Low-loss high-reliability full-suspension flywheel energy storage device and method

Abstract

The application belongs to the technical field of flywheel energy storage, and relates to a low-loss and high-reliability full-suspension flywheel energy storage device and method.The device comprises a vacuum protection shell, a flywheel rotor, a power generator / motor and a rotor support system.The rotor support system comprises an axial support unit and a radial support unit.The axial support unit is composed of an axial electromagnetic bearing and an axial permanent magnet biasing assembly.The radial support unit is composed of two radial permanent magnet bearings arranged on the upper and lower shaft sections of the flywheel rotor.In the application, an extrusion oil film damper is integrated on the outside of the radial permanent magnet bearing.The damper provides external positive damping for the rotor system by using the damping oil film in the closed cavity, effectively offsets the negative damping effect generated by the permanent magnet bearing during high-speed rotation, especially through the critical speed, so that stable suspension in the full speed range is realized.The application cancels the complex radial active electromagnetic bearing and its control system, significantly reduces the cost, and improves the reliability and stability of the system.

Description

Technical Field

[0001] This invention belongs to the field of flywheel energy storage technology, and relates to a low-loss, high-reliability fully suspended flywheel energy storage device and method, particularly to a low-loss, high-reliability fully suspended flywheel energy storage device and method that uses an axial permanent magnet biased electromagnetic bearing and a radial permanent magnet bearing with a squeeze oil film damper. Background Technology

[0002] Flywheel energy storage technology, due to its high power density, long lifespan, and fast response characteristics, has broad application prospects in fields such as kinetic energy recovery in rail transit, grid frequency regulation, and UPS uninterruptible power supplies. With technological advancements, flywheel energy storage devices are evolving towards higher power and larger energy output. However, reducing costs and improving reliability remain key factors restricting its large-scale commercialization.

[0003] In existing flywheel rotor support systems, the mainstream solutions mostly employ five-axis active electromagnetic bearings or a hybrid support scheme of "electromagnetic bearings + mechanical bearings". These solutions have the following significant drawbacks: 1. High cost: The active electromagnetic bearing and its matching power amplifier, sensor and complex control circuit account for a large proportion of the total cost of the machine, usually reaching 15%-30% of the total system cost.

[0004] 2. Stability Bottleneck: According to Earnshaw's theorem, a static permanent magnetic field cannot simultaneously achieve stable levitation in all degrees of freedom. While existing rotor support schemes using electromagnetic bearings in the axial direction and permanent magnet bearings in the radial direction are structurally simple, the rotor typically passes through the critical speeds of two rigid body modes—translational and torsional—during its acceleration from rest to its rated speed. When passing the first-order critical speed, the electromagnetic damping exhibited by the radial permanent magnet bearing often transforms into negative damping, leading to divergent eddy currents in the rotor system, which can easily cause system instability.

[0005] 3. Complex control: Multi-axis electromagnetic bearings require high-precision decoupling control algorithms, and under high-frequency interference (such as frequency multiplication interference), their output impedance increases and their suppression force decreases, making it difficult to guarantee stability under all operating conditions.

[0006] Therefore, there is an urgent need to develop a new flywheel support scheme that can significantly reduce hardware and control costs, solve the problem of instability at critical speeds through physical mechanisms, and achieve stable operation across the entire speed range. Summary of the Invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a low-loss and high-reliability fully suspended flywheel energy storage device and method. The present invention aims to solve the technical problems of high cost and complex control system caused by the reliance on multi-axis active electromagnetic bearings in the prior art, as well as the system instability caused by the negative damping effect of radial permanent magnet bearings when passing through the critical speed.

[0008] The technical solution adopted by the present invention to solve this problem is as follows: A low-loss, high-reliability, fully suspended flywheel energy storage device includes a vacuum protection shell, a flywheel rotor, a generator / motor, and a rotor support system, wherein: The flywheel rotor has a generator / motor connected internally or coaxially. The generator / motor can be placed on the upper shaft section of the flywheel rotor, below the squeeze film damper, or on the lower shaft section of the flywheel rotor, above the squeeze film damper. A rotor support system is used to support a flywheel rotor to levitate and rotate within a vacuum protective housing. The rotor support system includes an axial support unit for providing axial levitation force and stiffness, and a radial support unit for providing radial support force and dissipating vibration energy. The radial support unit integrates a damping structure.

[0009] In the above technical solution, the radial support unit includes: Two radial permanent magnet bearings are respectively installed on the upper and lower shaft sections of the flywheel rotor. The radial permanent magnet bearings include an inner ring of the radial permanent magnet bearing fixed on the upper and lower shaft sections and an outer ring of the radial permanent magnet bearing fixed on the inner side of the damper housing. A damping structure for generating damping force when a rotor vibrates, the damping structure comprising an extruded oil film damper integrated on a radial permanent magnet bearing.

