Variable-speed pump turbine set, regulation and control vibration damping device and method

Abstract

The invention provides a variable-speed water pump hydraulic turbine set and a regulation and control anti-vibration device and method. According to the regulation and control anti-vibration device of the variable-speed pump turbine set, the set comprises a lower ring, a seat ring and a top cover, the lower ring comprises an annular plate and a plurality of radial rib plates evenly distributed on the annular plate in the circumferential direction, and a cavity is formed between every two adjacent rib plates; the device comprises a plurality of connecting key mechanisms, each connecting key mechanism comprises a connecting key body and a pre-tightening force applying unit, and each connecting key body is arranged between every two adjacent rib plates and used for being connected with the side faces of the corresponding two adjacent rib plates; the pre-tightening force applying unit is integrated on or acts on the connecting key body and used for applying controllable axial pre-tightening force to the connecting key body so as to adjust the overall rigidity of the unit, and therefore the inherent frequency of the unit is changed. And in the whole variable-speed operation range of the unit, the rotating frequency of the unit can effectively avoid the inherent frequency of a fixed part, so that resonance is inhibited fundamentally.

Description

Technical Field

[0001] This application relates to the field of hydraulic machinery vibration and control technology, and in particular to a variable speed water pump turbine unit, a vibration damping device and method. Background Technology

[0002] Pump turbine units, especially modern variable-speed pumped storage units, can flexibly adjust their speed according to grid demand, thereby optimizing operating efficiency and enhancing grid stability. However, variable-speed operation also brings new challenges: changes in unit speed mean that its rotational frequency (such as rotor frequency and blade frequency) is also constantly changing. This can easily coincide with the natural frequency of stationary components (such as the mounting ring, volute, and lower ring), causing severe structural resonance, leading to excessive unit vibration, component fatigue damage, and even threatening the safety of the power plant.

[0003] Traditional vibration reduction methods often employ passive design, such as optimizing the structure during the design phase to minimize the difference between the natural frequency and the excitation frequency at rated speed, or installing dampers. However, these methods cannot adapt to operating conditions with large variations in speed. Once the unit operates at variable speeds, the original frequency "safe zone" will no longer exist, and the risk of resonance will greatly increase.

[0004] Therefore, there is an urgent need for a device that can actively and in real time adapt to changes in rotational speed and dynamically adjust the structural dynamic characteristics to avoid resonance. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of the prior art and provide a variable speed water pump turbine unit, a vibration damping device, and a method therefor. This device can adjust the overall stiffness of the lower ring and its connected fixed components online and dynamically, thereby changing its natural frequency. This ensures that throughout the entire variable speed operating range of the unit, its rotational frequency effectively avoids the natural frequency of the fixed components, fundamentally suppressing resonance.

[0006] In a first aspect, embodiments of this application provide a vibration damping device for a variable speed water pump turbine unit. The unit includes a lower ring, a seat ring, and a top cover. The lower ring includes an annular plate and a plurality of radial stiffeners evenly distributed circumferentially on the annular plate, with a cavity formed between adjacent stiffeners. The device includes: At least one connecting key mechanism, the connecting key mechanism including a connecting key body and a preload application unit, the connecting key body being disposed between two adjacent stiffeners for connecting to the sides of the two adjacent stiffeners; the preload application unit being integrated into or acting on the connecting key body for applying a controllable axial preload to the connecting key body to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit.

[0007] Optional, also includes: A vibration sensor, disposed in at least one of the lower ring, the seat ring, and the top cover, is used to monitor the vibration data of the unit, the vibration data including vibration amplitude and vibration frequency; The speed monitoring unit is used to monitor the current operating speed of the unit; The controller is electrically connected to the vibration sensor, the speed monitoring unit, and each of the preload application units. The controller is used to determine whether the operating status of the unit meets the adjustment requirements based on the signals from the vibration sensor and the speed monitoring unit. When the operating status of the unit meets the adjustment requirements, the controller calculates the required stiffness change of the unit and generates a control command to send to the preload application unit. The controller controls the preload application unit to adjust its output preload to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit.

