Continuously adjustable saturation throttle

Description

[0001] The invention relates to a device according to the preamble of claim 1.

[0002] Such a device is already known from EP 3 168 708 A1. There, a so-called "Full Variable Shunt Reactor" (FVSR) is disclosed, which represents a further development of a "Magnetically Controlled Shunt Reactor" (MCSR). The previously known device has two high-voltage windings connected in parallel, each enclosing a core leg of a closed iron core and connected at its high-voltage end to a phase conductor of a high-voltage network. The low-voltage sides of the high-voltage windings can be connected, by means of a transistor switch, either to a suitably polarized thyristor converter or directly to an earth connection. The thyristor converter is configured to generate a direct current in the high-voltage winding connected to it. The direct current is adjusted so that the core leg enclosed by the winding is driven into a desired saturation state.In this saturation state, the core material exhibits, for example, a very low magnetic permeability, which increases the magnetic resistance of the winding and reduces its inductance. The saturation of these core sections is polarization-dependent, so that an alternating current flowing through the windings essentially flows only through one of the two high-voltage windings, depending on its polarization. For example, a positive alternating current flows through the first high-voltage winding, while a negative alternating current flows to ground via the second high-voltage winding. If the current is driven through only one high-voltage winding, the other winding, which is not currently carrying the alternating current, can be supplied with a direct current to saturate the core section it encloses to the desired degree.

[0003] Magnetically controlled choke coils are also known from DE 20 2013 004 706 U1, WO 2004 / 054065 A1 and DE 10 2012 110 969.

[0004] The aforementioned device suffers from the disadvantage of being complex in its construction and therefore expensive. For example, RC circuits are necessary to prevent overvoltages on the low-voltage side of the high-voltage winding. Furthermore, transistor switches are required in addition to the thyristor converters.

[0005] The object of the invention is therefore to provide a device of the type mentioned above which is simple in its construction and thus cost-effective.

[0006] The invention solves this problem by providing each saturation switching branch with at least one two-pole sub-module with a bridge circuit which has power semiconductor switches and a DC voltage source, so that, depending on the control of the power semiconductor switches, the DC voltage source can either be switched in series with at least one high-voltage winding or bridged.

[0007] According to the invention, the saturation switching branch, which can be connected to either both or one high-voltage winding, comprises a bridge circuit. The bridge circuit allows for the flexible connection of a DC voltage source to achieve the desired saturation of the core section. For this purpose, the bridge circuit is configured so that the DC voltage source can be connected in series with the respective high-voltage winding, ensuring that the DC voltage source has the desired polarity. For example, during a negative half-cycle of the AC voltage of the first high-voltage winding, the DC voltage source is connected in series such that it drives a DC current through the first high-voltage winding, flowing from the DC voltage source to the high-voltage winding.In a second switching position of the bridge circuit, the DC voltage source is bypassed, so that alternating current can flow from the first high-voltage winding to, for example, a grounded potential point.

[0008] It should be added that, at any given time, only the connection of a saturation switching branch to a high-voltage winding is practically useful. Only in a bridging position of the switching branch(es) are all high-voltage windings connected to each other on their low-voltage side.

[0009] According to the invention, either the same DC voltage source or a different DC voltage source can be connected to the second high-voltage winding. The DC voltage sources are advantageously identical, but can also differ from one another within the scope of the invention. According to the invention, the DC voltage source of the second high-voltage winding is connected with an opposite polarity, so that, in a series connection, the saturation DC current flows from the second high-voltage winding to ground. This then ensures a correspondingly polarized saturation of the second core section.