[0010] In the above technical solution, the extrusion oil film damper includes: The damper housing is a closed cavity filled with damping medium; A damping body has a radial permanent magnet bearing outer ring disposed on its inner circumference. The damping body and the radial permanent magnet bearing outer ring are supported in the damper housing by an elastic reset element. And the gap oil film formed between the outer ring of the radial permanent magnet bearing, the damping body and the damper housing; The damping body and the outer ring of the radial permanent magnet bearing are enabled to generate radial displacement relative to the damper housing through elastic reset elements and gap oil film, and to provide external positive damping for the rotor system by utilizing the squeeze oil film effect.

[0011] In the above technical solution, the squeeze film damper further includes: The support structure includes an upper support plate and a lower support plate respectively disposed on the upper and lower parts of the damper housing; A fixed structure includes an upper fixing plate for the magnet and damping body and a lower fixing plate for the magnet and damping body. An upper thrust plane mechanical bearing is provided between the upper end face of the upper fixing plate of the damping body and an upper support plate. A lower thrust plane mechanical bearing is provided between the lower end face of the lower fixing plate of the damping body and a lower support plate. The damping body and the outer ring of the radial permanent magnet bearing are located between the upper fixing plate of the damping body and the lower fixing plate of the magnet and damping body.

[0012] In the above technical solution, the elastic reset element includes at least three squirrel cage spring rods evenly distributed along the circumference of the damping body, and the damping body is suspended between the upper support plate and the lower support plate by the squirrel cage spring rods.

[0013] In the above technical solution, the axial support unit includes: An axial electromagnetic bearing is disposed at one end of a flywheel rotor and includes an electromagnet core fixed in a vacuum protective housing by an electromagnet fixing connector and a coil wound on the electromagnet core. An axial permanent magnet biasing assembly is located at the other end of a flywheel rotor. It includes a permanent magnet biasing axial magnetic bearing rotor magnet fixed inside the flywheel rotor and a permanent magnet biasing axial magnetic bearing stator magnet fixed inside a vacuum protective housing.

[0014] In the above technical solution, the axial permanent magnet biasing component adopts any of the following configuration methods: Configuration 1: Suitable for small and medium-sized flywheel rotors, the outer ring of the radial permanent magnet bearing is offset axially downward relative to the inner ring of the radial permanent magnet bearing to form an axial offset gap, and the leakage magnetic field of the radial permanent magnet bearing provides part of the axial offset thrust. Configuration 2: Suitable for large flywheel rotors, the axial permanent magnet biasing component is a permanent magnet thrust bearing independently set at the bottom of the flywheel rotor, which cooperates with the radial permanent magnet bearing to maintain axial balance.

[0015] In the above technical solution, the upper end of the upper shaft section of the flywheel rotor is provided with an upper mechanical protection bearing for providing upper radial protection in the event of suspension failure, and the lower end of the lower shaft section is provided with a bottom conical bidirectional mechanical protection bearing, the bottom of which integrates a force sensor. The bottom tapered bidirectional mechanical protection bearing is configured to: limit large vibrations in the radial direction when the flywheel rotor falls, and to provide landing cushioning, installation positioning, magnetic center adjustment, and transport locking for the flywheel rotor in the axial direction.

[0016] In the above technical solution, the flywheel rotor has a cylindrical or disc-shaped structure and satisfies the following dynamic parameter conditions: When the flywheel rotor is cylindrical, the ratio of its diametrical moment of inertia to its polar moment of inertia is greater than 1.414. When the flywheel rotor is disc-shaped, the ratio of its polar moment of inertia to its diametrical moment of inertia is greater than 1.414.

[0017] In the above technical solution, the axial and radial permanent magnet bearings adopt a repulsive Halbach array structure.

[0018] The second objective of this invention is to provide a method for using a low-loss, high-reliability, fully suspended flywheel energy storage device, comprising the following steps: At startup, the axial electromagnetic bearing is energized, generating electromagnetic force to overcome gravity and lift the rotor. As the speed gradually increases, the flywheel rotor will pass through the first critical speed. At this time, the radial permanent magnet bearing itself may generate a negative damping effect, while the squeeze oil film damper generates a strong positive damping force, which can quickly attenuate the eddy vibration amplitude and allow the flywheel rotor to smoothly pass through the critical region. Once the rated speed is reached, the flywheel rotor operates stably under the combined action of the stiffness of the permanent magnet bearing and the oil film damping. At this time, the axial electromagnetic bearing only needs to provide a small dynamic adjustment force to maintain the axial balance position of the flywheel rotor, with extremely low power consumption. The radial permanent magnet bearing provides the main radial support stiffness, and the squeeze oil film damper continuously provides damping to suppress vibrations caused by external disturbances and internal imbalances. During discharge or shutdown, as the speed gradually decreases, the flywheel rotor passes the critical speed again. At this time, it also relies on oil film damping to smoothly pass through the critical speed zone until the speed drops to a safe range, and the flywheel rotor is safely seated on the bottom tapered bidirectional mechanical protection bearing and the upper mechanical protection bearing. Throughout the operation, the force sensor monitors changes in axial load in real time, which can be used to determine the suspension state of the flywheel rotor and the health status of the bearings, providing data support for intelligent monitoring and fault early warning of the system.

