Electrical operating means comprising a tap changer

Abstract

The invention relates to an electrical operating means (1) comprising: - at least one control winding (3), which has winding taps (n, n+1), and at least one partial winding (4, 5), - a tap changer (6) for changing a transformation ratio, an impedance, or a voltage of the electrical operating means (1), which voltage is used for excitation, wherein - the tap changer (6) comprises a first module (7) for connecting the winding taps (n, n+1) of the control winding (3) and a second module (8) for additively connecting, subtractively connecting, or by-passing the at least one partial winding (4, 5), and - the second module (8) comprises at least one sub-module (9), which has semiconductor switching elements, and a bypass switch (10).

Description

[0001] ELECTRICAL EQUIPMENT WITH STEP SWITCH

[0002] The invention relates to an electrical equipment comprising at least one control winding with winding taps, at least one partial winding and a step switch for changing a transformation ratio, an impedance or a voltage used for excitation of the electrical equipment.

[0003] When controlling power grids, a distinction is made between two different time domains. In the so-called steady-state domain, a stationary operating point is set in a power grid using suitable operating equipment, which enables reliable operation of the grid with minimal load and feed-in fluctuations. Control takes place in the time domain of minutes. In the dynamic domain, suitable operating equipment is used to respond to dynamic fluctuations in the grid, which can be caused, for example, by faults or rapid and possibly only temporary changes in the feed-in and load situation. In this case, very fast control in the range of milliseconds is required to keep the grid stable.

[0004] Since the reactive power demand changes with the respective feed-in and load situation, reactive power control represents an essential component of safe, efficient and loss-minimized grid management.

[0005] Suitable state-of-the-art equipment is already available for both steady-state grid control and dynamic voltage regulation. For example, controllable transformers, phase shifters, or controllable shunt reactors are used to control steady-state grid operation. Static synchronous compensators (STATCOMs) or static reactive power compensators (SVCs) are used to control dynamic grid behavior.

[0006] In particular, the resources for control in the dynamic range will become increasingly relevant for secure grid operation in the foreseeable future due to the energy transition and the integration of decentralized energy generation into grid operation, as the feed-in from renewable energies is less predictable.

[0007] In addition to the control of power grids, the previously mentioned different time domains also play a key role in the power supply of arc furnaces. Furnace transformers used to supply arc furnaces typically contain tap changers, which enable the furnace transformer's power to be controlled in a range of a few seconds to minutes. However, due to rapidly changing operating conditions in arc furnaces, such as the breaking off of the arcs used for melting, undesirable grid perturbations, such as flicker, with time constants in the millisecond range, frequently occur in arc furnaces. Complex and cost-intensive compensation systems (SVC) are also typically used to limit these grid perturbations.

[0008] Another application area where the aforementioned time ranges play a role is electrolysis plants for hydrogen production, which use rectifier transformers controlled by tap changers. For participation in the balancing energy market, the ability to control in the dynamic time range is particularly relevant in order to provide positive or negative balancing energy to the grid as quickly as possible.

[0009] A device that enables control in the steady-state range, i.e., seconds to minutes, as well as in the dynamic range, i.e., milliseconds, has not yet been disclosed in the state of the art.

[0010] It is therefore an object of the present invention to provide an improved concept for controlling energy supply networks or energy supply systems, which provides a combined, flexible control solution for serving both time ranges, which is also cost-effective, space-saving and low-loss in operation and production.

[0011] This object is achieved by the subject matter of the independent claim. Further embodiments are the subject matter of the dependent claims.

[0012] The improved concept is based on the idea of ​​combining a conventional tap changer, as is well known from the state of the art, with a power electronic tap changer connected in series. Since the power electronic tap changer can change its switching position quickly, namely within milliseconds, and assume any desired position, it enables rapid voltage adjustment to rapidly changing load and feed-in conditions. The conventional tap changer serves the steady-state range, covering the widest possible control range. This allows for a high degree of flexibility for grid management as well as plant and process control.

