HIGH-TEMPERATURE SUPRAL CONDUCTING SWITCHING DEVICE

Description

[0001] The invention relates to a high-temperature superconducting switching device.

[0002] High-temperature superconducting conductors, hereinafter referred to as "HTSL" or "HTSC" (English), are used, for example, for high-current applications where direct or alternating current in the kiloampere to megaampere range is to be transmitted. Their conductor material consists essentially of high-temperature superconductors that can conduct direct current without loss in the nominal temperature range below the so-called transition temperature. These HTSL are often not available in the classic wire form, but rather as ribbon material in common widths of 4, 10, and 12 mm, and planned widths up to 100 mm, as well as in thicknesses of 20 to 300 µm. To achieve the required high current-carrying capacity of the system element, they are bundled into stacks. One or more stacks form a strand. One or more strands determine the current-carrying capacity of the entire system.The invention is described below by way of example using commercially available high-temperature superconducting tapes (HTSL tapes) as an example, which can incorporate all the features mentioned herein into the invention. HTSL tapes essentially consist of a thin ceramic layer built up on a metallic support or substrate, which becomes superconducting when the so-called transition temperature is undershot. The composition of the layers of an HTSL tape varies depending on the requirements, manufacturer, or manufacturing process. Typically, the superconducting layer is coated with a thin silver layer of 0.5–2 µm. The finished HTSL tape can additionally be coated with a copper stabilizer, either electroplated or laminated. Furthermore, the conductor can be coated with solder, either electroplated or by immersion in a bath.

[0003] When HTSL bands are stacked, they influence each other via their self-generated magnetic fields. The current-carrying capacity of each individual HTSL band decreases as the magnetic field to which it is exposed at its stacking position increases. It is known that superconductors can be made highly resistive by current, magnetic fields, and / or temperature. This is used, for example, in current limiters to limit short-circuit currents and in flux pumps to charge superconducting magnets using magnetic fields. For the transmission of high to very high currents in the kiloampere to megaampere range, the power loss equation PV = I² < ΔR necessitates very low electrical contact resistance at the junctions of the superconductors in high-temperature superconductivity applications.

[0004] The HTSL stacks or strands that conduct the current through the superconducting busbar system consist of a large number of individual HTSL bands, from about twenty to several hundred, depending on the temperature and the required current to be transmitted.

[0005] WO 2021 / 080443 A1 discloses a superconducting switch comprising a closed loop of two parallel superconducting branches. Switching is achieved using a time-varying magnetic field to induce a screening current in the loop. The high-impedance state is reached when the sum of the transport current and the induced screening current reaches or exceeds the critical current (Ic) of the superconducting material.

[0006] GAWITH JAMIE ET ​​AL: "HTS Transformer-Rectifier Flux Pump Optimization" and WO 2017 / 021674 A1 describe the fundamental physical principle of so-called "AC field switches" or "dynamic resistance switches." In these devices, resistance is generated by the interaction of a DC transport current with an applied AC magnetic field. It is demonstrated that the strength of the AC magnetic field can be significantly lower than the critical static magnetic field (Bc) required to suppress superconductivity.

[0007] US 6,894,406 B2 discloses a superconducting switching element that is switched by irradiation with high-frequency electromagnetic energy. The mechanism used consists of selectively transitioning the high-temperature superconductor from the superconducting to the normal-conducting state.

[0008] It is therefore an object of the invention to provide an improved high-temperature superconducting switching device.

[0009] This task is accomplished by a high-temperature superconducting switching device with the features of the main claim. Advantageous embodiments are the subject of the dependent claims.

[0010] The high-temperature superconducting switching device according to the invention initially has a current connection which branches into at least two independently switchable alternative current paths. The current connection and the current paths consist entirely of high-temperature superconducting layers (HTSL), so that the current does not have to flow through any normal conductor on its path. The HTSL are designed to conduct a transport current, which can be calculated by a person skilled in the art. Furthermore, a cooling device is provided for cooling the HTSL below their transition temperature.