[0008] Optionally, the adjustment requirements include at least one of the following: The vibration amplitude and frequency of the unit exceeded the safety threshold; The difference between the unit's current frequency and its inherent frequency is within the set range.

[0009] Optionally, the controller includes a storage unit that stores a mapping table of the unit's operating speed and prestress. The controller determines the prestress corresponding to the unit's current speed based on the mapping table, thereby calculating the required stiffness change of the unit.

[0010] Optionally, both ends of the connecting key body are provided with connecting parts, which are fixed to the stiffening plate by bolts, pins or welding.

[0011] Optionally, the preload application unit includes a hydraulic tensioner, a piezoelectric actuator, or a servo electric cylinder; and / or The annular plate is provided with a limiting hole, and one end of the pre-tightening force application unit is disposed in the limiting hole.

[0012] Secondly, embodiments of this application provide a variable speed water pump turbine unit, comprising: The lower ring includes a lower ring, a seat ring, and a top cover. The lower ring includes an annular plate and a plurality of radial stiffeners evenly distributed along the circumference of the annular plate, with a cavity formed between two adjacent stiffeners. The seat ring is disposed on the top of the lower ring, and the top cover is disposed on the top of the seat ring. The vibration damping device as described in the first aspect.

[0013] Secondly, embodiments of this application provide a method for regulating and mitigating vibration in a variable-speed pump-turbine unit as described in the second aspect, comprising: Acquire the unit's vibration data and current operating speed, wherein the vibration data includes vibration amplitude and vibration frequency; Based on the vibration data and the current operating speed, it is determined whether the operating status of the unit meets the adjustment requirements. When the operating status of the unit meets the adjustment requirements, the required stiffness change of the unit is calculated, and a control command is generated and sent to the preload application unit to control the preload application unit to adjust its output preload to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit.

[0014] Optionally, the adjustment requirements include at least one of the following: The vibration amplitude and frequency of the unit exceeded the safety threshold; The difference between the unit's current frequency and its inherent frequency is within the set range.

[0015] Optionally, calculating the required stiffness change of the unit includes: determining the prestress corresponding to the current speed of the unit according to a preset mapping table of the unit's operating speed and prestress, thereby calculating the required stiffness change of the unit.

[0016] The variable speed water pump turbine unit, vibration damping device and method provided in this application apply a controllable axial preload to the connecting key body through a preload application unit. This allows for online and dynamic adjustment of the overall stiffness of the lower ring and its connected fixed components, thereby adjusting the overall stiffness of the unit and changing its natural frequency. This ensures that the rotational frequency of the unit can effectively avoid the natural frequency of the fixed components throughout the entire variable speed operating range, fundamentally suppressing resonance.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] Figure 1 This is a schematic diagram of the structure of the regulating and vibration damping device of the variable speed water pump turbine unit provided in this embodiment.

[0020] Figure 2 This is an enlarged schematic diagram of the connection key mechanism of the regulating vibration damping device of the variable speed water pump turbine unit provided in this embodiment.

[0021] Figure 3 This is a structural block diagram of the regulating and vibration damping device for the variable speed water pump turbine unit provided in this embodiment. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0023] To better understand the technical solution of this application, the following detailed description of the control and vibration damping device and method for the variable speed water pump turbine unit, in conjunction with the accompanying drawings, is provided. Unless otherwise specified, the features in the following embodiments and implementation methods can be combined with each other.

[0024] See Figure 1 and Figure 2 As shown, an embodiment of this application provides a vibration damping device for a variable speed pump-turbine unit. The variable speed pump-turbine unit can be a variable speed pumped storage unit, belonging to the field of hydropower and pumped storage technology. The variable speed pump-turbine unit includes a lower ring 10, a seat ring 20, and a top cover 30. The seat ring 20 is disposed on the top of the lower ring 10, and the top cover 30 is disposed on the top of the seat ring 20. The lower ring 10 includes an annular plate 11 and a plurality of radial stiffeners 12 evenly distributed circumferentially on the annular plate 11, with a cavity formed between two adjacent stiffeners 12.

