Method and device for changing transformation ratio, impedance or voltage for excitation
By combining tap-and-electronic tap-and-tap switches, semiconductor switching elements are used to quickly adjust the transformer ratio and impedance of electrical equipment, solving the problems of steady-state and dynamic adjustment in the prior art, achieving high flexibility and low cost Electrical equipment management.
Patent Information
- Application Number
- CN202380039549.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-11
- Filing Date
- 2023-04-24
- Publication Date
- 2024-12-20
AI Technical Summary
The prior art is difficult to simultaneously adjust the transformer ratio and impedance of electrical equipment in the steady state and dynamic range, especially under rapid changing conditions such as arc furnaces, resulting in network reaction and the use of high-cost compensation equipment.
Combining a typical tap-off switch with a power electronic tap-off switch, using semiconductor switching elements to quickly change voltage and load matching, achieve adjustment in the millisecond range, and switching winding taps without interruption through selector and switch, combined with evaluation unit optimization Adjustment strategy.
It realizes flexible adjustment in steady-state and dynamic range, reduces cost and space requirements, improves network management flexibility and response speed, and reduces losses.
Smart Images
Figure CN119174076A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for changing the transformation ratio, impedance or voltage for excitation of an electrical device and a device for changing the transformation ratio, impedance or voltage for excitation of an electrical device. Background Art
[0002] When regulating an energy supply network, a distinction is made between two different time ranges. In the so-called steady-state range, a static operating point is set with the aid of suitable devices in the energy supply network, which allows reliable operation of the network in the event of small loads and supply fluctuations. Regulation is carried out in this case in cycles of minutes. In the dynamic range, suitable devices are used to react to dynamic fluctuations in the network, which can be caused, for example, by faults or by rapid and possibly only temporary changes in the supply and load conditions. In this case, very rapid regulation in the millisecond range is necessary in order to keep the network stable.
[0003] Since the reactive power demand also changes with the respective supply and load conditions, reactive power regulation represents an important factor for reliable, efficient and loss-minimized network management.
[0004] Suitable devices are already known from the prior art for both network regulation in the steady-state range and for dynamic voltage regulation. Thus, for regulating static network operation, for example, adjustable transformers, phase shifters or adjustable shunt reactors are used. For regulating dynamic network behavior, for example, static synchronous compensators (STATCOM) or static VAR compensators (SVC) are used.
[0005] In particular, devices for regulating in a dynamic range will become increasingly important for the management of grid operation with reliable supply in the future due to energy transition and the integration of decentralized energy generation into grid operation, since the supply from renewable energy sources may not be easily planned.
[0006] In addition to the regulation of the energy supply network, the above-mentioned different time frames also play an important role in the energy supply of the electric arc furnace. The corresponding furnace transformer for supplying the electric arc furnace usually contains a tap changer, by means of which the power of the furnace transformer is regulated in the range of a few seconds to a few minutes. Due to the rapidly changing operating conditions in the electric arc furnace, such as the sudden interruption of the arc for the melt, however, in the electric arc furnace, undesirable network reactions, such as flickers, are often caused with time constants in the millisecond range. In order to limit these network reactions, complex and costly compensation devices (SVC) are usually also used.
[0007] To date, no devices are known from the prior art which are capable of combining both regulation in the steady-state range or in the range of seconds to minutes and regulation in the dynamic range or in the millisecond range. Summary of the invention
[0008] The object of the present invention is therefore to propose an improved design for regulating an energy supply network or an energy supply device, which provides a combined flexible regulation solution for serving / coping with these two time ranges, which is also cost-effective, space-saving and low-loss in operation and in production.
[0009] This object is achieved by the methods and the subject matter of the independent claims. Further embodiments are the subject matter of the dependent claims.
[0010] The improved design is based on the idea of combining a typical tap changer (as is well known from the prior art) with a power electronic tap changer connected in series with the typical tap changer. Since the power electronic tap changer can change its connection position quickly (i.e. in the millisecond range) and can assume any arbitrary position in the process, this allows the voltage to be quickly adapted to rapidly changing load situations. The steady-state range is served by means of the typical tap changer, wherein the largest possible regulation range is covered. Thus, a high degree of flexibility can be achieved for network management and also for device management or process management.
[0011] According to a first aspect of the improved design, a method for changing a transformation ratio, an impedance or a voltage for excitation of an electrical device is provided. The electrical device comprises at least one main winding, a regulating winding having a winding tap and at least one sub-winding. In addition, the electrical device comprises a tap changer for changing a transformation ratio, an impedance or a voltage for excitation of the electrical device.
[0012] The electrical device can be designed as a controllable transformer, in particular also as a phase shifter transformer, as a controllable inductor or as a controllable transformer with a capacitor.
