Continuously adjustable saturable reactor

Abstract

This invention relates to a device for reactive power compensation in a high-voltage power grid having at least one phase conductor. A high-voltage connector is provided for each phase of the high-voltage power grid. Here, each high-voltage connector is connected to a first high-voltage winding surrounding a first core section and a second high-voltage winding surrounding a second core section. The core section is part of a closed magnetic circuit. The low-voltage end of each high-voltage winding can be connected to at least one saturation switch branch, which is designed to saturate the core section and has a controllable power semiconductor switch. Furthermore, a control unit for controlling the power semiconductor switch is provided. To manufacture the device as inexpensively as possible, each saturation switch branch has at least one bipolar submodule with a bridge circuit having a power semiconductor switch and a DC voltage source, such that, depending on the control of the power semiconductor switch, the DC voltage source can either be connected in series with at least one high-voltage winding or bridged.

Description

[0001] This application is a divisional application of the Chinese patent application filed on April 9, 2018, with application number 201880092238.8 and title "Infinitely Adjustable Saturated Reactor". Technical Field

[0002] The present invention relates to a device according to the preamble of claim 1. Background Technology

[0003] Such a device is known from EP 3 168 708 A1. Therein is disclosed a so-called "Full Variable Shunt Reactor" (FVSR), which shows a further improvement on the "Magnetically Controlled Shunt Reactor" (MCSR). The previously known device has two high-voltage windings connected in parallel, each winding enclosing a core of a closed iron core and connected at its high-voltage end to a phase conductor of a high-voltage grid. The low-voltage side of the high-voltage windings can be connected either to a suitably polarized thyristor converter or directly to ground by means of a transistor switch. The thyristor converter is designed to generate a direct current in the high-voltage windings connected to it. Here, the direct current is regulated such that the core surrounded by the windings is driven to a desired saturation state. In the saturation state, the core material, for example, has a very small permeability, thereby increasing the magnetic reluctance of the windings and decreasing their inductance. The saturation of the core section mentioned is related to polarization, so that the alternating current flowing through the windings essentially flows through only one of the two high-voltage windings according to its polarization. Therefore, a positive alternating current flows, for example, 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, then the corresponding other winding (which is just not being saturated by alternating current) can be applied with direct current so that the core column it surrounds is saturated to the desired degree.

[0004] In addition, magnetically controlled reactor coils are known from DE 20 2013 004 706 U1 and DE 10 2012 110 969.

[0005] The device mentioned at the beginning has the following drawbacks: it is structurally costly and therefore expensive. Therefore, RC components are required, for example, to prevent overvoltage on the low-voltage side of the high-voltage winding. Furthermore, transistor switches are needed in addition to the thyristor converter. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a device of the type mentioned at the beginning, which is simple and therefore inexpensive in its structure.

[0007] The present invention solves the technical problem in such a way that each saturated switch branch has at least one bipolar submodule, the submodule having a bridge circuit having a power semiconductor switch and a DC voltage source, such that, depending on the control of the power semiconductor switch, the DC voltage source can be either connected in series with at least one high-voltage winding or bridged.

[0008] According to the invention, the saturation switching branch includes a bridge circuit, which can be connected either to two high-voltage windings or to one high-voltage winding. The bridge circuit enables flexible switching of a DC voltage source that provides the desired saturation of the core segment. For this purpose, the bridge circuit is designed such that the DC voltage source can be connected in series with the corresponding high-voltage winding, ensuring that the DC voltage source has the desired polarity. Thus, for example, in the negative half-wave of the AC voltage, the DC voltage source is connected in series with the first high-voltage winding such that the DC voltage source drives a DC current to flow through the first high-voltage winding, and the DC current flows from the DC voltage source to the high-voltage winding. Conversely, in the second switching position of the bridge circuit, the DC voltage source is bridged, allowing AC current to flow from the first high-voltage winding to, for example, a potential point grounded.

[0009] Therefore, it is important to note that at the predetermined time point, only the connection between the saturated switching branch and the high-voltage winding is practically meaningful. All high-voltage windings are interconnected on their low-voltage sides only in the bridging position of one or more switching branches.