[0010] Within the scope of the invention, the bridge circuit is a circuit consisting of power semiconductor switches and a DC voltage source. This circuit allows either the voltage drop across the DC voltage source or a zero voltage (where the DC voltage source is bypassed) to be generated at the two terminals of the bridge circuit, or with other values ​​of the submodule. For example, the bridge circuit can be a half-bridge circuit, or in other words, a half-bridge. In this advantageous further development of the invention, a separate saturation switching branch is required for each of the first and second high-voltage windings. The DC voltage source assigned to the first high-voltage winding has a polarity opposite to that of the DC voltage source connected to the second high-voltage winding.If each branch of the circuit comprises multiple submodules and thus multiple DC voltage sources, these submodules have the same polarity with respect to their respective high-voltage windings. A half-bridge circuit has a single series branch consisting of two power semiconductor switches, which is connected in parallel to the DC voltage source. One terminal of the submodule is connected to the potential point between the power semiconductor switches of the series branch, and the other terminal is connected to one pole of the DC voltage source.

[0011] Preferably, however, the bridge circuit is configured as a so-called full bridge circuit or H-circuit, so that by controlling the power semiconductor switches, not only the voltage drop across the DC voltage source but also the inverse voltage of the source can be applied to the terminals. Both the half-bridge and the full-bridge circuits allow for bridging their DC voltage source.

[0012] In particular, the bridge circuit provides a cost-effective further development of the aforementioned device within the scope of the invention. RC circuits for voltage limiting have become unnecessary within the scope of the invention. Furthermore, the need for thyristor converters in addition to a transistor switch is eliminated. Within the scope of the invention, each saturation switching branch comprises at least one two-pole submodule with a bridge circuit. Each switching branch can be connected at its end furthest from the respective high-voltage winding to a potential point common to both high-voltage windings.

[0013] According to an advantageous further development, each saturation switching branch can be connected to an earth terminal on its side facing away from the associated high-voltage winding. In other words, the low-voltage potential point to which both high-voltage windings can be connected is an earth terminal.

[0014] Advantageously, each submodule is a full bridge circuit comprising a first series branch and a second series branch, each connected in parallel to the DC voltage source. Each series branch has a series connection of power semiconductor switches. The potential point between the power semiconductor switches of the first series branch is connected to a first terminal of the submodule, and the potential point between the power semiconductor switches of the second series branch is connected to the second terminal of the submodule. As explained above, such a full bridge circuit allows for the generation of either the source voltage across the DC voltage source, a zero voltage, or the inverse of the source voltage at the two terminals.In a full bridge, a single saturation switching branch is therefore generally sufficient to drive saturation direct currents with the desired polarization through each high-voltage winding.

[0015] However, as part of this further development, it is also possible that each high-voltage winding is assigned its own separate saturation switching branch, with both saturation switching branches having submodules with full bridge circuitry.

[0016] Within the scope of the invention, all submodules are preferably designed identically.

[0017] Advantageously, each power semiconductor switch is a so-called IGBT with a reverse-biased parallel freewheeling diode, a so-called GTO, a transistor switch, or the like. For the purposes of this invention, power semiconductor switches are controllable power semiconductors. Controllable power semiconductors include, for example, thyristors, IGBTs, GTOs, transistor switches, or the like. While the freewheeling diodes themselves are not controllable, when connected in reverse-biased parallel to a controllable power semiconductor, such as an IGBT, they are included in the term "power semiconductor switch." In this case, they merely serve to protect the controllable power semiconductor, which is also covered by the term, from overvoltage. Preferably, both switchable and switchable power semiconductor switches are used within the scope of the invention.Power semiconductor switches, such as thyristors, do not fall into this category, as they can only be triggered and not returned to their off state by a control signal. However, such power semiconductor switches are very familiar to those skilled in the art, so a more detailed explanation is unnecessary here.

[0018] Advantageously, each saturation switching branch has a series connection of at least two submodules. The two-pole submodules allow for easy scalability of the saturation switching branch. Each power semiconductor switch is limited to a specific maximum switching voltage. This is, for example, between 2 and 5 kV. If higher voltages are required to saturate the core sections, this requirement can be easily met by connecting the submodules in series.