[0013] The tap changer comprises a first module for connecting winding taps of a regulating winding and a second module having semiconductor switching elements for rapidly switching on, reversing or bridging the at least one partial winding.
[0014] The at least one subwinding has a number of turns which is preferably greater than the maximum number of turns between two adjacent winding taps of the regulating winding. In the case where the electrical device has a plurality of subwindings, the number of turns of the plurality of subwindings can be integer multiples of each other.
[0015] According to one embodiment, the first module is configured as an on-load tap changer for switching between different winding taps of a regulating winding of an electrical device without interruption, and has a selector and an on-load switch, wherein the selector is used to preselect the winding tap of the electrical device to be switched thereto without power, and the on-load switch is used to switch from the winding tap that has been connected so far to a new preselected winding tap without interruption. In order to preselect the winding tap without power, the selector usually has two movable selector contacts, which connect the winding taps. The on-load switch usually has a switching contact and a resistor for real on-load switching. The switching contact is configured as a vacuum switching tube, for example. The resistor is used to limit the loop current that flows briefly in the on-load switch during the switching process and is also called a transition resistor.
[0016] According to one embodiment, the second module comprises at least one submodule having a semiconductor switching element, preferably a plurality of submodules if the electrical device has a plurality of subwindings, each submodule being assigned at least one subwinding and each submodule being configured to quickly switch on, reverse or bridge the assigned subwinding.
[0017] According to another embodiment, the semiconductor switching elements each include a pair of thyristors or a pair of IGBTs connected in anti-parallel.
[0018] A method for changing a transformation ratio, an impedance or a voltage for excitation of an electrical device comprises the following steps:
[0019] a) Input requirements for changing the transformation ratio, impedance or excitation voltage of electrical equipment,
[0020] b) checking at least one relevant characteristic parameter,
[0021] c) Depending on the checking of the at least one relevant characteristic variable, a transformation ratio, an impedance or a voltage for excitation of the electrical device is changed either by means of the first module or by means of the second module.
[0022] According to one embodiment, the relevant characteristic variable includes the value of the deviation of the actual voltage of the electrical device (for example, the voltage on the primary side or the secondary side of the transformer) from a preset theoretical voltage. If the value of the deviation from the theoretical voltage is greater than the tap voltage present between two adjacent winding taps of the regulating winding, the transformation ratio is changed by means of the second module.
[0023] According to this embodiment, the electrical device is designed as an adjustable transformer. In other words, when the voltage to be adjusted or the desired voltage change takes on a value that is too great to be achieved by actuating the first module, the transformation ratio of the transformer is changed, that is, adapted to the desired setpoint voltage on the primary side or the secondary side of the transformer, by means of the second module.
[0024] According to another embodiment, the relevant characteristic variable includes the value of the deviation of the impedance of the electrical device from a predefined theoretical impedance. If the value of the deviation from the theoretical impedance is greater than the impedance acting between two adjacent winding taps of the regulating winding, the impedance is changed by means of the second module.
[0025] According to this embodiment, the electrical device is designed as an adjustable choke. In other words, the impedance of the choke is changed, that is to say matched to the desired setpoint impedance, by means of the second module, when the value of the impedance to be adjusted or the desired impedance change is too great to be achieved by actuating the first module.
[0026] According to another embodiment, the relevant characteristic variable comprises the value of the deviation of the actual voltage in the first inductive component for excitation of the second inductive component from a predefined setpoint voltage. The actual voltage is measured, for example, on the primary side of the first inductive component or on the secondary side of the second inductive component. If the value of the deviation from the setpoint voltage is greater than the tap voltage present between two adjacent winding taps of the regulating winding, the voltage for excitation of the second inductive component is adjusted by means of the second module.
[0027] According to this embodiment, the electrical device comprises a first inductive component and a second inductive component. The second inductive component is excited by means of an actual voltage in the first inductive component, thereby increasing the power of the first inductive component.
[0028] In the arrangement, an excitation transformer, a first inductive component, a step-up transformer, and a second inductive component are added, thereby making it possible to more flexibly adjust the operating parameters (current and voltage) of the tap changer, especially in units with high power.
[0029] In other words, the voltage for excitation of the step-up transformer is regulated by means of the second module when the desired voltage for excitation of the step-up transformer assumes such a value that the change cannot be achieved by actuating the first module.
[0030] According to one implementation form of this embodiment, the electrical device can be designed as a phase shifter, and the first inductive component can be designed as an excitation transformer, and the second inductive component can be designed as a step-up transformer. Therefore, the method can also be used similarly to operate a phase shifter transformer.
