Variable damping system and method for suppressing low-frequency oscillation

Abstract

The invention relates to a variable damping system and method for suppressing low-frequency oscillation. The system comprises an execution module, a monitoring module, a data processing module and a control module. Specifically, the execution module is arranged at the bottom of the tail water channel and is mainly composed of a plurality of rows of cylindrical telescopic damping rods. The section of each damping rod is circular, and the bottom of each damping rod is provided with a hydraulic telescopic mechanism. The execution module dynamically adjusts the water flow damping in the tail water by changing the telescopic length and the section form of a part of damping rods; the hydraulic cylinder provides controllable pressure oil through the hydraulic system, when the monitoring module and the data processing module send out instructions, the hydraulic system drives the piston to move, and therefore the telescopic length and height of the damping rod are adjusted. The adjusting process changes the flow cross section and the head loss characteristic of the tail water channel, and then the damping effect of water flow is affected.

Description

Technical Field

[0001] The present invention relates to the field of hydropower generation, and in particular to a variable damping system and method for suppressing low-frequency oscillation. Background Art

[0002] The hydro-turbine generator is a core device widely used in hydroelectric power stations. Its working principle is to use the kinetic energy of water flow to drive the water wheel to rotate, thereby driving the generator to generate electricity. During operation, water flows into the water wheel through the waterway and water guide mechanism, and is converted into mechanical energy by the water wheel blades, and finally converted into electrical energy by the generator. However, due to the instability of water flow, load fluctuations and the limitation of the unit's regulation performance, the hydro-turbine generator set may produce low-frequency oscillations during operation, affecting the safety and economy of the system.

[0003] Low-frequency oscillations are usually caused by multiple factors such as the power system, control system and hydraulic system. In the power system, the power system stabilizer (PSS) is usually configured to provide additional damping to suppress low-frequency oscillations; in the control system, the negative damping effect of the governor can be reduced by adjusting the governor parameters, especially the primary frequency modulation parameters, so as to alleviate the oscillation. However, in addition to these factors, the characteristics of the hydraulic system are also an important factor leading to low-frequency oscillations. For example, periodic fluctuations in reservoir water levels and pressure pulsations in tailwater pipes may cause low-frequency oscillations, especially when the water diversion system is complex and the unit is operating at full load. This phenomenon is particularly obvious.

[0004] The water inertia and pressure fluctuations in the tailwater area can easily cause tailwater pressure oscillations, which are not related to the regulation of the power system or control system, but are determined by the characteristics of the hydraulic system. Therefore, the traditional solutions to tailwater pressure oscillations mainly include two methods: one is to adjust the unit operation mode, such as limiting the power output of the turbine generator to temporarily alleviate the oscillation, but this method is only a stopgap measure, which not only affects the power generation efficiency, but also has poor economic performance; the second is to optimize the hydraulic structure, such as building a damping sill in the tailwater flow channel to increase positive damping to suppress pressure oscillations, but this method will increase the friction loss of the tailwater flow channel, thereby reducing the overall efficiency of the turbine generator unit.

[0005] Currently, there is a lack of a solution that combines flexible adjustment capabilities, low losses, and efficient oscillation suppression. Therefore, there is an urgent need for an innovative technology that can effectively suppress the low-frequency oscillation of the hydro-generator set, optimize water flow, reduce friction losses, and improve the stability and operating efficiency of the set under all operating conditions. Summary of the invention

[0006] The present invention provides a variable damping system and method for suppressing low-frequency oscillations, the purpose of which is to effectively suppress low-frequency oscillations in the operation of a hydro-generator set, while optimizing water flow, reducing head loss, and improving the stability and operating efficiency of the set.

