Composite excitation and current stabilizing circuit and method for high temperature superconducting magnet

Abstract

This application belongs to the field of superconducting electrical technology, specifically disclosing a composite excitation and current stabilization circuit and method for high-temperature superconducting magnets. This application employs a composite excitation and current stabilization circuit, achieving energy transfer through electrical connections between modules. The superconducting closed-loop module forms a basic closed-loop circuit via a superconducting switch and a load magnet. By adjusting the superconducting switch, the circuit can efficiently store energy through the load magnet in a high-resistivity state, and after energy storage is complete, it switches to a superconducting state to maintain low-loss operation. Based on this, the excitation and compensation module charges the high-resistivity circuit in the first operating stage, achieving high efficiency in the charging process. In the second operating stage, based on the principles of electromagnetic induction and rectification, it compensates for current attenuation caused by factors such as resistance, thereby solving the common problems in high-temperature superconducting magnet charging technology, such as current attenuation and the difficulty in balancing efficiency during charging and stability during operation.

Description

Technical Field

[0001] This application belongs to the field of superconducting electric technology, specifically relating to a composite excitation and current stabilization circuit and method for high-temperature superconducting magnets. Background Technology

[0002] High-Temperature Superconductivity (HTS) closed-loop coils have attracted considerable attention due to their ability to operate in Persistent Current Mode (PCM). In this mode, the coil can maintain a stable direct current without an external power source, thereby generating a stable magnetic field. This makes it a promising candidate for cutting-edge applications such as magnetic levitation trains, nuclear magnetic resonance (NMR), and magnetic resonance imaging (MRI). To enable an HTS closed-loop coil to enter and maintain PCM, it must first be charged and excited.

[0003] Existing high-temperature superconducting magnet charging technologies can be achieved through two paths. The first is a direct charging method based on a persistent current switch (PCS) using current leads. The second is a charging method that utilizes a metal-oxide-semiconductor field-effect transistor (MOSFET) switch to construct a transformer-rectifier circuit.

[0004] However, regardless of the charging technology used, a common technical challenge faced by the system is that after charging ends and the system enters continuous current mode, the current in the closed loop will inevitably decay over time, causing the magnetic field to be unable to remain constant for a long period of time.

[0005] Therefore, existing technologies often struggle to effectively balance high efficiency during the charging phase with current stability during operation. This technological bottleneck restricts the widespread application of high-temperature superconducting magnets in precision scientific instruments requiring extremely high magnetic field stability and in industrial equipment needing long-term operation. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a composite excitation and current stabilization circuit and method for high-temperature superconducting magnets, aiming to solve the problem that current HTS charging technology generally suffers from current decay, making it difficult to balance high efficiency during the charging phase with current stability during the operation phase.

[0007] The first aspect of this application relates to a composite excitation and current stabilization circuit for a high-temperature superconducting magnet, comprising: an excitation and compensation module, and a superconducting closed-loop module; a first output terminal of the excitation and compensation module is connected to a first input terminal of the superconducting closed-loop module; a second output terminal of the excitation and compensation module is connected to a second input terminal of the superconducting closed-loop module; the superconducting closed-loop module is configured to include at least a superconducting switch and a load magnet, the superconducting switch and the load magnet forming a closed-loop circuit; when the closed-loop circuit is in a high-resistivity state, energy is stored through the load magnet; and after energy storage is completed, the superconducting switch is adjusted to make the closed-loop circuit in a superconducting state; the excitation and compensation module is configured to charge the closed-loop circuit in the high-resistivity state in a first operating stage, and stop charging when the load magnet current reaches a preset operating current; in a second operating stage, energy is replenished to the closed-loop circuit in the superconducting state based on the principle of electromagnetic induction and rectification to compensate for current attenuation.

[0008] In one embodiment, when the excitation and compensation functions of the excitation and compensation module are executed independently, the excitation and compensation module includes: an excitation unit and a compensation unit; the output terminal of the excitation unit is connected to the first input terminal of the superconducting closed-loop module; the output terminal of the compensation unit is connected to the second input terminal of the superconducting closed-loop module; the excitation unit is configured to charge the closed-loop circuit in a high-resistivity state during the first working stage, and to stop charging when the load magnet current reaches a preset working current; the compensation unit is configured to replenish energy to the closed-loop circuit in a superconducting state during the second working stage based on the principle of electromagnetic induction and rectification, so as to compensate for current attenuation.

[0009] In one embodiment, the excitation unit includes: a first switching switch and a DC power supply; the DC power supply is connected to the first input terminal of the superconducting closed-loop module through the first switching switch; the first switching switch is a mechanical isolation switch.

[0010] In one embodiment, the compensation unit includes: a second switching switch, a coupling inductor, and an AC power supply; the AC power supply output is coupled through the coupling inductor and connected to the second input terminal of the superconducting closed-loop module through the second switching switch; the second switching switch is a semiconductor switch.

[0011] In one embodiment, when the superconducting closed-loop module includes a first superconducting switch and a load magnet: the load magnet is connected in parallel with the first superconducting switch; the first terminal of the DC power supply is connected to the first terminal of the first switching switch; the second terminal of the first switching switch is connected to the first terminal of the load magnet and the first terminal of the second switching switch; the second terminal of the second switching switch is connected to the first terminal of the secondary coil of the coupling inductor; the second terminal of the secondary coil of the coupling inductor is connected to the second terminal of the load magnet and the second terminal of the DC power supply, respectively; the primary coil of the coupling inductor is connected in parallel with the AC power supply.

[0012] In one embodiment, when the superconducting closed-loop module includes a second superconducting switch, a third superconducting switch, and a load magnet: the first terminal of the DC power supply is connected to the first terminal of the first switching switch; the second terminal of the first switching switch is connected to the first terminals of the second and third superconducting switches respectively; the second terminal of the third superconducting switch is connected to the first terminal of the load magnet; the second terminal of the load magnet is connected to the second terminal of the second superconducting switch and the second terminal of the DC power supply respectively; the first terminal of the second switching switch is connected to the first terminal of the third superconducting switch; the second terminal of the second switching switch is connected to the first terminal of the secondary coil of the coupling inductor; the second terminal of the secondary coil of the coupling inductor is connected to the second terminal of the third superconducting switch respectively; the primary coil of the coupling inductor is connected in parallel with the AC power supply.