[0019] The advantages and positive effects of this invention are as follows: The radial permanent magnet bearing of this invention integrates a squeezed oil film damper on its exterior. This damper utilizes the damping oil film within a closed cavity to provide external positive damping for the rotor system, effectively counteracting the negative damping effect generated by the permanent magnet bearing during high-speed rotation, especially when passing through the critical speed, thereby achieving stable levitation across the entire speed range. This invention eliminates the complex radial active electromagnetic bearing and its control system, significantly reducing costs and improving the reliability and stability of the system.

[0020] The present invention has the following significant advantages: 1. Significantly reduced costs: By eliminating the expensive radial active electromagnetic bearing, radial displacement sensor and corresponding power drive module, and retaining only the single-axis (axial) active control system, hardware costs and control complexity are significantly reduced, and the total system cost is expected to be reduced by 10%-25%.

[0021] 2. Stable operation across the entire speed range: The innovative introduction of a squeeze film damper solves the problem of negative damping instability of radial permanent magnet bearings when they exceed the critical speed from a physical structure perspective. It can achieve smooth acceleration and deceleration from standstill to rated speed without the need for complex active damping control algorithms.

[0022] 3. High reliability and long life: The radial support has no electrical components and no wear (in the suspended state), and the structure is simple and robust; the squeeze oil film damper is in a closed vacuum shell, with an excellent working environment and a service life of 15-20 years; the design of the tapered bidirectional mechanical protection bearing improves the safety of the system during start-up, shutdown, failure and transportation.

[0023] 4. Compact structure: The damper structure design, which integrates a thrust plane mechanical bearing, avoids the problem of easy deformation and breakage of traditional squirrel cage springs when subjected to force alone, and improves the volume utilization and structural strength of the device. Attached Figure Description

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0025] Figure 1 This is a schematic diagram of the overall structure of the flywheel energy storage device in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the radial permanent magnet bearing with an extrusion oil film damper in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the axial electromagnetic bearing in Embodiment 1 of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1-Flywheel rotor, 2-Axial electromagnetic bearing, 3-Generator / motor, 4-Flywheel rotor upper shaft, 5-Radial permanent magnet bearing squeeze oil film damper, 6-Upper mechanical protection bearing, 7-Permanent magnet biased axial magnetic bearing rotor magnet, 8-Permanent magnet biased axial magnetic bearing stator magnet, 9-Flywheel rotor lower shaft, 10-Bottom tapered bidirectional mechanical protection bearing, 11-Force sensor, 12-Vacuum protection housing; 201-Electromagnet fixing connector, 202-Electromagnet core, 203-Coil; 501-Lower support plate, 502-Damping medium, 503-Lower thrust plane mechanical bearing, 504-Lower fixing plate of magnet and damping body, 505-Inner ring of radial permanent magnet bearing, 506-Outer ring of radial permanent magnet bearing, 507-Upper support plate, 508-Upper thrust plane mechanical bearing, 509-Upper fixing plate of magnet and damping body, 510-Damping body, 511-Squirrel cage spring rod, 512-Through hole of damping body, 513-Fixing nut, 514-Damper housing. Detailed Implementation

[0027] First, it should be noted that the specific structure, features, and advantages of the present invention will be described in detail below by way of examples. However, all descriptions are for illustrative purposes only and should not be construed as limiting the present invention in any way. Furthermore, any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature shown or implied in the accompanying drawings, can still be arbitrarily combined or deleted among these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned herein. Additionally, for the sake of simplifying the drawings, the same or similar technical features may be indicated only in one place in the same drawing.

[0028] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," and "screw-in" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. The invention will now be described in detail with reference to the accompanying drawings. Example 1

[0029] A low-loss, high-reliability, fully suspended flywheel energy storage device includes a vacuum protection housing 12, a flywheel rotor 1, and a rotor support system for supporting the flywheel rotor 1 to suspend and rotate within the vacuum protection housing 12, wherein: Flywheel rotor 1, which is internally or coaxially connected to a generator / motor 3; A rotor support system includes an axial support unit for providing axial levitation force and stiffness, and a radial support unit for providing radial support force and dissipating vibration energy, wherein a damping structure is integrated on the radial support unit.

