energy storage device

Abstract

The application provides a kind of energy storage device, it relates to energy conversion technical field.The energy storage device includes: annular energy storage coil;Permanent magnet is configured to be able to move relative to energy storage coil along the axial direction of energy storage coil;Annular compensation coil is coaxially sleeved on the periphery of permanent magnet, and is configured to move synchronously with permanent magnet, and the magnetic flux of energy storage coil changes and generates induced current in the process of approaching energy storage coil: mechanical energy is converted into electromagnetic energy and is stored;Compensation coil is configured to generate the same magnetic field as the magnetic field direction of permanent magnet, to compensate the reverse magnetic flux generated by energy storage coil under the action of permanent magnet.

Description

Technical Field

[0001] At least one embodiment of the present invention relates to the field of energy conversion technology, and more particularly to an energy storage device. Background Technology

[0002] Existing vehicle regenerative braking energy storage technologies mostly use flywheels or supercapacitors, but they all need to be used in conjunction with electric motors or generators to achieve the conversion of kinetic energy into electrical energy, resulting in multiple energy conversion stages and limited efficiency.

[0003] Superconducting energy conversion or storage devices in related technologies utilize the direct interaction between a permanent magnet and a closed superconducting coil. By moving the permanent magnet to change the magnetic flux of the coil, mechanical energy is directly converted into electromagnetic energy. This method boasts advantages such as simple structure and high conversion efficiency, and has application potential in the field of regenerative braking for urban rail transit. However, in superconducting energy storage devices, when the permanent magnet approaches the energy storage coil, the coil induces a reverse magnetic flux, weakening the positive magnetic field of the permanent magnet and thus limiting the maximum energy storage capacity. Summary of the Invention

[0004] In view of this, the present invention provides an energy storage device that can increase the maximum energy storage capacity of the energy storage device.

[0005] According to an embodiment of the present invention, an energy storage device is provided, comprising: a ring-shaped energy storage coil; a permanent magnet configured to move relative to the energy storage coil along the axial direction of the energy storage coil; and a ring-shaped compensation coil coaxially disposed around the permanent magnet and configured to move synchronously with the permanent magnet. As the permanent magnet approaches the energy storage coil, the magnetic flux of the energy storage coil changes and generates an induced current, converting mechanical energy into electromagnetic energy and storing it. The compensation coil is configured to generate a magnetic field in the same direction as the magnetic field of the permanent magnet to compensate for the reverse magnetic flux generated by the energy storage coil under the action of the permanent magnet.

[0006] According to an embodiment of the present invention, the compensation coil includes a superconducting coil that, during the cooling process to below the superconducting transition temperature in the magnetic field environment generated by the permanent magnet, generates a pinning effect to lock the positive magnetic flux of the permanent magnet, and induces a magnetic field with the same direction as the magnetic field of the permanent magnet as the permanent magnet approaches the energy storage coil.

[0007] According to an embodiment of the present invention, the compensation coil further includes a normal conducting coil having a first end and a second end that are insulated from each other, so that during the process of the permanent magnet releasing energy from the maximum energy storage position, a direct current is passed through the first end and the second end, so that the normal conducting coil generates a magnetic flux opposite to the magnetic field direction of the permanent magnet, thereby canceling or weakening the magnetic field generated by the permanent magnet, and enabling the permanent magnet to translate axially relative to the energy storage coil under the action of an external force.

[0008] According to an embodiment of the present invention, the superconducting tape wound with the superconducting coil and the conventionally conducting tape wound with the conventionally conducting coil are stacked in the thickness direction of the superconducting tape. The compensation coil further includes a filler conductor, which is filled between the conventionally conducting tape and the superconducting tape and is adapted to electrically connect the conventionally conducting tape and the superconducting tape so that in the event of a quench failure in the superconducting coil, the current of the superconducting coil is allowed to migrate to the conventionally conducting coil through the filler conductor.

[0009] According to an embodiment of the present invention, the compensation coil further includes: a pair of buffer strips respectively disposed on both sides of the superconducting tape in the width direction, which are suitable for preventing the filler conductor from overflowing from the conventional conductive tape and the superconducting tape in the molten state.

[0010] According to an embodiment of the present invention, the buffer strip includes: a main body portion that partially extends between the superconducting strip and the conventionally conducting strip; and a first protrusion portion that protrudes from the side of the main body portion away from the filling conductor, wherein the superconducting strip is partially disposed on the first protrusion portion on both sides opposite to each other in the width direction, so as to cooperate with the main body portion, the conventionally conducting strip, and the main body portion of another buffer strip to form a closed space, thereby confining the filling conductor within the closed space.

[0011] According to an embodiment of the present invention, the buffer strip further includes a second protrusion that protrudes from the side of the first protrusion away from the superconducting strip, so as to abut against the second protrusion of the adjacent winding turn to form a nested structure.

[0012] According to an embodiment of the present invention, the geometric center of the compensation coil and the geometric center of the permanent magnet are located in a plane perpendicular to the axial direction.

[0013] According to an embodiment of the present invention, the superconducting coil is configured to: lock the positive magnetic flux of the permanent magnet and the magnetic flux generated by the initial current during the process of charging an initial current through an external excitation device and cooling to below the superconducting transition temperature in the magnetic field environment, so as to adjust the maximum energy storage of the energy storage coil.

[0014] According to an embodiment of the present invention, the compensation coil is a double-pane coil or a multi-pane coil.