[0011] Typically, the cooling device for cooling the high-temperature superconductor below its transition temperature comprises a liquid cooling medium, with the high-temperature superconductor being immersed in the cooling medium. The coolant usually flows around the superconductor.

[0012] The switching of the switchable alternative current paths is achieved via switchable magnets. This utilizes the known effect that superconductors can be made highly resistive by magnetic fields. For this purpose, a switchable magnet is spatially assigned to each current path, and the magnets are connected to a control unit. Any technically suitable solution can be used to switch the magnets, e.g., mechanically driven magnets. However, electromagnets with a corresponding electrical control using an alternating current source are preferred according to the invention, so that an alternating current can flow through the electromagnets. The advantage lies in the fact that magnetic fields can be generated very quickly, flexibly, and with freely selectable frequency and magnetic field strength.

[0013] Furthermore, it is essential that each switchable magnet can only act on its assigned current path with its magnetic field. A specialist can determine the necessary design, distances, shielding, magnetic field strengths, and alternating magnetic field frequencies. The result is... Each switchable magnet is arranged in relation to its assigned current path and can be controlled by the controller in such a way that it generates an alternating magnetic field in the HTSL of the assigned current path. a can generate dynamic resistance, which makes the current path high-impedance, whereby at the same time each switchable magnet is arranged in relation to the current path not assigned to it and can be controlled by the controller in such a way that it generates an alternating magnetic field in the HTSL of the not assigned current path none can generate dynamic resistance so that the unassigned current path remains superconducting.

[0014] This utilizes the following otherwise undesirable effect to significantly reduce the size of magnetic coils and the currents required for their operation: The dynamic resistance generated by an alternating magnetic field impairs the direct current carrying capacity of a superconductor. When superconductors are used in applications such as power cables, transformers, and motors, a direct current transport current flows in a superconductor within an external alternating magnetic field. In this case, power is undesirably dissipated in the superconductor due to transport and magnetization losses, which is referred to as "dynamic resistance." This dynamic resistance can be estimated, e.g., Dynamic resistance in a slab-like superconductor with Jc(B) dependence; MP Oomen et al. 1999 Supercond. Sci. Technol. 12 382.

[0015] In contrast, for static magnetic fields, the following three physical quantities are typically used to calculate the current-carrying capacity, and these have a decisive impact on the application of superconductivity: the critical temperature Tc, the critical current density jc, and the critical external magnetic field Hc. In an XYZ coordinate system with these three quantities as axes, a space curve results as the boundary of the superconducting state. The superconducting state exists within the space curve, and the normal conducting state outside of it. The space curve defines the relationship between the critical values ​​Tc, jc, and Hc. The critical external magnetic field Hc refers to a static external magnetic field.

[0016] By using an alternating magnetic field to generate the dynamic resistance, the superconductor in question is rendered highly resistive, even at magnetic field strengths that are sometimes several orders of magnitude lower than those of static magnetic springs. The critical static magnetic field strength is greater than the critical field strength of the alternating magnetic field, usually by several times and in many cases by several orders of magnitude. A person skilled in the art can design the system for the intended application with respect to field strength and frequency.

[0017] In other words, dynamic resistance means that the superconductor, when subjected to a magnetic field that is too weak as a static field not to significantly reduce the current-carrying capacity of the superconductor, is driven into resistance simply by applying frequency.

[0018] Advantageous frequencies of the alternating magnetic field are in the range of 40 - 4,000 Hz, preferably 200 - 2,000 Hz and particularly preferably 400 - 1,200 Hz.

[0019] According to the invention, a new type of changeover switch is provided that operates without wear-prone and slow mechanical disconnects (e.g., switching contacts) or power-lossy electronic power semiconductors (diodes, transistors, tyrostors). The main advantages over this prior art lie in the very low conduction losses, since the forward voltages of high-temperature superconductors are almost negligible compared to power semiconductors. Furthermore, the high current-carrying capacity of high-temperature superconductors allows for excellent scalability to higher currents. The circuit can also be scaled to high voltages.