[0019] Advantageously, each DC voltage source includes an energy storage device. Electrical energy storage devices, preferably unipolar, are advantageously suitable as energy storage devices. Examples include capacitors, supercapacitors, superconducting coils, accumulators, supercapacitors, or the like. The aforementioned or other electrical energy storage devices can appear individually in a submodule or be connected in series, with the term "energy storage device" referring to this entire series connection.

[0020] Advantageously, the energy storage device is connected to a charging unit for recharging the energy storage device. Within the scope of the invention, the charging unit can be designed as desired. However, it is essential that it provides the electrical power required for operation of the energy storage device.

[0021] According to a practical further development, the charging unit has a rectifier connected to an AC voltage source. In this case, the energy storage device is advantageously designed as a capacitor. The AC voltage source is, for example, an AC voltage source independent of the high-voltage grid. For instance, the AC voltage source is a standard high-voltage connection in the low-voltage range. In contrast, the voltage level of the AC voltage source is in the medium-voltage range, i.e., in a range between 1 kV and 52 kV. Furthermore, within the scope of the invention, it is possible to draw the power required for charging from the AC or high-voltage grid, for whose reactive power compensation the device according to the invention serves.

[0022] Advantageously, a saturation switching branch is provided for each high-voltage winding. As already explained above, such a saturation switching branch within the scope of the invention comprises at least one two-pole submodule, which expediently has a full or half-bridge circuit.

[0023] According to a further development of the invention, so-called compensating windings are provided, which filter the alternating voltage so that no major network distortions occur in the connected high-voltage network. According to an advantageous further development, these compensating windings can be inductively coupled to the energy storage device. Of course, inductive coupling for supplying energy to the energy storage device is also possible without compensating windings.

[0024] Advantageously, each core section, each high-voltage winding, and each saturation switching branch is arranged in a vessel filled with an insulating fluid. The vessel is advantageously at ground potential. Alternatively, the core sections and windings are arranged in a first vessel, and each switching branch is arranged in a second, separate vessel, each vessel being filled with an insulating fluid. Different insulating fluids, i.e., an insulating liquid and / or an insulating gas, can be used in the vessels. Advantageously, the first and second vessels, both at ground potential, are electrically connected to each other via high-voltage bushings.

[0025] The invention also relates to a method for reactive power compensation in a high-voltage network having at least one phase conductor and carrying an AC mains voltage, wherein each phase conductor is connected via a high-voltage terminal to a first high-voltage winding and a second high-voltage winding connected in parallel to it, each enclosing a first and a second core section, wherein each high-voltage winding can be connected via at least one saturation switching branch to an earth terminal, which has at least one submodule with a bridge circuit consisting of a DC voltage source and power semiconductor switches, wherein, for example, at a positive AC mains voltage, the power semiconductor switches are controlled such that a negative DC current flows through the second high-voltage winding, and at a negative AC mains voltage, the power semiconductors are controlled such thatthat a positive direct current flows through the first high-voltage winding, whereby the direct currents are adjusted so that a desired saturation of the core sections enclosed by the high-voltage windings is produced.

[0026] According to the invention, a bridge circuit, which is part of a two-pole submodule, can be used to saturate the core section whose winding carries no current or an alternating current that does not exceed a predetermined threshold during the prevailing half-cycle of the alternating voltage. The control of the bridge circuit enables the desired core saturation in a particularly simple manner. While the coordinated control of transistor switches and thyristor valves can achieve the same result, it is comparatively complex, so the invention provides a simple and cost-effective method.

[0027] Further advantageous embodiments and benefits of the invention are the subject of the following description of exemplary embodiments of the invention with reference to the figures of the drawing, wherein the same reference numerals refer to identically functioning components and wherein Figure 1 shows an embodiment of the device according to the invention in a schematic representation, Figure 2 shows the saturation switching branches of the device according to Figure 1 Figure 3 shows a further embodiment of the device according to the invention, Figure 4 shows a possible charging unit for the device according to the invention, Figure 5 shows a submodule for a saturation switching branch in a schematic representation, Figure 6 shows a further embodiment of the device according to the invention with a charging unit for two saturation switching branches and Figure 7 shows a further embodiment of the device according to the invention.