[0010] Within the scope of this invention, the second high-voltage winding can be connected to either the same DC voltage source or a different DC voltage source. Suitably, the DC voltage sources are designed to be identical, however, within the scope of this invention, they can also be different from each other. Within the scope of this invention, the DC voltage sources are connected to the second high-voltage winding with opposite polarities, thereby allowing saturated DC current to flow from the second high-voltage winding to ground in a series circuit. This thereby ensures saturation of the corresponding polarization of the second core segment.

[0011] Within the scope of this invention, a bridge circuit is a circuit composed of power semiconductor switches and DC voltage sources. This circuit enables either a voltage drop across the DC voltage source or a zero voltage to be generated at the two connection terminals of the bridge circuit, or in other words, a submodule. In the case of zero voltage, the DC voltage source is bridged. Therefore, the bridge circuit is, for example, a half-bridge circuit, or in other words, implemented as a half-bridge. In an advantageous improvement of the invention, a corresponding saturated switching branch is required for the first and second high-voltage windings, wherein the DC voltage source associated with the first high-voltage winding and the DC voltage source associated with the second high-voltage winding have opposite polarities. If each switching branch includes multiple submodules and therefore multiple DC voltage sources, the multiple DC voltage sources have the same polarity relative to their respective associated high-voltage windings. The half-bridge circuit has a single series circuit branch composed of two power semiconductor switches connected in parallel with the DC voltage source. One connection terminal of the submodule is connected to the potential point between the power semiconductor switches of the series circuit branch, and the other connection terminal is connected to the pole of the DC voltage source.

[0012] However, preferably, the bridge circuit is constructed as a so-called full-bridge circuit or H-circuit, so that by controlling the power semiconductor switches, not only the power supply voltage dropped on the DC voltage source, but also the reverse power supply voltage can be supplied to the connection terminals. Both half-bridge and full-bridge circuits are capable of bridging their DC voltage sources.

[0013] Within the scope of this invention, a further low-cost improvement to the aforementioned device is provided, particularly by means of a bridge circuit. Within the scope of this invention, RC elements for limiting voltage become redundant. Furthermore, thyristor converters are not required in addition to transistor switches. Within the scope of this invention, each saturated switching branch includes at least one bipolar submodule with a bridge circuit. Each circuit branch can be connected at its end opposite to the corresponding high-voltage winding to a common potential point for both high-voltage windings.

[0014] With a further advantageous improvement, each saturated switching branch can be connected to ground on its side opposite to the associated high-voltage winding. In other words, the potential point on the low-voltage side to which both high-voltage windings can be connected is ground.

[0015] Advantageously, each submodule is a full-bridge circuit, having a first series circuit branch and a second series circuit branch connected in parallel with a DC voltage source, respectively. Each series circuit branch has a series circuit composed of power semiconductor switches. The potential point between the power semiconductor switches in the first series circuit branch is connected to the first connection terminal of the submodule, and the potential point between the power semiconductor switches in the second series circuit branch is connected to the second connection terminal of the submodule. As further implemented above, in this full-bridge circuit, it is possible that either a power supply voltage decreasing on the DC voltage source (zero voltage) or a reversed power supply voltage is generated at the two connection terminals. Therefore, in principle, in a full-bridge, a single saturated switching branch is sufficient to drive a saturated DC current through each high-voltage winding with the desired polarization.

[0016] Within the scope of this further improvement, it is also possible to assign each high-voltage winding its own separate saturation switching branch, wherein two saturation switching branches have sub-modules with full-bridge circuitry.

[0017] Within the scope of this invention, all submodules are preferably designed to be identical.