[0031] According to another embodiment, the relevant characteristic variable comprises the gradient of the required voltage change. If the gradient of the required voltage change is greater than a determined limit value, the transformation ratio is changed by means of the second module.
[0032] According to this embodiment, the electrical device is designed as a regulated transformer. In other words, if the gradient of the required voltage change is so high (for example, the required voltage change speed is in the millisecond range) that the change of the transformation ratio cannot be carried out quickly enough by means of the first module, the change of the transformation ratio of the transformer, that is, the adaptation to the desired setpoint voltage on the primary side or the secondary side of the transformer is carried out by means of the second module. Accordingly, the determined limit value is, for example, one second.
[0033] According to another embodiment, the relevant characteristic variable comprises the gradient of the required impedance change. If the gradient of the required impedance change is greater than a determined limit value, the impedance is changed by means of the second module.
[0034] According to this embodiment, the electrical device is designed as an adjustable choke. In other words, if the gradient of the required impedance change is so high (for example, the required impedance change speed is in the millisecond range) that the impedance cannot be changed quickly enough by means of the first module, the impedance of the choke is changed, that is, the adaptation to the desired theoretical impedance is carried out by means of the second module. Accordingly, the limit value determined is, for example, one second.
[0035] According to another embodiment, the relevant characteristic variable comprises a fundamental oscillation of the voltage present at the electrical device together with harmonic components. If the harmonic components are greater than a determined limit value, the transformation ratio is changed by means of the second module.
[0036] According to this embodiment, the electrical device is designed as an adjustable transformer. In other words, when the harmonic components above the fundamental oscillation of the voltage present at the transformer are so high that the harmonics can no longer be adjusted / leveled by means of the first module, the transformation ratio of the transformer is changed, that is to say, adapted to the desired setpoint voltage on the primary side or the secondary side of the transformer, by means of the second module. The definition of the limit values depends on the respective device configuration and the network connection conditions.
[0037] According to a further embodiment, a Fourier analysis is carried out in order to determine harmonic components above a fundamental oscillation of the voltage present at the electrical device, preferably above a fundamental oscillation of the voltage present on the grid connection side of the electrical device.
[0038] According to another embodiment, after the transformation ratio, the impedance or the voltage for excitation is changed by means of the second module, the first module and the second module are manipulated so that the second module assumes a neutral position in which the at least one sub-winding is bridged. Bridged, that is, at potential but without current flowing. In other words, the semiconductor switching elements of the second module are connected to one another in such a way that a bypass is formed for the at least one sub-winding.
[0039] According to one specific embodiment, the first module and the second module are actuated alternately.
[0040] According to a further embodiment, the first module and the second module are actuated alternately until the first module has reached a position which indicates a new static operating point of the energy supply network and the second module is in a neutral position.
[0041] In other words, after switching the second module, the first module is tightened in stages by adjusting the winding ratio by switching between the winding taps of the regulating winding with the aid of the first module and by disconnecting the at least one partial winding again in this case by actuating the semiconductor switching elements of the second module in stages. Finally, the tap changer is then in a position in which the first module has once again assumed a new static operating point and the second module is in a neutral position.
[0042] In this embodiment, it is advantageous if the tap changer is then back in the original position in which no current flows through the at least one partial winding and if, starting from the neutral position, the entire control range is again available to the second module in both directions.
[0043] According to another embodiment, after changing the transformation ratio, the impedance or the voltage for excitation by means of the second module, the first module and the second module are manipulated so that the second module occupies a first end position, from which the entire dynamic adjustment range of the second module is available from the first end position to the second end position.
[0044] For example, in a first end position of the second module, the at least one subwinding of the regulating winding is connected, that is, the turns of the subwinding are added to the regulating winding, and in a second end position, the subwinding of the regulating winding is reversed, that is, the turns of the subwinding are subtracted from the regulating winding.
[0045] In this embodiment, it is advantageous if the entire regulating range of the second module is available for certain network requirements, which require a rapid response in one direction.
[0046] According to another embodiment, a plurality of relevant characteristic parameters are checked and weighted with respect to their importance. Depending on the checking and weighting of the relevant characteristic parameters, the transformation ratio, the impedance or the voltage for excitation is changed either by means of the first module or by means of the second module.
[0047] According to one specific embodiment, the first module and the second module are not actuated simultaneously.
[0048] According to a second aspect of the improved design, a device for changing a transformation ratio, an impedance or a voltage for excitation of an electrical device is provided. Preferably, the device is configured to implement the method according to the first aspect of the present invention.
[0049] With regard to the device, reference is made in an analogous manner to the above explanations, preferred features, functions and / or advantages as have already been explained with respect to the method, so that a corresponding repetition is dispensed with.