[0028] Figure 1Figure 1 shows an embodiment of the device 1 according to the invention, which comprises a vessel 2 filled with an insulating fluid. Suitable insulating fluids include mineral oils, ester liquids, or the like. The insulating fluid provides the necessary dielectric strength for components of the device 1, which are at a high-voltage potential, relative to the vessel 2 at ground potential. Furthermore, the insulating fluid serves to cool the components that generate heat during operation.

[0029] Inside the vessel 2 is a core composed of a magnetizable material, in this case, sheets of iron laid flat against each other, forming a first core leg 3 and a second core leg 4 as core sections. The first core leg 3 is enclosed by a first high-voltage winding 5. The second core leg 4 is surrounded by a second high-voltage winding 6. To form a closed magnetic or iron circuit, yokes (not shown) extend from the upper end of the first core leg 3 to the upper end of the second core leg 4, and from the lower end of core leg 3 to the lower end of core leg 4. In addition, two return legs (also not shown) are provided, which are not enclosed by any winding and extend parallel to core legs 3 and 4, respectively, to the right and left.In other words, a so-called 2 / 2 core is provided.

[0030] The first high-voltage winding 5 and the second high-voltage winding 6 each have a high-voltage end 7, which is connected to a high-voltage terminal 8. If the device 1 is arranged in a vessel filled with insulating fluid, the high-voltage terminal 8 is, for example, designed as a bushing. The bushing extends through the vessel wall and is equipped with an air connection at its free end, located outside the vessel. The air connection, not shown in the figure, serves to connect an air-insulated conductor.At their low-voltage end 9, the first high-voltage winding 5 and the second high-voltage winding 6 are each connected to a saturation switching branch 10 and 11, respectively, each saturation switching branch 10, 11 comprising a two-pole submodule 12 which is connected via a first terminal 13 to the respective high-voltage winding 5 or 6 and via a second terminal 14 to a common potential point 15. In the illustrated embodiment, the potential point 15 is grounded. In other words, the high-voltage windings 5 ​​and 6 are connected in parallel or at least can be connected in parallel.

[0031] The high-voltage windings 5 ​​and 6 are connected via the high-voltage terminal 8 to a phase conductor 16 of a high-voltage network 17, the high-voltage network 17 having two further phase conductors 18 and 19, each of which is again connected via a high-voltage terminal 8 to two high-voltage windings and two saturation switching branches. In other words, the device 1 has an identical structure for each phase 16, 18, 19 of the high-voltage network 17, although for the sake of clarity only the structure for one phase conductor 16 is shown here.

[0032] Essential to the invention is that each saturation switching branch 10 or 11 has a two-pole sub-module 12 which has a bridge circuit of power semiconductor switches 20, 21, 22 and 23 and a DC voltage source 24, which is preferably unipolar and thus has a fixed positive and a fixed negative pole.

[0033] The bridge circuit can be a half-bridge or a full bridge within the scope of the invention. Figure 1Each submodule has a full bridge with four power semiconductor switches 20, 21, 22, 23. A half bridge comprises only two power semiconductor switches. A control unit 26 is provided for the appropriate control of the four power semiconductor switches 20, 21, 22, and 23. This control unit can be supplied with setpoint values ​​for the voltage UAC target, the alternating current IAC target, and the reactive power QAC target. A current sensor 27 is used to detect the alternating current IAC flowing from the phase conductor 16 to the high-voltage windings 5 ​​and 6, while a voltage sensor 28 detects the voltage drop across the high-voltage windings 5 ​​and 6. The current sensor 27 and the voltage sensor 28 are connected to the control unit 26 via signal lines (not shown).Sensors 29 and 30 are also visible on the low-voltage side 9 of the high-voltage winding 5 or 6, which are also connected to the control unit 26 via signal lines and detect currents flowing between the respective sub-module 12 and the respective high-voltage winding 5 or 6.