[0013] In one embodiment, when the excitation and compensation functions of the excitation and compensation module are executed in a mixed manner, the excitation and compensation module includes: an AC power supply, a coupling inductor, a third switching switch, and a fourth switching switch; both the third switching switch and the fourth switching switch are semiconductor switches; the AC power supply is connected in parallel with the primary coil of the coupling inductor; the first end of the secondary coil of the coupling inductor is connected to the first end of the third switching switch; the second end of the third switching switch is connected to the first end of the fourth switching switch; and the second end of the fourth switching switch is connected to the second end of the secondary coil of the coupling inductor.

[0014] In one embodiment, to achieve half-wave rectification, the superconducting closed-loop module includes: a fourth superconducting switch, a fifth superconducting switch, and a load magnet; the fourth superconducting switch is connected in parallel with a third switching switch; the fifth superconducting switch and the fourth switching switch are connected in parallel to form a freewheeling branch, which is connected in parallel with the load magnet.

[0015] In one embodiment, to achieve full-wave rectification, the superconducting closed-loop module includes: a fourth superconducting switch, a fifth superconducting switch, and a load magnet; the fourth superconducting switch is connected in parallel with a third switching switch; the fifth superconducting switch is connected in parallel with the fourth switching switch; the first end of the load magnet is connected to the center tap of the secondary coil of the coupled inductor; the second end of the load magnet is connected to the second end of the third switching switch.

[0016] The second aspect of this application relates to a composite excitation and current stabilization method for a high-temperature superconducting magnet. The method utilizes the composite excitation and current stabilization circuit of the high-temperature superconducting magnet described in the first aspect, comprising: adjusting a superconducting switch to bring the closed-loop circuit of the superconducting closed-loop module into a high-resistance state; controlling the excitation and compensation module to enter a first operating stage to charge the closed-loop circuit in the high-resistance state; controlling the excitation and compensation module to exit the first operating stage when the load magnet current reaches a preset operating current; adjusting the superconducting switch to bring the closed-loop circuit of the superconducting closed-loop module into a superconducting state; and controlling the excitation and compensation module to enter a second operating stage to replenish energy to the closed-loop circuit in the superconducting state to compensate for current attenuation.

[0017] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This application employs a composite excitation and current stabilization circuit comprising an excitation and compensation module and a superconducting closed-loop module, and achieves energy transfer through electrical interconnection between modules, providing a structural foundation for phased operation. Specifically, the superconducting closed-loop module forms a basic closed-loop circuit through a superconducting switch and a load magnet. By adjusting the superconducting switch, the circuit can efficiently store energy through the load magnet in a high-resistivity state, and switch to a superconducting state after energy storage is complete to maintain low-loss operation. A scheme for implementing the charging and operation circuit is proposed.

[0018] Based on this, the excitation and compensation module charges the high-resistivity circuit in the first working stage, quickly reaching the preset working current and achieving high efficiency in the charging process; in the second working stage, it replenishes energy to the superconducting closed-loop circuit based on the principle of electromagnetic induction and rectification, effectively compensating for the current attenuation caused by factors such as resistance, thereby solving the common problems of current attenuation and difficulty in balancing high efficiency in the charging stage and stability in the operating stage in high-temperature superconducting magnet charging technology.

[0019] Compared with existing technologies, this solution achieves the technical effect of ensuring long-term current stability while fast charging through circuit structure design and phased control. Attached Figure Description

[0020] Figure 1 This is one of the structural block diagrams of the composite excitation and current stabilization circuit of the high-temperature superconducting magnet provided in the embodiments of this application; Figure 2 This is the second structural block diagram of the composite excitation and current stabilization circuit of the high-temperature superconducting magnet provided in the embodiments of this application; Figure 3 This is a state diagram of the first operating stage of the first circuit topology provided in the embodiments of this application; Figure 4 This is a second operating stage state diagram of the first circuit topology provided in the embodiments of this application; Figure 5 This is a state diagram of the first operating stage of the second circuit topology provided in the embodiments of this application; Figure 6 This is a state diagram of the second operating stage of the second circuit topology provided in the embodiments of this application; Figure 7 This is a state diagram of the third circuit topology provided in the embodiments of this application; Figure 8 This is a state diagram of the fourth circuit topology provided in the embodiments of this application; Figure 9 This is a schematic flowchart of the composite excitation and current stabilization method for high-temperature superconducting magnets provided in the embodiments of this application.

[0021] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 10 is the excitation and compensation module; 11 is the excitation unit; 12 is the compensation unit; 20 is the superconducting closed-loop module; S1 is the first switching switch; S2 is the second switching switch; R1 is the first superconducting switch; Lload is the load magnet; R2 is the second superconducting switch; R3 is the third superconducting switch; S3 is the third switching switch; S4 is the fourth switching switch; R4 is the fourth superconducting switch; R5 is the fifth superconducting switch. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0023] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0024] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages. The term "electrical connection" in this application can refer to a direct circuit connection or signal transmission via a communication protocol.

[0025] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0026] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0027] Currently, the direct charging method using current leads in a PCS (Polymer Capacitor System) temporarily disconnects the closed loop during the charging phase, allowing a high-power external DC power supply to rapidly inject current into the coil via physical current leads. The significant advantages of this method are high excitation voltage and fast charging speed, enabling the magnet to reach the preset operating current in a short time. However, this approach heavily relies on a bulky external power supply system and physical current leads, which not only increases the system's complexity and thermal load but also diminishes the portability and compactness advantages sought by the closed-loop coil during continuous operation.

[0028] The charging method for transformer-rectifier circuits using MOSFET switches leverages the advantages of MOSFETs, such as faster switching times and simpler control systems at low temperatures, to construct a high-speed rectifier circuit. Energy is injected into the closed-loop circuit through electromagnetic induction. This method eliminates the need for physical current leads, effectively removing heat leakage caused by leads, and making the system structure more compact and portable.