[0007] To achieve the above object, the first aspect of the present invention provides a variable damping system for suppressing low-frequency oscillation, comprising the following modules:

[0008] The execution module includes a plurality of damping rods, which are installed side by side at the bottom of the tailwater channel of the turbine, and a telescopic adjustment mechanism is provided at the bottom of each damping rod;

[0009] A monitoring module, including a sensor, which monitors the vibration frequency and amplitude of the turbine in real time and transmits the data to a data processing module;

[0010] The data processing module calculates the optimal damping parameters required in the current state according to the vibration frequency and amplitude data of the turbine;

[0011] The control module controls the extension amount and extension height of the damping rod of the execution module according to the damping lookup table so that the total damping of the damping rod reaches the optimal damping parameter.

[0012] Furthermore, the damping rod is cylindrical, and the damping rods are arranged in a single row or multiple rows in a staggered manner, and the width of a single row of multiple damping rods is equal to the width of the tailrace channel.

[0013] Furthermore, the telescopic adjustment mechanism is a hydraulic telescopic mechanism or a mechanical telescopic mechanism.

[0014] To achieve the above object, the present invention provides a variable damping method for suppressing low-frequency oscillation, comprising the following steps:

[0015] Arrange one or more rows of execution modules at the bottom of the tailrace, the execution modules are composed of a cylindrical damping rod and a hydraulic telescopic mechanism, the hydraulic telescopic mechanism changes the effective length of the damping rod through the telescopic movement of the hydraulic cylinder;

[0016] Real-time monitoring of the operating status data of the hydro-generator, wherein the operating status data includes the vibration frequency, amplitude, power output and water flow parameters of the unit;

[0017] Determine whether low-frequency oscillation occurs based on real-time monitored operating status data;

[0018] If low-frequency oscillations are detected, the optimal damping parameters required under the current state are calculated to determine the required total damping level;

[0019] Based on the calculated total damping level, the most suitable damping rod expansion combination is found by table lookup method;

[0020] According to the damping rod deployment combination determined by the table lookup method, the hydraulic telescopic mechanism is controlled to adjust the extension height of the damping rod, and the damping rod after adjustment makes the damping of the tail race system reach the required total damping level to suppress low-frequency oscillation;

[0021] After the oscillation subsides, the damping rod is commanded to retract to a minimum cross-section state;

[0022] When a new oscillation signal is detected, the extension and retraction height of the damping rod is recalculated and adjusted.

[0023] Furthermore, the method for determining whether low-frequency oscillation occurs includes:

[0024] By monitoring the vibration frequency and amplitude of the hydro-generator set and comparing them with the set low-frequency threshold and amplitude threshold, it is determined whether low-frequency oscillation occurs. The judgment conditions are:

[0025]

[0026] Among them, f peak Indicates the detected vibration frequency, A peak represents the peak amplitude of vibration, f LFO A0 represents the frequency threshold of low-frequency oscillation, and A1 represents the amplitude threshold.

[0027] Furthermore, if low-frequency oscillation is detected, the method of calculating the optimal damping parameters required in the current state and determining the total damping level includes:

[0028] According to the real-time monitored water flow parameters and oscillation characteristics, the required damping parameters are calculated and a target total damping value is set, which represents the total damping level required at the current moment;

[0029] Calculate the contribution D of all damping rods total (L1,L2,...,L N ), where L N represents the extension length of the Nth damping rod, N represents the number of damping rods, and the damping calculation formula is:

[0030]

[0031] Among them, f i (L i ) indicates that the i-th damping rod is extended to a length L i The damping contribution below.

[0032] Calculate the optimal extension height based on the current unit status and water flow conditions:

[0033]

[0034] So that:

[0035]

[0036] Among them, D * (t) is the target total damping.

[0037] Furthermore, the table lookup method enumerates or partially enumerates different extension combinations of multiple damping rods through an off-line analysis or simulation method, records the corresponding total damping levels, and stores them as a damping lookup table.

[0038] Furthermore, the specific method of using the table lookup method to find the most suitable damping rod deployment combination includes:

[0039] Pre-building a damping lookup table, the damping lookup table lists different damping rod extension combinations and their corresponding total damping levels, the damping lookup table including the head loss and energy consumption of each combination;

[0040] For the target total damping at the current moment, find the closest damping combination by table lookup method So that:

[0041]

[0042] Among them, k * is such that the total damping D total,k Closest to target damping D * (t) combined entry index, D total,k is the total damping level corresponding to entry k in the lookup table;

[0043] Extract the corresponding telescopic column deployment strategy from the lookup table The control system commands the hydraulic / mechanical telescopic unit to adjust the extension height of each damping rod.