[0015] In this embodiment, the compensation coil is configured to generate a magnetic field in the same direction as the permanent magnet's magnetic field. This unidirectional magnetic field effectively compensates for the positive flux loss caused by the reverse magnetic flux of the energy storage coil, ensuring that the effective magnetic flux of the permanent magnet is maintained throughout the energy storage process and avoiding flux attenuation caused by the reverse magnetic flux. Therefore, the energy storage coil can obtain a larger change in magnetic flux as the permanent magnet moves from its initial position to its maximum energy storage position, thereby inducing a higher current and converting more mechanical energy into electromagnetic energy stored in the energy storage coil, thus increasing the maximum energy storage capacity of the energy storage device. Attached Figure Description

[0016] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0017] Figure 1 A perspective view of an energy storage device according to an embodiment of the present invention is shown;

[0018] Figure 2 A state change diagram of an energy storage device according to an embodiment of the present invention is shown;

[0019] Figure 3 A perspective view of a compensation coil according to an embodiment of the present invention is shown;

[0020] Figure 4 A perspective view of a compensation coil according to another embodiment of the present invention is shown;

[0021] Figure 5 A cross-sectional view of a single-turn compensation coil according to an embodiment of the present invention is shown;

[0022] Figure 6 A cross-sectional view of a compensation coil according to an embodiment of the present invention is shown.

[0023] The annotations in the attached figures are explained as follows:

[0024] 1. Energy storage coil;

[0025] 2. Permanent magnet;

[0026] 3. Compensating coil; 31. Superconducting tape; 32. Normally conducting tape; 33. Filler conductor; 34. Buffer strip; 341. Main body; 342. First protrusion; 343. Second protrusion. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0029] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0030] When using expressions such as "at least one of A, B, and C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C. Similarly, when using expressions such as "at least one of A, B, or C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C.

[0031] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of the present invention. Throughout the accompanying drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding the present invention.

[0032] In the process of realizing this invention, it was discovered that in existing superconducting energy storage devices, a structure is typically employed where a permanent magnet is coupled with a closed superconducting energy storage coil. The permanent magnet can move along the axial direction of the energy storage coil. When the permanent magnet approaches the energy storage coil, the magnetic flux within the coil increases. According to Lenz's law, an induced current is generated in the energy storage coil. The magnetic field generated by this induced current is in the opposite direction to the magnetic field of the permanent magnet, thus forming a reverse magnetic flux. This reverse magnetic flux directly cancels out part of the positive magnetic flux generated by the permanent magnet, resulting in the net magnetic flux passing through the energy storage coil (i.e., the effective magnetic flux of the permanent magnet) being less than the original magnetic flux of the permanent magnet itself.

[0033] Since the magnitude of the induced current in the energy storage coil depends on the rate of change of magnetic flux and the total amount of magnetic flux change, and the upper limit of the amount of magnetic flux change is restricted after the effective magnetic flux of the permanent magnet is weakened, even if the permanent magnet moves from the initial position to a position that is completely opposite to the energy storage coil, the maximum value of the magnetic flux change that the coil can experience is far lower than the theoretical value corresponding to the original magnetic flux of the permanent magnet.

[0034] Therefore, the maximum current that the energy storage coil can induce is limited to a low level, resulting in the maximum electromagnetic energy that the energy storage device can store being far below the theoretical limit. More seriously, as the permanent magnet moves closer, the reverse magnetic flux continuously increases, and the weakening effect on the permanent magnet's magnetic field becomes more and more obvious, causing the stored energy to show a premature saturation trend with changes in displacement, thus fundamentally limiting the maximum energy storage capacity of existing superconducting energy storage devices.

[0035] Therefore, increasing the maximum energy storage capacity of energy storage devices has become an urgent technical problem to be solved in this field.

[0036] Figure 1 A perspective view of an energy storage device according to an embodiment of the present invention is shown. Figure 2 A diagram showing the state changes of an energy storage device according to an embodiment of the present invention is provided.

[0037] According to an embodiment of the present invention, an energy storage device is provided. For example... Figure 1 and Figure 2 As shown, the energy storage device includes a ring-shaped energy storage coil 1, a permanent magnet 2, and a ring-shaped compensation coil 3. The permanent magnet 2 is configured to move along the axial direction of the energy storage coil 1 ( Figure 1 The compensation coil 3 moves relative to the energy storage coil 1 (the direction of the extension of the central axis). The compensation coil 3 is coaxially fitted around the permanent magnet 2 and configured to move synchronously with the permanent magnet 2. As the permanent magnet 2 approaches the energy storage coil 1... Figure 2 (a) towards Figure 2 (b) During the movement): the magnetic flux of the energy storage coil 1 changes and generates an induced current, converting mechanical energy into electromagnetic energy and storing it; the compensation coil 3 is configured to generate a magnetic field in the same direction as the magnetic field of the permanent magnet 2 to compensate for the reverse magnetic flux generated by the energy storage coil 1 under the action of the permanent magnet 2.

[0038] In this embodiment, the compensation coil 3 is configured to generate a magnetic field in the same direction as the magnetic field of the permanent magnet 2. This unidirectional magnetic field effectively compensates for the positive flux loss caused by the reverse magnetic flux of the energy storage coil 1, ensuring that the effective magnetic flux of the permanent magnet 2 is maintained throughout the energy storage process and avoiding flux attenuation caused by the reverse magnetic flux. Therefore, the energy storage coil 1 can obtain a larger change in magnetic flux as the permanent magnet 2 moves from its initial position to its maximum energy storage position, thereby inducing a higher current and converting more mechanical energy into electromagnetic energy stored in the energy storage coil 1, thus increasing the maximum energy storage capacity of the energy storage device. Simultaneously, since the compensation coil 3 moves synchronously with the permanent magnet 2, no additional drive or control mechanism is required, resulting in a compact structure that is easy to integrate without altering the original energy storage working principle, exhibiting good engineering applicability and reliability.

[0039] As an example, the permanent magnet 2 can be a roughly cylindrical structure. Roughly cylindrical can be understood as the permanent magnet 2 being similar to a cylinder in general, that is, having a parallel upper and lower base and a side surface, but there may be certain manufacturing tolerances or minor deformations in the diameter of the base, height, shape of the base (such as roundness), perpendicularity of the axis to the base, or the profile of the side surface, which may result in it not completely conforming to the strict geometric definition of a cylinder.

