Vibration control method and system for variable-speed pump turbine set

Abstract

The invention provides a vibration control method and system for a variable-speed pump turbine set, and the method comprises the steps: building a fluid-structure interaction model of the pump turbine set, employing a sound-structure interaction modal analysis method, and obtaining the modal parameters of the fluid-structure interaction model of the pump turbine set in a water environment through calculation, and the modal parameters comprise the inherent frequency of a set order. And according to the current operation rotating speed or the predicted operation rotating speed of the pump turbine set, the hydraulic excitation frequency of the pump turbine set is obtained through calculation, and the inherent frequency closest to the hydraulic excitation frequency is determined from the modal parameters to serve as the modal frequency. Comparing the modal frequency with the hydraulic excitation frequency, determining a new operation rotating speed at the moment, and controlling the pump turbine set to operate at the new operation rotating speed, so that the pump turbine set operates at the new operation rotating speed; wherein fe is the hydraulic excitation frequency, fn is the modal frequency, and delta is the safety margin threshold value.

Description

Technical Field

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

[0002] With the transformation of the energy structure, pumped storage power stations are playing an increasingly prominent role in grid peak shaving and frequency regulation. To improve operational efficiency and grid responsiveness, variable-speed constant-frequency pump-turbine units have become a development trend. However, variable-speed operation means that the unit will experience a wider speed range, and the hydraulic excitation frequency generated by its rotating components (such as the runner) will also change accordingly. When the changing excitation frequency coincides with a certain natural frequency of the unit structure (including the water in the flow channel), it will trigger strong structural resonance, leading to a sharp increase in unit vibration and noise, seriously threatening the safe and stable operation of the unit, and even causing structural fatigue damage.

[0003] Existing vibration control methods are mostly "passive," meaning they mitigate vibration at specific speed points after it occurs by strengthening the structure, installing dynamic dampers, or performing post-event analysis. These methods suffer from hysteresis and cannot adapt to the wide range of dynamic operating conditions of variable speed units. Traditional modal analysis typically only considers the "dry modes" of the structure in air, neglecting the "added mass effect" of the surrounding water, resulting in calculated natural frequencies that are too high and deviate significantly from actual conditions. Consequently, vibration avoidance strategies developed based on this are unreliable. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of related technologies and provide a vibration control method and system for a variable speed water pump turbine unit. This system can accurately calculate the actual mode of the unit in the water and actively adjust the rotational speed to avoid resonance, thereby achieving active and intelligent vibration suppression.

[0005] In a first aspect, embodiments of this application provide a vibration control method for a variable speed pump-turbine unit, comprising: A fluid-structure interaction model of a pump-turbine unit was established, and the modal parameters of the pump-turbine unit in an aquatic environment were calculated using the acoustic-structure interaction modal analysis method. The fluid-structure interaction model includes a fluid model and a structural solid model of the pump-turbine unit in an aquatic environment, and the modal parameters include natural frequencies of a set order. Based on the current operating speed or the expected operating speed of the pump-turbine unit, the hydraulic excitation frequency of the pump-turbine unit is calculated, and the natural frequency that is closest to the hydraulic excitation frequency is determined from the modal parameters as the modal frequency. The modal frequency is compared with the hydraulic excitation frequency. The new operating speed is determined and the pump-turbine unit is controlled to operate at the new operating speed, so that the pump-turbine unit can operate at the new operating speed. ; where f e Let f be the hydraulic excitation frequency. n The modal frequency, δ This is the safety margin threshold.

[0006] Optionally, establishing the fluid-structure interaction model of the pump-turbine unit includes: Establish a fluid model and a structural solid model of the entire flow path, including the runner, main shaft, movable guide vanes, top cover, seat ring, volute, and tailrace of the water pump turbine unit.

[0007] Optionally, the method of employing acoustic-structure interaction modal analysis to calculate the modal parameters of the pump-turbine unit's fluid-structure interaction model in an aquatic environment includes: The fluid domain of the fluid model is set as a compressible acoustic medium, and the structural domain of the structural solid model is set as a solid medium. Coupling conditions are set at the coupling interface between the fluid model and the structural solid structure, and modal analysis is performed to obtain the natural frequencies of the set order of the fluid-structure interaction model of the pump-turbine unit in the water environment.