[0025] The vibration damping device may include at least one connecting key mechanism 40, the stiffness of which is adjustable to adjust the overall stiffness of the unit, thereby changing the unit's natural frequency so that its natural frequency avoids the excitation frequency and rotational frequency (rotational frequency), achieving the vibration damping effect. The connecting key mechanism 40 includes a connecting key body 41 and a preload application unit 42. The connecting key body 41 is disposed between two adjacent stiffening plates 12 and is used to connect to the sides of the two adjacent stiffening plates 12. The preload application unit 42 is integrated into or acts on the connecting key body 41 to apply a controllable axial preload to the connecting key body 41 to adjust the overall stiffness of the unit, thereby changing the unit's natural frequency so that its natural frequency avoids the excitation frequency and rotational frequency (rotational frequency), achieving the vibration damping effect.

[0026] Understandably, the lower ring 10 includes a horizontal annular plate 11 and numerous vertical radial stiffeners 12. The number of connecting key mechanisms 40 can be set according to the number of stiffeners 12 and the actual stiffness adjustment requirements of the unit; this application does not limit this. In this embodiment, a set of connecting key mechanisms 40 is installed in the cavity between every two adjacent stiffeners 12.

[0027] The variable speed pump turbine unit vibration damping device provided in this application applies a controllable axial preload to the connecting key body 41 through the preload application unit 42. This allows for online and dynamic adjustment of the overall stiffness of the lower ring 10 and its connected fixed components, thereby adjusting the overall stiffness of the unit and changing its natural frequency. This ensures that the rotational frequency of the unit can effectively avoid the natural frequency of the fixed components throughout the entire variable speed operating range, fundamentally suppressing resonance.

[0028] like Figure 2 As shown, in some optional embodiments, both ends of the connecting key body 41 are provided with connecting portions, which are fixed to the stiffening plate 12 by bolts 14, pins, or welding. The preload application unit 42 includes a hydraulic tensioner, a piezoelectric ceramic actuator, or a servo electric cylinder.

[0029] In this embodiment, the annular plate 11 is provided with a limiting hole 13, and one end of the preload application unit 42 is disposed in the limiting hole 13. The connecting key mechanism 40 includes a high-strength connecting key body 41 with an I-shaped cross-section. The two ends of the connecting key body 41 are fastened to the side of the stiffening plate 12 by several high-strength bolts 14. A hydraulic tensioner is integrated as the preload application unit 42 in the central through hole of the connecting key body 41.

[0030] Understandably, the two ends of the connecting key body 41 can be fixed to the stiffening plates 12 by means of bolts 14, pins, or welding. When the preload application unit 42 (such as a hydraulic tensioner) is activated, it applies a huge axial tensile force (or thrust) to the connecting key body 41. This force is transmitted to the two adjacent stiffening plates 12 through the connecting parts at both ends of the connecting key body 41, which is equivalent to applying a strong "clamping" force between the stiffening plates 12, thereby achieving the purpose of adjusting the overall stiffness of the unit and changing the natural frequency of the unit. In this way, the overall stiffness of the lower ring 10 and its connected fixed components can be adjusted online and dynamically, thereby adjusting the overall stiffness of the unit and changing the natural frequency of the unit. This ensures that the rotational frequency of the unit can effectively avoid the natural frequency of the fixed components throughout the entire speed range of the unit, fundamentally suppressing resonance.

[0031] Combination Figure 1 , Figure 2 and Figure 3 As shown, in some optional embodiments, the vibration damping device may further include: a vibration sensor 50, a speed monitoring unit 60 (such as a key phase sensor), and a controller 70 (such as a PLC or industrial computer). The vibration sensor 50 and the speed monitoring unit 60 can serve as a monitoring and control system.

[0032] Vibration sensor 50 is disposed in at least one of the lower ring 10, the seat ring 20, and the top cover 30, and is used to monitor and collect vibration data of the unit in real time, the vibration data including vibration amplitude and vibration frequency. Figure 1 As shown, in this embodiment, there are three vibration sensors 50, which are respectively disposed on the lower ring 10, the seat ring 20 and the top cover 30.