[0013] According to the improved concept, an electrical equipment is specified which comprises at least one main winding, at least one control winding with winding taps, at least one partial winding and a step switch for changing a transformation ratio, an impedance or a voltage used for excitation of the electrical equipment.

[0014] The electrical equipment can be designed as a controllable transformer, as a phase-shifting transformer, as a controllable choke or as a controllable transformer with a capacitor.

[0015] According to one embodiment, the electrical equipment is designed as a controllable transformer and the tap changer is designed to change the transformation ratio of the controllable transformer.

[0016] According to one embodiment, the electrical equipment is designed as a controllable choke and the step switch is designed to change the impedance of the controllable choke.

[0017] According to a further embodiment, the electrical equipment comprises a first inductive arrangement and a second inductive arrangement. The actual voltage in the first inductive arrangement excites the second inductive arrangement, thereby increasing the power of the first inductive arrangement. In other words, according to this embodiment, an excitation transformer, a first inductive arrangement, is supplemented by a booster transformer, a second inductive arrangement. The voltage used to excite the booster transformer is changed by means of the tap changer. This arrangement makes it possible to adjust the operating parameters of the tap changer, current and voltage, more flexibly, particularly in high-power units.

[0018] According to a further embodiment, the electrical equipment is designed as a phase-shifting transformer. Phase-shifting transformers are special power transformers that can specifically influence the phase angle of the voltage or the electrical load flow across an overhead line by introducing a quadrature voltage or a diagonal voltage. According to this embodiment, the phase-shifting transformer comprises a series transformer and an excitation transformer. The tap changer is designed to set a specific phase shift by changing the transformation ratio of the excitation transformer.

[0019] The tap changer comprises a first module for connecting the winding taps of the control winding and a second module with semiconductor switching elements for quickly connecting, counter-connecting, or bypassing at least one partial winding. The second module comprises at least one sub-module with semiconductor switching elements and a bypass switch.

[0020] According to one embodiment, the at least one partial winding is at least as large as a portion of the control winding located between two adjacent winding taps of the control winding. In other words, the at least one partial winding has a specific number of turns that is at least as large as the smallest number of turns present between two adjacent winding taps of the control winding. If the electrical equipment has multiple partial windings, the number of turns of the multiple partial windings can be integer multiples of one another.

[0021] According to one embodiment, the first module is designed as an on-load tap-changer, in particular as a resistance-type tap-changer for uninterrupted switching between different winding taps of the control winding of the electrical equipment. It comprises a selector for powerless preselection of the winding tap of the electrical equipment to which switching is to take place, as well as a load transfer switch for the actual, uninterrupted switching from the previously connected winding tap to the new, preselected winding tap. For powerless preselection of the winding taps, the selector generally comprises two movable selector contacts that connect the winding taps. The load transfer switch typically comprises switching contacts and resistors for the actual load switching. The switching contacts are designed, for example, as vacuum interrupters.The resistors serve to limit the short-term circulating current flowing in the load changeover switch during the switching process and are also referred to as switching resistors.

[0022] According to a further embodiment, the first module is designed as a reactor switch. According to the reactor switching principle, the circulating current is limited by chokes, also referred to as reactors.

[0023] According to one embodiment, the electrical equipment comprises a plurality of partial windings, and the second module comprises a plurality of submodules with semiconductor switching elements. At least one partial winding is assigned to each submodule, and each submodule is designed for rapid connection, counter-connection, or bridging of the at least one associated partial winding. Bridging, in concrete terms, means that no current flows through the respective partial winding.

[0024] According to one embodiment, a submodule comprises, for example, four commutation cells configured as a bridge circuit. According to one embodiment, each commutation cell comprises two anti-parallel thyristor paths, whereby a path can also consist of several series-connected thyristors.

[0025] According to a further embodiment, the bypass switch is designed to bridge the second module with the at least one sub-module with semiconductor switching elements.

[0026] According to one embodiment, the bypass switch is designed as a circuit breaker or load-break switch.