[0034] The power semiconductor switches 20, 21, 22 and 23 of a submodule 12 can be switched by the control unit 26 from a disconnected position, in which a current flow through the power semiconductor switches is interrupted, to a through position, in which a current flow through the power semiconductor switches is enabled, or vice versa, from the through position to the disconnected position by suitable control signals, which are represented by dashed lines.

[0035] The operating mode of the device 1 is as follows: If the voltage detected by the voltage sensor 28 is positive, the power semiconductor switches 22 and 23 of the saturation circuit 10 are closed. It is assumed here that the core leg 3 has previously been saturated by a direct current flowing from the submodule 12 of the first saturation branch to the high-voltage winding 5, so that for the positive half-cycle of the alternating voltage, the AC resistance of the high-voltage winding 5 is smaller than the AC resistance of the high-voltage winding 6. Thus, almost the entire alternating current IAC flows to ground via the current path designated I1. During the positive half-cycle of the alternating voltage, the power semiconductor switches 21 and 22 are therefore closed, so that the DC voltage source 24 of the saturation circuit 11 drives a direct current that flows from the high-voltage winding 6 to ground 15.During the positive half-wave of the alternating voltage in the phase conductor 16, the second core leg 4 can thus be saturated in the desired manner.

[0036] During the negative half-wave, in which the voltage measured by the sensor 28 is negative, the alternating current IAC flows essentially through the second high-voltage winding 6, so that by closing the power semiconductor switches 20 and 23 and opening the power semiconductor switches 21 and 22 of the sub-module 12 of the first saturation switching branch 10 a saturation direct current is generated, which flows from the sub-module 12 to the first high-voltage winding 5 or vice versa and ensures the desired saturation of the core leg 3.

[0037] Figure 2Figure 1 shows the structure of the submodules 12 of the first and second saturation circuits 10 and 11 in more detail. It is evident that the submodules for both saturation circuit branches 10 and 11 are identically constructed. It is also evident that the power semiconductor switches 20, 21, 22, and 23 comprise an IGBT 31 to which a freewheeling diode 32 is connected in parallel with the reverse bias. The basic structure of an IGBT with a freewheeling diode is well-known, so its operation need not be discussed in detail here. The essential point is that the free-air diode 22 serves to protect the IGBT from reverse overvoltages. The IGBT 31 and diode 32 are typically housed in a common switch package. Here, the IGBT 31 and the freewheeling diode 32 are collectively referred to as the power semiconductor.

[0038] Each module 12 is designed as a so-called full bridge and comprises a first series branch 33 and a second series branch 34, each consisting of two series-connected power semiconductor switches 20, 21 and 22 and 23, respectively. The potential point between the power semiconductor switches 20, 21 of the first series branch 33 is connected to the first terminal 13, and the potential point between the power semiconductor switches 22 and 23 of the second series branch 34 is connected to the terminal 14 of the submodule 12.

[0039] Figure 3 Figure 1 shows a further embodiment of the device 1 according to the invention, wherein, for the sake of clarity, only the components for connection to a phase of the high-voltage network 17 are shown. Furthermore, the high-voltage connections 8 and the boiler 2 are no longer shown.

[0040] It can be seen that each saturation switching branch 10 or 11 consists of a series connection of several submodules 12, which are controlled either identically or differently by the control unit 26, so that the DC voltage for generating the DC current used to saturate the core legs 3, 4 is scalable according to the respective requirements.