[0040] As an example, the compensation coil 3 is sleeved outside the permanent magnet 2. The inner side of the compensation coil 3 can be spaced apart from the permanent magnet 2 or it can be in contact with the permanent magnet 2.

[0041] According to an embodiment of the present invention, the energy storage coil 1 is a closed annular coil wound from a superconducting tape 31. The superconducting material of the superconducting tape 31 may include a type II superconductor with an operating temperature in the liquid nitrogen temperature range (approximately -196°C), possessing a high critical current density and a high critical magnetic field, and capable of stable operation in the strong magnetic field environment provided by the permanent magnet 2.

[0042] As an example, Class II superconductors may include rare earth barium copper oxide (ReBCO) and bismuth strontium calcium copper oxide (2223 phase) (Bi-2223).

[0043] The energy storage coil 1 can be wound into a double-pane coil (or multiple double-pane stacks) by superconducting tape 31 to enhance magnetic field uniformity and mechanical strength.

[0044] According to an embodiment of the present invention, the geometric center of the compensation coil 3 and the geometric center of the permanent magnet 2 are located in a plane perpendicular to the axial direction.

[0045] In such an embodiment, it is possible to ensure that during the energy storage process ( Figure 2 (a) towards Figure 2 During the (b) movement process, when the permanent magnet 2 moves to the maximum energy storage position directly opposite the energy storage coil 1, Figure 2 When the position shown in (b) is reached, the compensation coil 3 is also directly opposite the energy storage coil 1, so that the magnetic field generated by the compensation coil 3 and the positive magnetic field generated by the permanent magnet 2 can be coaxially superimposed to the maximum extent and pass through the energy storage coil 1, compensating for the reverse magnetic flux with the highest efficiency and maintaining the effective magnetic flux of the permanent magnet 2. At the same time, since the geometric center of the compensation coil 3 and the geometric center of the permanent magnet 2 are aligned in the axial direction, the change in magnetic flux of the permanent magnet 2 passing through the compensation coil 3 and the change in magnetic flux passing through the energy storage coil 1 remain synchronized throughout the entire stroke of the permanent magnet 2 moving from the initial position to the maximum energy storage position. This avoids inconsistent magnetic flux change rates or radial force components caused by eccentricity, ensuring the smoothness and consistency of the energy storage process. In addition, center alignment can also reduce unnecessary radial electromagnetic forces between the permanent magnet 2 and the compensation coil 3, reduce vibration and noise, improve the mechanical stability of the energy storage device, and geometrically optimize the magnetic circuit coupling, providing a structural basis for improving energy storage efficiency and device reliability.

[0046] Figure 3 A perspective view of a compensation coil according to an embodiment of the present invention is shown. Figure 4 A perspective view of a compensation coil according to another embodiment of the present invention is shown.

[0047] According to embodiments of the present invention, such as Figure 3 and Figure 4 As shown, the compensation coil 3 includes a superconducting coil. During the cooling process to below the superconducting transition temperature in the magnetic field environment generated by the permanent magnet 2, the superconducting coil generates a pinning effect to lock the positive magnetic flux of the permanent magnet 2, and induces a magnetic field with the same direction as the magnetic field of the permanent magnet 2 as the permanent magnet 2 approaches the energy storage coil 1.

[0048] The superconducting material used in superconducting coils may include type II superconductors.

[0049] Type II superconductors contain microscopic defects (such as grain boundaries, dislocations, and non-superconducting inclusions). When a Type II superconductor is cooled to a superconducting state in the magnetic field generated by permanent magnet 2, the magnetic field lines are pinned to these microscopic defects and cannot move freely.

[0050] After cooling, the superconducting coil locks in the positive magnetic flux of the permanent magnet 2 passing through it, which becomes the locking reference for the coil. During subsequent energy storage, when the permanent magnet 2 approaches the energy storage coil 1, the coil generates a reverse magnetic flux. This reverse magnetic flux also passes through the compensation coil 3 and attempts to change its locked positive magnetic flux.

[0051] According to Lenz's law, the superconducting closed loop formed by the superconducting coil resists any change in magnetic flux, thereby inducing an additional current in the compensation coil 3. The magnetic field generated by this induced current is in the same direction as the positive magnetic flux during locking, that is, in the same direction as the magnetic field of the permanent magnet 2. This same-direction magnetic field can effectively compensate for the weakening effect of the reverse magnetic flux on the magnetic field of the permanent magnet 2, so that the effective magnetic flux of the permanent magnet 2 can be maintained during the energy storage process, thereby ensuring that the energy storage coil 1 can obtain a larger change in magnetic flux and achieve higher energy storage.

[0052] According to an embodiment of the present invention, when the superconducting coil in the compensation coil 3 is cooled to a superconducting state in the background magnetic field generated by the permanent magnet 2, it locks the positive magnetic flux of the permanent magnet 2 through a pinning effect, thereby establishing a stable magnetic flux reference. During subsequent energy storage when the permanent magnet 2 approaches the energy storage coil 1, the energy storage coil 1 generates a reverse magnetic flux due to changes in magnetic flux. This reverse magnetic flux attempts to weaken the positive magnetic flux of the permanent magnet 2. At this time, the superconducting coil, already in a superconducting state, acts as a closed loop and induces an additional current according to Lenz's law. The magnetic field generated by this current is in the same direction as the positive magnetic flux at the time of locking, i.e., consistent with the magnetic field direction of the permanent magnet 2. This unidirectional magnetic field can compensate for the weakening effect of the reverse magnetic flux on the magnetic field of the permanent magnet 2 in real time and automatically, keeping the effective magnetic flux of the permanent magnet 2 essentially constant throughout the entire energy storage process.