[0018] Suitablely, each power semiconductor switch is a so-called IGBT with a freewheeling diode connected in anti-parallel, a so-called GTO, a transistor switch, etc. In the sense of this invention, a power semiconductor switch is a controllable power semiconductor. Controllable power semiconductors include, for example, thyristors, IGBTs, GTOs, transistor switches, etc. Although the freewheeling diode itself is uncontrollable, it should also be included in the term "power semiconductor switch" if it is connected in anti-parallel with a controllable power semiconductor (e.g., an IGBT). In this case, the freewheeling diode is only used to protect the controllable power semiconductor, also included in the term, from overvoltage. Preferably, a power semiconductor switch that can be turned on and off is used within the scope of this invention. Power semiconductor switches, such as thyristors, do not fall into this category because they can only be triggered and cannot be switched to their blocking position by a control signal. However, such power semiconductor switches are well known to those skilled in the art, and thus a more detailed explanation is omitted at this point.

[0019] Advantageously, each saturated switching branch has a series circuit consisting of at least two submodules. The bipolar submodules enable simple scalability of the saturated switching branches. Each power semiconductor switch is limited to a specific maximum switchable voltage, such as between 2 and 5 kV. If a higher voltage is required to saturate the core segment, this requirement can be easily met through the series circuit of the submodules.

[0020] Advantageously, each DC voltage source includes an energy storage device. Advantageously, a unipolar electrical energy storage device is preferably considered as the energy storage device. Thus, capacitors, supercapacitors, superconducting coils, batteries, supercapacitors, etc., are considered as energy storage devices. The listed or other electrical energy storage devices may appear individually in the submodule or connected in series, wherein the term "energy storage device" generally refers to the series circuit.

[0021] Suitably, the energy storage device is connected to a charging unit for charging the energy storage device. Within the scope of this invention, the charging unit can be constructed in any manner. However, it is important that the charging unit provides the energy storage device with the electrical power required for operation.

[0022] According to a suitable further improvement, the charging unit has a rectifier connected to an AC voltage source. In this case, the energy storage device is suitably constructed as a capacitor. The AC voltage source is, for example, an AC voltage source independent of a high-voltage power grid. For example, the AC voltage source is a common high-current connection in the low-voltage range. In contrast, the voltage level of the AC voltage source is in the medium-voltage range, i.e., between 1kV and 52kV. Furthermore, within the scope of the invention, it is possible to extract the power required for charging from an AC voltage grid or a high-voltage power grid, and the device according to the invention is used to provide reactive power compensation for it.

[0023] Advantageously, a saturation switching branch is provided for each high-voltage winding. As further implemented above, within the scope of the invention, such a saturation switching branch has at least one bipolar submodule, which suitably has a full-bridge or half-bridge circuit.

[0024] According to a further improvement of the invention, a so-called compensating winding is provided, which provides filtering of the AC voltage, thereby preventing greater grid distortion in the connected high-voltage grid. According to an advantageous further improvement, the compensating winding can be inductively coupled to the energy storage device. Clearly, inductive coupling for powering the energy storage device is possible even without the compensating winding.

[0025] Advantageously, each core segment, each high-voltage winding, and each saturated switch branch is arranged in a kessel filled with an insulating fluid. Advantageously, the kessel is at ground potential. In contrast, the core segment and winding are arranged in a first kessel, and each switch branch is arranged in a separate second kessel, each filled with an insulating fluid. Here, different insulating fluids, i.e., insulating liquids and / or insulating gases, can be used in the kessels. Suitably, the first and second kessels (both at ground potential) are electrically connected to each other via high-voltage bushings.

[0026] The present invention also relates to a method for reactive power compensation in a high-voltage power grid having at least one phase conductor, the phase conductor guiding the AC voltage of the power grid, wherein each phase conductor is connected via a high-voltage connector to a first high-voltage winding and a second high-voltage winding connected in parallel with the first high-voltage winding, the first and second high-voltage windings respectively surrounding first and second core sections, wherein each high-voltage winding may be connected to a ground connector via at least one saturation switch branch, the saturation switch branch having at least one submodule, the submodule having a bridge circuit consisting of a DC voltage source and a power semiconductor switch, wherein, in a positive AC voltage of the power grid, for example, the power semiconductor switch is controlled such that a negative DC current flows through the second high-voltage winding, and in a negative AC voltage of the power grid, the power semiconductor switch is controlled such that a positive DC current flows through the first high-voltage winding, wherein the DC current is adjusted such that a desired saturation is generated in the core section surrounded by the high-voltage windings.