[0033] The speed monitoring unit 60 is used to monitor the current operating speed of the unit in real time. The controller 70 is electrically connected to the vibration sensor 50, the speed monitoring unit 60, and each of the preload application units 42, and is used to receive signals from the vibration sensor 50 and the speed monitoring unit 60. The controller 70 is used to determine whether the operating state of the unit meets the adjustment requirements based on the signals from the vibration sensor 50 and the speed monitoring unit 60. When the operating state of the unit meets the adjustment requirements, it calculates the required stiffness change of the unit (based on a built-in algorithm) and generates a control command to send to the preload application unit 42. The controller controls the preload application unit 42 to adjust its output preload to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit so that the natural frequency of the unit avoids the excitation frequency and rotation frequency (rotation frequency), achieving the effect of vibration isolation.

[0034] Optionally, the adjustment requirements include at least one of the following: (1) the vibration amplitude and frequency of the unit exceed the safety threshold. (2) the difference between the current rotation frequency of the unit and the natural frequency of the unit is within the set range, that is, whether the current rotation frequency of the unit is close to the known natural frequency of the unit. In other words, when the vibration amplitude and frequency of the unit exceed the safety threshold, or when the current rotation frequency of the unit is close to the known natural frequency of the unit, the adjustment requirements are met. The algorithm built into the controller 70 can be, for example, determining whether the vibration amplitude of the unit exceeds the safety threshold, whether the current rotation frequency of the unit is close to the known natural frequency, etc.

[0035] Understandably, by adjusting the magnitude of the preload output by the preload application unit 42 to the connecting key body 41, the tightness and stress state of the connection between the stiffening plates 12 can be significantly changed, thereby effectively altering the overall stiffness of the structure composed of the annular plate 11 of the lower ring 10, the stiffening plates 12, and the connecting key mechanism 40. According to structural dynamics theory, the natural frequency of a structure is proportional to the square root of its stiffness. Therefore, increasing the preload can improve the overall stiffness of the unit, thereby increasing its natural frequency; decreasing the preload can reduce the overall stiffness of the unit, thereby reducing its natural frequency. In this way, online and active adjustment of the natural frequency of the unit's fixed components is achieved.

[0036] In some alternative embodiments, the controller 70 includes a storage unit that stores a mapping table of the unit's operating speed and prestress (hereinafter referred to as the "speed-optimal prestress" mapping table). The controller 70 determines the prestress corresponding to the unit's current speed based on the mapping table, thereby calculating the required stiffness change of the unit.

[0037] Understandably, the controller can calculate the current excitation frequency (rotation frequency) of the unit based on its current rotational speed. According to structural dynamics theory, the natural frequency of a structure is proportional to the square root of its stiffness. Therefore, to effectively avoid the natural frequencies of the unit's fixed components and fundamentally suppress resonance, after determining the unit's rotational frequency, the required natural frequency that the unit needs to reach to avoid the rotational frequency can be determined. Then, the required stiffness change of the unit can be determined, thereby determining the magnitude of the prestress that the prestressing unit needs to apply to the connecting key body. The correspondence between operating speed and prestress can be pre-formed into a mapping table based on simulation or experimental data and stored in the storage unit.

[0038] The controller can also use model calculations to determine the target natural frequency required to avoid resonance in real time based on the unit's current operating speed, and then calculate the amount of prestress that the prestressing unit needs to apply to the connecting key body. Increasing the prestress can improve the overall stiffness of the unit, thereby increasing its natural frequency; decreasing the prestress can reduce the overall stiffness of the unit, thereby decreasing its natural frequency. In this way, online and active adjustment of the natural frequency of the unit's stationary components is achieved.

[0039] The working process of the vibration damping control device in this embodiment can be as follows: S1: System initialization, controller 70 reads the current operating speed n of the unit.

[0040] S2: The controller 70 calculates the main excitation frequency (e.g., rotational frequency f = n / 60) based on the operating speed n.

[0041] S3: The controller 70 retrieves the internally stored "speed-optimal preload" mapping table or calculates it through the model to determine the target natural frequency required to avoid resonance, and then calculates the target preload magnitude F that the preload application unit needs to apply to the connecting key body. This mapping table can be obtained through early-stage unit simulation or testing.

[0042] S4: The controller 70 sends a control command to the prestressing application unit 42, causing it to output the target preload F to tighten or loosen the connecting key body 41.

