wherein said voltage converter (10) comprises only two primary windings (41a, 42a) and two secondary windings (41b, 42b).

10. A voltage converter according to any one of claims 1 to 9, wherein the device for transforming electrical energy (40) comprises a single transformer comprising said first and second. primary windings (41 a, 42a) as well as said first and second secondary windings (41 b, 42b).

11. A voltage converter according to any one of claims 1 to 9, wherein the device for transforming electrical energy (40) comprises: a first transformer comprising the first primary winding (41a) and the first secondary winding (41b) ; and a second transformer comprising the second primary winding (42a) and the second secondary winding (42b).

12. Voltage converter according to any one of claims 1 to 11, comprising at least one filter module (80) connected in series with the arm (20) and configured to limit the AC component of a current (IDC) flowing. in said arm.

13. Voltage converter according to claim 12, in which the filtering module (80) comprises at least one passive component and / or one active component.

14. Voltage converter according to claim 12 or 13, wherein the filtering module (80) comprises an additional chain of sub-modules comprising a plurality of sub-modules (SM) individually controllable by a control member specific to each sub. -module and each submodule of said chain of additional submodules comprising at least one capacitor connectable in series with the arm (20) when the control member of the submodule is in a first state.

15. High voltage direct current transmission installation (8) comprising a direct electric power supply network (12), an alternating electric power supply network (14) and a voltage converter (10) according to any one of claims 1 to 14, said voltage converter being configured to electrically connect said AC and DC power supply networks to one another.

16. A method of controlling a voltage converter (10) making it possible to convert an alternating voltage into a direct voltage and vice versa, the voltage converter comprising: first and second DC terminals (16,18) configured to be electrically connected to a DC power supply network (12); first, second and third AC terminals (30,32,34) configured to be electrically connected to an AC power supply network (14); an arm (20) extending between the first and second DC terminals and having a first electrical conversion module (22) and a second electrical conversion module (24) connected in series in said arm or in parallel with each other to the other, the first and second electrical conversion modules each having a first DC terminal (22a, 24a) and a second DC terminal (22b, 24b) between which it extends, as well as a first AC terminal (23a , 25a) and a second alternating terminal (23b, 25b); an electrical energy transforming device (40) comprising a first primary winding (41a) connected between the first and second alternating terminals and a second primary winding (42a) connected between the second and third alternating terminals, the transforming device of electrical power further comprising a first secondary winding (41a) connected between the first and second AC terminals (23a, 23b) of the first electrical conversion module and a second secondary winding (42b) connected between the first and second AC terminals (25a, 25b) of the second electrical conversion module, the voltage converter comprising only two electrical conversion modules, the method comprising the steps of: generating a first controllable alternating current (h) flowing in the first secondary winding, using the first electrical conversion module; generating a second controllable alternating current () flowing in the second secondary winding, using the second electrical conversion module; the first and second electrical conversion modules are controlled so that the first alternating current flowing in the first secondary winding and the second alternating current flowing in the second secondary winding are out of phase.

7. The control method according to claim 16, wherein the first and second electrical conversion modules (22,24) are controlled so that the first alternating current (h) flowing in the first secondary winding (41b) and the second current AC (I2) circulating in the second secondary winding (42b) are phase-shifted by an angle between 55 ° and 65 °, preferably by an angle substantially equal to 60 °.