[0044] Furthermore, the method further comprises the step of optimizing energy loss, wherein when D total,k ≥D * (t), a combination with the minimum head loss or energy consumption is found by setting the following composite objective function:

[0045]

[0046] Where Δh k represents the incremental loss of the local head in the tailrace due to combination k, and Φ(·) is the self-defined objective function that comprehensively balances “damping demand” and “head loss”.

[0047] Furthermore, when a new oscillation signal is detected, the method for recalculating and adjusting the telescopic height of the damping rod includes:

[0048] When a new oscillation signal is detected, the method of recalculating and adjusting the telescopic height of the damping rod includes:

[0049] Beneficial effects of the present invention:

[0050] Compared with the prior art, the variable damping system and method for suppressing low-frequency oscillations provided by the present invention realizes precise adjustment of the damping of the tailwater channel by setting a dynamically adjustable cylindrical damping rod at the bottom of the tailwater channel and combining it with a real-time monitoring and control system. When low-frequency oscillation occurs in the hydro-turbine generator set, the system can quickly extend part of the damping rod through the hydraulic telescopic adjustment mechanism, thereby increasing the friction and energy dissipation in the water flow and suppressing the oscillation; and in the absence of oscillation, the damping rod can automatically retract to reduce the water flow resistance and reduce energy loss. This scheme not only effectively improves the suppression effect of low-frequency oscillations, but also avoids the head loss and efficiency reduction caused by increasing damping in traditional methods. In addition, through real-time monitoring and intelligent control, the system can adjust the damping characteristics in real time according to the changes in the unit operating conditions, ensuring that the optimal operating effect is always maintained under various complex conditions, significantly improving the stability, efficiency and economy of the hydro-turbine generator set. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0052] Figure 1 The present invention discloses a structural schematic diagram of a damping rod for suppressing low-frequency oscillation of a hydro-generator.

[0053] Figure 2 The invention discloses a tailrace structure and a schematic diagram of the position of an execution module.

[0054] Figure 3 It is a schematic diagram of the arrangement structure of different numbers of execution modules in a tailrace channel disclosed in an embodiment of the present invention.

[0055] Figure 4 It is a schematic diagram of a single execution module and a monitoring system disclosed in an embodiment of the present invention.

[0056] Figure 5 The present invention discloses a flow chart of a variable damping method for suppressing low-frequency oscillation.

[0057] Figure 6 It is a schematic diagram of a simulation structure of a tailwater system of a power station disclosed in an embodiment of the present invention.

[0058] Figure 7 It is a simulated waveform diagram of tailwater pressure of a power station before adding local head loss, disclosed in an embodiment of the present invention.

[0059] Figure 8 It is a simulated waveform diagram of tailwater pressure after adding local head loss in a power station disclosed in an embodiment of the present invention.

[0060] Figure numerals: 1, execution module; 1-1, damping rod. DETAILED DESCRIPTION

[0061] To make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them.

[0062] Therefore, the following detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents some embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0063] like Figure 1 As shown, the present invention provides a variable damping system for suppressing low-frequency oscillations, and the system includes an execution module 1, a monitoring module, a data processing module, and a control module. Specifically, the execution module 1 is arranged at the bottom of the tailwater channel, and is mainly composed of multiple rows of cylindrical retractable damping rods 1-1. The cross-section of each damping rod 1-1 is circular, and the bottom is equipped with a hydraulic telescopic mechanism, which is composed of a hydraulic cylinder, a piston, a sealing ring, and a guide component. The execution module 1 dynamically adjusts the water flow damping inside the tailwater by changing the telescopic length and cross-sectional shape of part of the damping rod 1-1.