[0027] According to the present invention, core sections whose windings are not saturated or are not saturated by AC current during the corresponding dominant half-cycle of the AC voltage can be saturated by means of a bridge circuit (which is part of a bipolar submodule). Here, control of the bridge circuit enables the desired core saturation to be achieved in a particularly simple manner. Coordinated control of the transistor switches and thyristor valves (which in principle can lead to the same success) is relatively costly; therefore, the present invention also provides a simple and inexpensive method. Attached Figure Description

[0028] Further suitable designs and advantages of the invention are the subject of the following description of embodiments of the invention with reference to the accompanying drawings, wherein like reference numerals denote components with like functions, and wherein...

[0029] Figure 1 An embodiment of the device according to the present invention is illustrated in schematic diagram;

[0030] Figure 2 It shows according to Figure 1 The saturation switching branch of the device;

[0031] Figure 3 Another embodiment of the device according to the invention is shown;

[0032] Figure 4 A possible charging unit for the device according to the invention is shown;

[0033] Figure 5 A submodule for the saturation switch branch is illustrated in the diagram;

[0034] Figure 6Another embodiment of the device according to the invention is shown, which has a charging unit for two saturation switching branches; and

[0035] Figure 7 Another embodiment of the device according to the invention is shown. Detailed Implementation

[0036] Figure 1 An embodiment of a device 1 according to the present invention is shown, the device having a container 2 filled with an insulating fluid. Mineral oil and ester solutions are considered as insulating fluids. Compared to the container 2 which is at ground potential, the insulating fluid provides the necessary withstand voltage for the components of device 1 located at high voltage potential. Furthermore, the insulating fluid is used to cool components that generate heat during operation.

[0037] A core is arranged within container 2, consisting of a magnetizable material and iron plates that are planarly attached to each other, forming a first core post 3 and a second core post 4 as core sections. The first core post 3 is surrounded by a first high-voltage winding 5. The second core post 4 is surrounded by a second high-voltage winding 6. A yoke, not shown in the figures, is used to form a closed magnetic circuit or railway, extending from the upper end of the first core post 3 to the upper end of the second core post 4 and from the lower end of the core post 3 to the lower end of the core post 4. Additionally, two return columns, also not shown in the figures, are provided, which are not surrounded by windings and extend parallel to core posts 3 or 4 on the right and left sides. In other words, a so-called 2 / 2 core is provided.

[0038] The first high-voltage winding 5 and the second high-voltage winding 6 each have a high-voltage end 7, which are connected to a high-voltage connector 8. If the device 1 is arranged in a container filled with an insulating fluid, the high-voltage connector 8 is implemented, for example, as a sleeve. The sleeve passes through the container wall and is equipped with an open-face connector at its free end, which is located outside the container. The open-face connector, not shown in the figures, is used to connect an air-insulated conductor. At its low-voltage end 9, the first high-voltage winding 5 and the second high-voltage winding 6 are connected to a saturation switch branch 10 or 11, respectively, wherein each saturation switch branch 10, 11 has a bipolar submodule 12, which is connected to the corresponding high-voltage winding 5 or 6 via a first connection terminal 13 and to a common potential point 15 via a second connection terminal 14. The potential point 15 is grounded in the illustrated embodiment. In other words, the high-voltage windings 5 ​​and 6 are connected in parallel or at least can be connected in parallel.

[0039] High-voltage windings 5 ​​and 6 are connected to phase conductors 16 of high-voltage grid 17 via high-voltage connector 8. High-voltage grid 17 has two additional phase conductors 18 and 19, which are respectively connected to two high-voltage windings and two saturation switch branches via high-voltage connector 8. In other words, device 1 has the same structure for each phase 16, 18, 19 of high-voltage grid 17, with only the structure for one phase conductor 16 shown here for clarity.

[0040] Importantly within the scope of this invention, each saturated switch branch 10 or 11 has a bipolar submodule 12, which has a bridge circuit consisting of power semiconductor switches 20, 21, 22 and 23 and a DC voltage source 24, which is preferably constructed unipolarly and thus has a fixed positive and a fixed negative terminal.