[0020] Apart from the fact that superconductors require dramatically less space for the same current-carrying capacity, the superconducting switching elements according to the invention, whose HTSLs are located, for example, under liquid nitrogen, can be made much smaller, since the insulation distances in liquid nitrogen are significantly smaller, especially at high voltages.

[0021] Preferably, during the commutation process, the control system controls the switchable magnets in such a way that, when one current path is superconducting and the other has high resistance, and a switching operation is to take place in which one current path becomes high resistance and the other becomes superconducting, the control system maintains both current paths in a superconducting state for a defined period during the switching operation. Thus, both current paths should be superconducting for a specific time during the switch from one current path to the other. By precisely adjusting these switching times, switching losses can be minimized, resulting in higher efficiencies in the operation of the switching devices according to the invention.

[0022] All high-temperature superconductors are ceramic materials, which are very brittle. These can be processed into wire as follows: The "first generation of wire" is manufactured using the powder-in-tube method. The superconducting material is filled as a powder into a silver tube, which is then processed to create very thin wires that are bundled together into filaments. Since this wire consists of 70% silver, it is correspondingly expensive. The "second generation of wire" consists of coated ribbon conductors, so-called coated conductors. The performance of the ribbon conductors varies depending on the coating process. It is expected that the price of superconductors will fall below that of conventional copper conductors. For example, ribbons with a YBCO-based superconducting coating have been developed, overcoming not only the brittleness of the ceramic conductor material.Furthermore, all crystals of the conductor material must be uniformly aligned in the coating, since charge transport in high-temperature superconductors is highly direction-dependent and occurs almost exclusively in certain layers of their crystal structure.

[0023] Preferably, the HTSLs are formed by HTSL tapes of the so-called second generation of HTSL tape conductors based on ReBCO material. Re stands for Rare Earth, and depending on the manufacturer, various materials such as yttrium or gadolinium are used. For example, yttrium-barium-copper oxide and bismuth-strontium-calcium-copper oxide substances, with their transition temperatures of 93 K and 110 K respectively, can easily be cooled below their transition temperature using liquid nitrogen.

[0024] Advantageously, it is important to ensure that the electrical connection has the same current-carrying cross-section made of HTSL as the alternative current paths combined. Preferably, each of the alternative current paths has the same current-carrying cross-section made of HTSL. This contradicts the usual design rule that the cross-section of the electrical connection need not be larger than the cross-section of each individual alternative current path. However, this design offers the possibility of exploiting a manufacturing advantage, as no complex and resistance-inducing contacting of the power supply with the alternative current paths is necessary: ​​According to the invention, the electrical connection and all alternative current paths are made in one piece from HTSL, preferably HTSL strips, so that they have no joining zones with contact resistance. Instead of connecting the supply to the paths, the supply is simply branched, e.g.By cutting along the longitudinal axis: For this purpose, the HTSL bands are cut / separated perpendicular to their band plane along their longitudinal axis only outside the current connection and / or at least within the effective range of the switchable magnets assigned to the respective current path, to form the alternative current paths. This cutting / separation thus replaces a complex, resistance-laden joining of the current connection and alternative current paths. This clever design avoids connection points.

[0025] To date, so-called "cold switching" has not been implemented. This refers to switching the superconductors using a switching device, where the switching element is also immersed in a liquid gas, e.g., N, He, H, Ne, cooled below the transition temperature. When the contact opens, an arc can occur, which locally causes a phase transition from liquid to gaseous due to the input of heat, resulting in an undesirable volume expansion of the liquid gas, typically by a factor of 700. This is prevented by the invention.

[0026] As explained above, the switching device according to the invention can be used as a lossless power switch for switching a current from one current path to another. Furthermore, it is proposed that these switching elements be provided as an essential component of low-loss operating devices. Converter, rectifier or inverter circuits.