[0041] Figure 4 shows a submodule 12 according to Figure 2The energy storage device 24 is configured as a unipolar capacitor. A charging unit 35 is also shown, comprising an AC power source 36 and a rectifier 37. The rectifier 37 consists of two phase module branches 38 and 39, each having a DC voltage connection 40 or 41 and an AC voltage connection 42 or 43, respectively. A switching branch, equipped with at least one power semiconductor, is arranged between the AC voltage connection 42, 43 and each DC voltage connection 40 or 41. The DC voltage connection 40 is connected to a first terminal of the capacitor 24, and the DC voltage connection 41 is connected to the second terminal of the capacitor 24. However, such a rectifier is known, so a more detailed description of its topology and operation can be omitted here.

[0042] The AC voltage source 36 is implemented as a transformer comprising a primary winding 44 and a secondary winding 45, which are inductively coupled to each other via a core 46. A smoothing choke 47 serves to smooth the resulting AC voltage. The charging unit 35 also has a switch 48, which is connected in parallel to a switching resistor 49. The resistor 49 can be switched on or bypassed by means of the switch 48, so that the desired charging of the capacitor 24 of the submodule 12 occurs. A circuit capacitor 50 serves to prevent overvoltages on the secondary winding 45.

[0043] Figure 5 Figure 1 shows a further embodiment of a submodule 12 which, instead of a single capacitor, has a series connection of several batteries 51 as a DC voltage source 24. In a different embodiment of the invention, rechargeable batteries can be used instead of batteries 51.

[0044] Figure 6 shows a further embodiment of the device according to the invention, which differs from the device according to Figure 4 The device features a different charging unit 35. The charging unit shown is intended only for the initial charging of the switching branches until the operating state is established. Subsequently, the charging branch 35 can be removed, and each switching branch can be supplied from the load current by means of intelligent control. The DC voltage source 24 of the submodules 12 is again implemented as a capacitor. In this case, however, each saturation switching branch 10 or 11 can be connected to the charging unit 35 via a charging switch 52 or 53, respectively, so that only one charging unit is provided for both saturation switching branches 10 and 11. In the diagram shown... Figure 6In the schematically shown case, the charging unit 35 again has a DC voltage source 54, which is connected to the respective charging switches 52 and 53 via suitable circuit resistors 55. The DC voltage source 54 includes, for example, a rectifier connected to an AC source. Alternatively, the DC voltage source 54 may be implemented as a battery, supercapacitor, accumulator, or the like.

[0045] Figure 7Figure 1 shows a further embodiment of the device 1 according to the invention, which differs from the device 1 shown in the previous figures in that only one saturation circuit 10 is provided, which is connected to both the low-voltage end 9 of the first high-voltage winding 5 and the low-voltage end 9 of the second high-voltage winding 6. For this purpose, the first terminal 13 of the submodule 12 is connected to the second high-voltage winding 6, while the second terminal 14 of the submodule 12 is connected to the low-voltage side 9 of the first high-voltage winding 5. Both the first terminal 13 and the second terminal 14 can be connected to earth potential 15 by means of the earthing switches 55 and 56, respectively, wherein the switches 55 and 56 are designed as power semiconductor switches and can be controlled by the control unit 26.The necessary signal lines are connected to the charging switches 55, 56 and the control unit 26 and are in . Figure 7 Shown in dashed lines. To connect the submodule 12 with the desired polarization between the first high-voltage winding 5 and earth 15, the earthing switch 55 is opened and the earthing switch 56 is closed. By closing the power semiconductor switches 21 and 22, the DC voltage source 24 is connected in series with the first high-voltage winding 5 and drives a saturated DC current from the submodule 12 to the high-voltage winding 5. By opening the earthing switch 56 and closing the earthing switch 55, and by closing the power semiconductor switches 22 and 21, with the power semiconductor switches 20 and 23 open, the DC voltage source 24 can be connected in series with the second high-voltage winding 6 with the desired polarization.