[0064] The hydraulic cylinder provides controllable pressure oil through the hydraulic system. When the monitoring module and data processing module issue instructions, the hydraulic system drives the piston to move, thereby adjusting the telescopic length and height of the damping rod. This adjustment process changes the water flow section and head loss characteristics of the tailwater channel, thereby affecting the damping effect of the water flow.

[0065] like Figure 2 As shown, the execution module 1 is arranged at a key position at the bottom of the tailwater channel to form a variable local head loss area in the tailwater section of the unit. When the damping rod is extended moderately, it generates local resistance in the water flow, thereby improving the damping ratio, consuming and dispersing the oscillation energy contained in the water flow. The width of the top connection of multiple damping rods 1-1 is equivalent to the width of the tailwater channel, which can achieve full-section damping when the damping rod 1-1 is extended, evenly regulate the water flow, and avoid new disturbances caused by local uneven resistance.

[0066] When the unit tends to oscillate, the damping rod 1-1 will extend rapidly under the command of the monitoring module, thereby enhancing the friction and energy dissipation in the water flow and suppressing the expansion of low-frequency oscillations; when the unit runs smoothly without oscillation, the damping rod 1-1 will retract to the minimum cross-section, reducing the resistance to the water flow, reducing the head loss and additional energy consumption, and ensuring the efficient operation of the unit under non-oscillation conditions.

[0067] The monitoring module in this embodiment is equipped with a sensor to monitor the vibration frequency and amplitude of the turbine in real time and transmit the data to the data processing module; the latter calculates the optimal damping parameters required under the current working conditions based on these data. The control module adjusts the number and extension height of the damping rods 1-1 of the execution module 1 according to the damping lookup table to ensure that the damping effect is optimal.

[0068] In the execution module 1, the overall structure of the damping rod 1-1 is cylindrical. This design not only helps to evenly distribute the water flow stress under different telescopic states, but also has good structural stability and adaptability. In order to achieve fast, accurate and reliable length adjustment, a hydraulic telescopic mechanism is configured at the bottom of the damping rod 1-1. The mechanism changes the effective length of the damping rod 1-1 through the telescopic movement of the hydraulic cylinder, thereby adjusting the flow area and damping characteristics of the tailwater channel. As an alternative or supplementary solution, the present invention can also adopt a mechanical telescopic system to adapt to specific working conditions and ensure the stability and reliability of the device under various operating conditions.

[0069] In order to ensure that the damping rod 1-1 always has a good regulating effect on the water flow in any telescopic state, multiple rows of damping rods 1-1 are provided in this embodiment, and the width of each row is roughly equivalent to the width of the tail raceway. Through this design, no matter the damping rod 1-1 is in the minimum cross-section or maximum telescopic state, the water flow within the full width of the tail raceway bottom can be uniformly regulated, thereby ensuring a more balanced and efficient damping effect.

[0070] The damping rod 1-1 is made of metal material, has good pressure resistance and corrosion resistance, and can adapt to complex hydraulic environments. In particular, when the damping is insufficient, such as Figure 3 (a), you can set Figure 3 (b) and Figure 3 The multiple rows of damping rods 1-1 shown in (c) enhance the damping effect.

[0071] like Figure 4As shown, the schematic diagram of the connection between a single damping rod 1-1 and the monitoring system clearly shows the working principle of the method of the present invention. By collecting the water pressure change, water flow speed and direction in the tailwater channel, and the vibration data of the turbine guide vane and runner in real time, the data processing module converts the sensor signal into usable parameters and calculates the damping adjustment required under the current working condition through the set control algorithm. The execution module 1 drives the hydraulic telescopic mechanism to implement precise telescopic adjustment according to the calculation results to achieve the required damping effect.