[0053] This avoids the attenuation of the positive magnetic flux in the permanent magnet 2 caused by the reverse magnetic flux, allowing the energy storage coil 1 to obtain a larger change in magnetic flux, thereby increasing the maximum energy storage capacity of the energy storage device. Simultaneously, this compensation is adaptive, requiring no external control or additional energy input, simplifying the system structure and improving energy conversion efficiency. Through the pinning and locking of the superconducting coil and inductive compensation, the energy storage performance is optimized.

[0054] As an example, such as Figure 3 and Figure 4 As shown, when the first and last ends of the superconducting tape 31 are electrically connected to form a superconducting closed loop, a superconducting joint is formed at the connection between the first and last ends. The superconducting joint can be in contact with the normal conducting tape 32 or separated from the normal conducting tape 32.

[0055] According to embodiments of the present invention, such as Figure 3 and Figure 4 As shown, the compensation coil 3 also includes a normally conducting coil. The normally conducting coil has a first end and a second end that are insulated from each other, so that when the permanent magnet 2 starts to release energy from its maximum energy storage position, a direct current is passed through the first end and the second end, so that the normally conducting coil generates a magnetic flux in the opposite direction to the magnetic field of the permanent magnet 2, thereby canceling or weakening the magnetic field generated by the permanent magnet 2, and enabling the permanent magnet 2 to translate axially relative to the energy storage coil 1 under the action of an external force.

[0056] The normally conducting coil is wound from a normally conducting strip 32. The two ends of the normally conducting strip 32 are an open circuit, namely a first end and a second end. The portion of the normally conducting strip 32 located between the first end and the second end is wound to form a coil.

[0057] Normally conductive tape 32 refers to a metallic conductive tape with normal resistance (non-superconductivity), such as copper or aluminum, which are good conductors. Normally conductive tape 32 has resistance at both room temperature and low temperature, and generates Joule heating when current is passed through it, but it has good conductivity and can carry large currents.

[0058] In this invention, the normal conducting strip 32 is used to wind the normal conducting coil in the compensation coil 3. The first end and the second end of the normal conducting strip 32 are insulated from each other to form an open-circuit coil. A direct current can be passed through it as needed to generate a magnetic field opposite to that of the permanent magnet 2, so as to achieve the function of canceling the magnetic field of the permanent magnet 2 and assisting in energy release.

[0059] According to an embodiment of the present invention, when the permanent magnet 2 reaches its maximum energy storage position and needs to begin releasing energy, a direct current can be supplied to the normally conducting coil to generate a magnetic flux in the normally conducting coil opposite to the magnetic field direction of the permanent magnet 2, thereby actively canceling or weakening the magnetic field generated by the permanent magnet 2. At this time, the electromagnetic force between the permanent magnet 2 and the energy storage coil 1 is significantly reduced or even eliminated, allowing the permanent magnet 2 to smoothly move away from the energy storage coil 1 along the axial direction under the drive of an external force (such as gravity, spring force, or external mechanical device), thus realizing the energy release process. This achieves free switching between energy storage and energy release states, overcoming the shortcomings of traditional devices that can only passively switch the relative position of the permanent magnet 2 and cannot release energy on demand; during the energy release process, the impact and wear of the mechanical structure by the huge electromagnetic force are avoided, improving the reliability and service life of the device.

[0060] Meanwhile, since the normal conducting coil is only briefly energized during the energy release phase and remains open during normal energy storage, it will not interfere with the compensation function of the superconducting coil. This balances the dual requirements of efficient energy storage and flexible energy release, and improves the adaptability and controllability of the energy storage device under dynamic operating conditions.

[0061] Figure 5 A cross-sectional view of a single-turn compensation coil according to an embodiment of the present invention is shown.

[0062] According to embodiments of the present invention, such as Figures 3 to 5 As shown, the superconducting tape 31 for winding the superconducting coil and the conventionally conducting tape 32 for winding the conventionally conducting coil are stacked in the thickness direction of the superconducting tape 31. The compensation coil 3 also includes a filler conductor 33. The filler conductor 33 fills the space between the conventionally conducting tape 32 and the superconducting tape 31, and is suitable for electrically connecting the conventionally conducting tape 32 and the superconducting tape 31 so that in the event of a quench failure in the superconducting coil, the current in the superconducting coil can migrate to the conventionally conducting coil through the filler conductor 33.

[0063] According to an embodiment of the present invention, a superconducting tape 31 for winding a superconducting coil and a conventionally conducting tape 32 for winding a conventionally conducting coil are stacked vertically in the thickness direction, and a conductive filler conductor 33 is filled between the superconducting tape 31 and the conventionally conducting tape 32 to form a tight electrical connection and thermal contact.

[0064] According to an embodiment of the present invention, the filler conductor 33 may include a low-temperature solder (e.g., a solder with a melting point below 183°C), which may include indium solder or an indium-containing alloy.

[0065] According to an embodiment of the present invention, under normal superconducting conditions, current mainly flows along the zero-resistance superconducting tape 31, while the filler conductor 33 and the normally conducting tape 32 carry almost no current. When the superconducting coil experiences quenching (transitioning from the superconducting state to the normal state) due to overcurrent, overheating, or excessive magnetic field strength, the resistance of the superconducting tape 31 increases sharply. At this time, the filler conductor 33 provides a low-resistance bypass path for the current, allowing it to migrate from the quenched superconducting tape 31 to the normally conducting tape 32, where the current is temporarily carried. This avoids the generation of huge Joule heat locally in the superconducting tape 31 during quenching, preventing the superconducting tape 31 from burning out and improving the reliability and safety of the energy storage device. Simultaneously, it ensures the continuity of current during quenching, enabling the energy storage device to maintain operation or achieve controlled shutdown, avoiding the impact of sudden energy interruption. The normally conducting tape 32 has good thermal capacity and thermal conductivity, capable of absorbing and dissipating the heat generated by quenching, delaying thermal runaway, and providing time for external protection circuits to operate.