[0050] The electrical device comprises at least one main winding, a regulating winding having winding taps, at least one sub-winding and a tap changer for changing a transformation ratio, an impedance or a voltage for excitation of the electrical device.
[0051] The device comprises at least one sensor for measuring the voltage present at a suitable measuring point and / or at least one sensor for measuring the current flowing at a suitable measuring point.
[0052] Furthermore, the device has an evaluation unit which is designed to carry out the method according to the first aspect of the development.
[0053] According to one embodiment, the tap changer comprises a first module for connecting the winding taps of the regulating winding and a second module having a semiconductor switching element for quickly switching on, reversing or bridging the at least one sub-winding. The first module comprises a first control unit and the second module comprises a second control unit. The evaluation unit is configured to operate the first control unit and the second control unit.
[0054] According to one embodiment, the first module is designed as an on-load tap changer for switching between different winding taps of a regulating winding of an electrical device without interruption and has a selector for powerless preselection of the winding tap of the electrical device to which it is to be switched and an on-load switch for truly non-interruptible switching from the previously connected winding tap to a new preselected winding tap. For powerless preselection of the winding tap, the selector usually has two movable selector contacts, which connect the winding taps. The on-load switch has mechanical switching contacts, such as vacuum switching tubes, for true on-load switching.
[0055] According to a further embodiment, the first control unit is designed as a motor drive which actuates the selector contacts and the switching contacts of the on-load tap changer.
[0056] According to one embodiment, the second module includes at least one submodule having a semiconductor switching element, and preferably includes multiple submodules in the case where the electrical device has multiple subwindings. Each submodule is equipped with at least one subwinding, and each submodule is configured to quickly connect, reverse, or bridge the assigned subwinding.
[0057] According to another embodiment, the second control unit is designed to actuate the at least one or more submodules or their associated semiconductor switching elements in a suitable manner such that the at least one or more partial windings are quickly connected or reversed to the regulating winding or bridged.
[0058] The second control unit is designed as a microcontroller, for example. BRIEF DESCRIPTION OF THE DRAWINGS
[0059] In the following, the invention is explained in detail on the basis of exemplary embodiments with reference to the drawings. Identical components or components with the same function or having the same effect may be provided with the same reference numerals. Identical components or components with the same function may only be explained with respect to the drawing in which they first appear. The explanation does not have to be repeated in the subsequent drawings.
[0060] Figure 1 A first embodiment of the device according to the improved design is shown in a schematic diagram;
[0061] Figure 2 A second embodiment of the device is shown in a schematic illustration;
[0062] Figure 3 A third embodiment of the device is shown in a schematic illustration;
[0063] Figure 4 A fourth embodiment of the device is shown in a schematic illustration;
[0064] Figure 5 A fifth embodiment of the device is shown in a schematic illustration;
[0065] Figure 6 A sixth embodiment of the device is shown in a schematic illustration;
[0066] Figure 7 A preferred embodiment of the method according to the improved design is shown;
[0067] Figure 8The adjustment range of the tap changer in the device according to one embodiment of the method according to the improved design is shown;
[0068] Fig. 9 A further adjustment range of a tap changer in an arrangement according to a further specific embodiment of the method according to this further development is shown. DETAILED DESCRIPTION
[0069] exist Figure 1 In FIG. 1 , an advantageous embodiment of the device 1 according to this improved design is shown in a schematic illustration.
[0070] The device 1 is used to change the transformation ratio of an electrical device 14 which is designed as a single-phase adjustable transformer. The adjustable transformer 14 has a main winding 2, a regulating winding 3 with n winding taps and two partial windings 4 and 5 on the primary side or the secondary side.
[0071] The subwinding 5 has a greater number of turns, for example three times as many turns, than the subwinding 4. Furthermore, the number of turns of the subwinding 4 and thus also of the subwinding 5 is greater than the maximum number of turns present between two adjacent winding taps of the regulating winding 3, for example between n and n+1.
[0072] The number of partial windings is not limited to two. In principle, a plurality of partial windings can also be provided, the number of windings of which can each have an integer multiple of the number of partial windings 4.
[0073] Furthermore, the transformer 14 has a tap changer 6 for changing the transformation ratio of the transformer 14. The tap changer 6 comprises a first module 7 for connecting the winding taps n, n+1 of the regulating winding 3 and a second module 8 connected in series to the first module 7 and for connecting, reversing or bridging the sub-windings 4, 5. The first module 7 is provided for regulation in the steady-state range and the second module 8 is provided for regulation in the dynamic time range.
[0074] Preferably, the first module 7 as an on-load tap changer comprises a selector for power-free preselection of winding taps n, n+1 and an on-load switch for switching from the previously connected winding tap to the preselected new winding tap n+1 without interruption. Furthermore, the on-load tap changer can have a preselector, which can be designed as a coarse selector or a diverter. However, for the sake of greater clarity, the first module 7 is not shown in FIG. Figure 1 2 is shown in a significantly simplified manner.