[0008] Optionally, calculating the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed includes: According to the calculation formula f e = k×N / 60 determines the hydraulic excitation frequency; where k is the number of blades or movable guide vanes of the water pump-cooled unit's impeller, and N is the current operating speed or the expected operating speed of the water pump-turbine unit.

[0009] Optionally, the safety margin threshold can be set in the range of 5%-15%.

[0010] Optionally, determining the new operating speed includes: Within the permissible speed range of the pump-turbine unit, several candidate operating speeds are determined; The hydraulic excitation frequency and output power of the pump-turbine unit when operating at each of the selected operating speeds were calculated. From a number of candidate operating speeds, the one that maximizes the difference between the hydraulic excitation frequency and the modal frequency of the pump-turbine unit and keeps the change in output power within a set range is selected as the new operating speed.

[0011] Secondly, embodiments of this application provide a vibration control system for a variable speed pump-turbine unit, comprising: The modeling and analysis unit is used to establish a fluid-structure interaction model of the pump-turbine unit and to calculate the modal parameters of the fluid-structure interaction model of the pump-turbine unit in an aquatic environment using the acoustic-structure interaction modal analysis method. The fluid-structure interaction model includes a fluid model and a structural solid model of the pump-turbine unit in an aquatic environment, and the modal parameters include natural frequencies of a set order. The control unit, electrically connected to the modeling and analysis unit, is used to calculate the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed; determine the natural frequency closest to the hydraulic excitation frequency from the modal parameters as the modal frequency; and compare the modal frequency with the hydraulic excitation frequency. The new operating speed is determined and the pump-turbine unit is controlled to operate at the new operating speed, so that the pump-turbine unit can operate at the new operating speed. ; where f e Let f be the hydraulic excitation frequency. n The modal frequency, δ This is the safety margin threshold.

[0012] Optionally, establishing the fluid-structure interaction model of the pump-turbine unit includes: Establish a fluid model and a structural solid model of the entire flow path, including the runner, main shaft, movable guide vanes, top cover, seat ring, volute, and tailrace of the water pump turbine unit.

[0013] Optionally, the method of employing acoustic-structure interaction modal analysis to calculate the modal parameters of the pump-turbine unit's fluid-structure interaction model in an aquatic environment includes: The fluid domain of the fluid model is set as a compressible acoustic medium, and the structural domain of the structural solid model is set as a solid medium. Coupling conditions are set at the coupling interface between the fluid model and the structural solid structure, and modal analysis is performed to obtain the natural frequencies of the set order of the fluid-structure interaction model of the pump-turbine unit in the water environment.

[0014] Optionally, calculating the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed includes: According to the calculation formula f e = k×N / 60 determines the hydraulic excitation frequency; where k is the number of blades or movable guide vanes of the water pump-cooled unit's impeller, and N is the current operating speed or the expected operating speed of the water pump-turbine unit.

[0015] Optionally, the safety margin threshold can be set in the range of 5%-15%.

[0016] Optionally, determining the new operating speed includes: Within the permissible speed range of the pump-turbine unit, several candidate operating speeds are determined; The hydraulic excitation frequency and output power of the pump-turbine unit when operating at each of the selected operating speeds were calculated. From a number of candidate operating speeds, the one that maximizes the difference between the hydraulic excitation frequency and the modal frequency of the pump-turbine unit and keeps the change in output power within a set range is selected as the new operating speed.

[0017] Thirdly, embodiments of this application provide a computer system including one or more processors and a memory, the memory storing computer program instructions that, when executed by the processor, implement the method described in the first aspect.

[0018] The vibration control method and system for variable speed pump-turbine units provided in this application employs acoustic-structure coupled modal analysis to accurately determine the natural frequencies of the pump-cooled unit in an aquatic environment, taking into account the added mass effect of the water body, thus ensuring the accuracy of the modal parameters. This method can accurately predict the actual dynamic characteristics of the unit and proactively and forward-lookingly avoid resonance risks during operation.