[0066] Furthermore, by stacking and integrating the superconducting tape 31 and the conventionally conducting tape 32, the coil can be formed in one step during winding, avoiding the complexity of separate winding and assembly. This improves the fill factor and mechanical integrity of the coil, and provides functional redundancy when the superconducting performance is temporarily lost, allowing the energy storage device to still operate at a degraded level. It provides a passive, self-triggered quench protection mechanism for the superconducting coil, enhancing the engineering practicality of the energy storage device.

[0067] According to embodiments of the present invention, such as Figure 5 As shown, the conventional conductive strip 32 and the superconducting strip 31 are stacked in the thickness direction and electrically connected by solder (filler conductor 33) to form a composite sub-cable, which provides a quench protection channel and integrates two coils with different functions into one.

[0068] According to an embodiment of the present invention, in a one-turn compensation coil 3, the normal conducting strip 32 may be located inside the superconducting strip 31 (near the center of the coil), or the normal conducting strip 32 may be located outside the superconducting strip 31 (away from the center of the coil).

[0069] Figure 6 A cross-sectional view of a compensation coil according to an embodiment of the present invention is shown.

[0070] According to embodiments of the present invention, such as Figure 5 and Figure 6 As shown, the compensation coil 3 also includes a pair of buffer strips 34. The pair of buffer strips 34 are respectively disposed on both sides of the superconducting tape 31 in the width direction, which is suitable for preventing the filler conductor 33 from overflowing from the conventional conductive tape 32 and the superconducting tape 31 in the molten state.

[0071] According to an embodiment of the present invention, the material of the buffer strip 34 is selected to maintain elasticity and some mechanical strength at low temperatures (below the superconducting transition temperature), such as Teflon (polytetrafluoroethylene, PTFE) or polychlorotrifluoroethylene (PCTFE).

[0072] In this embodiment, by providing buffer strips 34 on both sides of the superconducting strip 31, the molten solder can be effectively blocked during the welding process, preventing the solder from overflowing between the normal conductive strip and the superconducting strip in the molten state, preventing welding defects (such as incomplete soldering or voids) caused by solder loss, and preventing the overflowed solder from forming uneven accumulation between adjacent turns, ensuring that the coil is tightly wound and the contact resistance between turns is uniform, thus ensuring the consistency of the electromagnetic performance and the integrity of the mechanical structure of the compensation coil 3.

[0073] According to an embodiment of the present invention, the buffer strip 34 includes a main body 341 and a first protrusion 342. The main body 341 extends partially between the superconducting strip 31 and the conventionally conducting strip 32. The first protrusion 342 protrudes from the side of the main body 341 opposite to the filling conductor 33. The two opposite sides of the superconducting strip 31 are partially attached to the first protrusion 342 to cooperate with the main body 341, the conventionally conducting strip 32, and the main body 341 of the other buffer strip 34 to form a closed space, thereby confining the filling conductor 33 within the closed space.

[0074] According to an embodiment of the present invention, the main body 341 can be a strip structure with a cross-section orthogonal to the length direction, and the cross-sectional shape of the main body 341 includes a rectangle. Similarly, the first protrusion 342 is also a strip structure, and the cross-sectional shape of the first protrusion 342 includes a rectangle.

[0075] According to an embodiment of the present invention, the first protrusion 342 and the main body 341 form a stepped structure. The stepped structure is used to support and position the two sides of the superconducting tape 31 in the thickness direction, so that the superconducting tape 31 is partially placed on the first protrusion 342, thereby forming a closed space together with the main body 341 of another buffer strip 34 and the normal conducting tape 32.

[0076] In such an embodiment, the enclosed space confines the molten solder within a predetermined area between the superconducting strip 31 and the conventionally conducting strip 32, preventing the solder from being lost or overflowing during the welding process. This avoids welding defects such as incomplete soldering and voids caused by insufficient solder, ensuring a continuous, uniform, and low-resistance electrical connection between the superconducting strip and the conventionally conducting strip, and guaranteeing that the overrun current can reliably migrate from the superconducting strip to the conventionally conducting strip.

[0077] In addition, the design of superconducting strip 31 being mounted on the first protrusion 342 enhances the mechanical engagement between the buffer strip 34 and the superconducting strip 31, preventing the buffer strip 34 from shifting during winding or operation, further ensuring the integrity of the enclosed space, achieving effective constraint on the solder, and improving the manufacturing consistency, electrical reliability and mechanical stability of the compensation coil 3.

[0078] According to an embodiment of the present invention, the buffer strip 34 further includes a second protrusion 343. The second protrusion 343 protrudes from the side of the first protrusion 342 opposite to the superconducting strip 31, so as to abut against the second protrusion 343 located in the adjacent winding turn to form a nested structure.

[0079] According to an embodiment of the present invention, the second protrusion 343 may be a strip structure with a cross section orthogonal to the length direction, and the cross-sectional shape of the second protrusion 343 may include a rectangle.

[0080] As an example, the protrusion height of the second protrusion 343 is greater than or equal to the thickness of the normal conductive strip 32.

[0081] The normally conducting strip 32 of adjacent turns is confined within the space enclosed by the second protrusion 343, which provides radial and axial positioning constraints for the normally conducting strip 32 during winding. This prevents the normally conducting strip 32 from shifting or twisting due to uneven winding tension or subsequent processing, ensuring the winding accuracy of the coil and the consistency of the inter-turn gap. In addition, the multi-level stepped structure formed by the second protrusion 343 and the first protrusion 342 creates a more continuous buffer layer on the coil end face, further improving the dispersion effect of mechanical stress.

