MAGNETICALLY CONTROLLABLE INDUCTOR COIL IN A SERIES CIRCUIT

Abstract

An apparatus for dynamic load flow control in high-voltage networks has at least one phase conductor and first high-voltage connection for connection to each phase conductor. Each first high-voltage connection has first and second core sections of a closed magnetic circuit and first and second high-voltage windings surrounding respective core portions and connected in parallel. The core portions and windings are in a tank filled with ester fluids. At least one saturation switching branch outside the tank saturates the core sections and has controllable power semiconductor switches. A control unit controls the power semiconductor switches. The first and second high-voltage windings are connected at high-voltage ends to associated first high-voltage connections and at low-voltage ends to respective saturation switching branches. The device is connectable in series into the high-voltage network, with the saturation switching branches electrically insulated from ground potential.

Claims

1-12. (canceled)

13. An apparatus for dynamic load flow control in a high-voltage network having at least one phase conductor and at least one first high-voltage connection for connection to each respective phase conductor, the apparatus comprising, for each first high-voltage connection: a tank; first and second core sections being part of a closed magnetic circuit and being disposed in said tank; a first high-voltage winding surrounding said first core section; a second high-voltage winding surrounding said second core section, said second high-voltage winding connected in parallel with said first high-voltage winding; at least one saturation switching branch configured to saturate said core sections, said at least one saturation switching branch having controllable power semiconductor switches, said at least one saturation branch being disposed outside of said tank and mounted to be electrically insulated from ground potential; and a control unit for controlling said power semiconductor switches; said first and second high-voltage windings being connected to the first high-voltage connection and said first and second high-voltage windings configured to be connected to said at least one saturation switching branch; and a second high-voltage connection for connection to the phase conductor, said second high-voltage connection being connected directly, or through said at least one saturation switching branch, to said high-voltage windings.

14. The apparatus according to claim 13, which further comprises a high-voltage platform having a supporting structure and electrically insulating supporting columns supporting said high-voltage platform on the ground, said at least one saturation switching branch being disposed on said high-voltage platform.

15. The apparatus according to claim 13, which further comprises at least one high-voltage bushing installed on said tank, said at least one high-voltage bushing connecting said at least one saturation switching branch to at least one of said high-voltage windings.

16. The apparatus according to claim 13, wherein at least one of said high-voltage windings has a center connection connecting said at least one high-voltage winding to said at least one saturation branch, and said high-voltage windings have winding ends each being connected to a respective one of the first and second high-voltage connections.

17. The apparatus according to claim 13, wherein each of said high-voltage windings has a center connection connected to said at least one saturation switching branch.

18. The apparatus according to claim 13, wherein said at least one saturation switching branch has at least one two-pole submodule with a bridge circuit having power semiconductor switches and a DC voltage source, said DC voltage source being either connected in series with said at least one high-voltage winding or bridged, depending on a control of said power semiconductor switches.

19. The apparatus according to claim 18, wherein: said at least one two-pole submodule forms a full-bridge circuit having a first series circuit branch and a second series circuit branch each being connected in parallel with said DC voltage source; said at least one two-pole submodule has first and second connection terminals; each of said series circuit branches has a series circuit including two power semiconductor switches; said first series circuit branch has a potential point between said power semiconductor switches being connected to said first connection terminal; and said second series circuit branch has a potential point between said power semiconductor switches being connected to said second connection terminal.

20. The apparatus according to claim 18, wherein each of said power semiconductor switches is an IGBT with a freewheeling diode connected in parallel in an opposite sense, a GTO or a transistor switch.

21. The apparatus according to claim 18, wherein each of said DC voltage sources includes an energy storage device.

22. The apparatus according to claim 21, wherein said energy storage devices are configured to be connected to a supply network.

23. The apparatus according to claim 13, which further comprises compensation windings inductively coupled to said high-voltage windings, and at least one capacitively acting component part connected to said compensation windings.