[0043] S5: Vibration sensor 50 continuously monitors the vibration level of the unit. If the vibration amplitude still exceeds the safety threshold, controller 70 makes fine adjustments to further optimize the preload until the unit vibration is suppressed within the allowable range.

[0044] S6: When the unit's operating speed n changes, repeat steps S1-S5 above to achieve real-time, adaptive frequency tracking and vibration damping. That is, the target preload is fine-tuned through closed-loop feedback based on the real-time vibration signal to optimize the vibration damping effect.

[0045] Compared with existing related technologies, this application has the following advantages and beneficial effects: 1. Active vibration damping: It transforms passive vibration into active vibration damping, and can dynamically adjust the structural stiffness according to the real-time speed of the unit to achieve "machine changes with speed", so that the natural frequency of the unit always avoids the excitation frequency.

[0046] 2. High adaptability: It is particularly suitable for water pump turbine units with wide-range variable speed operation, solving the problem that traditional designs cannot cope with multi-speed operating conditions.

[0047] 3. Significant effect: It directly suppresses resonance from the vibration source (frequency coupling), and the vibration reduction effect is more fundamental and effective than simply increasing damping or mass blocks.

[0048] 4. Reasonable structure: The space between the lower ring stiffeners is fully utilized to install the connecting key mechanism, resulting in a compact structure that does not change the main structure of the unit, making it easy to integrate into new units or to modify existing units.

[0049] Combination Figure 1 and Figure 2 As shown, an embodiment of this application also provides a variable speed pump-turbine unit, including: a vibration damping device, a lower ring 10, a seat ring 20, and a top cover 30. The lower ring 10 includes an annular plate 11 and a plurality of radial stiffeners 12 evenly distributed circumferentially on the annular plate 11, with a cavity formed between adjacent stiffeners 12. The seat ring 20 is disposed on the top of the lower ring 10, and the top cover 30 is disposed on the top of the seat ring 20. It should be noted that the description of the vibration damping device in the above embodiments and implementations is also applicable to the variable speed pump-turbine unit of this embodiment, and will not be repeated here.

[0050] The variable speed pump turbine unit provided in this application applies a controllable axial preload to the connecting key body 41 through the preload application unit 42. This allows for online and dynamic adjustment of the overall stiffness of the lower ring 10 and its connected fixed components, thereby adjusting the overall stiffness of the unit and changing its natural frequency. This ensures that the rotational frequency of the unit can effectively avoid the natural frequency of the fixed components throughout the entire variable speed operating range, fundamentally suppressing resonance.

[0051] This application also provides a method for regulating and mitigating vibration in a variable-speed pump-turbine unit. It should be noted that the variable-speed pump-turbine unit can be the variable-speed pump-turbine unit described in the above embodiments and implementation methods. The vibration regulation and mitigation method can be executed by the controller 70, and the method may include: Step 1: Acquire the unit's vibration data and current operating speed. The vibration data includes vibration amplitude and vibration frequency. Understandably, the controller 70 acquires the unit's vibration data and current operating speed by receiving signals from the vibration sensor 50 and the speed monitoring unit 60.

[0052] Step 2: Based on the vibration data and the current operating speed, determine whether the unit's operating status meets the adjustment requirements. When the unit's operating status meets the adjustment requirements, calculate the required stiffness change of the unit and generate a control command to send to the preload application unit 42. Control the preload application unit 42 to adjust its output preload to adjust the overall stiffness of the unit, thereby changing the unit's natural frequency so that the unit's natural frequency avoids the excitation frequency and rotation frequency (rotation frequency), achieving the vibration isolation effect.

[0053] Optionally, the adjustment requirements include at least one of the following: (1) the vibration amplitude and frequency of the unit exceed the safety threshold. (2) the difference between the current rotation frequency of the unit and the natural frequency of the unit is within the set range, that is, whether the current rotation frequency of the unit is close to the known natural frequency of the unit. In other words, the adjustment requirements are met when the vibration amplitude and frequency of the unit exceed the safety threshold, or when the current rotation frequency of the unit is close to the known natural frequency of the unit.