[0041] Within the scope of this invention, the bridge circuit can be a half-bridge or a full-bridge. Figure 1 In this design, each submodule has a full-bridge configuration with four power semiconductor switches 20, 21, 22, and 23. Half-bridge configurations consist of only two power semiconductor switches. To properly control the four power semiconductor switches 20, 21, 22, and 23, a control unit 26 is provided, which can be supplied with voltage UAC from the input side. soll Alternating current (IAC) soll and reactive power QAC soll The rated values ​​are specified. Current sensor 27 is used to detect the alternating current IAC flowing from phase conductor 16 to high-voltage windings 5 ​​and 6, while voltage sensor 28 detects the voltage drop on the high-voltage side of high-voltage windings 5 ​​and 6. Current sensor 27 and voltage sensor 28 are connected to control unit 26 via signal lines not shown in the figures. Sensors 29 and 30 are also visible on the low-voltage side 9 of high-voltage windings 5 ​​or 6; these sensors are also connected to control unit 26 via signal lines and detect the current flowing between the respective submodule 12 and the respective high-voltage winding 5 or 6.

[0042] The power semiconductor switches 20, 21, 22 and 23 of submodule 12 can be switched from the off position to the on position, or vice versa, by the control unit 26 via a suitable control signal shown by the dashed line. In the off position, the current flowing through the power semiconductor switches is interrupted, and in the on position, the current is allowed to flow through the power semiconductor switches.

[0043] The device 1 operates as follows: If the voltage detected by voltage sensor 28 is positive, power semiconductor switches 22 and 23 of saturation switching circuit 10 are closed. In this case, it is assumed that core 3 has already been saturated beforehand by the DC current flowing from submodule 12 of the first saturation switching branch to the high-voltage winding 5, so that for the positive half-wave of the AC voltage, the alternating resistance of high-voltage winding 5 is less than the alternating resistance of high-voltage winding 6. Therefore, almost the entire AC current IAC flows to ground via the current path denoted by I1. Thus, during the positive half-wave of the AC voltage, power semiconductor switches 21 and 22 are closed, thereby driving DC current from high-voltage winding 6 to ground 15 via DC voltage source 24 of saturation switching circuit 11. Therefore, during the positive half-wave of the AC voltage in phase conductor 16, the second core 4 can be saturated in a desired manner.

[0044] Conversely, during the negative half-wave period (where the voltage measured by sensor 28 is negative), the alternating current IAC flows substantially through the second high-voltage winding 6, thereby generating a saturated DC current by closing the power semiconductor switches 20 and 23 of the submodule 12 of the first saturated switch branch 10 and opening the power semiconductor switches 21 and 22. The saturated DC current flows from the submodule 12 to the first high-voltage winding 5 or vice versa, and ensures the desired saturation of the core 3.

[0045] Figure 2 The structure of submodule 12 of the first and second saturated switching circuits 10, 11 is shown more precisely. It can be seen that submodules for the two saturated switching branches 10 or 11 are constructed identically. Furthermore, it can be seen that the power semiconductor switches 20, 21, 22, 23 include a so-called IGBT 31, with a freewheeling diode 32 connected in reverse parallel to the IGBT. The structure of an IGBT with a freewheeling diode is known in principle, so there is no need to discuss their operation in more detail in this case. Importantly, the freewheeling diode 22 is used to protect the IGBT from overvoltage in the reverse direction. Here, the IGBT 31 and the diode 32 are typically housed in a common switch housing. The IGBT 31 and the freewheeling diode 32 are collectively referred to here as power semiconductors.

[0046] Each module 12 is implemented as a so-called full bridge and includes a first series circuit branch 33 and a second series circuit branch 34 consisting of two corresponding series-connected power semiconductor switches 20, 21 or 22 and 23. The potential point between the power semiconductor switches 20, 21 of the first series circuit branch 33 is connected to the first connection terminal 13, and the potential point between the power semiconductor switches 22 and 23 of the second series circuit branch 34 is connected to the connection terminal 14 of the submodule 12.