[0029] However, regardless of the charging technology used, a common technical challenge faced by the system is that after charging ends and the system enters continuous current mode, the current in the closed-loop circuit inevitably decays over time. This decay stems from a constant, albeit small, energy loss within the circuit.

[0030] Specifically, in PCS-based systems, the resistance of the superconducting junction is the primary cause of current loss; while in MOSFET-based rectifier circuits, even in the superconducting temperature range, the MOSFET switches themselves still exhibit non-negligible on-resistance. Furthermore, the inherent flux creep effect of high-temperature superconducting materials is also an intrinsic factor contributing to the current decay of the HTS coil.

[0031] In summary, existing technologies are typically limited to a single charging mode, making it difficult to effectively balance efficiency during charging with current stability during operation. The lack of an effective mechanism for actively and continuously compensating for closed-loop current decay prevents the magnetic field from remaining constant over long periods.

[0032] Based on this, this application proposes a composite excitation and current stabilization circuit for high-temperature superconducting magnets. Please refer to... Figure 1 This is one of the structural block diagrams of the composite excitation and current stabilization circuit of the high-temperature superconducting magnet provided in the embodiments of this application.

[0033] In this embodiment, the composite excitation and current stabilization circuit of the high-temperature superconducting magnet includes: an excitation and compensation module 10 and a superconducting closed-loop module 20.

[0034] The first output terminal of the excitation and compensation module 10 is connected to the first input terminal of the superconducting closed-loop module 20; the second output terminal of the excitation and compensation module 10 is connected to the second input terminal of the superconducting closed-loop module 20.

[0035] Understandably, these two modules work together via an electrical connection. The output and input terminals here indicate the direction of energy and signal transmission. This connection ensures that during circuit operation, the electrical energy generated by the excitation and compensation module 10 can be effectively transmitted and applied to the superconducting closed-loop module 20.

[0036] It is worth noting that in the specific implementation of the circuit, the first input terminal or the second output terminal are functional definitions of the electrical connection relationship of the module. They point to a logical access part, rather than limiting its physical structure to a single port.

[0037] It should be noted that the superconducting closed-loop module is configured to include at least a superconducting switch and a load magnet, which together form a closed-loop circuit. When the closed-loop circuit is in a high-resistivity state, energy is stored through the load magnet. After energy storage is completed, the superconducting switch is adjusted to bring the closed-loop circuit into a superconducting state. The excitation and compensation module is configured to charge the closed-loop circuit in the high-resistivity state during the first operating phase, and stop charging when the load magnet current reaches a preset operating current. During the second operating phase, energy is replenished to the closed-loop circuit in the superconducting state based on the principles of electromagnetic induction and rectification to compensate for current attenuation.

[0038] It is understandable that the excitation and compensation module 10 refers to a circuit unit that can provide initial excitation current to the magnet and replenish energy to the circuit to compensate for losses during subsequent operation. The superconducting closed-loop module 20 refers to a functional unit that includes a load magnet made of superconducting material and can form a near-zero resistance closed path through the adjustment of internal switches.

[0039] Understandably, the specific configuration of the superconducting closed-loop module 20 includes at least one superconducting switch and one load magnet. The load magnet here specifically refers to a coil wound from high-temperature superconducting materials, such as REBCO or Bi-2223 tape, which is a key component in the circuit for storing electromagnetic energy and generating a stable magnetic field. A superconducting switch is a device that utilizes the zero-resistance or finite-resistance characteristics of superconducting materials at or below their critical temperature to achieve switching between on and off states, such as a PCS.

[0040] It should be noted that the closed-loop circuit formed by the superconducting switch and the load magnet refers to a physically closed loop network consisting of one or more superconducting switches and load magnets connected by superconducting wires. The key is that the network as a whole can be controlled, switching between a high-resistivity state and a superconducting state, rather than being limited to a simple series connection of all components.

[0041] Specifically, the high-resistivity state is achieved by controlling one or more key superconducting switches to a high-resistivity state, thus making the entire closed loop electrically non-conductive and creating an open circuit to the external charging power supply. The superconducting state is achieved by adjusting all superconducting switches to a superconducting state. At this point, the entire loop, including the switches, magnets, and connecting wires, is in a superconducting state with no resistance, forming a perfect superconducting closed loop.

[0042] Understandably, in the initial stage of operation, the high-resistivity closed-loop circuit provides a path for the initial establishment of current. When the charging process ends, by adjusting the operating state of the superconducting switch, such as changing the power of its heater to put it into the superconducting state, the basic closed-loop circuit is transformed into the superconducting state. That is, the current mainly flows through the closed path formed by the load magnet and the superconducting switch in the superconducting state, thereby utilizing the zero-resistance characteristic of the superconductor to maintain the current for a long time.

[0043] Understandably, the operation of the excitation and compensation module 10 is divided into two stages. In the first stage, this module acts as an excitation source to charge the superconducting closed-loop module 20. This charging can be achieved by applying voltage, for example, forcing the current in the basic closed-loop circuit to build up from zero and increase until a preset operating current is reached that can generate the target magnetic field in the load magnet. In the second stage, after the superconducting closed-loop circuit is formed, the loop current will still slowly decay due to minor factors such as connector resistance and AC losses. At this time, the excitation and compensation module 10 replenishes energy to the superconducting closed-loop circuit based on the principles of electromagnetic induction and rectification.

[0044] Therefore, the first working stage is the charging and excitation stage, and the second working stage is the energy compensation stage.

[0045] It should be noted that supplementing energy to a closed-loop circuit in a superconducting state based on the principles of electromagnetic induction and rectification refers to a non-contact, lossless energy injection method used to maintain the stability of the persistent current in the superconducting closed-loop circuit. Specifically, electromagnetic induction refers to the physical principle of generating an induced electromotive force in a closed conductor using a changing magnetic field. Rectification refers to the process of converting alternating current into direct current. In the context of this application, its function is to convert the induced alternating voltage into a unidirectional current pulse that is in the same direction as the original current in the superconducting closed-loop circuit.