[0027] According to a further embodiment, the step switch can be operated in a predefined operating mode in which the bypass switch is closed and the at least one sub-module is bridged with semiconductor switching elements.

[0028] According to a further embodiment, when the tap changer is in the predefined operating mode, only the first module is used to change the transformation ratio, the impedance or the voltage used for excitation of the electrical equipment.

[0029] According to a further embodiment, when the tap changer is in the predefined operating mode, the second module assumes a neutral position in which the at least one partial winding is bridged. Bridged, meaning at potential, but no current flowing through it. In other words, the semiconductor switching elements of the second module are interconnected in such a way that a bypass is formed for the at least one partial winding.

[0030] The advantage of this embodiment is that the electrical equipment with the first module can be operated without interruption, while the bypass switch carries the continuous current and thus bridges the semiconductor switching elements. This may be necessary, for example, when the second module is being serviced or when a malfunction occurs due to a failure of the power supply for controlling the semiconductor switching elements. Furthermore, operating the tap changer in the predefined operating mode can prevent losses from the semiconductor switching elements of the second module.

[0031] According to a further embodiment, the tap changer is operated in a predefined, second operating mode in which the change in the transformation ratio, the impedance or the voltage used for excitation is carried out by means of the second module.

[0032] The advantage of this design is that when the step switch is operated in the second operating mode, the mechanics and the electrically switching contacts of the first module are protected and its service life is extended due to less wear on the corresponding components.

[0033] According to one embodiment, the first module comprises a first control unit, the second module comprises a second control unit, and the electrical equipment comprises a system controller configured to actuate the first and second control units.

[0034] According to one embodiment, the second module and the first control unit and the second control unit and the system controller are each arranged in a separate housing.

[0035] According to one embodiment, the second module and the first control unit and the second control unit and the system controller are arranged in a common housing.

[0036] According to one embodiment, the second module and the second control unit are arranged in a common housing.

[0037] According to one embodiment, the second module and the first control unit are arranged in a common housing.

[0038] According to one embodiment, the second module and the second control unit and the system controller are arranged in a common housing.

[0039] According to one embodiment, the second module and the first control unit and the system controller are arranged in a common housing.

[0040] According to one embodiment, the second module and the first control unit and the second control unit are arranged in a common housing.

[0041] According to one embodiment, the first control unit and the second control unit are arranged in a common housing.

[0042] According to one embodiment, the first control unit and the second control unit and the system controller are arranged in a common housing. According to one embodiment, the second module is arranged in a housing of the electrical equipment.

[0043] According to a further embodiment, the bypass switch is arranged in a separate housing or with the second module in a common housing.

[0044] According to a further embodiment, the first control unit comprises a motor drive. The motor drive is preferably designed to actuate the selector contacts and the switching contacts of the on-load tap-changer for connecting the winding taps of the control winding. The motor drive can be designed as a direct drive without an intermediate gear.

[0045] The second control unit is designed as a microcontroller, for example.

[0046] According to one embodiment, the second control unit is designed to actuate the at least one or more sub-modules or their associated commutation cells in a suitable manner such that the at least one or more partial windings are quickly connected to or counter-connected to the control winding or are bridged.

[0047] The invention will now be explained in detail using exemplary embodiments with reference to the drawings. Components that are identical, functionally identical, or have an identical effect may be provided with identical reference numerals. Identical components or components with identical functions may only be explained with reference to the figure in which they first appear. The explanation is not necessarily repeated in subsequent figures.

[0048] It shows

[0049] Figure 1 shows a first embodiment of an electrical device according to the improved concept in a schematic representation;

[0050] Figure 2 shows a second embodiment of the electrical equipment according to the improved concept in a schematic representation;

[0051] Figure 3 shows a third embodiment of the electrical equipment according to the improved concept in a schematic representation;

[0052] Figure 4 shows a preferred embodiment of a method according to the improved concept. Figure 1 shows a schematic representation of a first embodiment of an electrical device 1 according to the improved concept.