[0082] In this embodiment, when the compensation coil 3 is wound, the first turn (inner coil) and the second turn (outer coil) are radially adjacent, that is, one turn is arranged outward next to another. The second protrusion 343 protrudes further outward from the first protrusion 342 (located on both sides of the width direction of the superconducting tape 31). When multiple turns are wound, the second protrusion 343 of the inner coil and the second protrusion 343 of the outer coil abut and interlock with each other in the radial direction, forming a nested structure. This radial nesting can effectively resist the radial electromagnetic force (usually the outward expansion Lorentz force) generated when the coil is energized, prevent relative slippage or loosening between turns in the radial direction, avoid coil unraveling, and avoid the increase in inter-turn gap due to uneven winding tension or subsequent processing, thus ensuring the geometrical accuracy and fill factor consistency of the coil. In addition, the continuous buffer layer formed on the end face of the coil by the nested structure can absorb and disperse the mechanical vibration and impact stress caused by the electromagnetic force, protecting the superconducting tape 31 and the conventionally conductive tape 32 from local stress concentration or wear.

[0083] The superconducting tape 31 is welded to the conventionally conducting tape 32 via a filler conductor 33 to form a non-insulating structure. When the superconducting tape 31 loses its quench, the current can migrate to the conventionally conducting tape 32 through the low-temperature metal solder to protect the superconducting tape 31.

[0084] The composite wound shielded coil contains at least one set of superconducting closed coils. These superconducting closed coils are cooled to a superconducting state in the background field of the permanent magnet 2. The superconducting closed coils shield the reverse magnetic flux during energy storage, preventing significant changes in the magnetic flux magnitude of the permanent magnet 2. Furthermore, the superconducting closed coils can be connected to an external excitation device (such as a flux pump) to adjust the magnetic flux magnitude between the permanent magnet 2 and the composite wound shielded coil, enabling adjustable energy storage. The composite wound shielded coil includes at least one set of normally conducting open-circuit coils, with their ends insulated from each other or connected to an external circuit, maintaining an open-circuit or controlled-conduction state under normal conditions. When the energy storage device requires fault maintenance, a controlled current is applied to the normally conducting open-circuit coil, causing it to generate a reverse magnetic flux opposite to the magnetic field direction of the permanent magnet 2. By counteracting the magnetic field generated by the permanent magnet 2, the Ampere force on the energy storage coil 1 experienced by the permanent magnet 2 and the composite wound shielded coil can be eliminated, thereby enabling the displacement of the permanent magnet 2 and the compensation washer under the action of no electromagnetic force (or a small electromagnetic force), and realizing the free switching between the energy storage and energy release states.

[0085] According to an embodiment of the present invention, the compensation coil 3 can be a multi-turn coil wound from composite sub-cables.

[0086] According to an embodiment of the present invention, the compensation coil 3 is a single-pane coil, a double-pane coil, or a multi-pane coil. This allows for sufficient turns and magnetic field strength within a limited space, while ensuring winding feasibility and operational reliability.

[0087] like Figure 2 As shown in (a), the energy storage device is in the energy storage state.

[0088] Under the drive of an external force, permanent magnet 2 and compensation coil 3 approach energy storage coil 1 along an axial direction parallel to the energy storage coil 1 (indicated by the arrow in the diagram). During this process, the positive magnetic flux through energy storage coil 1 gradually increases. According to Faraday's law of electromagnetic induction, an induced electromotive force is generated in the closed energy storage coil 1, which in turn forms an induced current. Since energy storage coil 1 is in a superconducting state (zero resistance), this induced current will not decay due to Joule heating, thus converting the mechanical energy of permanent magnet 2 into electromagnetic energy, which is stored in energy storage coil 1 for a long time. At the same time, the superconducting closed loop in compensation coil 3, having pre-locked the positive magnetic flux of permanent magnet 2, will automatically induce a compensation magnetic field in the same direction as permanent magnet 2 when the reverse magnetic flux generated by energy storage coil 1 appears, in order to maintain the effective magnetic flux of permanent magnet 2 and further improve energy storage efficiency.

[0089] As the permanent magnet 2 and the compensation coil 3 move toward the energy storage coil 1, the magnetic field generated by the induced current in the energy storage coil 1 is in the opposite direction to the magnetic field of the permanent magnet 2. This causes the direction of the Ampere force on the permanent magnet 2 to be opposite to its direction of motion, and the Ampere force does negative work. Therefore, the mechanical energy of the permanent magnet 2 is gradually converted into electromagnetic energy stored in the compensation coil 3 and the energy storage coil 1, and the total energy stored in the energy storage device increases accordingly.

[0090] like Figure 2 As shown in (b), the energy storage device is in its maximum energy storage state. When the geometric centers of the permanent magnet 2, the compensation coil 3, and the energy storage coil 1 are in the same plane perpendicular to the axial direction (i.e., their axial positions are the same and they are coaxial), almost all of the positive magnetic flux generated by the permanent magnet 2 passes through the energy storage coil 1. During the process of moving from the initial position to this position, the change in magnetic flux passing through the energy storage coil 1 reaches its maximum value. According to Faraday's law of electromagnetic induction, the magnitude of the induced electromotive force is proportional to the rate of change (or the total change) of magnetic flux. Therefore, the induced current in the energy storage coil 1 reaches its peak value at this position, and the stored electromagnetic energy also reaches its maximum value. At this time, the reverse magnetic flux generated by the energy storage coil 1 is at its maximum, and the shielding current induced in the compensation coil 3 is also at its maximum.