[0027] In the technical field of power engineering, converter, rectifier, and inverter circuits are common. A converter, also known as an AC / AC inverter, is a power converter that generates a new AC voltage with a different frequency and amplitude from an AC voltage. Rectifiers are used to convert AC voltage into DC voltage. An inverter is an electrical device that converts DC voltage into AC voltage. The aforementioned devices fall under the general term "power converter," meaning electrical devices or systems without moving parts used to convert one type of electrical current (DC or AC) into the other, or to change characteristic parameters such as voltage and frequency.

[0028] All power converters and switches contain power electronic components. This is associated with high conduction and switching losses, as well as significant insulation requirements at high voltages and corresponding dimensions. Semiconductors, such as diodes, IGBTs, etc., are used in converter and rectifier circuits. Semiconductor components have high conduction losses and are generally designed for maximum voltages per component.

[0029] The invention according to the invention rectifier The switching device described above is designed in such a way that when the power supply is connected to an alternating voltage, the control one current path is only activated and thus made high-impedance as long as the alternating voltage passes through positive voltages; and the other current path is only activated and thus made high-impedance as long as the alternating voltage passes through negative voltages.

[0030] In essence, one current path is superconducting only during the positive half-cycle, while the other current path is superconducting only during the negative half-cycle. One current path therefore forms the (unsmoothed) positive terminal and the other the negative terminal.

[0031] It has already been described that during the switching process, it is essential to prevent all current paths from becoming high-impedance for a brief moment. Voltage spikes during the switching off of inductive loads can generate excessive current flow in the high-impedance current paths, causing them to heat up unnecessarily. Therefore, it is preferably provided that the control system briefly de-energizes both current paths during the zero crossing of the AC voltage, thus maintaining their superconductivity. This zero-crossing period can be adjusted by a person skilled in the art to suit the rectifier design. The following has proven advantageous: a time of 1 / 1000 of the period of the alternating current before and after the zero crossing; or a time during which the absolute value of the alternating voltage is less than 0.6% of the peak voltage of the alternating current.

[0032] Analogous to the rectifier, the inventive inverter The switching device described above is designed such that, when the power supply is connected to a DC voltage, the control system alternately drives one current path or the other at a specific frequency, making it high-impedance. This switching process occurs at the desired AC frequency.

[0033] The switching device according to the invention can also be used as a modulation device or pulse width modulation device.

[0034] The rectifiers and inverters described above have so far been described using only a single switching device, and thus only with one current connection corresponding to a single input pole. On the output side, i.e., at the free ends of the alternative current paths, there is a multi-pole output. Advantageously, however, the rectifier or inverter preferably has not just one, but two current connections and thus two input poles for applying an AC or DC voltage. In simplified terms, two identical switching devices according to the invention, driven in the same direction, are provided with pairwise crossed, connected alternative current paths, thus providing two current connections or input poles: The free ends of the alternative current paths of both switching devices are cross-connected to each other, i.e.,The first current path of the first switching device is connected on its output side to the second current path of the second switching device, and similarly, the second current path of the first switching device is connected on its output side to the first current path of the second switching device. The free ends of these paired alternative current paths thus form the two output terminals of the rectifier or inverter. Furthermore, the control system operates both switching devices in the same direction; that is, the switchable magnets assigned to the current paths switch the two first alternative current paths or the two second alternative current paths synchronously.

[0035] Preferably, the rectifier or inverter therefore has a second switching device according to the invention, wherein the current connection of the first switching device and the current connection of the second switching device form two input poles of the rectifier or inverter. Furthermore, the two independently switchable alternative current paths of the first switching device and the two independently switchable alternative current paths of the second switching device are crosswise superconducting to form two output poles of the rectifier or inverter. The first magnets (MA,MB) of the first switching device and the second magnets (MA1,MB1) of the second switching device are connected to a common control unit (S) and are controlled by it in the same direction.

[0036] According to the invention, a power converter is even disclosed which can be operated equally as a rectifier and an inverter, depending only on the control of the switchable magnets.