Claims

1. A device (1) for reactive-power compensation in a high-voltage network (17) having at least one phase conductor (16,18,19) with at least one high-voltage terminal (8) configured for connection to the phase conductor (16), wherein, for each high-voltage terminal (8), - a first and second core section (3,4) which are part of a closed magnetic circuit, - a first high-voltage winding (5) surrounding the first core section (3) and - a second high-voltage winding (6) surrounding the second core section (4) and connected in parallel to the first high-voltage winding (15), - at least one saturation switching branch (10,11) configured for saturating the core sections (3,4) and having controllable power semiconductor switches (20,21,22,23), and - a control unit (26) for controlling the power semiconductor switches (20,21,22,23) are provided, wherein the first and second high-voltage windings (5,6) are connected by their high-voltage ends (7) to the associated high-voltage terminal (8) and connectable on their low-voltage sides (9) to a saturation switching branch (10,11), characterised in that each saturation switching branch (10,11) has at least one two-pole submodule (12) with a bridge circuit which has the controllable power semiconductor switches (20,21,22,23) and a direct-voltage source (24), so that, in accordance with the control of the power semiconductor switches (20,21,22,23), the direct-voltage source (24) is either connectable in series to the high-voltage winding (5,6) connected to said saturation switching branch (10,11), or bridgeable.

2. The device (1) according to claim 1, characterised in that each saturation switching branch (10,11) is connectable to a ground terminal (15) on its side facing away from the associated high-voltage winding (5,6).

3. The device (1) according to any of the preceding claims, characterised in that each submodule (2) forms a full-bridge circuit having a first series-connection branch (33) and a second series-connection branch (34), each connected in parallel to the direct-voltage source (24), each series-connection branch (33,34) having a series connection consisting of two power semiconductor switches (20,21,22,23), wherein the potential point between the power semiconductor switches (20,21) of the first series-connection branch (33) is connected to a first terminal clamp (13) of the submodule (12) and the potential point between the power semiconductor switches (22,23) of the second series-connection branch (34) is connected to the second terminal clamp (14) of the submodule (12).

4. The device (1) according to any one of the preceding claims, characterised in that each power semiconductor switch (20,21,22,23) is an IGBT (33) with a freewheeling diode (32) connected in parallel in opposite directions, a GTO or a transistor switch.

5. The device (1) according to any of the preceding claims, characterised in that each saturation switching branch (10,11) is a series connection consisting of at least two submodules (12).

6. The device (1) according to any of the preceding claims, characterised in that each direct-voltage source (24) comprises an energy storage.

7. The device (1) according to claim 6, characterised in that the energy storage (24) is connectable to a charging unit (35) configured for charging the energy storage (24).

8. The device (1) according to claim 7, characterized in that the charging unit (35) has a rectifier (37) connected to an alternating-voltage source (36).

9. The device (1) according to any one of the preceding claims, characterised in that for each high-voltage winding (5,6), a saturation switching branch (10,11) is provided.

10. The device (1) according to claim 7, characterized in that the charging unit (35) is inductively coupled to the energy storage (24).

11. The device (1) according to any of the preceding claims, characterised in that each core section (3,4), each high-voltage winding (5,6) and each saturation switching branch (10,11) are arranged in a tank (2) filled with an insulating fluid.

12. A method for reactive-power compensation in a high-voltage network (17) having at least one phase conductor (16,18,19) conducting an alternating network voltage, wherein a device according to any of claims 1 to 11 is deployed, wherein each phase conductor (16,18, 19) is connected through a high-voltage terminal (8) to a first high-voltage winding (5) and a second high-voltage winding (6) connected in parallel thereto, each surrounding a first and second core section (3,4), wherein each high-voltage winding (5,6) is connectable through at least one saturation switching branch (10,11) to a grounding terminal (13) having at least one submodule (12) with a bridging circuit consisting of a direct-voltage source (24) and power semiconductor switches (20,21,22,23), in which - with a positive alternating network voltage, the power semiconductor switches are controlled such that a desired direct current flows through the second high-voltage winding, and - with a negative alternating network voltage, the power semiconductors are controlled such that a desired direct current flows through the first high-voltage winding, wherein the direct currents are set such that a desired saturation of the core sections (3,4) is generated.