[0091] like Figure 2As shown in (c), the energy storage device is in the energy release state. When energy needs to be released, a direct current is passed through the constant-conducting coil in the compensation coil 3, causing the compensation coil 3 to generate a magnetic field opposite to that of the permanent magnet 2, thus canceling or weakening the magnetic field of the permanent magnet 2 and eliminating the huge electromagnetic force between the permanent magnet 2 and the energy storage coil 1. Driven by an external force (such as gravity, spring force, or external mechanical device), the permanent magnet 2 and the compensation coil 3 move away from the energy storage coil 1 axially from the maximum energy storage position. As the permanent magnet 2 moves away, the positive magnetic flux through the energy storage coil 1 gradually decreases, the induced current in the energy storage coil 1 decreases accordingly, and the stored electromagnetic energy is converted into mechanical energy output, driving the permanent magnet 2 to move or perform work. After the energy release is completed, the current in the constant-conducting coil is disconnected, the magnetic field of the permanent magnet 2 is restored, and the device can re-enter the energy storage state.

[0092] As the permanent magnet 2 and the compensation coil 3 move away from the energy storage coil 1, the direction of the induced current generated in the energy storage coil 1 is opposite to that during energy storage. The direction of the magnetic field generated by the energy storage coil 1 is still opposite to the direction of the magnetic field of the permanent magnet 2. This results in the Ampere force on the permanent magnet 2 being in the same direction as its movement, and the Ampere force doing positive work. Therefore, the electromagnetic energy stored in the compensation coil 3 and the energy storage coil 1 is gradually converted into mechanical energy, and the stored energy of the energy storage device decreases accordingly.

[0093] In the process of realizing this invention, it was also discovered that in related technologies, the energy storage capacity of a superconducting energy storage device is mainly determined by the magnetic properties of the permanent magnet 2 and the geometric parameters (such as the number of turns, radius, length, etc.) of the energy storage coil 1. Once the device is manufactured, these parameters are fixed and cannot be adjusted in real time according to actual operating requirements.

[0094] Furthermore, the transition between the energy storage and release states depends entirely on the relative positions of the permanent magnet and the superconducting coil: when the permanent magnet approaches the coil, the energy storage device enters the energy storage process; when the permanent magnet moves away, the energy storage device enters the energy release process. This mechanical position-determined operation means that if an attempt is made to release energy prematurely before the permanent magnet reaches its maximum energy storage position (i.e., not fully charged), the direction and magnitude of the electromagnetic force between the permanent magnet and the coil do not support a smooth energy release transition because the energy stored in the energy storage coil has not yet reached its maximum value. Typically, the permanent magnet must be moved further to its maximum energy storage position before it can be moved in the opposite direction to release energy, making mid-process or on-demand energy release impossible. Similarly, during energy storage, the user cannot change the output state by adjusting the position of the permanent magnet (e.g., supplying power while partially storing energy).

[0095] The aforementioned limitations are particularly prominent in the application scenarios of regenerative braking energy recovery in urban rail transit: the energy generated by train braking is random, intermittent and fluctuating, and the energy storage device needs to be able to flexibly absorb or release energy according to real-time operating conditions such as grid voltage and load demand. However, the traditional design of fixed energy storage and fixed state switching points cannot meet this dynamic response requirement, which restricts the promotion and practical application of this type of superconducting energy storage device in actual lines.

[0096] According to an embodiment of the present invention, the superconducting coil is configured to: lock the positive magnetic flux of the permanent magnet 2 and the magnetic flux generated by the initial current during the process of charging an initial current through an external excitation device and cooling to below the superconducting transition temperature in a magnetic field environment, so as to adjust the maximum energy storage of the energy storage coil 1.

[0097] As an example, an external excitation device may include a flux pump.

[0098] An initial current is introduced into the superconducting coil via an external excitation device, and the coil is cooled below its superconducting transition temperature under the magnetic field generated by the permanent magnet. At this point, the superconducting coil locks in the total magnetic flux passing through it. This total magnetic flux consists of two parts: a positive magnetic flux (a fixed value) generated by the permanent magnet itself, and a magnetic flux generated by the initial current itself (the magnitude of the magnetic flux generated by the initial current is proportional to the initial current, and its direction is determined by the current direction). During subsequent energy storage, the permanent magnet moves from its initial position to its maximum energy storage position. The change in magnetic flux passing through the energy storage coil determines the maximum current induced in the coil, and thus the maximum stored energy. Since the upper limit of this change in magnetic flux is approximately equal to the total magnetic flux locked in the superconducting coil, the locked total magnetic flux can be changed by adjusting the magnitude and direction of the initial current, thereby continuously and flexibly adjusting the maximum stored energy of the energy storage device. This mechanism frees energy storage from fixed factors such as the performance of the permanent magnet and the geometric parameters of the coil, providing a feasible solution for adapting to dynamic operating conditions such as train regenerative braking.

[0099] In this embodiment, by changing the magnitude and direction of the initial current, the maximum energy storage capacity of the device can be continuously and flexibly adjusted, freeing the energy storage device from fixed factors such as the performance of the permanent magnet 2 and the geometric parameters of the coil. Under dynamic operating conditions such as regenerative braking energy recovery in urban rail transit, the randomness, intermittency, and fluctuation of train braking energy require the energy storage device to adjust its energy storage capacity in real time according to the grid voltage and load demand.

[0100] By presetting the initial current, the same energy storage device can be adapted to braking scenarios with different energy levels, avoiding over-storage waste or under-storage insufficiency caused by fixed energy storage. Simultaneously, the adjustability of the maximum energy storage provides a basis for flexible switching between energy storage and release states. Users can set the upper limit of energy storage according to actual needs without changing the hardware structure, improving the adaptability and practical value of the energy storage device to complex operating conditions. This overcomes the technical shortcomings of traditional superconducting energy storage devices, which have fixed energy storage and cannot be dynamically adjusted, providing a feasible solution for the engineering application of superconducting energy storage in fields such as rail transportation.

[0101] As another aspect of the present invention, a method for preparing any of the above-mentioned compensation coils is also provided. The preparation method includes:

[0102] Superconducting tape 31 and conventional conductive tape 32 are aligned and stacked in the thickness direction, and low-temperature solder (such as indium-based alloy) is pre-placed between superconducting tape 31 and conventional conductive tape 32.