[0053] The electrical equipment 1 is embodied here, for example, as a single-phase, variable-speed transformer. The variable-speed transformer 1 has a main winding 2 on the primary or secondary side, a control winding 3 with n winding taps, and two partial windings 4 and 5. Partial winding 5 has a larger number of turns than partial winding 4, for example, three times as many. Furthermore, the number of turns of partial winding 4, and consequently also that of partial winding 5, is larger than the smallest existing number of turns between two adjacent winding taps, for example, between n and n+1, of the control winding 3.

[0054] The number of partial windings is not limited to two. In principle, multiple partial windings can also be provided, each of which can be an integer multiple of the number of partial windings 4.

[0055] Furthermore, the transformer 1 has a tap changer 6 for changing the transformation ratio of the transformer 1. The tap changer 6 comprises a first module 7 for connecting the winding taps n, n+1 of the control winding 3 and a second module 8 connected in series with the first module 7 for connecting, counter-connecting, or bridging the partial windings 4, 5. The first module 7 is intended for control in the steady-state range, and the second module 8 for control in the dynamic time range.

[0056] Preferably, the first module 7 is an on-load tap-changer consisting of a selector for powerless preselection of the winding taps n, n+1 and a load transfer switch for uninterrupted switching from the previously connected winding tap n to the new, preselected winding tap n+1. The on-load tap-changer can also have a preselector, which can be designed as a coarse tap or a reverser. For clarity, however, the first module 7 is shown in Figure 1 in a highly simplified manner.

[0057] The second module 8 preferably has two sub-modules 9, each with four commutation cells in an H-bridge circuit. Each commutation cell here has a pair of thyristors connected in antiparallel. A partial winding 4 or 5 is assigned to each sub-module 9, and each sub-module 9 is designed to quickly connect the respective partial winding 4 or 5 to or against the control winding 3, i.e., within 10 to 1000 milliseconds, by means of the commutation cells or semiconductor switching elements, or to bridge the respective partial winding 4 or 5, such that the partial winding 4, 5 has a specific potential but no current flows through it.

[0058] Furthermore, the second module 8 has a bypass switch 10, which is arranged in a connecting line 14 parallel to the second module 8 and is designed to bridge the second module 8 or the two sub-modules 9. The connecting line 14 terminates in a load discharge line 15.

[0059] The first module 7 comprises a first control unit 11, which is preferably designed as a motor drive, particularly preferably as a direct drive without an intermediate gear, which actuates the selector and the load changeover switch.

[0060] The second module 8 is controlled by a second control unit 12. The second control unit 12 is designed to actuate the two sub-modules 9 or their associated commutation cells in a suitable manner such that the two partial windings 4 and 5 are quickly connected to, counter-connected to, or bridged with the control winding 3. Furthermore, the second control unit 12 is designed to actuate the bypass switch 10.

[0061] The first control unit 11 and the second control unit 12 are operated by a system controller 13 in dependence on one another.

[0062] Figure 2 shows a schematic representation of a second embodiment of the electrical device according to the improved concept. With regard to the electrical device 1 in Figure 2, reference is made analogously to the preceding explanations regarding the electrical device in Figure 1, and only the differences and additions to the electrical device 1 in Figure 1 are discussed below.

[0063] Figure 2 shows an electrical device 1 designed as a controllable choke. Such arrangements are used for reactive power control in the energy supply network. The controllable choke 1 has, in addition to a main winding 2, a control winding 3 with n winding taps and two partial windings 4 and 5, a coarse step winding 16 and a coarse step controller 17. The coarse step controller 17 can assume a first position in which it contacts a first end A of the coarse step winding 16, and a second position in which it contacts a second end B of the coarse step winding 16. If the coarse step controller 17 is in the first position, no current flows through the coarse step winding 16. If, on the other hand, the coarse step controller 17 is in the second position, current flows through the coarse step winding 16 and is consequently added to the main winding 2 and the control winding 3. In this way, the control range of throttle 1 is increased.