[0046] Therefore, this module can be implemented using a coupled inductor. The primary winding of this coupled inductor is connected to a controlled AC power supply, while the secondary winding is magnetically coupled to the superconducting closed-loop circuit. When the AC power supply generates an alternating current in the primary winding, it establishes an alternating magnetic flux in the iron core or air, thereby inducing an alternating voltage in the secondary winding. Through the natural rectification characteristics of the superconducting switch or an external rectifier, the alternating energy is converted into DC pulses, which are then directionally injected into the superconducting circuit to compensate for current losses and maintain its stability. The continuous execution of these two stages solves the problems of rapid initial current establishment and long-term stable maintenance, respectively.

[0047] In this embodiment, a composite excitation and current stabilization circuit, including an excitation and compensation module and a superconducting closed-loop module, is adopted, and electrical interconnection is achieved through the connection between the modules, providing a structural basis for phased operation. The superconducting closed-loop module forms a basic closed-loop circuit through a superconducting switch and a load magnet, and converts into a superconducting closed-loop circuit after charging, forming a superconducting path to maintain the current and solving the problem of switching between charging and operating circuits. In the first operating stage, the excitation and compensation module charges the superconducting closed-loop module to quickly reach the preset operating current, directly improving charging efficiency. In the second operating stage, energy is replenished to the superconducting circuit based on the principles of electromagnetic induction and rectification, effectively compensating for current attenuation, thereby solving the stability problem in the operating stage.

[0048] Compared with existing technologies, this solution achieves a balance between high charging efficiency and stable operating current through circuit structure design and phased control.

[0049] Based on the above, this application provides specific embodiments for illustration.

[0050] It should be noted that one implementation focuses on the internal functional architecture of the excitation and compensation module 10, wherein the excitation and compensation functions of the module are executed independently. Independent execution here means that for the two different operating stages of charging excitation and energy compensation, physically or logically independent circuit units are set up to complete them separately, thereby allowing for specialized design and optimized control of each unit.

[0051] Specifically, please refer to Figure 2 , Figure 2 This is the second structural block diagram of the composite excitation and current stabilization circuit of the high-temperature superconducting magnet provided in the embodiments of this application.

[0052] At this time, the excitation and compensation module 10 includes an excitation unit 11 and a compensation unit 12. The output terminal of the excitation unit 11 is connected to the first input terminal of the superconducting closed-loop module 20; the output terminal of the compensation unit 12 is connected to the second input terminal of the superconducting closed-loop module 20.

[0053] It should be noted that the excitation unit 11 is configured to charge the closed loop in the high-resistance state during the first working stage, and to stop charging when the load magnet current reaches the preset working current; the compensation unit 12 is configured to supplement the closed loop in the superconducting state with energy during the second working stage based on the principle of electromagnetic induction and rectification, so as to compensate for the current decay.

[0054] Understandably, the excitation unit 11 is a circuit section specifically designed to implement the functions of the first operating stage, and its core task is to inject current into the superconducting closed-loop module 20. The compensation unit 12, on the other hand, is a circuit section specifically designed to implement the functions of the second operating stage, and its core task is to maintain the long-term stability of the current after the magnet enters the continuous current operation mode.

[0055] Specifically, please refer to Figure 3 and Figure 4 , Figure 3 This is a state diagram of the first operating stage of the first circuit topology provided in the embodiments of this application; Figure 4 This is a state diagram of the second working stage of the first circuit topology provided in the embodiments of this application.

[0056] The excitation unit 11 includes a first switching switch S1 and a DC power supply; the DC power supply is connected to the first input terminal of the superconducting closed-loop module 20 through the first switching switch S1.

[0057] It should be noted that the DC power supply I DC It is an external high-power DC power supply, operating in constant current source mode, used to provide strong excitation current during the fast charging phase.

[0058] It should be noted that the first switching switch S1 is a mechanical isolation switch, which can be a mechanical contactor or relay located outside the cryogenic container, used to completely physically isolate the external power system from the internal superconducting circuit after charging is completed.

[0059] The compensation unit 12 includes a second switching switch S2, a coupling inductor, and an AC power supply. The AC power supply output is coupled through the coupling inductor and connected to the second input terminal of the superconducting closed-loop module 20 through the second switching switch S2.

[0060] It should be noted that AC power supply i AC Representing an external AC power source, it can output an asymmetrical triangular wave current to provide energy input during the compensation phase. T The period of the alternating current.

[0061] It should be noted that the second switching switch S2 is a semiconductor switch, which can be a MOSFET switch located in the low-temperature region. It is disconnected during the fast charging phase; during the compensation phase, the control system located in the room-temperature region applies a sufficient turn-on voltage to the gate of the parallel MOSFET through the gate drive circuit, causing it to fully conduct, thereby reliably connecting the secondary coil of the coupled inductor into the superconducting closed loop. To minimize the additional resistance introduced during conduction, multiple MOSFETs can be connected in parallel to significantly reduce the on-resistance.

[0062] It should be noted that the coupled inductor is formed by the coupling of a primary coil L1 and a secondary coil L2. The primary coil L1 is a copper winding coil located in the room temperature region and directly connected to the AC power supply. The secondary coil L2 is a high-temperature superconducting coil located in the low-temperature region. The mutual inductance M is the magnitude of the electromagnetic coupling between the primary and secondary coils. It characterizes the ability of energy to wirelessly transfer across physical barriers (i.e., the Dewar wall) from the room temperature region to the low-temperature region.

[0063] The superconducting closed-loop module 20 includes: when the first superconducting switch R1 and the load magnet Lload are connected in parallel with the first superconducting switch R1; the first terminal of the DC power supply is connected to the first terminal of the first switching switch S1; the second terminal of the first switching switch S1 is connected to the first terminal of the load magnet Lload and the first terminal of the second switching switch S2; the second terminal of the second switching switch S2 is connected to the first terminal of the secondary coil of the coupling inductor; the second terminal of the secondary coil of the coupling inductor is connected to the second terminal of the load magnet Lload and the second terminal of the DC power supply respectively; and the primary coil of the coupling inductor is connected in parallel with the AC power supply.