[0075] Preferably, the second module 8 has two submodules, which have semiconductor switching elements, such as anti-parallel thyristor pairs or IGBT pairs. Each submodule is respectively equipped with a subwinding 4 or 5 and each submodule is designed to quickly connect or reverse the corresponding subwinding 4 or 5 of the regulating winding 3 by means of a semiconductor switching element, that is, within 10 to 1000 milliseconds, or bridge the corresponding subwinding 4 or 5 so that the subwindings 4, 5 have a certain potential, but no current flows. For the sake of clarity, the second module 8 is Figure 1 2 is also shown in a significantly simplified manner.
[0076] Furthermore, the device 1 has a voltage sensor 9 and a current sensor 10. The voltage sensor 9 is arranged, for example, at the high-voltage end of the main winding 2 and is designed to measure the system voltage or actual voltage. The current sensor 10 is arranged between the second module 8 and the load lead 15 and is designed to measure the current flowing between the second module 8 and the load lead 15.
[0077] The first module 7 comprises a first control unit 11 , which is preferably designed as a motor drive, which actuates the selector and the on-load changeover switch mechanically, for example via a drive train with a gear mechanism.
[0078] The second module 8 is controlled by a second control unit 12. The second control unit 12 is configured to actuate the two submodules or their associated semiconductor switching elements in a suitable manner so that the two subwindings 4 and 5 are quickly connected or reversed to the regulating winding 3 or bridged. The second control unit 12 is configured, for example, as a microcontroller or an IGBT driver.
[0079] The first control unit 11 and the second control unit 12 are controlled by the evaluation unit 13 in a manner dependent on one another.
[0080] exist Figure 2 In FIG. 1 , a second embodiment of the device 1 according to the invention is schematically shown. Figure 2 The device 1 is similarly referred to above with respect to Figure 1 and only discusses the device from Figure 1 The difference between the devices.
[0081] Figure 2A device 1 for changing the impedance of an electrical device 14 is shown, which is designed as an adjustable choke. Such components are used for reactive power regulation in energy supply networks. In addition to a main winding 2, a regulating winding 3 with n winding taps and two sub-windings 4 and 5, the adjustable choke 14 additionally has a coarse winding 16 and a coarse regulator 17. The coarse regulator 17 can assume a first position, in which the coarse regulator is in contact with a first end A of the coarse winding 16, and a second position, in which the coarse regulator is in contact with a second end B of the coarse winding 16. If the coarse regulator 17 is in the first position, no current flows through the coarse winding 16. Conversely, if the coarse regulator 17 is in the second position, current flows through the coarse winding 16 and is thereby added to the main winding 2 and the regulating winding 3. In this way, the adjustment range of the choke 14 is increased. The intake of reactive power from the grid is regulated by means of the device 1 according to this embodiment.
[0082] exist Figure 3 In FIG. 1 , a third embodiment of the device 1 according to the invention is schematically shown. Figure 3 The device 1 is similarly referred to above with respect to Figure 1 and Figure 2 An explanation of the device of FIG. 1 is given below and only the differences are discussed below.
[0083] Figure 3 The device 1 for changing the transformation ratio of an electrical device 14 is shown, which is designed here as a variable transformer 14 with a connected capacitor 18. The supply of capacitive reactive power into the network is regulated by means of the device 1 according to this embodiment. The variable transformer 14 can, for example, include a series winding 19, a regulating winding 3 and a main winding 2 with a load lead 15. The capacitor 18 is arranged between the first module 7 and the second module 8 of the tap changer 6.
[0084] exist Figure 4 In the figure, a fourth embodiment of the device 1 according to the invention is schematically shown, which is Figure 3 1 is also shown for changing the transformation ratio of an electrical device 14, which is designed as an adjustable transformer 14 with a connected capacitor 18. Therefore, in this case, reference is also made in a similar manner to the above description of the voltage transformer from Figure 1 , Figure 2 and Figure 3 An explanation of the device of FIG. 1 is given below and only the differences are discussed below.
[0085] In this embodiment, the adjustable transformer 14 comprises a main winding 2, a regulating winding 3 with n winding taps, two sub-windings 4 and 5 and an additional coarse winding 16 with a coarse regulator 17. A capacitor 18 for leveling the capacitive reactive power into the energy supply network is arranged in an electrical line 20 which branches between the main winding 2 and the coarse winding 16 and ends in the load lead 15.