[0037] Preferably, the magnets controlled in the same direction (MA, MA1 or MB, MB1) can each be designed as a common magnet, wherein Each common magnet is arranged in relation to its assigned current paths (A, A1 or B, B1) and can be controlled by the controller in such a way that it can generate a dynamic resistance by creating an alternating magnetic field in the HTSL of the assigned current paths (A, A1 or B, B1), which makes the current paths high-impedance, wherein each common magnet is arranged in relation to the unassigned current paths (A, A1 or B, B1) and can be controlled by the controller in such a way that it cannot generate a dynamic resistance by creating an alternating magnetic field in the HTSL of the unassigned current paths (A, A1 or B, B1), so that the unassigned current path remains superconducting.

[0038] Finally, a converter can be easily implemented on the basis of the switching device according to the invention by connecting the output poles, i.e. the free ends of the alternative current paths of the rectifier according to the invention, to the current connections of an inverter according to the invention connected downstream.

[0039] The concept according to the invention can also be transferred to multi-phase systems, e.g. 3-phase alternating current, in a manner obvious to those skilled in the art.

[0040] Fig. 1Figure 1 shows the basic form of the high-temperature superconducting switching device, with an input current connection E. This branches into at least two independently switchable alternative current paths A and B. The current connection E and the current paths A and B are designed as high-temperature superconducting circuits (HTSLs) throughout and are configured to carry a transport current from the current connection E to the free ends of the alternative current paths A and B. Not shown is the cooling device used to keep the current connection E below its transition temperature up to the free ends of the alternative current paths A and B.

[0041] Furthermore, each current path A, B is spatially assigned a switchable magnet MA, MB. These magnets MA, MB are connected to a controller S so that individual current paths A, B can be selectively made highly resistive: The switchable magnet MA is positioned relative to its assigned current path A and controlled by the controller S in such a way that it can generate an alternating magnetic field in the HTSL of the assigned current path A, thus creating a dynamic resistance that makes the current path highly resistive. To prevent unintended unwanted influence on current path B, which is not assigned to the magnet MA, each switchable magnet MA is positioned relative to the unassigned current path B and controlled by the controller in such a way that it can generate an alternating magnetic field in the HTSL of the unassigned current path B. none can generate dynamic resistance so that the unassigned current path remains superconducting.

[0042] During the commutation process, care must be taken to ensure that the control unit S controls the switchable magnets MA, MB in such a way that if one current path A is superconducting and the other current path B is high-resistance, and a switching operation is to take place in which one current path A becomes high-resistance and the other current path B becomes superconducting, the control unit keeps both current paths A,B superconducting for a defined time during the switching operation.

[0043] The basic form from Fig. 1 It only has one electrical connection E and is therefore single-pole.

[0044] Fig. 2 shows the two-pole arrangement of two switching devices. Fig. 1In this process, two identical switching devices 10, 11 according to the invention, controlled in the same direction, are provided with pairwise crossed and connected alternative current paths A, B, A1, B1, which thus provide two current connections E, E1 or input poles: The free ends of the alternative current paths A, B, A1, B1 of both switching devices 10, 11 are cross-connected to each other, i.e., the first current path A of the first switching device 10 is connected on the output side to the second current path B1 of the second switching device 11, and analogously, the second current path B of the first switching device 10 is connected on the output side to the first current path A1 of the second switching device 11. The free ends of the alternative current paths A, B, A1, B1, thus connected in pairs, form the two output poles P, P1 of the rectifier or inverter. Furthermore, both switching devices are operated in the same direction via the control system, i.e., the current paths A, B and P1 are connected on the output side.The switchable magnets assigned to A1,B1 (MA,MB or MA1,MB1) synchronously switch the first two alternative current paths A,A1 and the second two alternative current paths B,B1, respectively. The commutation process described above also applies here.

[0045] In contrast to Fig. 2 It is preferred that each individual path from the current input E, or E1, to the output pole P, or P1, is implemented continuously and without interruption from a single track or stack of HTSL. The in Fig. 2 The nodes shown, e.g., of current path B with current path A1, are for illustrative purposes only and should be avoided in the execution.