[0019] 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

[0020] 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.

[0021] Figure 1 This is a flowchart of the vibration control method for a variable speed water pump turbine unit provided in this embodiment.

[0022] Figure 2 This is a logical schematic diagram of the vibration control method for the variable speed water pump turbine unit provided in this embodiment.

[0023] Figure 3 This is a structural block diagram of the vibration control system of the variable speed water pump turbine unit provided in this embodiment. Detailed Implementation

[0024] 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.

[0025] To better understand the technical solution of this application, the vibration control method and system for a variable speed water pump turbine unit of this application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the features in the following embodiments and implementation methods can be combined with each other.

[0026] See Figure 1 As shown, an embodiment of this application provides a vibration control method 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 method may include: Step S1: Establish a fluid-structure interaction model of the pump-turbine unit and use acoustic-structure interaction modal analysis to calculate the modal parameters of the fluid-structure interaction model of the pump-turbine unit in an aquatic environment; the fluid-structure interaction model includes a fluid model and a structural solid model of the pump-turbine unit in an aquatic environment, and the modal parameters include natural frequencies of a set order.

[0027] Understandably, this step is the high-precision modeling and modal analysis stage: A detailed fluid-structure interaction model of the pump-turbine unit is established, and the acoustic-structure interaction modal analysis method is used to accurately solve for the natural frequencies {f} of the set order of the fluid-structure interaction model of the pump-turbine unit considering the added mass effect of the water body in the aquatic environment. n The wet modal frequencies (n=1,2,3…) are the unit's wet modal frequencies. These frequencies are lower than the dry modal frequencies calculated in air, better reflecting the unit's true dynamic characteristics and ensuring the accuracy of the modal parameters. It should be noted that acoustic-structure interaction refers to the interaction between sound waves and a solid medium as sound waves propagate through it. This is a two-way coupling process; solid vibrations drive the fluid to generate sound pressure waves, while pressure waves in the fluid also act on the solid, causing it to vibrate.

[0028] Each natural frequency reflects the inherent vibration characteristics of a structure under a specific vibration mode (mode shape). It is an inherent property of the structure itself and is independent of external excitation. When the external excitation frequency is equal to or close to a certain natural frequency, the vibration mode corresponding to that natural frequency will resonate. Methods to avoid resonance mainly include: changing the structure's natural frequencies (such as adjusting structural mass and stiffness), reducing or eliminating the frequency components of the excitation source, increasing structural damping to reduce the resonance amplitude, and changing the external excitation frequency. This application primarily avoids resonance in the unit by changing the external excitation frequency, as detailed below. The number of natural frequencies can be set according to actual needs; this application does not impose any restrictions on this.

[0029] Step S2: Based on the current operating speed or the expected operating speed of the pump-turbine unit (which can be achieved through a monitoring system), calculate the hydraulic excitation frequency of the pump-turbine unit, and determine the natural frequency closest to the hydraulic excitation frequency from the modal parameters as the modal frequency.

[0030] Understandably, this step is the real-time monitoring and risk prediction stage. It involves real-time monitoring of the unit's current operating speed or the expected operating speed N, and calculating the unit's main hydraulic excitation frequency f under the current or planned operating conditions based on the hydraulic design. e Then, the natural frequency closest to the hydraulic excitation frequency is determined from the modal parameters as the modal frequency f. n .

[0031] Step S3: Compare the modal frequency with the hydraulic excitation frequency. When (Equation 1) determines the new operating speed and controls the pump-turbine unit to operate at the new operating speed (this can be achieved by controlling the speed regulation system through the control system), so that the pump-turbine unit operates at the new operating speed. ; where f e Let f be the hydraulic excitation frequency. n The modal frequency, δ This is a safety margin threshold. Optionally, the safety margin threshold ranges from 5% to 15%, preferably 10%, and this threshold can be dynamically adjusted based on the unit's historical vibration intensity data, structural importance, or operational experience.