[0086] exist Figure 5 A fifth embodiment of the device 1 according to the invention is schematically shown in FIG. Figure 5 The device 1 is similarly referred to above with respect to Figure 1 , Figure 2 , Figure 3 and Figure 4 An explanation of the device of FIG. 1 is given below and only the differences are discussed below.
[0087] Figure 5 A device 1 for changing the voltage for excitation of an electrical device 14 is shown, which is used, for example, in arc furnace applications. In this case, the electrical device 14 comprises a first inductive component 22, which is designed as an excitation transformer, and a second inductive component 23, which is designed as a step-up transformer. The excitation transformer 22 comprises a main winding 2, a regulating winding 3 with n winding taps, and two sub-windings 4 and 5. The step-up transformer 23 has a primary winding 24 and a secondary winding 25, wherein an arc furnace 21 is arranged on the secondary side. The regulating winding 3 of the excitation transformer 22 is electrically conductively connected to the primary winding 24 of the step-up transformer 23. In this embodiment, the voltage of the excitation transformer 22 is adjusted by a tap changer 6, which voltage is used for the excitation of the step-up transformer 23. Depending on whether the adjustment is carried out in the steady-state range or in the dynamic range, the first module 7 or the second module 8 is used.
[0088] exist Figure 6 , a sixth embodiment of the device 1 according to the invention is schematically shown. Figure 6 The device 1 is similarly referred to above with respect to Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 An explanation of the device of FIG. 1 is given below and only the differences are discussed below.
[0089] Figure 6Another device 1 for changing the voltage for excitation of an electrical device 14 is shown, which is used, for example, in arc furnace applications. Here, the electrical device 14 also includes a first inductive component 22 and a second inductive component 23, the first inductive component being designed as an excitation transformer and the second inductive component being designed as a step-up transformer. In this embodiment, the excitation transformer 22 has a primary winding 26 and a secondary winding 27, and the step-up transformer 23 has a regulating winding 24 on the primary side. The secondary winding 27 of the excitation transformer 22 is electrically conductively connected to the regulating winding 24 or to the primary side of the step-up transformer 23. At the regulating winding 24 of the step-up transformer 23, the voltage excited / excited in the step-up transformer 23 by the excitation transformer 22 is adjusted by means of the tap changer 6.
[0090] Figure 7 A flow chart of an advantageous embodiment of the method according to the improved design is shown. The method is carried out by means of an apparatus according to any of the embodiments described (such as it has been combined with Figures 1 to 6 In step a, a request for changing the transformation ratio, impedance or voltage for excitation of the electrical device 14 is input. The request can be input by a higher-level system, for example, by a dispatch station of an energy supply network operator, or can be input by a control mechanism before this location, for example, a voltage regulator. Then, in step b, at least one relevant characteristic variable is checked, and in step c, the transformation ratio, impedance or voltage for excitation of the electrical device 14 is changed by means of the first module 7 or the second module 8 of the tap changer 6 depending on the check of the at least one relevant characteristic variable.
[0091] Step b and step c are carried out by means of an evaluation unit 13 which, depending on the check carried out in step b, actuates either the first control unit 11 or the second control unit 12 .
[0092] In step b, different relevant characteristic parameters can be checked. For example, the relevant characteristic variable can be the value of the deviation of the actual voltage of the electrical device 14 from the preset theoretical voltage. For this purpose, the actual voltage or the device voltage is measured by means of the voltage sensor 9, and the measured value is compared with the preset theoretical voltage by means of the evaluation unit 13. In this case, when the value of the deviation from the theoretical voltage is greater than the tap voltage present between two adjacent winding taps of the regulating winding 3, for example between n and n+1, the transformation ratio is changed by means of the second module 8. Another example of a relevant characteristic variable that can be checked is the value of the deviation of the impedance of the electrical device 14 from the preset theoretical impedance. For this purpose, the impedance of the electrical device 14 is determined based on the current value measured by means of the current sensor 10, and the determined value is compared with the preset theoretical impedance by means of the evaluation unit 13. When the value of the deviation from the theoretical impedance is greater than the impedance acting between two adjacent winding taps n and n+1 of the regulating winding 3, the impedance is changed by means of the second module 8. Other examples of relevant characteristic variables are the gradient of the required voltage change, the gradient of the required impedance change, or the value of the deviation of the actual voltage in first inductive component 22 for excitation of second inductive component 23 from a predefined setpoint voltage.
[0093] If the transformation ratio, the impedance or the voltage for excitation is changed with the aid of the second module 8, then according to an advantageous embodiment of the method the first module 7 and the second module 8 are alternately actuated until the first module 7 has reached a position indicating a new static operating point of the energy supply network or process drive system and the second module 8 is in a neutral position in which the sub-windings 4 and 5 are bridged, i.e. are at electrical potential but no current flows.