[0030] The rotor support system is designed as follows: 1. Axial support: An axial electromagnetic bearing 2 is provided on the upper end face of the flywheel rotor 1, such as... Figure 3As shown, it consists of an iron core 202 and a coil 203, employing a permanent magnet bias mode to reduce coil current. A permanent magnet bias axial magnetic bearing rotor magnet 7 is provided on the lower end face of the flywheel rotor 1, which, in conjunction with the permanent magnet bias axial magnetic bearing stator magnet 8, provides the main axial load. For heavy-duty flywheels, the independently mounted permanent magnet thrust bearing at the bottom can bear the majority of the gravity load, while the axial electromagnetic bearing only needs to provide a small adjustment force.

[0031] 2. Radial support: Radial permanent magnet bearing inner rings 505 are respectively installed on the upper shaft section 4 and lower shaft section 9 of the flywheel rotor. The corresponding stator side is a squeeze film damper 5 integrated on the radial permanent magnet bearing outer ring 506.

[0032] 3. Protection and Monitoring: An upper mechanical protection bearing 6 is installed at the upper end of the flywheel rotor, and a bottom tapered bidirectional mechanical protection bearing 10 is installed at the lower end of the flywheel rotor, with a force sensor 11 mounted on the bottom surface. This tapered bearing maintains a clearance with the rotor during normal operation, only contacting during startup, shutdown, malfunction drops, or transport locking, serving as a radial limit and axial buffer. The force sensor 11 can monitor the impact force and axial load changes of the rotor upon landing in real time, and is used for installation positioning and magnetic center adjustment.

[0033] In this embodiment, the main body of the device is placed inside the vacuum protective housing 12 to reduce windage losses. The flywheel rotor 1 is supported by the upper shaft section 4 and the lower shaft section 9. The generator / motor 3 adopts an internal structure, with the motor shaft directly connected to the flywheel rotor 1, realizing mechatronics integration.

[0034] In this embodiment, the radial support unit includes: Two radial permanent magnet bearings are respectively installed on the upper shaft section 4 and the lower shaft section 9 of the flywheel rotor 1. The radial permanent magnet bearings include an inner ring 505 fixed on the upper shaft section 4 and the lower shaft section 9 and an outer ring 506 fixed on the inside of the damper housing 514. A damping structure for generating damping force when the rotor vibrates, the damping structure comprising a squeeze film damper 5 integrated on a radial permanent magnet bearing.

[0035] like Figure 1 As shown, the axial support unit consists of an axial electromagnetic bearing 2 disposed on the upper end face of the flywheel rotor 1 and an axial permanent magnet biasing assembly disposed on the lower end of the flywheel rotor 1, which is used to provide axial suspension force and stiffness. The radial support unit consists of two radial permanent magnet bearings respectively located on the upper shaft section 4 and the lower shaft section 9 of the flywheel rotor, and each radial permanent magnet bearing is integrated with a squeeze oil film damper 5.

[0036] In this embodiment, the squeeze oil film damper 5 includes: The damper housing 514 is a closed cavity filled with damping medium 502; The damping body 510 has a radial permanent magnet bearing outer ring 506 disposed on its inner circumference. The damping body 510 and the radial permanent magnet bearing outer ring 506 are supported in the damper housing 514 by an elastic reset element. And the gap oil film formed between the radial permanent magnet bearing outer ring 506, the damping body 510 and the damper housing 514; The damper 510 and the radial permanent magnet bearing outer ring 506 are enabled to generate radial displacement relative to the damper housing 514 through the elastic reset element and the gap oil film, and provide external positive damping for the rotor system by utilizing the squeeze oil film effect.

[0037] like Figure 2 As shown, the squeezed oil film damper 5 includes a damper housing 514, a damping medium filled in the housing, and a gap oil film formed between the radial permanent magnet bearing outer ring 506 and the damping body 510 and the damper housing 514; the radial permanent magnet bearing outer ring 506 and the damping body 510 are supported in the damper housing 514 by an elastic reset element, and are configured to generate radial displacement relative to the housing, so as to provide external positive damping for the rotor system by utilizing the squeezed oil film effect.

[0038] In this embodiment, the squeeze oil film damper 5 further includes: The support structure includes an upper support plate 507 and a lower support plate 501 respectively disposed on the upper and lower parts of the damper housing 514. The fixed structure includes an upper fixing plate 509 for the magnet and damping body and a lower fixing plate 504 for the magnet and damping body. An upper thrust plane mechanical bearing 508 is provided between the upper end face of the upper fixing plate 509 and the upper support plate 507. A lower thrust plane mechanical bearing 503 is provided between the lower end face of the lower fixing plate 504 and the lower support plate 501. The damping body 510 and the radial permanent magnet bearing outer ring 506 are located between the upper fixing plate 509 and the lower fixing plate 504 for the magnet and damping body.