[0046] Fig. 3A, 3B and 4 explain the operation of the two-pole switching devices according to the invention. Fig. 2as different power converters. The switchable magnets and the control system are not shown, but are present, and only the magnet pairs switched at the depicted time, e.g. MB, MB1, are marked together with an "X", which indicates the current paths made high-impedance and thus blocked by the switched magnet pairs.

[0047] Fig. 3A Figure 1 shows the operation of a rectifier according to the invention using the example of an alternating voltage AC with period T or frequency 1 / T applied to the current connections E,E1 on the input side. The free ends of the alternative current paths A,B1 and B,A1, which are crossed and joined in pairs, form the two output poles P and P1, respectively.

[0048] At time t1 = 0.25 T, the positive half-wave of the AC voltage is present at the input. The current supply E of the first switching device shown above is therefore at a positive voltage. Since the first current path A of the first switching device is open and the second current path B of the first switching device is closed by the switched magnet MB, there is also a positive voltage at the output at the free end of the first current path A, which leads to the upper output terminal P. Similarly, for the current connection E1 of the second switching device shown below: A negative voltage is present at E1. Since the first current path A1 of the second switching device is open and the second current path B1 of the second switching device is closed by the switched magnet MB1, there is also a negative voltage at the output at the free end of the first current path A1, which leads to the lower output terminal P1.

[0049] At time t2 = 0.75 T, the negative half-wave of the AC voltage is present at the input. The current connection E of the first switching device shown above is therefore at a negative voltage. Since the first current path A of the first switching device is closed by the switched magnet MA and the second current path B of the first switching device is open, a negative voltage is also present at the output at the free end of the second current path B, which leads to the lower output terminal P1. Similarly, for the current connection E1 of the second switching device shown below: A positive voltage is now present at E1. Since the first current path A1 of the second switching device is closed by the switched magnet MA1 and the second current path B1 of the second switching device is open, a positive voltage is also present at the output at the free end of the second current path B1, which leads to the upper output terminal P.

[0050] At time t3 = 1.25 T, the positive half-wave of the alternating voltage AC is again present on the input side, so that the same state as at the already described time t1 = 0.25 T is reached.

[0051] It is evident that, due to the switching of the magnets and the crossed, connected alternative current paths, a positive voltage is always present at the upper pole P and a negative voltage at the lower pole P. Any necessary smoothing of the output DC voltage can be provided by a qualified electrician.

[0052] In Fig. 3A The commutation process at time t = nx T / 2 (zero crossing of the alternating voltage) was not shown.

[0053] Fig. 3B shows analogous to Fig. 3AThe operation of an inverter according to the invention is described using the example of an input DC voltage applied to the current connections E, E1, which is converted into an AC voltage with period T or frequency 1 / T. The free ends of the paired, crossed alternative current paths A,B1 and B,A1 form the two output poles P and P1, respectively.

[0054] A DC voltage is permanently present at the input, including at time t1 = 0.25 T. At this time t1, the inverter is to apply a positive voltage to the first output terminal P and a negative voltage to the second output terminal P1. The current connection E of the first switching device (shown above) is therefore at a positive voltage, and the current connection E1 of the second switching device (shown below) is at a negative voltage. Since the first current path A of the first switching device is open and the second current path B of the first switching device is closed by the switched magnet MB, a positive voltage is also present at the output at the free end of the first current path A, which leads to the upper output terminal P. Similarly, for the current connection E1 of the second switching device (shown below), a negative voltage is present at E1.Since the first current path A1 of the second switching device is open and the second current path B1 of the second switching device is closed by the switched magnet MB1, there is also a negative voltage at the output side at the free end of the first current path A1, which leads into the lower output pole P1.