[0064] It should be noted that the first superconducting switch R1 here is a physical entity, typically a section of high-temperature superconducting tape or coil with a specific critical current value. This component achieves resistance switching through different mechanisms at different stages: in Figure 3 Marked as R1, this acts as a thermal switch, equipped with an external heater, and switches between a superconducting state (zero resistance) and a normal state (high resistance) controlled by temperature. Figure 4 The middle part is marked as R1'. At this time, it acts as a current-triggered self-rectifier bridge. Instead of using a heater, it passively triggers the resistor state by using whether the amplitude of the current flowing through it exceeds the critical current, thus realizing the rectification function.

[0065] Therefore, by utilizing the circuit topology described above, rapid excitation and lossless maintenance of the magnet can be achieved through two time-division multiplexing stages.

[0066] It should be noted that the first stage of operation utilizes an external power source for rapid charging, such as... Figure 3At this stage, the system uses an external power source to establish an initial magnetic field, and the first superconducting switch R1 operates in thermal control mode. The first switching switch S1 is closed, and the second switching switch S2 is opened. The heater is then activated, heating the first superconducting switch R1 above its critical temperature, causing it to exhibit a high-resistance state. At this point, the DC power supply I is activated. DC The current is increased linearly. Since the first superconducting switch R1 is in a high-resistance state, current is injected into the load magnet Lload, forming a basic closed-loop circuit. When the load current reaches the preset target value, the power supply maintains a constant current while the heater is turned off. The first superconducting switch R1 cools and returns to a zero-resistance superconducting state, locking the magnet current within the superconducting closed loop, thus converting it into a superconducting closed-loop circuit. Subsequently, the first switching switch S1 is disconnected, removing the external power supply, and the system enters continuous current mode.

[0067] It should be noted that the second working stage is based on self-rectification compensation of asymmetric waveforms, such as... Figure 4 During this stage, electromagnetic induction is used to compensate for losses, and the first superconducting switch switches to the current-triggered self-rectification mode, which is the first superconducting switch R1'. The first switching switch S1 is kept open in the circuit, and the second switching switch S2 is closed, connecting the secondary coil L2 in series with the first superconducting switch R1' to form a closed loop.

[0068] At this time, control AC power supply i AC An asymmetrical triangular wave current is injected into the primary circuit.

[0069] Understandably, during the pump-in (rectification) half-cycle: at the steep change edge of the asymmetric waveform (high di / dt), a large transient current is induced in the secondary coil L2, causing the total current flowing through the first superconducting switch R1' to momentarily exceed its critical current. The component thus loses quench and transitions from a superconducting state to a resistive state. The voltage across this resistor acts as an equivalent electromotive force, injecting energy into the load magnet Lload. During the reset (freewheeling) half-cycle: at the gentle change edge of the waveform (low di / dt), the induced current is smaller, and the total current falls back below the critical current. The first superconducting switch R1' recovers and remains in a superconducting state with zero resistance, and the circuit is in a lossless freewheeling state.

[0070] Understandably, through this periodic overcurrent super-rectification mechanism, the system actively and precisely compensates for energy loss in the circuit without the need for continuous thermal control, thus achieving long-term stable maintenance of the superconducting magnet current.

[0071] Based on this implementation method, the superconducting switches in the two modes can be separated to form an independent switch-type architecture. Please refer to... Figure 5 and Figure 6 , Figure 5 This is a state diagram of the first operating stage of the second circuit topology provided in the embodiments of this application;Figure 6 This is a state diagram of the second working stage of the second circuit topology provided in the embodiments of this application.

[0072] In this design, while keeping the excitation unit 11 and compensation unit 12 unchanged, the superconducting closed-loop module 20 is modified. The superconducting closed-loop module 20 includes: a second superconducting switch R2, a third superconducting switch R3, and a load magnet Lload. The first terminal of the DC power supply is connected to the first terminal of the first switching switch S1; the second terminal of the first switching switch S1 is connected to the first terminals of the second superconducting switch R2 and the third superconducting switch R3; the second terminal of the third superconducting switch R3 is connected to the first terminal of the load magnet Lload; the second terminal of the load magnet Lload is connected to the second terminal of the second superconducting switch R2 and the second terminal of the DC power supply; the first terminal of the second switching switch S2 is connected to the first terminal of the third superconducting switch R3; the second terminal of the second switching switch S2 is connected to the first terminal of the secondary coil of the coupling inductor; the second terminal of the secondary coil of the coupling inductor is connected to the second terminal of the third superconducting switch R3; the primary coil of the coupling inductor is connected in parallel with the AC power supply.

[0073] It is understandable that the second superconducting switch R2 operates in thermal control mode; the third superconducting switch R3 operates in current-triggered self-rectification mode.

[0074] It should be noted that, in Figure 5 During the rapid charging phase using an external power source, the first switching switch S1 is closed, while the second switching switch S2 in the compensation branch is open. At this time, only the second superconducting switch R2 in the main circuit is activated. During operation, the heater is first started to drive the second superconducting switch R2 to its normal high-resistance state, and then the external DC power supply I is activated. DC Due to the high resistance state of the second superconducting switch R2, the injected current flows into the load magnet Lload. During this process, the opening of the second switching switch S2 effectively isolates the secondary coil from the circuit. Simultaneously, due to the external AC power supply i AC With the circuit in the off state, the independent third superconducting switch R3 is not triggered by the induced current and remains in a superconducting state with zero resistance. Therefore, the entire compensation branch is in an open circuit or unobstructed state, without generating any rectified voltage or additional impedance, ensuring that the fast charging process is undisturbed.