[0032] Understandably, this step is the intelligent decision-making and control stage: establishing a resonance risk assessment and speed control strategy (or a control model). The hydraulic excitation frequency f... e With a given modal frequency f n Perform a comparison. If found... If a resonance risk is detected, the control model immediately initiates an optimization algorithm to find one or more safe alternative speeds N' within the unit's permissible speed range. These alternative speeds N' avoid the resonance point while minimizing the impact on the unit's power and efficiency. The control system generates speed adjustment commands and sends them to the unit's speed control system, controlling the unit to switch to the safe alternative speed N' and controlling the pump-turbine unit to perform a speed switch to the new operating speed N'. Simultaneously, the system continuously monitors vibration signals to verify the vibration control effect and can perform self-learning optimization of the control model parameters.

[0033] The vibration control method for variable-speed pump-turbine units provided in this application employs acoustic-structure coupled modal analysis to accurately determine the natural frequencies of the pump-turbine unit in a water environment, taking into account the added mass effect of the water body, thus ensuring the accuracy of the modal parameters. This method can accurately predict the actual dynamic characteristics of the unit and proactively and forward-lookingly avoid resonance risks during operation.

[0034] Therefore, the core idea of ​​this application is as follows: First, by using acoustic-structure coupled modal analysis, the modal frequencies and mode shapes of the overall structure of the pump-turbine unit, considering the added mass effect of the surrounding water body, are accurately calculated; second, the unit's hydraulic excitation frequency under current or expected operating speed is monitored or predicted in real time; then, a control strategy or control model is established to determine whether the hydraulic excitation frequency resonates with or is close to resonating with a calculated modal natural frequency (i.e., modal frequency); finally, if the risk of resonance is predicted, a new operating speed is determined through the control strategy or control model, and a speed adjustment command is generated to dynamically adjust the unit to operate at the new operating speed. This ensures that when the pump-turbine unit operates at the new operating speed, its hydraulic excitation frequency actively avoids the natural frequency of the structure, thereby suppressing strong vibrations from the source and ensuring the safe, stable, and efficient operation of the unit.

[0035] Compared with existing related technologies, this application has the following significant advantages and beneficial effects: 1. Foresight and initiative: Shifting from "passive response" to "active avoidance," the problem is fundamentally solved by adjusting the rotational speed before resonance occurs.

[0036] 2. High precision and reliability: By adopting acoustic-structure coupled modal analysis, the dynamic effects of water are fully considered, and the obtained modal frequencies are closer to reality, which greatly improves the scientificity and reliability of the vibration avoidance strategy.

[0037] 3. Adaptive and intelligent: The established control model has multi-objective optimization capabilities, which can take into account both the operating efficiency of the unit and the load demand of the power grid while avoiding vibration, thus realizing intelligent operation control.

[0038] 4. High versatility: This method is applicable to all types of variable speed pump-turbine units, especially reversible pump-turbine units with complex operating conditions, and has broad engineering application prospects.

[0039] In some optional implementations, in step S1, establishing the fluid-structure interaction model of the pump-turbine unit includes: using 3D CAD software and finite element analysis software (finite element preprocessing software, such as ANSYS, COMSOL) to establish a fluid model and a structural solid model of the entire flow channel, including the runner, main shaft, movable guide vanes, top cover, seat ring, volute, and tailrace of the pump-turbine unit, and performing high-quality mesh generation on the model to complete high-precision modeling.

[0040] In some optional implementations, in step S1, the step of using acoustic-structure interaction modal analysis to calculate the modal parameters of the pump-turbine unit's fluid-structure interaction model in an aquatic environment includes: setting the fluid domain of the fluid model as a compressible acoustic medium (acoustic element), setting the structural domain of the structural solid model as a solid medium (solid element), setting coupling conditions (e.g., satisfying the continuity conditions of displacement and pressure) at the coupling interface (i.e., the fluid-structure interface) between the fluid model and the structural solid model, and performing modal analysis to obtain the modal parameters of the pump-turbine unit's fluid-structure interaction model in an aquatic environment, including setting the natural frequencies of each order, i.e., the natural frequencies {f}. n (n=1,2,3,...) and their corresponding mode shapes. A natural frequency library can be established for each order of natural frequencies.