[0039] like Figure 2 As shown, the specific structure of the extrusion oil film damper 5 includes: The upper support plate 507 and the lower support plate 501 are fixed to the top and bottom of the damper housing 514, respectively. The elastic reset element includes at least three squirrel cage spring rods 511 evenly distributed along the circumference. The upper end of the rods is fixed to the upper support plate 507, and the lower end passes through the damping body through hole 512. The rods are connected to the magnets that carry the radial permanent magnet bearing outer ring 506 and the damping body 510 and the lower fixing plate 504 of the damping body through the fixing nut 513. The lower thrust plane mechanical bearing 503 and the upper thrust plane mechanical bearing 508 are respectively disposed between the upper and lower end faces of the upper fixing plate 509 and the lower fixing plate 504 of the damping body and the corresponding support plate, and are used to limit the axial displacement of the damping body 510 and bear the axial installation force.

[0040] like Figure 2 As shown, the core structure of the squeeze oil film damper 5 includes: a closed damper shell 514, a damping medium 502 filled inside the damper shell 514, a radial permanent magnet bearing outer ring 506 and a damper body 510 fixed on a magnet and a lower fixing plate of the damper body, and the damper body 510 suspended between an upper support plate 507 and a lower support plate 501 by at least three squirrel cage spring rods 511 evenly distributed along the circumference.

[0041] Key improvements: Upper thrust plane mechanical bearings 508 and lower thrust plane mechanical bearings 503 are respectively installed between the upper and lower end faces of the fixed plates 509 and 504 and the corresponding support plates. This design solves the problem that early pure squirrel cage spring structures are prone to bending deformation or even breakage during installation or impact. The thrust bearings bear the axial installation force and impact force, while the squirrel cage springs are only responsible for radial elastic restoring, significantly improving reliability.

[0042] A small gap is left between the outer surface of the damper body 510 and the damper housing 514, and between the inner side of the permanent magnet bearing outer ring 506 and the damper housing 514, forming a squeezed oil film. When the rotor whirls, the permanent magnet bearing outer ring 506 drives the damper body 510 to move, and the squeezed oil film generates damping force, dissipating vibration energy.

[0043] In this embodiment, the elastic reset element includes at least three squirrel cage spring rods 511 evenly distributed along the circumference of the damping body 510. The damping body 510 is suspended between the upper support plate 507 and the lower support plate 501 by the squirrel cage spring rods 511.

[0044] In this embodiment, the axial support unit includes: An axial electromagnetic bearing 2 is disposed at one end of a flywheel rotor 1 and includes an electromagnet core 202 fixed in a vacuum protective housing 12 by an electromagnet fixing connector 201 and a coil 203 wound on the electromagnet core 202. An axial permanent magnet biasing assembly is disposed at the other end of the flywheel rotor 1. It includes a permanent magnet biasing axial magnetic bearing rotor magnet 7 fixed in the flywheel rotor 1 and a permanent magnet biasing axial magnetic bearing stator magnet 8 fixed in the vacuum protective housing 12.

[0045] like Figure 3As shown, the axial electromagnetic bearing 2 is a permanent magnet biased electromagnetic bearing, including an iron core 202 fixed to the housing and a coil 203 wound on the iron core. The axial electromagnetic bearing 2 is used to adjust the axial balance position.

[0046] The axial permanent magnet biasing assembly includes a permanent magnet biasing axial magnetic bearing rotor magnet 7 disposed on the lower end face of the flywheel rotor 1 and a corresponding permanent magnet biasing axial magnetic bearing stator magnet 8, which are used to provide the main axial biasing magnetic force.

[0047] In this embodiment, the axial permanent magnet biasing component adopts any of the following configurations: Configuration 1: Suitable for small and medium-sized flywheel rotors, the outer ring 506 of the radial permanent magnet bearing is axially offset relative to the inner ring 505 of the radial permanent magnet bearing to form an axial offset gap, and the leakage magnetic field of the radial permanent magnet bearing provides part of the axial offset thrust. Configuration 2: Suitable for large flywheel rotors, the axial permanent magnet biasing component is a permanent magnet thrust bearing independently set at the bottom of the flywheel rotor, which cooperates with the radial permanent magnet bearing to maintain axial balance.

[0048] In this embodiment, the upper shaft section 4 of the flywheel rotor 1 is provided with an upper mechanical protection bearing 6 for providing upper radial protection in the event of suspension failure, and the lower shaft section 9 is provided with a bottom tapered bidirectional mechanical protection bearing 10. The bottom of the bottom tapered bidirectional mechanical protection bearing 10 integrates a force sensor 11.

[0049] like Figure 1 As shown, the upper mechanical protection bearing 6 is located at the end of the upper shaft section 4 of the flywheel rotor and is used to provide upper radial protection in the event of suspension failure.

[0050] A bottom tapered bidirectional mechanical protection bearing 10 is disposed on the end face of the lower shaft section 9 of the flywheel rotor, and a force sensor 11 is integrated at the bottom of the bottom tapered bidirectional mechanical protection bearing 10.