24. The apparatus according to claim 23, wherein said capacitively acting component part has capacitors.

Description

[0023] Further expedient configurations and advantages 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 identical reference signs refer to identically acting component parts, and wherein

[0024] FIG. 1 shows a schematic illustration of an exemplary embodiment of the apparatus according to the invention,

[0025] FIG. 2 shows the saturation switching branches of the apparatus according to FIG. 1,

[0026] FIG. 3 shows a further exemplary embodiment of the apparatus according to the invention,

[0027] FIG. 4 shows a further exemplary embodiment of the apparatus according to the invention with elevated saturation switching branches,

[0028] FIG. 5 shows a further exemplary embodiment of the apparatus according to the invention, and

[0029] FIG. 6 shows yet another further exemplary embodiment of the apparatus according to the invention.

[0030] FIG. 1 shows an exemplary embodiment of the apparatus 1 according to the invention which has a tank 2 filled with an insulating fluid. Mineral oils or else ester fluids or the like come into consideration as the insulating fluid. Gaseous insulating fluids are also possible within the scope of the invention.

[0031] The insulating fluid provides, on the one hand, the necessary dielectric strength for component parts of the apparatus 1, which are at a high-voltage potential, with respect to the tank 2 which is at ground potential. In addition, the insulating fluid is used to cool the components which generate heat during operation. In the exemplary embodiment shown in FIG. 1, the tank is filled with an ester fluid.

[0032] Arranged inside the tank 2 is a core which is composed of a magnetizable material, preferably a ferromagnetic material, for example iron. In order to avoid eddy currents, the core is assembled on iron sheets which rest flat on one another. In this case, the core forms a first core limb 3 and a second core limb 4 as core sections.

[0033] The first core limb 3 is surrounded by a first high-voltage winding 5. The second core limb 4 is surrounded by a second high-voltage winding 6. In order to form a closed magnetic or iron circuit, the yokes which are not illustrated in the figures and extend from the upper end of the core limb 3 to the upper end of the core limb 4 and from the lower end of the core limb 3 to the lower end of the core limb 4. Two return limbs which are likewise not illustrated in the figures, are not surrounded by a winding and extend parallel to the core limbs 3 and 4 on the right and on the left are also provided. In other words, a so-called 2/2 core is provided.

[0034] The first high-voltage winding 5 and the second high-voltage winding 6 each have a winding end 7, by way of which they are connected to a high-voltage bushing 8 which is used to guide the connection lines, which are at a high-voltage potential during operation, through the wall of the tank 2 that is at ground potential.

[0035] In this case, the high-voltage bushing 8 engages through the wall of the tank 2 and is equipped with an open-air connection at its free end arranged outside the tank 2. The open-air connection which is not illustrated in the figures is used to connect an air-insulated conductor 40, via which the high-voltage windings 5 and 6 are connected to a first high-voltage connection 42, via which the entire apparatus 1 can be connected to a phase conductor 16 of a high-voltage supply network. For each other phase conductor of the high-voltage network, which are not shown here for reasons of clarity, the apparatus 1 has an identical structure to that shown in FIG. 1. These components are also not shown for reasons of clarity. It goes without saying that cable connections are also possible within the scope of the invention.

[0036] At their ends 9 facing away from the first high-voltage connection 42, 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, arranged outside the tank 2, wherein each saturation switching branch 10, 11 has a two-pole submodule 12 connected, by way of a first connection terminal 13, to the respective high-voltage winding 5 and 6. By way of their second connection terminal 14, the submodules 12 are connected to the second high-voltage connection 44. A bushing 8 is again used to guide the connection line between high-voltage winding 5, 6 and saturation switching branch 10, 11 through the wall of the tank 2. In the exemplary embodiment shown, the second high-voltage connection 44 is likewise connected to the phase conductor 16. In other words, the apparatus 1 according to the invention which is shown is connected into the supply network in series with the phase conductor 16.

[0037] Within the scope of the invention, it is important for each saturation switching branch 10 or 11 to have a two-pole submodule 12 which has a bridge circuit comprising power semiconductor switches 20, 21, 22 and 23 and a DC voltage source 24 which is preferably unipolar and therefore has a fixed positive pole and a fixed negative pole. The saturation switching branches 10, 11 are mounted such that they are insulated from ground potential. Expedient insulation component parts, such as for example insulating posts or the like, are used for this purpose.