[0047] Figure 3Another embodiment of the device 1 according to the invention is shown, wherein, for clarity, only the component for connection to a high-voltage power grid 17 is shown. The high-voltage connector 8 and the container 2 are not described further.

[0048] As can be seen, each saturation switch branch 10 or 11 consists of a series circuit composed of multiple sub-modules 12, which are controlled by the control unit 26 either all the same or different, thereby expanding the DC voltage used to generate the DC current used to saturate the cores 3 and 4 according to the corresponding requirements.

[0049] Figure 4 It shows according to Figure 2 Submodule 12, wherein the energy storage unit 24 is configured as a unipolar capacitor. A charging unit 35, consisting of an AC current source 36 and a rectifier 37, is also described. The rectifier 37 consists of two phase module branches 38 and 39, each having a DC voltage connector 40 and 41 and an AC voltage connector 42 and 43. A switching branch, equipped with at least one power semiconductor, is arranged between the AC voltage connectors 42 and 43 and each DC voltage connector 40 or 41. The DC voltage connector 40 is connected to the first terminal of the capacitor 24, and the DC voltage connector 41 is connected to the second terminal of the capacitor 24. However, such rectifiers are known, so a more precise depiction of their topology and operation is omitted in this case.

[0050] The AC voltage source 36 is implemented as a transformer, having a primary winding 44 and a secondary winding 45 inductively coupled to each other via a core 46. A smoothing reactor 47 is used to smooth the formed AC voltage. The charging unit 35 further includes a switch 48 connected in parallel with a switching resistor 49. The switch 48 can be used to turn on or bridge the resistor 49, thereby causing the desired charging of the capacitor 24 of the submodule 12. A buffer capacitor 50 is used to prevent overvoltage on the secondary winding 45.

[0051] Figure 5 Another embodiment of submodule 12 is shown, which, instead of a single capacitor, has a series circuit of multiple batteries 51 as a DC voltage source 24. Instead of batteries 51, rechargeable batteries can be used in different designs of the invention.

[0052] Figure 6 Another embodiment of the device according to the invention is shown, the device having relative to the invention according to... Figure 4The device has different charging units 35. The charging units shown are only used for the initial charging of the switching branches until the operating state is established. The charging branches 35 can then be removed, and each switching branch can be supplied with load current by clever adjustment. The DC voltage source 24 of the submodule 12 is again implemented as a capacitor. However, in this case, each saturated switching branch 10 or 11 can be connected to the charging unit 35 via the charging switch 52 or 53, so that only one charging unit is set for the two saturated switching branches 10, 11. Figure 6 In the schematic illustration, the charging unit 35 also includes a DC voltage source 54, which is connected to a corresponding charging switch 52 or 53 via a suitable buffer resistor 55. The DC voltage source 54 may include, for example, a rectifier connected to an AC current source. Alternatively, the DC voltage source 54 may be implemented as a battery, supercapacitor, storage battery, etc.