[0041] Understandably, the aforementioned acoustic-structure coupled modal analysis method specifically treats the fluid domain as a compressible acoustic medium and the structural domain as a solid medium. It satisfies the continuity conditions of displacement and pressure at the fluid-structure coupling interface and solves the eigenvalue problem of the coupled system using the finite element method to obtain the wet modal frequencies. These frequencies are lower than the dry modal frequencies calculated in air and better reflect the true dynamic characteristics of the unit. For example, the first 10 wet modal frequencies of the unit were calculated, with the third natural frequency f3 = 48.5 Hz, and the mode shape being the pitch-diameter oscillation of the turbine runner.

[0042] In some optional implementations, in step S2, calculating the hydraulic excitation frequency of the pump-turbine unit based on its current operating speed or expected operating speed includes: calculating according to the formula... f e = k× N / 60 (Equation 2) determines the hydraulic excitation frequency; where k is the number of blades or movable guide vanes of the water pump-cooled unit's impeller (which can be understood as the number of blades of the movable guide vanes), and N is the current operating speed or the expected operating speed of the water pump-turbine unit (unit: rpm).

[0043] Understandably, the current operating speed of the unit or the planned operating speed N (unit: rpm) is obtained in real time, and its main hydraulic excitation frequency f is determined based on the hydraulic design parameters of the pump turbine. e The hydraulic excitation frequency f e =k×N / 60, where k is the excitation order, determined by the number of impeller blades Z. s and the number of active guide vanes Z g Decision. For example, the number of rotor blades Z. s =15, Number of active guide vanes Z g =20, then the main blade frequency excitation is f eZs =15×N / 60, f eZg =20×N / 60. When N=450rpm, f eZs =112.5Hz, f eZg =150Hz. f eZs and f eZg Whichever frequency is closer to a certain natural frequency in the natural frequency library, Equation 1 will select that frequency as the hydraulic excitation frequency f. e It should be noted that the hydraulic excitation frequency f e It can include not only the rotational frequency and its harmonics, but also the blade frequency excitation f caused by the interference between the impeller and the moving guide vane. eBlade That is, f eZs =Z s ×N / 60 and f eZg =Z g ×N / 60, and the low-frequency excitation caused by the partial load vortex band. Whichever of these is closer to a natural frequency in the natural frequency library is selected as the hydraulic excitation frequency f in Equation 1. e .

[0044] In some alternative implementations, in step S3, determining the new operating speed includes: Within the permissible speed range of the pump-turbine unit, several candidate operating speeds are determined; The hydraulic excitation frequency and output power of the pump-turbine unit when operating at each of the selected operating speeds were calculated. From a number of candidate operating speeds, the one that maximizes the difference between the hydraulic excitation frequency and the modal frequency of the pump-turbine unit and keeps the change in output power within a set range is selected as the new operating speed.

[0045] It is understood that the aforementioned regulation strategy or regulation model is a multi-objective optimization model, and its optimization objectives include: 1. Primary Objective: By changing the operating speed of the unit, select the speed that maximizes the difference between the hydraulic excitation frequency of the pump-turbine unit and the modal frequency, thereby maximizing the interval between the current hydraulic excitation frequency and the closest natural frequency. The current hydraulic excitation frequency can be understood as the hydraulic excitation frequency f calculated using the new operating speed N'. e ', that is, Max(|f e '-f n |).

[0046] 2. Secondary objective: Minimize the impact of speed adjustment on the unit's output power or efficiency, that is, select a speed that ensures the change in output power of the pump turbine unit at the operating speed N and at the new operating speed N' is within a set range, i.e., Min(|P(N')-P(N)|), where P is the power.

[0047] 3. Constraints: The replacement speed N' must be within the safe operating speed range of the unit [Nmin, Nmax].