[0064] The reactor 1 is housed in a tank 18 and has a core 19 on which the windings 2, 3, 16, 4, 5 are arranged. The on-load tap-changer 7 is also arranged in this tank 18. The electrical lines of the on-load tap-changer 7 and the windings 2, 3, 16, 4, 5 are led out of the tank 18 via bushings 20. Outside the tank 18, flexible cables, for example, can be connected to the bushings 20, which in turn lead to the second module 8 and / or the control units 11, 12.

[0065] According to this exemplary embodiment, the second module 8, which is shown here in a simplified manner, and the bypass switch 10 are arranged together in a first housing 21, and the first control unit 11, the second control unit 12, and the system controller 13 are arranged together in a second housing 22. The housings 21 and 22 can be designed as commercially available switch cabinets or containers and can be arranged directly on the tank 18 of the reactor 1 or the electrical equipment, or in close proximity, for example within the substation in which the equipment 1 is located. It is also possible to arrange the second module 8, the bypass switch 10, the control units 11 and 12, and the system controller 13 in a common housing, or to provide separate housings for the individual units.

[0066] Figure 3 shows a third embodiment of the electrical device according to the improved concept in a schematic representation. With regard to the electrical device 1 in Figure 3, reference is made analogously to the preceding explanations regarding the electrical device in Figures 1 and 2, and only the differences and additions to the electrical device 1 in Figures 1 and 2 are discussed below.

[0067] Figure 3 shows an electrical device 1 designed as a phase-shifting transformer. For the sake of clarity, the phase-shifting transformer 1 is shown here as a single-phase example. The phase-shifting transformer 1 shown in Figure 3 is designed as a cross-regulator for active power control and has a dual-core design consisting of a series transformer 23 and an excitation transformer 24, each arranged on a core. The excitation transformer 24 has a primary side with a main winding 2 and a secondary side comprising a control winding 3 with n winding taps and two partial windings 4 and 5 as well as an on-load tap changer 6. A voltage is coupled out on the primary side of the excitation transformer 24, and this voltage is regulated on the secondary side as an additional voltage via the control winding 3 and the two partial windings 4 and 5 by means of the on-load tap changer 6.In the series transformer 23, this additional voltage, generated in the excitation transformer 24, is connected in a delta configuration. This results in a phase shift of the additional voltage by 90 degrees relative to the input voltage at the phase-shifting transformer.

[0068] The electrical device shown in Figure 3 in the form of a phase-shifting transformer is not limited to the embodiment shown. The phase-shifting transformer can equally well be designed in a symmetrical or asymmetrical dual-core design, in a single-core design with a control winding at the star point, as a quadrature regulator or skew regulator, or even as an autotransformer with two iron circuits and a grounded booster circuit.

[0069] Figure 4 shows a flow diagram of an advantageous embodiment of a method according to the improved concept, in particular a method for commissioning an electrical equipment 1 according to one of the embodiments as explained in connection with Figures 1 to 3.

[0070] In the initial situation, a circuit breaker associated with electrical equipment 1 is open, meaning the circuit between the electrical equipment and a corresponding power grid to which the electrical equipment is associated is interrupted. In other words, the electrical equipment is disconnected from the associated power grid. Likewise, bypass switch 10 is open.

[0071] To commission the electrical equipment, the bypass switch 10 is now closed in step a. In the next step b, the circuit breaker is closed, thus connecting the electrical equipment 1 to the power grid. Connecting the electrical equipment 1 to the grid can result in increased inrush currents (the so-called inrush effect). However, these flow via the closed bypass switch 10 of the second module 8, so that the sub-modules 9 with the semiconductor switching elements are not damaged. From this point on, the second module is already ready for operation and can be used to change the transformation ratio, the impedance, or the voltage used for excitation of the electrical equipment 1. In the next step c, the second module 8 is commutated to the neutral position, in which the sub-windings 4 and 5 are bridged, i.e., no current flows through them.In the next step (d), the bypass switch 10 is opened again. The second module 8 is now also ready for operation and can be used alongside the first module 7 to change the transformation ratio, the impedance, or the voltage used for excitation of the electrical equipment.