[0055] At time t2 = 0.75 T, the inverter applies a negative voltage to the first output terminal P and a positive voltage to the second output terminal P1. This represents a polarity reversal compared to the previous time t1. The current connection E of the first switching device (shown above) remains at a positive voltage, while the current connection E1 of the second switching device (shown below) is at a negative voltage. Since the second current path B of the first switching device is open and the first current path A of the first switching device is closed by the switched magnet MA, a positive voltage is also present at the output end of the second current path B, which leads to the lower output terminal P1. Similarly, a negative voltage is present at the current connection E1 of the second switching device (shown below).Since the second current path B1 of the second switching device is open and the first current path A1 of the second switching device is closed by the switched magnet MA1, there is also a negative voltage at the output side at the free end of the second current path B1, which leads into the upper output pole P.

[0056] At time t3 = 1.25 T, i.e. one period after t1, the same state exists as at the previously described time t1 = 0.25 T.

[0057] It can be seen that by switching the magnets and the crossed, connected alternative current paths, the positive voltage is alternately applied to the upper pole P and the lower pole P1. This example generates a square-wave alternating voltage at poles P and P1 with period T. Other alternating voltage waveforms, such as sine waves, modulation, or pulse-width modulation, can be provided by a person skilled in the art.

[0058] In Fig. 3AThe commutation process at time t = nx T / 2 (pole change) was not shown.

[0059] Fig. 4 shows that by connecting the rectifier in series from Fig. 3A and the inverter Fig. 3B A converter is feasible. The diagram shows the conversion of an input rectangular AC voltage with period T into an output rectangular AC voltage with twice the period T' = 2T, provided at poles P and P1. The following applies to the operation of the rectifier shown on the left: Fig. 3A As stated above, this provides a DC voltage for the downstream inverter shown on the right, which may also be smoothed by the usual measures, e.g. in the case of an input sinusoidal AC voltage.

[0060] The inverter shown here is operated as described below. Fig. 3Bexplained, with the exception that this generates an alternating voltage with a period T' = 2 T, and therefore does not yet undergo a pole change at time t2 = 0.75 t = 0.0375 T'. This only occurs at T = 0.5 T'.

[0061] The magnets MA, MA1, MB, MB2 of the rectifier and MA', MA1', MB', MB2' of the inverter are preferably connected to a common control, which is not shown here.

Claims

1. A high-temperature superconducting switching device (10), in particular for converter, rectifier or inverter circuits, comprising at least one current connection (E) which branches into at least two independently switchable alternative current paths (A, B), wherein the current connection and the current paths have continuous high-temperature superconducting conductors, abbreviated "HTSL", and the HTSL are adapted for conducting a transport current, comprising a cooling device for cooling the HTSL below their transition temperature, wherein a switchable magnet (MA, MB) is spatially assigned to each current path (A, B); the magnets (MA, MB) are connected to a controller (S) having an alternating current source for generating an alternating magnetic field; each switchable magnet (MA) is arranged relative to the current path (A) assigned to it and is able to be controlled by the controller such that it can generate a dynamic resistance by generating an alternating magnetic field in the HTSL of the assigned current path (A), which makes the current path high-impedance, wherein each switchable magnet (MA) is arranged relative to the current path (B) not assigned to it and is able to be controlled by the controller such that it cannot generate any dynamic resistance by generating an alternating magnetic field in the HTSL of the current path (B) not assigned to it, so that the non-assigned current path remains superconducting characterised in that the current connection (E) and all alternative current paths (A, B) consist of HTSL tapes in one piece, so that these have no joining zones with transition resistance, wherein the HTSL tapes are cut perpendicular to their tape plane along their longitudinal axis at least in the effective range of the switchable magnets assigned to the respective current path for forming alternative current paths.

2. The switching device according to claim 1, characterised in that the controller controls the switchable magnets such that when one current path is superconducting and the other current path is high-impedance and a switching operation is to take place in which the one current path becomes high-impedance and the other current path becomes superconducting, the controller keeps both current paths superconducting for a defined time during the switching operation.

3. The switching device according to one of the preceding claims, characterised in that the HTSL are formed as HTSL tapes; and / or the current connection (E) has the same current-carrying cross-section of HTSL as the alternative current paths (A, B) together, wherein preferably each of the alternative current paths has the same current-carrying cross-section of HTSL.