[0038] Within the scope of the invention, the bridge circuit may be a half-bridge or a full-bridge. In FIG. 1, each submodule has a full-bridge and comprises four power semiconductor switches 20, 21, 22 and 23. A half-bridge comprises only two of the power semiconductor switches. In order to expediently control the four power semiconductor switches 20, 21, 22 and 23, provision is made of a control unit 26 which can be supplied, on the input side, with desired values for the voltage U.sub.ACSoll, the alternating current I.sub.ACSoll and the reactive power Q.sub.ACSoll. A current sensor 27 is used to capture the alternating current I.sub.AC flowing from the phase conductor 16 to the high-voltage windings, wherein a voltage sensor 28 captures the voltage dropped on the high-voltage side of 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 which are not illustrated in the figures. On the other end of the high-voltage winding 5 and 6, respectively, it is likewise possible to see sensors 29 and 30 which are likewise connected to the control unit 26 via signal lines and capture currents which flow between the respective submodule 12 and the respective high-voltage winding 5 or 6. The power semiconductor switches 20, 21, 22 and 23 of a submodule 12 can be changed, by means of expedient control signals represented by dashed lines, by the control unit 26 from a disconnection position, in which a current flow is interrupted via the power semiconductor switches, to a conducting position, in which a current flow is possible via the power semiconductor switches, or vice versa from the conducting position to the disconnection position.

[0039] The method of operation of the apparatus 1 is as follows: if the voltage captured by the voltage sensor 28 is positive, the power semiconductor switches 22 and 23 of the saturation switching branch 10 are closed. It shall be presupposed at this that the core limb 3 has previously been saturated by a direct current flowing from the submodule 12 of the first saturation switching branch 10 to the high-voltage winding 5, with the result that the AC resistance of the high-voltage winding 5 is lower than the AC resistance of the high-voltage winding 6 for the positive half-wave of the AC voltage. Virtually the entire alternating current I.sub.AC therefore flows to the second high-voltage connection 44 via the current path denoted Ii. In the positive half-wave of the AC voltage, the power semiconductor switches 21 and 22 are therefore closed, with the result that the DC voltage source 24 of the saturation circuit 11 drives a direct current which flows from the high-voltage winding 6 to the second high-voltage connection 44. During the positive half-wave of the AC voltage in the phase conductor 16, the second core limb can therefore be saturated in the desired manner.

[0040] In contrast, during the negative half-wave in which the voltage measured by the sensor 28 is negative, an alternating current I.sub.AC flows substantially via the second high-voltage winding 6, with the result that a saturation direct current is generated by closing the power semiconductor switches 20 and 23 and opening the power semiconductor switches 21 and 22 of the submodule 12 of the first saturation switching branch 10, which saturation direct current flows from the submodule 12 to the first high-voltage winding 5 or vice versa and therefore ensures the desired saturation of the core limb 3.

[0041] FIG. 2 shows the structure of the submodules 12 of the first and second saturation circuits 10, 11 in more detail. It can be seen that the submodules for both saturation switching branches 10 and 11 have an identical structure. It can also be seen that the power semiconductor switches 20, 21, 22 and 23 comprise a so-called IGBT 31, with which a freewheeling diode 32 is connected in parallel in an opposite sense. The structure of an IGBT with a freewheeling diode is fundamentally known, with the result that its method of operation does not need to be discussed in any more detail at this point. The important fact is that the freewheeling diode 32 is used to protect the IGBT by means of voltages in the reverse direction. In this case, the IGBT 31 and diodes are accommodated in a common switch housing. The IGBT 31 and the freewheeling diode 32 are referred to together as power semiconductor switches here.

[0042] Each submodule 12 is in the form of a so-called full-bridge and comprises a first series circuit branch 32 and a second series circuit branch 34 each comprising two power semiconductor switches 20, 21 and 22 and 23, respectively, which are connected in series. The potential point between the power semiconductor switches 20 and 21 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.