[0048] The following is combined Figure 1 and Figure 2 Taking a 300MW variable-speed pumped-storage unit as an example, the method of this application may include the following steps: Step 1: High-precision modeling. Using 3D CAD software and finite element preprocessing software, a full-channel fluid model and structural solid model are created, including the impeller (15 blades), main shaft, 20 movable guide vanes, top cover, seat ring, volute, and tailrace pipe. High-quality mesh generation is then performed on the model.

[0049] Step 2: Acoustic-structure interaction modal analysis. In finite element analysis software (such as ANSYS or COMSOL), the fluid domain is set as acoustic elements and the structural domain as solid elements, and coupling conditions are set at the fluid-structure interface. Modal analysis is performed to obtain the first 10 wet modal frequencies of the unit, and a natural frequency library is established. For example, the calculation found that the third natural frequency f3 = 48.5 Hz, and the mode shape is the pitch-diameter oscillation of the turbine runner.

[0050] Step 3: Real-time monitoring and excitation calculation. The unit plans to increase its speed from 400 rpm to 450 rpm to increase output. The monitoring system acquires this plan. The number of turbine blades Z is known. s =15, Number of active guide vanes Z g =20, then the main blade frequency excitation is f eZs =15×N / 60, f eZg =20×N / 60. When N=450rpm, feZs =112.5Hz, f eZg =150Hz.

[0051] Step 4: Resonance Risk Assessment. The control model compares the hydraulic excitation frequency with the natural frequency library obtained in Step 2. It is found that when N is in the 430-440 rpm range, f eZs (107.5-110Hz) compared to f eZg It is closer to the natural frequency f8 = 108.2 Hz, therefore f is chosen. eZs As the hydraulic excitation frequency f e Setting a safety margin δ=10%, the calculation shows that |110-108.2| / 108.2≈1.6%<10%, indicating a high risk.

[0052] Step 5: Intelligent Control. The control model is optimized to avoid f8 while minimizing the impact on planned power. Calculations recommend two safe operating speeds: N1' = 425 rpm or N2' = 445 rpm. The f8 values ​​at these two speeds are... eZs All of them maintained a frequency interval of more than 10% from f8, and the impact on output power was within an acceptable range (<2%).

[0053] Step 6: Execution and Control. The control system adopted the recommended suggestions of the regulation model and selected N2'=445rpm as the new operating target. The speed regulation system smoothly adjusted the unit speed to 445rpm. The vibration monitoring system showed that at this speed, the unit vibration intensity remained at an excellent level, successfully avoiding resonance.

[0054] The embodiments of this application also provide a computer system, including one or more processors and a memory, wherein the memory stores computer program instructions, and when the instructions are executed by the processor, the above-described vibration control method for a variable speed water pump turbine unit is implemented.

[0055] See Figure 3 As shown in the figure, an embodiment of this application also provides a vibration control system for a variable speed water pump turbine unit, including: Modeling and analysis unit 10 is used to establish a fluid-structure interaction model of the pump-turbine unit and to calculate the modal parameters of the fluid-structure interaction model of the pump-turbine unit in an aquatic environment using the acoustic-structure interaction modal analysis method. The fluid-structure interaction model includes a fluid model and a structural solid model of the pump-turbine unit in an aquatic environment, and the modal parameters include natural frequencies of a set order.

[0056] Control unit 20, electrically connected to modeling and analysis unit 10, is used to calculate the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed, determine the natural frequency closest to the hydraulic excitation frequency from the modal parameters as the modal frequency, and compare the modal frequency with the hydraulic excitation frequency. The new operating speed is determined and the pump-turbine unit is controlled to operate at the new operating speed, so that the pump-turbine unit can operate at the new operating speed. ; where f e Let f be the hydraulic excitation frequency. n The modal frequency, δ This is the safety margin threshold.