[0094] In other words, after the second module 8 is switched, the first module 7 is "tightened" in stages. If, for example, the second module 8 is switched upwards from the neutral position (0) by two steps (+2), in the next step the first module 7 is switched upwards by one step (+1) and the second module is switched downwards by one step (-1). In the following step, the first module 7 is again switched upwards by one step (+1) and the second module 8 is again switched downwards by one step (-1). Finally, the first module 7 is two steps higher than before and the second module 8 is again in its neutral position. By means of the described "tightening" of the first module 7, the first module 7 has been adjusted to a new static operating point. Starting from the neutral position, the entire adjustment range upwards or downwards is again available to the second module 8.
[0095] exist Figure 8, the previously described content about the variable impedance is presented in a graphical manner. The adjustment range of the tap changer 6, more precisely the reactive power adjustment range, is shown here. The percentage share of the reactive power of the inductive device 14 is plotted on the y-axis. The position of the first module 7 of the tap changer 6 can be read on the x-axis, that is, which winding tap n of the regulating winding 3 is contacted by the first module 7 of the tap changer 6. Point 28 marks the possible positions that the first module 7 can assume, wherein the adjustment is carried out in the steady-state range, that is, in a cycle of minutes. Point 30 represents the static operating point, which is adjusted by the first module 7 according to this embodiment. The range bounded by the line 29 extending vertically upwards and downwards from the point 28 or 30 is the adjustment range covered by the second module 8. In the range bounded by the line 29, the adjustment is carried out quickly, that is, in the millisecond range, that is, in both directions, by means of the second module 8, so that dynamic fluctuations in the network or in the device can be reacted flexibly and quickly. As a result, the fast but also expensive semiconductor switching element does not have to be designed for the entire adjustment range of the tap changer 6 , but only for the range that must be adjusted quickly.
[0096] exist Fig. 9 In FIG. 1 , a further regulating range, more precisely a reactive power regulating range, of the tap changer 6 according to another embodiment of the method is presented in a diagrammatic manner. According to this embodiment, after the transformation ratio, the impedance or the voltage for excitation is changed by means of the second module 8, the first module 7 and the second module 8 are manipulated in such a way that the second module 8 assumes a first end position in which the turns of the partial windings 4 and 5 are either both added to the regulating winding 3 or subtracted from the regulating winding. In this embodiment, the respective end position describes the operating point 30. Depending on which case is applicable, the entire dynamic regulating range of the second module 8 is available starting from the operating point 30 in the direction from the first end position to the second end position or in the opposite direction. This embodiment is advantageous for certain network requirements, which require the tap changer 6 to react quickly in one direction.
[0097] The combination of a typical on-load tap changer (first module) and a power electronic tap changer (second module) enables a large adjustment range at high potential in a cost-effective and space-saving arrangement. Because the second module for fast adjustment in the dynamic adjustment range, which is more expensive than the first module, can be optimally designed for the corresponding application. As a result, the second module can be designed only for partial adjustment, and the second module based on power electronics provides advantages for partial adjustment due to its switching speed. It is achieved that this combined solution is significantly more space-saving than a solution based purely on power electronics. In summary, with the solution according to the invention, a greater degree of flexibility can be achieved with a relatively small space requirement for network management and furnace operation.
[0098] Reference numerals list
[0099] 1 device
[0100] 2 Main winding
[0101] 3 Adjustment winding
[0102] 4First sub-winding
[0103] 5 Second sub-winding
[0104] 6-tap switch
[0105] Module 1 of 76
[0106] Module 2 of 86
[0107] 9 Voltage sensor
[0108] 10Current sensor
[0109] 11First control unit
[0110] 12 Second control unit
[0111] 13 evaluation units
[0112] 14Electrical equipment
[0113] 15 Load leads
[0114] 16 Coarse winding
[0115] 17 Coarse regulator
[0116] 18 Capacitor
[0117] 19 Series winding
[0118] 20 electric lines
[0119] 21 Electric Arc Furnace
[0120] 22First inductive component
[0121] 23 Second inductive component
[0122] The primary winding or regulating winding of 2423
[0123] Secondary winding of 2523
[0124] 2622 primary winding
[0125] Secondary winding of 2722
[0126] 28 points
[0127] 29th line
[0128] First end of A16
[0129] The second end of B16
[0130] n-1, n, ... n+4 winding taps
Claims
1. A method for changing a transformation ratio, an impedance or a voltage for excitation of an electrical device (14), the electrical device (14) comprising: - at least one regulating winding (3) having winding taps (n, n+1) and at least one sub-winding (4, 5), - a tap changer (6) for changing the transformation ratio, impedance or voltage for excitation of the electrical device (14), in, - the tap changer (6) comprises a first module (7) for connecting the winding taps (n, n+1) of the regulating winding (3) and a second module (8) having a semiconductor switching element for connecting, reversing or bridging the at least one partial winding (4, 5), The method comprises the following steps: - inputting a request for changing the transformation ratio, impedance or voltage for excitation of the electrical device (14), - checking at least one relevant characteristic parameter, - depending on the checking of the at least one relevant characteristic variable, a transformation ratio, an impedance or a voltage for excitation of the electrical device (14) is changed either by means of the first module (7) or by means of the second module (8).