[0054] Understandably, by adjusting the magnitude of the preload output by the preload application unit 42 to the connecting key body 41, the tightness and stress state of the connection between the stiffening plates 12 can be significantly changed, thereby effectively altering the overall stiffness of the structure composed of the annular plate 11 of the lower ring 10, the stiffening plates 12, and the connecting key mechanism 40. According to structural dynamics theory, the natural frequency of a structure is proportional to the square root of its stiffness. Therefore, increasing the preload can improve the overall stiffness of the unit, thereby increasing its natural frequency; decreasing the preload can reduce the overall stiffness of the unit, thereby reducing its natural frequency. In this way, online and active adjustment of the natural frequency of the unit's fixed components is achieved.

[0055] In some alternative embodiments, the controller 70 includes a storage unit that stores a mapping table of the unit's operating speed and prestress (hereinafter referred to as the "speed-optimal prestress" mapping table). The controller 70 determines the prestress corresponding to the unit's current speed based on the mapping table, thereby calculating the required stiffness change of the unit.

[0056] Understandably, the controller can calculate the current excitation frequency (rotation frequency) of the unit based on its current rotational speed. According to structural dynamics theory, the natural frequency of a structure is proportional to the square root of its stiffness. Therefore, to effectively avoid the natural frequencies of the unit's fixed components and fundamentally suppress resonance, after determining the unit's rotational frequency, the required natural frequency that the unit needs to reach to avoid the rotational frequency can be determined. Then, the required stiffness change of the unit can be determined, thereby determining the magnitude of the prestress that the prestressing unit needs to apply to the connecting key body. The correspondence between operating speed and prestress can be pre-formed into a mapping table based on simulation or experimental data and stored in the storage unit.

[0057] The controller can also use model calculations to determine the target natural frequency required to avoid resonance in real time based on the unit's current operating speed, and then calculate the amount of prestress that the prestressing unit needs to apply to the connecting key body. Increasing the prestress can improve the overall stiffness of the unit, thereby increasing its natural frequency; decreasing the prestress can reduce the overall stiffness of the unit, thereby decreasing its natural frequency. In this way, online and active adjustment of the natural frequency of the unit's stationary components is achieved.

[0058] The working process of the vibration damping control device in this embodiment can be as follows: S1: System initialization, controller 70 reads the current operating speed n of the unit.

[0059] S2: The controller 70 calculates the main excitation frequency (e.g., rotational frequency f = n / 60) based on the operating speed n.

[0060] S3: The controller 70 retrieves the internally stored "speed-optimal preload" mapping table or calculates it through the model to determine the target natural frequency required to avoid resonance, and then calculates the target preload magnitude F that the preload application unit needs to apply to the connecting key body. This mapping table can be obtained through early-stage unit simulation or testing.

[0061] S4: The controller 70 sends a control command to the prestressing application unit 42, causing it to output the target preload F to tighten or loosen the connecting key body 41.

[0062] S5: Vibration sensor 50 continuously monitors the vibration level of the unit. If the vibration amplitude still exceeds the safety threshold, controller 70 makes fine adjustments to further optimize the preload until the unit vibration is suppressed within the allowable range.

[0063] S6: When the unit's operating speed n changes, repeat steps S1-S5 above to achieve real-time, adaptive frequency tracking and vibration damping. That is, the target preload is fine-tuned through closed-loop feedback based on the real-time vibration signal to optimize the vibration damping effect.

[0064] The vibration damping method for variable speed pump turbine units provided in this application applies a controllable axial preload to the connecting key body 41 through the preload application unit 42. This allows for online and dynamic adjustment of the overall stiffness of the lower ring 10 and its connected fixed components, thereby adjusting the overall stiffness of the unit and changing its natural frequency. This ensures that the rotational frequency of the unit can effectively avoid the natural frequency of the fixed components throughout the entire variable speed operating range, fundamentally suppressing resonance.