[0072] Based on the above description, if Figure 5 As shown, the present invention provides a variable damping method for suppressing low-frequency oscillation, and the specific steps are as follows:

[0073] Step S100, arranging one or more rows of execution modules at the bottom of the tailrace, wherein the execution modules are composed of a cylindrical damping rod and a hydraulic telescopic mechanism, wherein the hydraulic telescopic mechanism changes the effective length of the damping rod through the telescopic movement of a hydraulic cylinder;

[0074] Step S200, real-time monitoring of the operating status data of the hydro-generator, wherein the operating status data includes the vibration frequency, amplitude, power output and water flow parameters of the unit;

[0075] Step S300, judging whether low-frequency oscillation occurs according to the real-time monitored operation status data;

[0076] Step S400: If low-frequency oscillation is detected, the optimal damping parameters required in the current state are calculated to determine the required total damping level;

[0077] Step S500, based on the calculated total damping level, searching for the most suitable damping rod deployment combination by table lookup method;

[0078] Step S600: According to the damping rod deployment combination determined by the table lookup method, the hydraulic telescopic mechanism is controlled to adjust the extension height of the damping rod, and the damping rod after adjustment makes the damping of the tailrace system reach the required total damping level to suppress low-frequency oscillation;

[0079] Step S700, after the oscillation subsides, instruct the damping rod to retract to a minimum cross-section state;

[0080] Step S800: when a new oscillation signal is detected, recalculate and adjust the telescopic height of the damping rod.

[0081] It can be understood that this method sets a low-frequency threshold f LFO , if the detected tailwater oscillation is f peak , and the peak amplitude is A peak , the amplitude threshold is set to A0, then it can be determined that the system has low-frequency oscillation. The above judgment criteria for whether low-frequency oscillation occurs can be written as:

[0082]

[0083] Among them, f peak Indicates the detected vibration frequency, A peak represents the peak amplitude of vibration, f LFO A0 represents the frequency threshold of low-frequency oscillation, and A1 represents the amplitude threshold. In simple terms, the frequency and amplitude are used to confirm whether there is a low-frequency oscillation phenomenon. When certain conditions are met (low frequency and large amplitude), the system considers that a low-frequency oscillation has occurred.

[0084] The data processing module analyzes and judges the acquired data, and then calculates the optimal damping parameters required in the current state. In addition, the contribution D of all N damping rods is calculated. total (L1,L2,...,L N ) are superimposed (or combined in a suitable manner) to obtain the total damping level D of the tailrace system after the damping rod is deployed. total :

[0085]

[0086] Among them, f i (L i ) indicates that the i-th damping rod is extended to a length L i The damping contribution below.

[0087] The control system needs to ensure at any time t:

[0088]

[0089] Among them, D * (t) is the target total damping.

[0090] That is, by determining a set of optimal extension heights Make the combined total damping equal to the target total damping D * (t) is matched as much as possible, so as to achieve the purpose of suppressing the current low-frequency oscillation.

[0091] Since actual working conditions often require the control module to quickly and stably obtain the appropriate Furthermore, there may be discretization (such as presetting a number of deployable height segments). When the present invention is implemented, a "table lookup method" may be used to achieve rapid decision-making on the deployment combination of multiple damping rods.

[0092] The specific steps are as follows:

[0093] Offline analysis and table construction In the design or test phase, use simulation / experimental methods to enumerate or partially enumerate different extension combinations of multiple damping rods (L1, L2, ..., L N) and record the total damping level D achieved total . Associate each combination with its corresponding D total Stored as a "damping lookup table". This table contains not only "which damping rod needs to be extended", but also "approximately how much the extension height is" and "additional head loss" or "energy loss" caused by this combination, so that it can be comprehensively considered in actual operation. Table entries As shown in Table 1:

[0094] Table 1 Damping lookup table

[0095]

[0096]

[0097] Where: The combination number is the number of each group of damping rods, which is used to identify different telescopic combinations; the extension height of the damping rod {L1, L2, ..., L N} is the extension height (or telescopic length) of each damping rod in the current combination; the total damping D total is the sum of the damping of all damping rods in this combination.