[0075] It should be noted that, in Figure 6 In the compensation maintenance phase, the first switching switch S1 opens to isolate the external power supply, and the second switching switch S2 closes, connecting the compensation branch to the closed loop. At this time, the second superconducting switch R2 in the main circuit has stopped heating and returned to the superconducting state (zero resistance), forming a superconducting closed-loop circuit with the load magnet Lload, carrying the majority of the load current. External AC power supply i ACAn asymmetrical triangular wave current is output to the primary coil, inducing a current in the secondary coil through electromagnetic induction. The core of this stage lies in using an independent second superconducting switch R2 as a dedicated rectifier: during the steep peak of the induced current waveform, the total current flowing through the superconducting switch instantaneously exceeds its critical current, causing it to lose superconductivity and generate resistance, thereby pumping energy into the closed loop; while during the flattening of the waveform, the current falls back below the critical value, and the superconducting switch quickly returns to the superconducting state.

[0076] It should be noted that the improved independent switch architecture has the advantages of parameter decoupling and independent optimization compared to the aforementioned multiplexed architecture. In the multiplexed architecture, a single component must simultaneously meet both high voltage resistance (for fast charging) and fast response (for rectification compensation), resulting in a trade-off in the design. In this independent architecture, the second superconducting switch R2 and the third superconducting switch R3 can be optimized for their respective functions.

[0077] Specifically, the second superconducting switch R2 can be designed with a large inductance and long wire structure to achieve extremely high turn-off resistance, thereby supporting higher charging voltages and shortening excitation time. The third superconducting switch R3, on the other hand, can be designed with a low inductance and low heat capacity structure to achieve extremely fast thermal recovery, thus adapting to higher frequency compensation waveforms and significantly improving flux pumping efficiency. Furthermore, this physically separated design achieves thermal management isolation; the resistive heat generated by the third superconducting switch R3 during rectification will not be conducted to the second superconducting switch R2, further enhancing the system's thermal stability and reliability during long-term operation.

[0078] It should be noted that, in another embodiment, the excitation and compensation functions of the excitation and compensation module 10 are executed in a mixed manner. Please refer to... Figure 7 and Figure 8 , Figure 7 This is a state diagram of the third circuit topology provided in the embodiments of this application; Figure 8 This is a state diagram of the fourth circuit topology provided in the embodiments of this application.

[0079] At this time, the excitation and compensation module 10 includes: an AC power supply, a coupling inductor, a third switching switch S3, and a fourth switching switch S4; both the third switching switch S3 and the fourth switching switch S4 are semiconductor switches; the AC power supply is connected in parallel with the primary coil of the coupling inductor; the first end of the secondary coil of the coupling inductor is connected to the first end of the third switching switch S3; the second end of the third switching switch S3 is connected to the first end of the fourth switching switch S4; and the second end of the fourth switching switch S4 is connected to the second end of the secondary coil of the coupling inductor.

[0080] Among them, Figure 7In order to achieve half-wave rectification, the superconducting closed-loop module 20 includes: a fourth superconducting switch R4, a fifth superconducting switch R5, and a load magnet Lload; the fourth superconducting switch R4 is connected in parallel with the third switching switch S3; the fifth superconducting switch R5 is connected in parallel with the fourth switching switch S4 to form a freewheeling branch, which is connected in parallel with the load magnet Lload.

[0081] Among them, Figure 8 In order to achieve full-wave rectification, the superconducting closed-loop module 20 includes: a fourth superconducting switch R4, a fifth superconducting switch R5, and a load magnet Lload; the fourth superconducting switch R4 is connected in parallel with the third switching switch S3; the fifth superconducting switch R5 is connected in parallel with the fourth switching switch S4; the first end of the load magnet Lload is connected to the center tap of the secondary coil of the coupled inductor; the second end of the load magnet Lload is connected to the second end of the third switching switch S3.

[0082] It should be noted that this is consistent with the aforementioned implementation method. L1 is a room-temperature primary coil, and L2 is a low-temperature superconducting secondary coil. It is particularly important to note that... Figure 8 In the full-wave rectification implementation shown, the secondary coil adopts a center-tapped structure, consisting of two symmetrical windings L21 and L22; M is the cross-temperature mutual inductance, which characterizes the energy coupling capability between the primary and secondary windings.

[0083] It should be noted that AC power supply i AC Two output modes are required. During the charging phase, a high-power AC current, either a sine wave or a square wave, is output to drive the MOSFET circuit. During the compensation phase, a low-power AC current of a specific frequency / amplitude, such as an asymmetrical wave, is output to drive the superconducting switching circuit.

[0084] It should be noted that the third switching switch S3 and the fourth switching switch S4 are both low-temperature semiconductor switches; the fourth superconducting switch R4 and the fifth superconducting switch R5 are superconducting switches made of high-temperature superconducting tape.

[0085] In this embodiment, the core of the circuit is the construction of a hybrid switching unit, in which each cryogenic semiconductor switch (the third switching switch S3 and the fourth switching switch S4) is directly connected in parallel with a corresponding superconducting switching element (the fourth superconducting switch R4 and the fifth superconducting switch R5).

[0086] In this design, the semiconductor switch, composed of MOSFETs, is responsible for carrying the large current during the fast charging phase. The superconducting switching element is defined as a controllable impedance device equipped with a state control mechanism. This state control mechanism can respond to externally applied control signals, including but not limited to thermal, magnetic, or electric field excitations, and actively adjust the physical parameters of the superconducting element, such as temperature or magnetic flux density, to cause a reversible transition between a zero-resistance superconducting state and a high-resistance normal state. Through this parallel architecture, this application utilizes the physical law that current preferentially flows through low-resistance paths to achieve automatic and lossless current transfer between the semiconductor branch and the superconducting branch.

[0087] For half-wave rectification Figure 7 The working process of this embodiment is divided into three stages in sequence: MOSFET fast charging, automatic current transfer, and superconducting rectification compensation.

[0088] First, during the MOSFET fast charging phase, the system utilizes the high-frequency characteristics of the semiconductor switches to rapidly excite the magnet. In this phase, the state control device equipped with the superconducting switching elements is activated, applying external excitation, such as turning on the heater or applying an external magnetic field, forcing all superconducting switches (fourth superconducting switch R4 and fifth superconducting switch R5) to maintain a high-resistance normal state. At this time, due to the high impedance of the superconducting branch, it is approximately an open circuit in the circuit. The external power supply outputs high-power AC, and the MOSFET switches (third switching switch S3 and fourth switching switch S4) operate alternately according to a standard rectification sequence: during the charging half-cycle, third switching switch S3 is on, and fourth switching switch S4 is off, with energy mainly injected into the load magnet through the low-impedance third switching switch S3; during the freewheeling half-cycle, third switching switch S3 is off, and fourth switching switch S4 is on, with the magnet current forming a freewheeling loop through the fourth switching switch S4.