[0057] Understandably, a detailed fluid-structure interaction (FSI) model of the pump-turbine unit is established through a modeling and analysis unit. Then, using acoustic-structure interaction modal analysis, the natural frequencies {f} of the pump-turbine unit's FSI model, considering the added mass effect of the water body, are accurately determined in an aquatic environment, representing a predetermined order. n The wet modal frequencies (n=1,2,3…) are the unit's wet modal frequencies. These frequencies are lower than the dry modal frequencies calculated in air, better reflecting the unit's true dynamic characteristics and ensuring the accuracy of the modal parameters. It should be noted that acoustic-structure interaction refers to the interaction between sound waves and a solid medium as sound waves propagate through it. This is a two-way coupling process; solid vibrations drive the fluid to generate sound pressure waves, while pressure waves in the fluid also act on the solid, causing it to vibrate.

[0058] Each natural frequency reflects the inherent vibration characteristics of a structure under a specific vibration mode (mode shape). It is an inherent property of the structure itself and is independent of external excitation. When the external excitation frequency is equal to or close to a certain natural frequency, the vibration mode corresponding to that natural frequency will resonate. Methods to avoid resonance mainly include: changing the structure's natural frequencies (such as adjusting structural mass and stiffness), reducing or eliminating the frequency components of the excitation source, increasing structural damping to reduce the resonance amplitude, and changing the external excitation frequency. This application primarily avoids resonance in the unit by changing the external excitation frequency, as detailed below. The number of natural frequencies can be set according to actual needs; this application does not impose any restrictions on this.

[0059] A resonance risk assessment and speed control strategy can be established through the control unit (or a control model can be established). The hydraulic excitation frequency f... e With a given modal frequency f n Perform a comparison. If found... If a resonance risk is detected, the control model immediately initiates an optimization algorithm to find one or more safe alternative speeds N' within the unit's permissible speed range. These alternative speeds N' avoid the resonance point while minimizing the impact on the unit's power and efficiency. The control system generates speed adjustment commands and sends them to the unit's speed control system, controlling the unit to switch to the safe alternative speed N' and controlling the pump-turbine unit to perform a speed switch to the new operating speed N'. Simultaneously, the system continuously monitors vibration signals to verify the vibration control effect and can perform self-learning optimization of the control model parameters.

[0060] The vibration control system for the variable-speed pump-turbine unit provided in this application employs acoustic-structure coupled modal analysis to accurately determine the natural frequencies of the pump-cooled unit in an aquatic environment, taking into account the added mass effect of the water body, thus ensuring the accuracy of the modal parameters. It can accurately predict the actual dynamic characteristics of the unit and proactively and forward-lookingly avoid resonance risks during operation.

[0061] 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 control method for a variable speed water pump turbine unit, characterized in that, include: A fluid-structure interaction model of a pump-turbine unit was established, and the modal parameters of the pump-turbine unit in an aquatic environment were calculated using the acoustic-structure interaction modal analysis method. The fluid-structure interaction model includes a fluid model and a structural solid model of the pump-turbine unit in an aquatic environment, and the modal parameters include natural frequencies of a set order. Based on the current operating speed or the expected operating speed of the pump-turbine unit, the hydraulic excitation frequency of the pump-turbine unit is calculated, and the natural frequency that is closest to the hydraulic excitation frequency is determined from the modal parameters as the modal frequency. The modal frequency is compared with the hydraulic excitation frequency. The new operating speed is determined and the pump-turbine unit is controlled to operate at the new operating speed, so that the pump-turbine unit can operate at the new operating speed. ; where f e Let f be the hydraulic excitation frequency. n The modal frequency, δ This is the safety margin threshold.

2. The method according to claim 1, characterized in that, The establishment of the fluid-structure interaction model of the pump-turbine unit includes: Establish a fluid model and a structural solid model of the entire flow path, including the runner, main shaft, movable guide vanes, top cover, seat ring, volute, and tailrace of the water pump turbine unit.

3. The method according to claim 1, characterized in that, The acoustic-structure interaction modal analysis method is used to calculate the modal parameters of the pump-turbine unit's fluid-structure interaction model in an aquatic environment, including: The fluid domain of the fluid model is set as a compressible acoustic medium, and the structural domain of the structural solid model is set as a solid medium. Coupling conditions are set at the coupling interface between the fluid model and the structural solid structure, and modal analysis is performed to obtain the natural frequencies of the set order of the fluid-structure interaction model of the pump-turbine unit in the water environment.