[0098] Through reasonable interpolation or segmentation, a continuous interval mapping can be formed. * (t), by fast query (or interpolation) Find the closest or most suitable one to achieve D * (t) Combination item k * . From entry k * Read the corresponding damping rod deployment strategy from

[0099] The control module sends this strategy to the hydraulic / mechanical telescopic units of each damping rod, so that it can quickly reach the specified deployment height. At this point, the required total damping D total，k* ≈D * (t), thereby achieving the purpose of suppressing oscillation. Mathematically, the table lookup step can be described as:

[0100]

[0101] Among them, k * is such that D total,k Closest to D * (t) and find out the corresponding damper rod deployment height. Indicates that the index in the search is k * The extension height corresponding to the i-th damping rod at .

[0102] If you need to further optimize the energy loss, you can also satisfy Dtotal,k ≥D * (t), we look for a combination with the minimum head loss or energy consumption, that is, Set the composite objective function in:

[0103]

[0104] Where Δh k It represents the incremental loss of the local head of the tailrace channel caused by combination k. Φ(·) can be customized as the objective function of comprehensively balancing "damping demand" and "head loss". When looking up the table, you can first locate the interval that meets the damping demand, and then select the optimal solution by comparing the corresponding additional losses.

[0105] The combination obtained by the above table lookup step is only the optimal or suboptimal solution at the time t. As the unit oscillation characteristics and operating conditions change, A(t+Δt), ω(t+Δt) and D * (t+Δt) will also be updated; the control system can set a certain sampling period or trigger threshold. When the oscillation amplitude or frequency changes significantly, it will enter the table lookup process again and issue a new instruction to correct the telescopic height of each damping rod.

[0106] This cyclic online scheduling method allows the system to automatically increase the corresponding damping when the turbine oscillation intensifies, and retract the corresponding damping rod in time after the oscillation disappears, so as to ensure maximum energy saving and reduce head loss.

[0107] The actuator drives the telescopic adjustment mechanism of the damping rod according to the analysis results to implement a quick response, thereby effectively suppressing and controlling the generation and development of low-frequency oscillations in a short time. If the monitoring and operating system determines that the unit has returned to a stable state, it will instruct the damping rod to retract, reducing the resistance to the water flow and achieving the purpose of energy saving and efficiency improvement.

[0108] Since the variable damping system described in the present invention has strong versatility and flexibility in design, it can be applied to hydro-turbine generator sets of different types and specifications. Under various complex working conditions, such as frequent fluctuations in downstream head or unstable operating conditions, the system can still effectively suppress low-frequency oscillations and provide a safe, stable and efficient operating environment for the unit. At the same time, when there is no low-frequency oscillation in the system, the present invention can automatically retract the damping rod to the minimum cross-sectional area, making the water flow in the tailwater channel smoother, reducing head loss, and improving water energy utilization.

[0109] As for the influence of damping column expansion and contraction on water flow, the influence of damping column expansion and contraction on water flow can be quantified through fluid mechanics model. First, a quantitative model is established to predict the specific values ​​of head loss and energy consumption. The core of this model is based on the dynamic characteristics of water flow in the tailwater channel and the influence of damping column adjustment on water flow. By establishing a fluid mechanics model, combined with the velocity, flow rate, resistance and geometric characteristics of the water flow and the tailwater channel, the influence of damping column expansion and contraction on head loss and energy consumption can be quantified. Specifically:

[0110] In the tailrace, the head loss can be calculated by the Darcy-Weisbach equation or other suitable fluid mechanics equations. The head loss is not only related to the water velocity, flow rate, and channel shape, but also affected by the damping column. By simulating the situation of different combinations of damping columns, the head loss under each combination can be calculated; the energy consumption is related to the flow velocity, flow rate and friction of the damping column. The energy loss can be calculated by considering the friction of the water flow and the influence of the telescopic column.