[0051] The bottom tapered bidirectional mechanical protection bearing 10 is configured to: limit large vibrations of the flywheel rotor 1 in the radial direction when it falls, and to provide landing cushioning, installation positioning, magnetic center adjustment and transport locking for the flywheel rotor in the axial direction.

[0052] Example 2: Rotor dynamics optimization This embodiment features a specially optimized design for the rotational inertia of the flywheel rotor to improve the dynamic stability of the system.

[0053] When the flywheel rotor 1 is designed as a column, the ratio of its diametrical moment of inertia to its polar moment of inertia is controlled to be greater than 1.414; When the flywheel rotor 1 is designed as a disc, the ratio of its polar rotational inertia to its diametrical rotational inertia is controlled to be greater than 1.414.

[0054] The above ratio of moments of inertia is based on rotor dynamics theory: When the ratio of the polar moment of inertia to the diametrical moment of inertia of a disc flywheel rotor is greater than √2 (approximately 1.414), the critical speed of the rotor's second-order rigid body mode will be higher than its operating speed.

[0055] When the ratio of the diameter moment of inertia to the polar moment of inertia of a cylindrical flywheel rotor is greater than √2 (approximately 1.414), the critical speed of the rotor's second-order rigid body mode will be lower than its operating speed.

[0056] In conjunction with the aforementioned damped radial support system, the critical speed of the rigid body mode can be effectively avoided or smoothly passed, ensuring the dynamic stability of the system within the rated operating speed range.

[0057] Furthermore, by optimizing the material selection (such as high-strength carbon fiber composites or high-strength steel) and structural design of the flywheel rotor 1, the strength and safety margin of the rotor can be further improved, ensuring reliability under high-speed rotation conditions. Example 3

[0058] like Figures 1 to 3 As shown, the flywheel energy storage device in this embodiment includes a vacuum protection housing 12, a flywheel rotor 1, a generator / motor 3, and a rotor support system. The difference from Embodiment 1 is that: The flywheel rotor 1 is a disc-shaped structure without through holes, and its polar moment of inertia to diametrical moment of inertia ratio is 1.6, which is greater than 1.414. At this time, the frequency of the rotor's second-order torsional yaw mode is always higher than the operating frequency. From rest to the rated speed range, there will be no critical speed of the second-order torsional yaw mode, only the critical speed of the first-order translational mode. Under the action of the squeeze oil film damper, it can smoothly pass through the critical speed.

[0059] This structural configuration gives the rotor better gyroscopic stability, effectively suppressing rotor precession and eddy currents during high-speed rotation.

[0060] Because the rotor is heavy (a single rotor can weigh 500-2000 kg), this embodiment uses an independent permanent magnet thrust bearing assembly, which consists of a permanent magnet offset axial magnetic bearing rotor magnet (7) and a permanent magnet offset axial magnetic bearing stator magnet (8). Together with a radial permanent magnet bearing (5) with a squeeze oil film damper and an axial electromagnetic bearing (2), they maintain the axial free levitation of the flywheel rotor (1). The independent permanent magnet thrust bearing can provide greater axial load capacity to meet the support requirements of heavy rotors.

[0061] The squirrel cage spring rods (511) with radial permanent magnet bearings equipped with squeeze oil film dampers are arranged in six pieces, evenly distributed along the circumference, to further improve the structural stability and load-bearing capacity of the damper. The gap between the damper body (510) and the damper housing (514) is 1.0 mm, which is suitable for the vibration damping requirements of heavy rotors and ensures that sufficient positive damping is provided when passing through the critical speed.

[0062] The flywheel energy storage device in this embodiment can achieve stable acceleration and deceleration of heavy-duty flywheel rotors within the rated speed range (e.g., 5000-10000 rpm), meeting the high-power, high-energy storage requirements of kinetic energy recovery in rail transit. The system power density can reach 500-2000 W / kg, the energy density can reach 10-15 Wh / kg, and the charge-discharge cycle life exceeds 1 million cycles.

[0063] In this embodiment, the axial and radial permanent magnet bearings adopt a repulsive Halbach array structure. Example 4

[0064] A method for using a low-loss, high-reliability, fully suspended flywheel energy storage device includes the following steps: At startup, the axial electromagnetic bearing 2 is energized, generating electromagnetic force to overcome gravity and lift the rotor. As the speed gradually increases, the rotor will pass the first critical speed. At this time, the radial permanent magnet bearing itself may generate a negative damping effect, but the integrated squeeze oil film damper 5 generates a strong positive damping force, which rapidly attenuates the eddy vibration amplitude, allowing the rotor to smoothly pass through the critical region.