[0089] Secondly, once the load current reaches the preset target value, the system enters the automatic current transfer phase. During this phase, the AC power supply to the primary coil is stopped, and the fourth switching switch S4 on the continuous current side remains in the on state to maintain the loop current. Simultaneously, the external excitation applied to the fifth superconducting switch R5 is removed, such as turning off the heater or removing the external magnetic field. With the removal of the external excitation, the fifth superconducting switch R5 quickly returns to a superconducting state with zero resistance. At this time, since the impedance (zero) of the fifth superconducting switch R5 in the parallel branch is much smaller than the on-resistance of the fourth switching switch S4 in the on state, according to the parallel current shunting principle, the current in the load magnet will automatically and smoothly transfer completely from the lossy semiconductor branch to the lossless superconducting branch. After the current transfer is complete, the fourth switching switch S4 is turned off, and the system completes a seamless physical switch from semiconductor mode to pure superconducting mode.

[0090] Finally, the system enters the superconducting self-rectified compensation sustaining phase. During this phase, all MOSFET switches remain off. The dual-mode AC power supply switches to compensation mode, outputting a continuous low-power AC current of a specific frequency and amplitude, such as an asymmetrical triangular wave, to the primary coil as an active external excitation. This external excitation, combined with the critical current characteristics of the superconducting switching element itself, achieves the rectification function: during the pumping of induced current, the current flowing through the superconducting switch exceeds its critical current threshold, triggering it to transition to a resistive state, generating a rectified voltage to replenish energy to the load; during the reset process, the current falls back below the critical value, the superconducting switch returns to the superconducting state, and the current maintains a lossless freewheeling current. Through this mechanism of external electromagnetic excitation combined with internal physical characteristics, the system achieves continuous and precise compensation for magnet current attenuation.

[0091] For full-wave rectification Figure 8 Its working principle is consistent with the process described above. The circuit contains two symmetrical hybrid switching units. During the fast charging phase, the fourth superconducting switch R4 and the fifth superconducting switch R5 are kept in a high-resistance state, and full-wave charging is achieved by alternating the conduction of the third switching switch S3 and the fourth switching switch S4. During the current switching phase, the superconducting switches return to the superconducting state, and the automatic transfer of current is achieved by utilizing the resistance difference. During the compensation maintenance phase, the external power supply continuously outputs AC excitation, driving the fourth superconducting switch R4 and the fifth superconducting switch R5 to alternately enter the resistive state for full-wave rectification compensation, thereby obtaining higher energy transfer efficiency and a more stable magnetic field output.

[0092] In addition, this application proposes a composite excitation and current stabilization method for high-temperature superconducting magnets. Please refer to... Figure 9 , Figure 9 This is a schematic flowchart of the composite excitation and current stabilization method for high-temperature superconducting magnets provided in the embodiments of this application.

[0093] In this embodiment, the method utilizes the composite excitation and current stabilization circuit of the high-temperature superconducting magnet of the first aspect, including: Step A10: Adjust the superconducting switch to put the closed-loop circuit of the superconducting closed-loop module in a high-resistance state.

[0094] Step A20: Control the excitation and compensation module to enter the first working stage to charge the closed loop in a high-resistance state.

[0095] Step A30: When the load magnet current reaches the preset operating current, control the excitation and compensation module to exit the first working stage.

[0096] Step A40: Adjust the superconducting switch to put the closed-loop circuit of the superconducting closed-loop module into a superconducting state.

[0097] Step A50: Control the excitation and compensation module to enter the second working stage to replenish energy to the closed loop in the superconducting state in order to compensate for the current decay.

[0098] For details on the various implementation methods, please refer to the above text, which will not be elaborated here.

[0099] Understandably, this method precisely controls the establishment and switching of the two states of the closed-loop circuit through steps A10 and A40. The initialization operation in step A10 provides a path for charging by the external power supply, while the switching operation in step A40 is key to enabling the superconducting magnet to enter a near-zero loss continuous current operation mode. This directly corresponds to and realizes the core function of the superconducting closed-loop module in the circuit design. Steps A20 and A30 define an efficient and controlled charging process. By controlling the entry and exit of the first working stage, it ensures that the excitation unit can quickly and accurately charge the load magnet to the preset operating current. This corresponds to the technical means to solve the problem of efficiency in the charging stage.

[0100] Understandably, in the dynamic compensation stage of step A50, the closed-loop current will slowly decay due to extremely small connector resistance or AC losses. In the second stage, the excitation and compensation module replenishes a small amount of energy to the closed-loop circuit in some non-contact manner, such as inductive coupling, to accurately compensate for the decay and thus achieve current stabilization.

[0101] Specifically, step A50 defines a long-term current stabilization mechanism. By controlling the excitation and compensation module to periodically enter the second working stage, the energy replenishment function based on electromagnetic induction and rectification is activated, thereby dynamically offsetting the current decay in the circuit. This corresponds to the technical means to solve the stability problem during operation.

[0102] It is worth noting that the beneficial effect of the composite excitation and current stabilization method for high-temperature superconducting magnets provided in this application stems from the orderly and phased control of the aforementioned composite excitation and current stabilization circuit. Through steps A10 to A50, this method clearly defines the timing logic and control objectives of the operation, thereby transforming the functional potential of the circuit hardware into practical technical advantages.

[0103] In this embodiment, the charging function and the current stabilization function are decoupled in time and combined in an orderly manner through the aforementioned phased and repeatable process. During the charging phase, the damping provided by the superconducting switch in its normal state enables the rapid, stable, and controllable establishment of the charging current. During the operation phase, the superconducting closed-loop circuit formed by the superconducting switch in its superconducting state and the load magnet, combined with periodic inductive energy replenishment, achieves long-term high-precision stability of the operating current.