[0111] In summary, the present invention realizes effective suppression of low-frequency oscillation of the turbine generator by setting a dynamically adjustable cylindrical damping rod at the bottom of the tailwater channel and combining it with a monitoring and operating system with real-time monitoring and control capabilities. Compared with the current traditional wide-crowned weir device, this system can flexibly adjust the damping under different working conditions to improve the system operation efficiency; it can reduce or avoid excess head loss when there is no oscillation; it has real-time response capabilities, can quickly suppress oscillation when it occurs, and can automatically switch back to a low-damping state after the oscillation subsides; it is easy to implement and maintain, and the construction cost is significantly reduced compared to rebuilding a fixed gate or renovating a wide-crowned weir; it has a high degree of intelligence and can be linked with the unit speed governor, monitoring system, etc. to achieve intelligent control.

[0112] To verify the effectiveness of the present invention, it can be verified by comparing simulation with actual working conditions.

[0113] by Figure 6 The tailwater system of a power station shown in the figure is the simulation research object. Through simulation, the tailwater pressure simulation waveform of the tailwater system of the power station before adding the execution module can be reproduced. It can be seen that the oscillation amplitude is quite obvious. Figure 7 In order to eliminate the oscillation, the designed execution module that can increase the hydraulic loss is added to the branch canal. The corresponding results are shown in Figure 8 As shown in the figure, it is not difficult to find that the tailwater pressure simulation waveform after adding local head loss, due to the intervention of the damping rod provided by the present invention, the oscillation amplitude of the tailwater pressure is significantly reduced, and the water pressure fluctuations in various parts of the system basically disappear (the periodic oscillation amplitude is less than 0.01m). This is equivalent to a loss of 0.8MW output per unit at rated flow. This shows that the present invention can effectively dissipate the oscillation energy of the tailwater section, alleviate or suppress the occurrence of low-frequency oscillations, and improve the stability of the hydraulic system operation.

[0114] In specific implementation, the height, diameter, material and rated power of the damping rod can be appropriately designed and optimized according to the type of unit and the size of the tailwater channel. The damping rod maintains the minimum cross-sectional area when there is no low-frequency oscillation, and will not cause significant resistance loss to the normal water flow; after detecting the trend of low-frequency oscillation, the damping rod will quickly and appropriately extend to increase the damping force and reduce the oscillation amplitude. After a period of dynamic adjustment, the unit gradually returns to a stable operating state, and the damping rod retracts to achieve the optimization of the unit output and power generation efficiency.

[0115] In summary, this embodiment describes in detail the variable damping scheme proposed by the present invention through the structure and control process shown in the accompanying drawings. Through the controllable extension and retraction of the damping rod at the bottom of the tailwater channel, the present invention achieves effective suppression of the low-frequency oscillation of the hydro-generator and ensures the efficient operation of the hydraulic system when there is no oscillation. The scheme has the advantages of simple structure, flexible control and strong adaptability. It can be widely used in the oscillation control of the tailwater section of hydropower units of different types and sizes, and provides innovative ways and technical support for the stable and efficient operation of the hydropower generation system.

[0116] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0117] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0118] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A variable damping system for suppressing low-frequency oscillations, characterized in that: Includes the following modules: The execution module includes a plurality of damping rods, which are installed side by side at the bottom of the tailwater channel of the turbine, and a telescopic adjustment mechanism is provided at the bottom of each damping rod; A monitoring module, including a sensor, which monitors the vibration frequency and amplitude of the turbine in real time and transmits the data to a data processing module; The data processing module calculates the optimal damping parameters required in the current state according to the vibration frequency and amplitude data of the turbine; The control module controls the extension amount and extension height of the damping rod of the execution module according to the damping lookup table so that the total damping of the damping rod reaches the optimal damping parameter.

2. The variable damping system for suppressing low-frequency oscillation according to claim 1, characterized in that: The damping rod is cylindrical and arranged in a single row or multiple rows in a staggered manner. The width of a single row of multiple damping rods is equal to the width of the tailwater channel.

3. The variable damping system for suppressing low-frequency oscillation according to claim 1, characterized in that: The telescopic adjustment mechanism is a hydraulic telescopic mechanism or a mechanical telescopic mechanism.