[0065] Once the rated speed is reached, the system operates stably under the combined effect of the stiffness of the permanent magnet bearing and the oil film damping. At this point, the axial electromagnetic bearing only needs to provide a small dynamic adjustment force to maintain the axial balance of the rotor, resulting in extremely low power consumption. The radial permanent magnet bearing provides the main radial support stiffness, while the squeeze oil film damper continuously provides damping to suppress vibrations caused by external disturbances and internal imbalances.

[0066] During discharge or shutdown, the rotational speed gradually decreases, and the rotor passes the critical speed again. At this time, it also relies on oil film damping to smoothly pass through the critical speed zone until the rotational speed drops to a safe range, and the rotor is safely seated on the bottom tapered bidirectional mechanical protection bearing 10 and the upper mechanical protection bearing 6.

[0067] Throughout the operation, the force sensor 11 integrated into the bottom protective bearing monitors changes in axial load in real time, which can be used to determine the rotor's suspension state and bearing health status, providing data support for intelligent monitoring and fault early warning of the system.

[0068] In this invention, the rotor support system adopts a hybrid architecture of "single-axis active + dual radial passive damping": 1. Axial support: Employs permanent magnet biased electromagnetic bearings. Specifically, an axial electromagnetic bearing is installed on the upper end face of the flywheel rotor, and an axial permanent magnet biasing assembly is installed on the lower end face (for heavy-duty rotors, a separate bottom permanent magnet thrust bearing can be installed). The permanent magnets provide most of the static load, while the electromagnetic coils are only used for dynamic adjustment, thus simplifying the electromagnetic bearing structure and reducing power consumption and control complexity.

[0069] 2. Radial support: Radial permanent magnet bearings with squeeze film dampers (SDF) are used. Radial permanent magnet bearings are installed on the upper and lower shaft sections of the flywheel rotor, and a closed oil film cavity is constructed between the outer ring of the bearing and the fixed housing.

[0070] 3. Damping Mechanism: The squeeze-film damper includes a damper housing, a damping medium (damping oil), and an elastic support (such as a squirrel cage spring). The outer ring of the radial permanent magnet bearing and the damping body are suspended within the housing by the elastic support. When the rotor whirls, it drives the outer ring of the permanent magnet bearing and the damping body to move, squeezing the damping oil in the oil film cavity and generating a damping force (positive damping) opposite to the direction of velocity. This external positive damping can effectively counteract the internal negative damping generated by the permanent magnet bearing during high-speed rotation, thereby suppressing resonance peaks and allowing the rotor to smoothly pass through the critical speed.

[0071] 4. Protection and Monitoring: Equipped with an upper mechanical protective bearing and a bottom tapered bidirectional mechanical protective bearing. The bottom protective bearing integrates a force sensor, serving as a landing buffer, installation positioning, transportation locking, and operational status monitoring function.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-loss, high-reliability, fully suspended flywheel energy storage device, comprising a vacuum protection shell (12), characterized in that: Also includes: Flywheel rotor (1), which is internally or coaxially connected to a generator / motor (3); The rotor support system is used to support the flywheel rotor (1) to levitate and rotate within the vacuum protective housing (12). The rotor support system includes an axial support unit for providing axial levitation force and stiffness and a radial support unit for providing radial support force and dissipating vibration energy. The radial support unit is integrated with a damping structure.

2. The low-loss, high-reliability, fully suspended flywheel energy storage device according to claim 1, characterized in that: The radial support unit includes: Two radial permanent magnet bearings are respectively installed on the upper shaft section (4) and the lower shaft section (9) of the flywheel rotor (1). The radial permanent magnet bearings include an inner ring (505) of the radial permanent magnet bearing fixed on the upper shaft section (4) and the lower shaft section (9) and an outer ring (506) of the radial permanent magnet bearing fixed on the inside of the damper housing (514). A damping structure for generating damping force when the rotor vibrates, the damping structure comprising an extruded oil film damper (5) integrated on a radial permanent magnet bearing.

3. The low-loss, high-reliability, fully suspended flywheel energy storage device according to claim 1, characterized in that: The squeeze film damper (5) includes: The damper housing (514) is a closed cavity filled with damping medium (502); The damping body (510) has a radial permanent magnet bearing outer ring (506) on its inner circumference. The damping body (510) and the radial permanent magnet bearing outer ring (506) are supported in the damper housing (514) by an elastic reset element. And the gap oil film formed between the radial permanent magnet bearing outer ring (506), the damping body (510) and the damper housing (514).

4. The low-loss, high-reliability fully suspended flywheel energy storage device according to claim 3, characterized in that: The squeeze film damper (5) also includes: The support structure includes an upper support plate (507) and a lower support plate (501) respectively disposed on the upper and lower parts of the damper housing (514). The fixed structure includes an upper fixing plate (509) for the magnet and damping body and a lower fixing plate (504) for the magnet and damping body. An upper thrust plane mechanical bearing (508) is provided between the upper end face of the upper fixing plate (509) and the upper support plate (507). A lower thrust plane mechanical bearing (503) is provided between the lower end face of the lower fixing plate (504) and the lower support plate (501). The damping body (510) and the outer ring (506) of the radial permanent magnet bearing are located between the upper fixing plate (509) for the damping body and the lower fixing plate (504) for the magnet and damping body.