[0104] Compared with existing technologies, this method ensures the efficiency of the charging process in terms of process and ensures the stability of continuous current operation through unique compensation control logic, thus achieving a technical effect that balances both aspects at the overall operation level.

[0105] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0106] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0107] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A composite excitation and current stabilization circuit for a high-temperature superconducting magnet, characterized in that, include: Excitation and compensation module, and superconducting closed-loop module; The first output terminal of the excitation and compensation module is connected to the first input terminal of the superconducting closed-loop module; the second output terminal of the excitation and compensation module is connected to the second input terminal of the superconducting closed-loop module. The superconducting closed-loop module is configured to include at least a superconducting switch and a load magnet, the superconducting switch and the load magnet forming a closed-loop circuit; when the closed-loop circuit is in a high-resistivity state, energy is stored through the load magnet; and after the energy storage is completed, the superconducting switch is adjusted to make the closed-loop circuit in a superconducting state. The excitation and compensation module is configured to charge the closed loop in a high-resistance state during the first working phase, and to stop charging when the load magnet current reaches the preset working current. In the second working stage, energy is replenished to the closed loop in the superconducting state based on the principles of electromagnetic induction and rectification to compensate for current decay.

2. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 1, characterized in that, When the excitation and compensation functions of the excitation and compensation module are executed independently, the excitation and compensation module includes: an excitation unit and a compensation unit; The output terminal of the excitation unit is connected to the first input terminal of the superconducting closed-loop module; the output terminal of the compensation unit is connected to the second input terminal of the superconducting closed-loop module. The excitation unit is configured to charge the closed loop in a high-resistance state during the first working phase, and to stop charging when the load magnet current reaches the preset working current. The compensation unit is configured to replenish energy to the closed loop in the superconducting state during the second working phase based on the principles of electromagnetic induction and rectification, in order to compensate for current attenuation.

3. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 2, characterized in that, The excitation unit includes: a first switching switch and a DC power supply; The DC power supply is connected to the first input terminal of the superconducting closed-loop module through the first switching switch; the first switching switch is a mechanical isolation switch.

4. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 3, characterized in that, The compensation unit includes: a second switching switch, a coupling inductor, and an AC power supply; The AC power output is coupled through the coupling inductor and connected to the second input terminal of the superconducting closed-loop module via the second switching switch; the second switching switch is a semiconductor switch.

5. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 4, characterized in that, When the superconducting closed-loop module includes: a first superconducting switch and a load magnet: The load magnet is connected in parallel with the first superconducting switch; The first terminal of the DC power supply is connected to the first terminal of the first switching switch; the second terminal of the first switching switch is connected to the first terminal of the load magnet and the first terminal of the second switching switch; the second terminal of the second switching switch is connected to the first terminal of the secondary coil of the coupled inductor; the second terminal of the secondary coil of the coupled inductor is connected to the second terminal of the load magnet and the second terminal of the DC power supply, respectively. The primary coil of the coupled inductor is connected in parallel with the AC power supply.

6. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 4, characterized in that, When the superconducting closed-loop module includes: a second superconducting switch, a third superconducting switch, and a load magnet: The first terminal of the DC power supply is connected to the first terminal of the first switching switch; the second terminal of the first switching switch is connected to the first terminal of the second superconducting switch and the first terminal of the third superconducting switch; the second terminal of the third superconducting switch is connected to the first terminal of the load magnet; the second terminal of the load magnet is connected to the second terminal of the second superconducting switch and the second terminal of the DC power supply. The first end of the second switching switch is connected to the first end of the third superconducting switch; the second end of the second switching switch is connected to the first end of the secondary coil of the coupling inductor; the second end of the secondary coil of the coupling inductor is connected to the second end of the third superconducting switch. The primary coil of the coupled inductor is connected in parallel with the AC power supply.

7. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 1, characterized in that, When the excitation and compensation functions of the excitation and compensation module are executed in a mixed manner, the excitation and compensation module includes: an AC power supply, a coupling inductor, a third switching switch, and a fourth switching switch; Both the third and fourth switching switches are semiconductor switches; The AC power supply is connected in parallel with the primary coil of the coupled inductor; the first end of the secondary coil of the coupled inductor is connected to the first end of the third switching switch; the second end of the third switching switch is connected to the first end of the fourth switching switch; and the second end of the fourth switching switch is connected to the second end of the secondary coil of the coupled inductor.

8. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 7, characterized in that, To achieve half-wave rectification, the superconducting closed-loop module includes: a fourth superconducting switch, a fifth superconducting switch, and a load magnet; The fourth superconducting switch is connected in parallel with the third switching switch; the fifth superconducting switch is connected in parallel with the fourth switching switch to form a freewheeling branch, which is connected in parallel with the load magnet.

9. The composite excitation and current stabilization circuit for a high-temperature superconducting magnet as described in claim 7, characterized in that, To achieve full-wave rectification, the superconducting closed-loop module includes: a fourth superconducting switch, a fifth superconducting switch, and a load magnet; The fourth superconducting switch is connected in parallel with the third switching switch; the fifth superconducting switch is connected in parallel with the fourth switching switch; the first end of the load magnet is connected to the center tap of the secondary coil of the coupled inductor; the second end of the load magnet is connected to the second end of the third switching switch.

10. A composite excitation and current stabilization method for a high-temperature superconducting magnet, characterized in that, The method employs the composite excitation and current stabilization circuit of the high-temperature superconducting magnet as described in any one of claims 1 to 9, including: Adjust the superconducting switch to put the closed-loop circuit of the superconducting closed-loop module in a high-resistance state; The excitation and compensation module is controlled to enter the first working stage to charge the closed loop, which is in a high-resistance state. When the load magnet current reaches the preset operating current, the excitation and compensation module is controlled to exit the first working stage. Adjust the superconducting switch to put the closed-loop circuit of the superconducting closed-loop module into a superconducting state; The excitation and compensation module is controlled to enter the second working stage to replenish energy to the closed loop in the superconducting state in order to compensate for the current decay.

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