2. The method according to claim 1, wherein: - the relevant characteristic variable comprises a value of a deviation of an actual voltage of the electrical device (14) from a preset target voltage, - if the deviation from the setpoint voltage takes on a value greater than the tap voltage present between two adjacent winding taps (n, n+1) of the regulating winding (3), the transformation ratio is changed by means of the second module (8).
3. The method according to any one of the preceding claims 1 to 2, wherein: - the relevant characteristic variable comprises a value of a deviation of the impedance of the electrical device (14) from a preset theoretical impedance, - if the value of the deviation from the setpoint impedance is greater than the impedance acting between two adjacent winding taps (n, n+1) of the control winding (3), the impedance is changed by means of the second module (8).
4. The method according to any one of the preceding claims 1 to 3, wherein: - the relevant characteristic variable comprises a value of a deviation of an actual voltage in the first inductive component (22) for excitation of the second inductive component (23) from a predefined setpoint voltage, - adjusting the voltage for excitation of the second inductive component (23) by means of the second module (8) when the value of the deviation from the setpoint voltage is greater than the tap voltage present between two adjacent winding taps (n, n+1) of the regulating winding (3, 24).
5. The method according to any one of the preceding claims 1 to 4, wherein: - the relevant characteristic variables include the gradient of the required voltage change, - When the gradient of the required voltage change is greater than a determined limit value, the transformation ratio is changed by means of the second module (8).
6. The method according to any one of the preceding claims 1 to 5, wherein: - the relevant characteristic variables include the gradient of the required impedance change, - When the gradient of the required impedance change is greater than a determined limit value, the impedance is changed by means of the second module (8).
7. The method according to any one of claims 1 to 6, wherein: - the relevant characteristic variables include the fundamental oscillation of the voltage present in the electrical device (14) together with harmonic components, - When the harmonic component is greater than the determined limit value, the transformation ratio is changed by means of the second module (8).
8. The method according to claim 7, wherein: - A Fourier analysis is performed in order to determine the harmonic components above the fundamental oscillation of the voltage present at the electrical device (14).
9. The method according to any one of the preceding claims 1 to 8, wherein: - after changing the transformation ratio, the impedance or the voltage for excitation by means of the second module (8), The first module (7) and the second module (8) are manipulated such that the second module (8) assumes a neutral position in which the at least one partial winding (4, 5) is bridged.
10. The method according to any one of the preceding claims 1 to 8, wherein: - after changing the transformation ratio, the impedance or the voltage for excitation by means of the second module (8), The first module (7) and the second module (8) are manipulated such that the second module (8) occupies a first end position and the entire adjustment range of the second module is available from the first end position to the second end position.
11. The method according to any one of the preceding claims 1 to 10, wherein: - Check multiple related characteristic parameters, - the characteristic parameters are weighted with respect to their importance, - Depending on the checking and weighting of the relevant characteristic variables, the transformation ratio, the impedance or the voltage for excitation is changed either by means of the first module (7) or by means of the second module (8).
12. The method according to any one of claims 1 to 11, wherein: - The first module (7) and the second module (8) are not operated simultaneously.
13. A device (1) for changing the transformation ratio, impedance or voltage for excitation of an electrical device (14), wherein: The electrical device (14) has at least one regulating winding (3) with winding taps (n, n+1), at least one sub-winding (4, 5) and a tap changer (6) for changing the transformation ratio, impedance or voltage for excitation of the electrical device (14), and the device (1) comprises: - at least one sensor (9) for measuring the voltage present at a suitable measuring point, and / or - at least one sensor (10) for measuring the current flowing at a suitable measuring point, - an evaluation unit (13) which is designed to carry out the method according to claims 1 to 13.
14. The device (1) according to the preceding claim, wherein: - the tap changer (6) comprises a first module (7) for connecting the winding taps (n, n+1) of the regulating winding (3) and a second module (8) having a semiconductor switching element for connecting, reversing or bridging the at least one partial winding (4, 5), - the first module (7) comprises a first control unit (11), - the second module (8) comprises a second control unit (12), in, The evaluation unit (13) is designed to actuate the first control unit (11) and the second control unit (12).