[0072] The combination of a conventional on-load tap-changer, a first module, with a power electronic tap-changer, a second module, enables the realization of a large control range while simultaneously providing a cost-effective and space-saving arrangement with high potential. This is because the second module, which is more cost-intensive than the first module and is designed for fast control in the dynamic control range, can be optimized for the respective application. Consequently, the second module can be designed accordingly only for the part of the control for which the power electronic-based second module offers an advantage due to its speed of sound. In addition, the combined solution is significantly more space-saving than a purely power electronic-based solution. In summary, the solution according to the invention enables a high degree of flexibility with comparatively little space requirement for network management and furnace operation.

[0073] REFERENCE SYMBOL

[0074] Electrical equipment

[0075] Main winding

[0076] Control winding first partial winding

[0077] 5 second partial winding

[0078] 6 step switch first module of 6

[0079] 8 second module of 6

[0080] Submodule of 8

[0081] 10 Bypass switch first control unit

[0082] 12 second control unit

[0083] 13 Control Panel

[0084] connecting line

[0085] 15 Load transfer

[0086] coarse tap winding

[0087] Coarse step control

[0088] 18 boilers

[0089] 19 core

[0090] 20 Implementation

[0091] 21 first housing

[0092] 22 second housing

[0093] 23 Series transformer

[0094] 24 Excitation transformer

[0095] A first end of 16 B second end of 16 n-1 , n, ... n+4 winding taps

Claims

CLAIMS Electrical equipment (1 ) comprising - at least one control winding (3) with winding taps (n, n+1) and at least one partial winding (4, 5), a step switch (6) for changing a transformation ratio, an impedance or a voltage used for excitation of the electrical equipment (1), wherein - the tap changer (6) comprises a first module (7) for connecting the winding taps (n, n+1) of the control winding (3) and a second module (8) for quickly connecting, counter-connecting or bridging the at least one partial winding (4, 5), - the second module (8) comprises at least one sub-module (9) with semiconductor switching elements and a bypass switch (10). Electrical equipment (1) according to claim 1, wherein the at least one partial winding (4, 5) is at least as large as a portion of the control winding (3) located between two adjacent winding taps (n, n+1) of the control winding (3). Electrical equipment (1) according to one of the preceding claims 1 or 2, wherein - the bypass switch (10) is designed to bridge the second module (8) with the at least one sub-module (9) with semiconductor switching elements. Electrical equipment (1) according to one of the preceding claims 1 to 3, wherein - the bypass switch (10) is designed as a circuit breaker or load-break switch. Electrical equipment (1) according to one of the preceding claims 1 to 4, wherein - the step switch (6) can be actuated in a predefined operating mode in which the bypass switch (10) is closed and the at least one sub-module (9) is bridged with semiconductor switching elements.

6. Electrical equipment (1) according to claim 5, wherein - when the tap changer (6) is in the predefined operating mode, only the first module (7) is used to change the transformation ratio, the impedance or the voltage used for excitation of the electrical equipment (1).

7. Electrical equipment (1) according to one of the preceding claims 1 to 6, wherein - the first module (7) comprises a first control unit (11), - the second module (8) comprises a second control unit (12), - the electrical equipment (1) comprises a system controller (13) which is designed to actuate the first control unit (11) and the second control unit (12).

8. Electrical equipment (1) according to claim 7, wherein - the second module (8) and / or the first control unit (11) and / or the second control unit (12) and / or the system controller (13) are each arranged in a separate housing or in a common housing.

9. Electrical equipment (1) according to claim 7 or 8, wherein - the first control unit (11) comprises a motor drive, - the motor drive is designed as a direct drive without an intermediate gearbox.

10. Electrical equipment (1) according to one of the preceding claims 1 to 9, wherein - the bypass switch (10) is arranged in a separate housing or with the second module (8) in a common housing.

11. Electrical equipment (1) according to one of the preceding claims 1 to 10, wherein - the first module (7) is designed as a resistance switch or as a reactor switch.

Images