5. The low-loss, high-reliability, fully suspended flywheel energy storage device according to claim 4, characterized in that: The elastic reset element includes at least three squirrel cage spring rods (511) evenly distributed along the circumference of the damping body (510), and the damping body (510) is suspended between the upper support plate (507) and the lower support plate (501) by the squirrel cage spring rods (511).

6. The low-loss, high-reliability, fully suspended flywheel energy storage device according to claim 1, characterized in that: The axial support unit includes: An axial electromagnetic bearing (2) is disposed at one end of a flywheel rotor (1). It includes an electromagnet core (202) fixed in a vacuum protective housing (12) by an electromagnet fixing connector (201) and a coil (203) wound on the electromagnet core (202). An axial permanent magnet biasing assembly is disposed at the other end of the flywheel rotor (1), comprising a permanent magnet biasing axial magnetic bearing rotor magnet (7) fixed in the flywheel rotor (1) and a permanent magnet biasing axial magnetic bearing stator magnet (8) fixed in the vacuum protective housing (12).

7. The low-loss, high-reliability fully suspended flywheel energy storage device according to claim 6, characterized in that: The axial permanent magnet biasing component can be configured in any of the following ways: Configuration 1: Applicable to small and medium-sized flywheel rotors, the outer ring (506) of the radial permanent magnet bearing is axially offset relative to the inner ring (505) of the radial permanent magnet bearing to form an axial offset gap, and the leakage magnetic field of the radial permanent magnet bearing provides part of the axial offset thrust. Configuration 2: Suitable for large flywheel rotors, the axial permanent magnet biasing component is a permanent magnet thrust bearing independently set at the bottom of the flywheel rotor, which cooperates with the radial permanent magnet bearing to maintain axial balance.

8. The low-loss, high-reliability, fully suspended flywheel energy storage device according to claim 1, characterized in that: The upper shaft section (4) of the flywheel rotor (1) is provided with an upper mechanical protection bearing (6) for providing upper radial protection in case of suspension failure, and the lower shaft section (9) is provided with a bottom tapered bidirectional mechanical protection bearing (10). The bottom of the bottom tapered bidirectional mechanical protection bearing (10) integrates a force sensor (11). The bottom tapered bidirectional mechanical protection bearing (10) is configured to: limit large vibrations of the flywheel rotor (1) in the radial direction when it falls, and to provide landing cushioning, installation positioning, magnetic center adjustment and transport locking for the flywheel rotor (1) in the axial direction.

9. The low-loss, high-reliability, fully suspended flywheel energy storage device according to claim 1, characterized in that: The flywheel rotor (1) has a cylindrical or disc-shaped structure and satisfies the following dynamic parameter conditions: When the flywheel rotor (1) is cylindrical, the ratio of its diametrical moment of inertia to its polar moment of inertia is greater than 1.414; When the flywheel rotor (1) is disc-shaped, the ratio of its polar moment of inertia to its diametrical moment of inertia is greater than 1.

414.

10. A method of using a low-loss, high-reliability, fully suspended flywheel energy storage device, characterized in that: Includes the following steps: When started, the axial electromagnetic bearing (2) is energized, generating electromagnetic force to overcome gravity and make the rotor float. As the speed gradually increases, the flywheel rotor (1) will pass through the first critical speed. At this time, the radial permanent magnet bearing itself may generate a negative damping effect, while the squeeze oil film damper (5) generates a strong positive damping force, which can quickly attenuate the eddy vibration amplitude and make the flywheel rotor (1) smoothly pass through the critical zone. After reaching the rated speed, the flywheel rotor (1) operates stably under the combined action of the stiffness of the permanent magnet bearing and the oil film damping. At this time, the axial electromagnetic bearing (2) only needs to provide a small dynamic adjustment force to maintain the axial balance position of the flywheel rotor (1), and the power consumption is extremely low. The radial permanent magnet bearing provides the main radial support stiffness, and the squeeze oil film damper (5) continuously provides damping to suppress the vibration caused by external disturbances and internal imbalances. During the discharge or shutdown process, as the speed gradually decreases, the flywheel rotor (1) passes the critical speed again; at this time, it also relies on oil film damping to smoothly pass through the critical speed zone until the speed drops to a safe range, and the flywheel rotor (1) is safely seated on the bottom tapered bidirectional mechanical protection bearing (10) and the upper mechanical protection bearing (6); Throughout the operation, the force sensor (11) monitors the axial load change in real time, which can be used to determine the suspension state of the flywheel rotor (1) and the health status of the bearing, providing data support for the intelligent monitoring and fault warning of the system.

Images