[0053] Figure 7 A further embodiment of the device 1 according to the invention is shown, which differs from the device 1 shown in the previous figures in that it is provided with only one saturation switch circuit 10, which is connected not only to the low-voltage end 9 of the first high-voltage winding 5, but also to the low-voltage end 9 of the second high-voltage winding 6. For this purpose, the first connection terminal 13 of the submodule 12 is connected to the second high-voltage winding 6, while the second connection terminal 14 of the submodule 12 is connected to the low-voltage side 9 of the first high-voltage winding 5. The first connection terminal 13 and the second connection terminal 14 can be connected to the ground potential 15 via a grounding switch 55 or 56, wherein the switch 55 or 56 is configured as a power semiconductor switch and can be controlled by the control unit 26. The signal lines required for this purpose are connected to the charging switches 55, 56 and the control unit 26, and... Figure 7 The submodule 12 is shown in dashed lines. To connect the submodule 12 between the first high-voltage winding 5 and ground 15 with the desired polarization, ground switch 55 is opened and ground switch 56 is closed. By closing power semiconductor switches 21 and 22, 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 ground switch 56 and closing ground switch 55, and by closing power semiconductor switches 22 and 21, where power semiconductor switches 20 and 23 are open, 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 power grid (17) having at least one phase conductor (16, 18, 19), said device having at least one high-voltage connector (8) designed for connection to the phase conductor (16), wherein, Set for each high-voltage connector (8) - The first and second core sections (3, 4) are part of a closed magnetic circuit. - The first high-voltage winding (5), which surrounds the first core section (3), and - A second high-voltage winding (6) surrounds the second core section (4) and is connected in parallel with the first high-voltage winding (15). - At least one saturation switching branch (10, 11) is designed to saturate the core segment (3, 4) and has controllable power semiconductor switches (20, 21, 22, 23), and - Control unit (26) for controlling power semiconductor switches (20, 21, 22, 23), The first and second high-voltage windings (5, 6) are connected to the corresponding high-voltage terminals (8) via their high-voltage ends (7), and can be connected to the saturation switch branches (10, 11) on their low-voltage sides (9). The feature is that each saturated switch branch (10, 11) has at least one bipolar submodule (12) having a bridge circuit having controllable power semiconductor switches (20, 21, 22, 23) and a DC voltage source (24), such that, depending on the control of the power semiconductor switches (20, 21, 22, 23), the DC voltage source (24) can either be connected in series with or bridged with the high-voltage windings (5, 6) connected to the saturated switch branch (10, 11).

2. The device (1) according to claim 1, characterized in that, Each saturated switch branch (10, 11) can be connected to the ground terminal (15) on its side opposite to the associated high voltage winding (5, 6).

3. The device (1) according to any one of the preceding claims, characterized in that, Each submodule (2) forms a full-bridge circuit having a first series circuit branch (33) and a second series circuit branch (34) connected in parallel with a DC voltage source (24), respectively. Each series circuit branch (33, 34) has a series circuit 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 circuit branch (33) is connected to the first connection terminal (13) of the submodule (12), and the potential point between the power semiconductor switches (22, 23) of the second series circuit branch (34) is connected to the second connection terminal (14) of the submodule (12).

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

5. The device (1) according to any one of the preceding claims, characterized in that, Each saturated switch branch (10, 11) is a series circuit consisting of at least two sub-modules (12).

6. The device (1) according to any one of the preceding claims, characterized in that, Each DC voltage source (24) includes an energy storage device.

7. The device (1) according to claim 6, characterized in that, The energy storage device (24) can be connected to a charging unit (35) which is designed to charge the energy storage device (24).

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

9. The device (1) according to any one of the preceding claims, characterized in that, Saturation switch branches (10, 11) are set for each high voltage winding (5, 6).

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

11. The device (1) according to any one of the preceding claims, characterized in that, Each core section (3, 4), each high-voltage winding (5, 6), and each saturated switch branch (10, 11) is arranged in a container (2) filled with an insulating fluid.

12. A method for reactive power compensation in a high-voltage power grid (17) having at least one phase conductor (16, 18, 19), wherein the phase conductor guides the AC voltage of the power grid, The device (1) is arranged according to any one of claims 1 to 11, wherein each phase conductor (16, 18, 19) is connected via a high-voltage connector (8) to a first high-voltage winding (5) and a second high-voltage winding (6) connected in parallel with the first high-voltage winding, the first and second high-voltage windings respectively surrounding the first and second core sections (3, 4), wherein each high-voltage winding (5, 6) is connectable to a ground connector (13) via at least one saturation switch branch (10, 11), the saturation switch branch having at least one submodule (12), the submodule having a bridge circuit consisting of a DC voltage source (24) and power semiconductor switches (20, 21, 22, 23), wherein, - Under positive AC grid voltage, the power semiconductor switch is controlled to allow the desired DC current to flow through the second high-voltage winding, and - In a negative AC grid voltage, the power semiconductor switch is controlled so that a desired DC current flows through the first high-voltage winding, wherein the DC current is regulated to produce the desired saturation of the core segment (3, 4).

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