[0103] A buffer strip 34 is placed on each side of the superconducting strip 31 in the width direction. The buffer strip 34 has a main body 341 and a first protrusion 342. The main body 341 extends between the superconducting strip and the normal conducting strip, and the first protrusion 342 is used to support the edge of the superconducting strip.

[0104] The solder is melted by heating, filling the gap between the superconducting and conventional conductive strips. At the same time, the buffer strip 34 confines the molten solder within a closed space to prevent overflow. After cooling, the superconducting strip, conventional conductive strip, and the filler conductor 33 formed by the solidified solder together form a single composite sub-cable.

[0105] Prepare a circular winding frame (material can be stainless steel or insulating material) according to the design requirements. Fix one end of the composite sub-cable to the frame, and then wind it tightly and evenly along the circumference of the frame. Keep the composite sub-cable flat during winding, so that the buffer strip 34 is located on the upper and lower end faces of the coil. After each coil is wound, the second coil can be wound in the opposite direction to form a double-coil coil. Repeated stacking can form a multi-coil coil.

[0106] During the winding process, the buffer strips 34 of adjacent turns are nested or positioned with the normal conductive strips 32 of adjacent turns through the second protrusion 343, ensuring uniform gap between turns.

[0107] After winding, the conventional conductive strip 32 and solder are stripped from both ends of the coil, exposing only the beginning and end of the superconducting strip 31. The beginning and end of the superconducting strip 31 are then overlapped, and superconducting solder (such as indium) is filled in between or directly pressed together to form a superconducting joint. The resistance of the superconducting joint is extremely low (close to zero), making the entire superconducting strip 31 a superconducting closed circuit.

[0108] The two ends of the normally conductive strip 32 are kept insulated from each other (not connected), or led out as electrodes for subsequent direct current flow.

[0109] According to an embodiment of the present invention, the compensation coil 3 simultaneously includes a superconducting closed loop (for locking magnetic flux and induction compensation) and a normally conducting open loop coil (for passing current to cancel the magnetic field of the permanent magnet 2), and has a compact structure and high mechanical stability.

[0110] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. An energy storage device, characterized in that, include: A toroidal energy storage coil; A permanent magnet is configured to move relative to the energy storage coil along the axial direction of the energy storage coil; A ring-shaped compensation coil is coaxially fitted around the permanent magnet and configured to move synchronously with the permanent magnet. As the permanent magnet approaches the energy storage coil: The magnetic flux of the energy storage coil changes and generates an induced current, which converts mechanical energy into electromagnetic energy and stores it. The compensation coil is configured to generate a magnetic field in the same direction as the magnetic field of the permanent magnet, in order to compensate for the reverse magnetic flux generated by the energy storage coil under the action of the permanent magnet.

2. The energy storage device according to claim 1, characterized in that, The compensation coil includes: In the process of cooling to below the superconducting transition temperature in the magnetic field environment generated by the permanent magnet, the superconducting coil generates a pinning effect to lock the positive magnetic flux of the permanent magnet, and induces a magnetic field with the same direction as the magnetic field of the permanent magnet as the permanent magnet approaches the energy storage coil.

3. The energy storage device according to claim 2, characterized in that, The compensation coil also includes: A normally conducting coil has a first end and a second end that are insulated from each other. During the process of the permanent magnet releasing energy from its maximum energy storage position, a direct current is passed through the first end and the second end to make the normally conducting coil generate a magnetic flux opposite to the magnetic field of the permanent magnet, thereby canceling or weakening the magnetic field generated by the permanent magnet and enabling the permanent magnet to translate axially relative to the energy storage coil under the action of an external force.

4. The energy storage device according to claim 3, characterized in that, The superconducting tape wound around the superconducting coil and the conventionally conducting tape wound around the conventionally conducting coil are stacked in the thickness direction of the superconducting tape. The compensation coil further includes: A filler conductor, filled between the normal conducting tape and the superconducting tape, is suitable for electrically connecting the normal conducting tape and the superconducting tape to allow the current of the superconducting coil to migrate to the normal conducting coil through the filler conductor in the event of a quench failure in the superconducting coil.

5. The energy storage device according to claim 4, characterized in that, The compensation coil also includes: The paired buffer strips are respectively disposed on both sides of the width direction of the superconducting tape, which are suitable for preventing the filler conductor from overflowing from the normal conducting tape and the superconducting tape in the molten state.

6. The energy storage device according to claim 5, characterized in that, The buffer strip includes: The main body extends partially between the superconducting tape and the conventionally conducting tape; The first protrusion protrudes from the side of the main body away from the filling conductor. The superconducting tape is partially laid on the first protrusion on both sides opposite to each other in the width direction, so as to cooperate with the main body, the normal conducting tape, and the main body of the other buffer strip to form a closed space, thereby confining the filling conductor in the closed space.

7. The energy storage device according to claim 6, characterized in that, The buffer strip also includes: The second protrusion protrudes from the side of the first protrusion away from the superconducting tape, and abuts against the second protrusion of the adjacent winding turn to form a nested structure.

8. The energy storage device according to claim 1, characterized in that, The geometric center of the compensation coil and the geometric center of the permanent magnet are located in a plane perpendicular to the axial direction.

9. The energy storage device according to claim 2, characterized in that, The superconducting coil is configured to: lock the positive magnetic flux of the permanent magnet and the magnetic flux generated by the initial current during the process of being charged with an initial current by an external excitation device and cooled to below the superconducting transition temperature in the magnetic field environment, so as to adjust the maximum energy storage of the energy storage coil.

10. The energy storage device according to any one of claims 1-9, characterized in that, The compensation coil is a double-pane coil or a multi-pane coil.

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