4. A rectifier comprising a switching device (10) according to one of the preceding claims 1-3, characterised in that when the current connection is connected to an alternating voltage, the controller controls the one current path and thus makes it high-impedance only as long as the alternating voltage passes through positive voltages; and controls the other current path and thus makes it high-impedance only as long as the alternating voltage passes through negative voltages.

5. The rectifier according to claim 4, characterised in that the controller does not control any of the two current paths during the period of a zero crossing of the alternating voltage, thus making them superconducting, wherein preferably the period of the zero crossing is defined as: a time of 1 / 1,000 of the period of the alternating current before and after the zero crossing; or a time during which the absolute value of the alternating voltage is less than 0.6% of the peak voltage of the alternating current.

6. An inverter comprising a switching device (10) according to one of the preceding claims 1-3, characterised in that when the current connection is connected to a direct voltage, the controller alternately controls the one current path or the other current path at a frequency, making it high-impedance.

7. The inverter according to claim 6, characterised in that the controller does not control any of the two current paths for a period during the change from one current path to the other current path and thus does not make them high-impedance, so that both current paths are superconducting for this period.

8. The inverter according to claim 6 or 7, characterised in that the period is defined as 1 / 1,000 of the period of the frequency of the changing of the current paths.

9. The rectifier and / or inverter according to one of the preceding claims 4-5 or 6-8, respectively, characterised in that it comprises a second switching device (11) according to one of the preceding claims 1-5, wherein the current connection (E) of the first switching device (10) and the current connection (E1) of the second switching device (11) form two input poles of the rectifier and / or inverter and the two independently switchable alternative current paths (A, B) of the first switching device (10) and the two independently switchable alternative current paths (A1, B1) of the second switching device (11) are superconductively connected to one another in a crosswise manner to form two output poles of the rectifier and / or inverter, wherein the first magnets (MA, MB) of the first switching device and the second magnets (MA1, MB1) of the second switching device are connected to a common controller (S) and are controlled by it in the same sense.

10. The rectifier and / or inverter according to claim 9, characterised in that the magnets (MA, MA1 or MB, MB1, respectively) controlled in the same sense are each electrically connected in series and connected to the common controller (S).

11. The rectifier and / or inverter according to claim 9, characterised in that the magnets (MA, MA1 or MB, MB1, respectively) controlled in the same sense are each formed as a common magnet, and each common magnet is arranged relative to the current paths (A, A1 or B, B1, respectively) assigned to it and can be controlled by the controller such that it can generate a dynamic resistance by generating an alternating magnetic field in the HTSL of the assigned current paths (A, A1 or B, B1, respectively), which makes the current paths high-impedance, wherein each common magnet is arranged relative to the current paths (A, A1 or B, B1, respectively) not assigned to it and is able to be controlled by the controller such that it cannot generate any dynamic resistance by generating an alternating magnetic field in the HTSL of the current paths (A, A1 or B, B1, respectively) not assigned to it, so that the non-assigned current path remains superconducting.

12. A converter comprising a rectifier according to one of the preceding claims and an inverter according to one of the preceding claims connected downstream thereof, wherein at least one free end of one of the current paths of the rectifier is conductively connected to the current input of the inverter.

13. A method for operating the switching device or the rectifier or the inverter or the converter according to one of the preceding claims, wherein the controller with its alternating current source performs the control of the switchable magnet (MA) by generating an alternating magnetic field, wherein a dynamic resistance is generated in the HTSL of the current path (A) assigned to the magnet by the alternating magnetic field, which makes the current path high-impedance, wherein preferably the amplitude or the effective value of the alternating magnetic field is smaller than the critical magnetic static field strength which would be necessary to make the current path high-impedance in the same case, in particular preferably smaller by a multiple, wherein furthermore preferably the frequency of the alternating magnetic field is 40 - 4,000 Hz, preferably 200 - 2,000 Hz and particularly preferably 400 - 1,200 Hz.