[0065] This application discloses a variable-speed pump-turbine unit, an adjustable vibration damping device for the lower ring of the variable-speed pump-turbine unit, and its application method through the above-described technical solution. A connecting key mechanism is installed between adjacent ribs of the lower ring. This mechanism includes a connecting key body and a preload application unit. A controllable preload is applied to the connecting key body by the preload application unit, thereby dynamically and online adjusting the overall stiffness of the lower ring and connected fixed components, changing its natural frequency. Combined with a monitoring and control system, the unit's speed changes are tracked in real time. By adjusting the preload, the structure's natural frequency is kept away from the rotational excitation frequency, effectively suppressing structural resonance of the unit across the entire variable-speed range. This solves the technical problem of resonance easily caused by speed changes in variable-speed units, significantly improving the unit's operational safety and stability.

[0066] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A vibration damping device for a variable speed water pump turbine unit, characterized in that, The unit includes a lower ring, a seat ring, and a top cover. The lower ring includes an annular plate and a plurality of radial stiffeners evenly distributed circumferentially on the annular plate, with a cavity formed between adjacent stiffeners. The device includes: At least one connecting key mechanism, the connecting key mechanism including a connecting key body and a preload application unit, the connecting key body being disposed between two adjacent stiffeners for connecting to the sides of the two adjacent stiffeners; the preload application unit being integrated into or acting on the connecting key body for applying a controllable axial preload to the connecting key body to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit.

2. The apparatus according to claim 1, characterized in that, Also includes: A vibration sensor, disposed in at least one of the lower ring, the seat ring, and the top cover, is used to monitor the vibration data of the unit, the vibration data including vibration amplitude and vibration frequency; The speed monitoring unit is used to monitor the current operating speed of the unit; The controller is electrically connected to the vibration sensor, the speed monitoring unit, and each of the preload application units. The controller is used to determine whether the operating status of the unit meets the adjustment requirements based on the signals from the vibration sensor and the speed monitoring unit. When the operating status of the unit meets the adjustment requirements, the controller calculates the required stiffness change of the unit and generates a control command to send to the preload application unit. The controller controls the preload application unit to adjust its output preload to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit.

3. The apparatus according to claim 2, characterized in that, The adjustment requirements include at least one of the following: The vibration amplitude and frequency of the unit exceeded the safety threshold; The difference between the unit's current frequency and its inherent frequency is within the set range.

4. The apparatus according to claim 2, characterized in that, The controller includes a storage unit that stores a mapping table of the unit's operating speed and prestress. The controller determines the prestress corresponding to the unit's current speed based on the mapping table, thereby calculating the required stiffness change of the unit.

5. The apparatus according to claim 1, characterized in that, Both ends of the connecting key body are provided with connecting parts, which are fixed to the stiffening plate by bolts, pins or welding.

6. The apparatus according to claim 1, characterized in that, The preload application unit includes a hydraulic tensioner, a piezoelectric ceramic actuator, or a servo electric cylinder; and / or The annular plate is provided with a limiting hole, and one end of the pre-tightening force application unit is disposed in the limiting hole.

7. A variable speed water pump turbine unit, characterized in that, include: The lower ring includes a lower ring, a seat ring, and a top cover. The lower ring includes an annular plate and a plurality of radial stiffeners evenly distributed along the circumference of the annular plate, with a cavity formed between two adjacent stiffeners. The seat ring is disposed on the top of the lower ring, and the top cover is disposed on the top of the seat ring. The vibration damping device as described in any one of claims 1-6.

8. A method for regulating and mitigating vibration in a variable speed pump-turbine unit as described in claim 7, characterized in that, include: Acquire the vibration data and current operating speed of the unit, wherein the vibration data includes vibration amplitude and vibration frequency; Based on the vibration data and the current operating speed, it is determined whether the operating status of the unit meets the adjustment requirements. When the operating status of the unit meets the adjustment requirements, the required stiffness change of the unit is calculated, and a control command is generated and sent to the preload application unit to control the preload application unit to adjust its output preload to adjust the overall stiffness of the unit, thereby changing the natural frequency of the unit.

9. The method according to claim 8, characterized in that, The adjustment requirements include at least one of the following: The vibration amplitude and frequency of the unit exceeded the safety threshold; The difference between the unit's current frequency and its inherent frequency is within the set range.

10. The method according to claim 8, characterized in that, The calculation of the required stiffness change of the unit includes: determining the prestress corresponding to the current speed of the unit according to a preset mapping table of the unit's operating speed and prestress, thereby calculating the required stiffness change of the unit.

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