[0043] FIG. 3 shows a further exemplary embodiment of the apparatus 1 according to the invention which partly corresponds to the exemplary embodiment shown in connection with FIG. 1. In addition to the component parts or elements already described in FIG. 1, the exemplary embodiment of the apparatus 1, as shown in FIG. 7, also has a capacitively acting component part which is in the form of a capacitor 35 in the exemplary embodiment shown. The capacitor 35 is connected in parallel with a compensation winding 36, wherein the compensation winding 36 is composed of two partial compensation windings 37 and 38 which are connected in series with one another. The partial compensation winding 37 is inductively coupled to the first high-voltage winding and the second partial compensation winding 38 is inductively coupled to the high-voltage winding 6. In this case, the high-voltage windings 5 and 6 and the respective partial compensation winding 37 or 38 are arranged concentrically with respect to one another, wherein they surround the same core section 3 or 4 of the core which is otherwise not illustrated any further. FIG. 7 illustrates only one additional winding 36 for the phase shown there. However, further compensation windings are provided for the other phases in the tank 2 and have an identical structure and are connected to the capacitor 35 in the same manner. In this case, the compensation windings 36 of the different phases are connected to one another in a delta circuit. This delta circuit is indicated by arrows 39a and 39b. A switch 49 is also schematically illustrated in the parallel branch of the compensation winding, in which the capacitor 35 is arranged, which switch comprises two thyristors which are connected in parallel in opposite senses in the exemplary embodiment shown. With the aid of the electronic switch 49, the capacitor 35 can be connected in parallel with the compensation winding 36 or the action of the capacitively acting component part 35 can be suppressed.

[0044] The capacitor 35 is illustrated in FIG. 7 as an individual capacitor which is arranged outside the tank 2 of the FVSR. However, the capacitor 35 comprises a number of capacitors arranged in series or in parallel with one another and can therefore also be referred to as a capacitor bank. In this case, the number of capacitors connected in parallel or in series depends on the respective requirements, wherein the capacitive action can be increased or reduced.

[0045] The capacitor or, in other words, the capacitor bank 35 is arranged outside the tank 2 of the FVSR, like the switch 49. In a deviation from this, arrangement in a common tank is naturally also possible. In order to enable an electrical connection between the compensation winding 36 in the tank 2, expedient bushings 8 are provided again and make it possible to guide the high-voltage lines through the wall of the tank 2, which is at ground potential, with dielectric strength.

[0046] FIG. 4 shows a further exemplary embodiment of the apparatus 1 according to the invention having a first high-voltage connection 42 for connecting the phase conductor 16 and a second high-voltage connection 44 which is likewise provided for the purpose of connecting the phase conductor 16. The apparatus is therefore again connected in series with the phase conductor 16. As in exemplary embodiments shown in FIGS. 1 and 3, the saturation switching branches 10 and 11 are arranged outside the tank 2. High-voltage bushings 8 which each engage through the wall of the tank 2 are again used to connect the saturation switching branches to the high-voltage windings 5 and 6 arranged in the tank 2, wherein an outer insulating body provides the necessary dielectric strength with respect to the tank 2 at ground potential.

[0047] In this case, the saturation switching branches 10, 11 are arranged on a high-voltage platform 50 which has a planar supporting structure 51 and two insulating posts made of a non-conductive material which are provided with ribs on the outside. One end of the insulating posts 52 is permanently anchored in the ground and the end of the insulating posts facing away from the ground is permanently connected to the supporting plate 51.

[0048] Two insulating posts 52 can be respectively seen in FIGS. 4, 5 and 6. However, it is pointed out at this point that further insulating posts which are not illustrated in the figures are possible for supporting the supporting structure 51. The insulators or insulating posts 52 make it possible for the saturation switching branches 10 and 11 to be at a high-voltage potential. This therefore applies to the power electronics of the power semiconductor switches. Complicated potential isolation has become superfluous.

[0049] FIG. 5 shows a further exemplary embodiment of the apparatus according to the invention which differs from the exemplary embodiment shown in FIG. 4 in that the second high-voltage connection 44 is not directly connected to the saturation switching branches 10, 11 via a star point. Rather, the second high-voltage connection 44 is directly connected to the high-voltage winding ends 9 arranged in the tank 2 via a bushing 8. In this case, the high-voltage windings 5 and 6 each have a center connection 53 which is used to connect the saturation switching branches 10 and 11 arranged on the platform 50. The saturation switching branches 10 and 11 are connected to one another via an expedient interconnection 54.

[0050] FIG. 6 shows a further exemplary embodiment of the apparatus according to the invention which differs from the exemplary embodiment shown in FIG. 5 in that only one saturation switching branch is arranged on the high-voltage platform 50 and is connected to both high-voltage windings 5, 6, wherein expedient switches are provided in order to bring about the desired saturation of the core sections 3 and 4.