4. The method according to claim 1, characterized in that, The calculation of the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed includes: According to the calculation formula f e = k×N / 60 determines the hydraulic excitation frequency; where k is the number of blades or movable guide vanes of the water pump-cooled unit's impeller, and N is the current operating speed or the expected operating speed of the water pump-turbine unit.

5. The method according to claim 1, characterized in that, The safety margin threshold ranges from 5% to 15%.

6. The method according to claim 1, characterized in that, Determining the new operating speed includes: Within the permissible speed range of the pump-turbine unit, several candidate operating speeds are determined; The hydraulic excitation frequency and output power of the pump-turbine unit when operating at each of the selected operating speeds were calculated. From a number of candidate operating speeds, the one that maximizes the difference between the hydraulic excitation frequency and the modal frequency of the pump-turbine unit and keeps the change in output power within a set range is selected as the new operating speed.

7. A vibration control system for a variable speed water pump turbine unit, characterized in that, include: The modeling and analysis unit is used to establish a fluid-structure interaction model of the pump-turbine unit and to calculate the modal parameters of the fluid-structure interaction model of the pump-turbine unit in an aquatic environment using the acoustic-structure interaction modal analysis method. The fluid-structure interaction model includes a fluid model and a structural solid model of the pump-turbine unit in an aquatic environment, and the modal parameters include natural frequencies of a set order. The control unit, electrically connected to the modeling and analysis unit, is used to calculate the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed; determine the natural frequency closest to the hydraulic excitation frequency from the modal parameters as the modal frequency; and compare the modal frequency with the hydraulic excitation frequency. The new operating speed is determined and the pump-turbine unit is controlled to operate at the new operating speed, so that the pump-turbine unit can operate at the new operating speed. ; where f e Let f be the hydraulic excitation frequency. n The modal frequency, δ This is the safety margin threshold.

8. The system according to claim 7, characterized in that, The establishment of the fluid-structure interaction model of the pump-turbine unit includes: Establish a fluid model and a structural solid model of the entire flow path, including the runner, main shaft, movable guide vanes, top cover, seat ring, volute, and tailrace of the water pump turbine unit.

9. The system according to claim 7, characterized in that, The acoustic-structure interaction modal analysis method is used to calculate the modal parameters of the pump-turbine unit's fluid-structure interaction model in an aquatic environment, including: The fluid domain of the fluid model is set as a compressible acoustic medium, and the structural domain of the structural solid model is set as a solid medium. Coupling conditions are set at the coupling interface between the fluid model and the structural solid structure, and modal analysis is performed to obtain the natural frequencies of the set order of the fluid-structure interaction model of the pump-turbine unit in the water environment.

10. The system according to claim 7, characterized in that, The calculation of the hydraulic excitation frequency of the pump-turbine unit based on its current or expected operating speed includes: According to the calculation formula f e = k×N / 60 determines the hydraulic excitation frequency; where k is the number of blades or movable guide vanes of the water pump-cooled unit's impeller, and N is the current operating speed or the expected operating speed of the water pump-turbine unit.

11. The system according to claim 7, characterized in that, The safety margin threshold ranges from 5% to 15%.

12. The system according to claim 7, characterized in that, Determining the new operating speed includes: Within the permissible speed range of the pump-turbine unit, several candidate operating speeds are determined; The hydraulic excitation frequency and output power of the pump-turbine unit when operating at each of the selected operating speeds were calculated. From a number of candidate operating speeds, the one that maximizes the difference between the hydraulic excitation frequency and the modal frequency of the pump-turbine unit and keeps the change in output power within a set range is selected as the new operating speed.

13. A computer system, characterized in that, It includes one or more processors and a memory, the memory storing computer program instructions that, when executed by the processor, implement the method as described in any one of claims 1-6.

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