4. A variable damping method for suppressing low-frequency oscillations, characterized in that: The steps include: Arrange one or more rows of execution modules at the bottom of the tailrace, the execution modules are composed of a cylindrical damping rod and a hydraulic telescopic mechanism, the hydraulic telescopic mechanism changes the effective length of the damping rod through the telescopic movement of the hydraulic cylinder; Real-time monitoring of the operating status data of the hydro-generator, wherein the operating status data includes the vibration frequency, amplitude, power output and water flow parameters of the unit; Determine whether low-frequency oscillation occurs based on real-time monitored operating status data; If low-frequency oscillations are detected, the optimal damping parameters required under the current state are calculated to determine the required total damping level; Based on the calculated total damping level, the most suitable damping rod expansion combination is found by table lookup method; According to the damping rod deployment combination determined by the table lookup method, the hydraulic telescopic mechanism is controlled to adjust the extension height of the damping rod, and the damping rod after adjustment makes the damping of the tail race system reach the required total damping level to suppress low-frequency oscillation; After the oscillation subsides, the damping rod is commanded to retract to a minimum cross-section state; When a new oscillation signal is detected, the extension and retraction height of the damping rod is recalculated and adjusted.

5. The variable damping method for suppressing low-frequency oscillation according to claim 4, characterized in that: Methods for determining whether low-frequency oscillation occurs include: By monitoring the vibration frequency and amplitude of the hydro-generator set and comparing them with the set low-frequency threshold and amplitude threshold, it is determined whether low-frequency oscillation occurs. The judgment conditions are: Among them, f peak Indicates the detected vibration frequency, A peak represents the peak amplitude of vibration, f LFO A0 represents the frequency threshold of low-frequency oscillation, and A1 represents the amplitude threshold.

6. The variable damping method for suppressing low frequency oscillation according to claim 5, characterized in that: If low frequency oscillation is detected, the method for calculating the optimal damping parameters required under the current state and determining the overall damping level includes: According to the real-time monitored water flow parameters and oscillation characteristics, the required damping parameters are calculated and a target total damping value is set, which represents the total damping level required at the current moment; Calculate the contribution D of all damping rods total (L1,L2,...,L N ), where L N represents the extension length of the Nth damping rod, N represents the number of damping rods, and the damping calculation formula is: Among them, f i (L i ) indicates that the i-th damping rod is extended to a length L i The damping contribution below. Calculate the optimal extension height based on the current unit status and water flow conditions: So that: Among them, D * (t) is the target total damping.

7. The variable damping method for suppressing low frequency oscillation according to claim 4, characterized in that: The table lookup method enumerates or partially enumerates different extension combinations of multiple damping rods through an off-line analysis or simulation method, records the corresponding total damping levels, and stores them as a damping lookup table.

8. The variable damping method for suppressing low frequency oscillation according to claim 4, characterized in that: The specific method of looking up the table to find the most suitable damping rod deployment combination includes: Pre-building a damping lookup table, the damping lookup table lists different damping rod extension combinations and their corresponding total damping levels, the damping lookup table including the head loss and energy consumption of each combination; For the target total damping at the current moment, find the closest damping combination by table lookup method So that: Among them, k * is such that the total damping D total,k Closest to target damping D * (t) combined entry index, D total,k is the total damping level corresponding to entry k in the lookup table; Extract the corresponding telescopic column deployment strategy from the lookup table The control system commands the hydraulic / mechanical telescopic unit to adjust the extension height of each damping rod.

9. The variable damping method for suppressing low frequency oscillation according to claim 4, characterized in that: The method also includes a step of optimizing energy loss, wherein D total,k ≥D * (t), a combination with the minimum head loss or energy consumption is found by setting the following composite objective function: Where Δh k represents the incremental loss of the local head in the tailrace due to combination k, and Φ(·) is the self-defined objective function that comprehensively balances "damping demand" and "head loss".

10. The variable damping method for suppressing low frequency oscillation according to claim 4, characterized in that: When a new oscillation signal is detected, the method of recalculating and adjusting the extension height of the damping rod includes: According to the unit's oscillation characteristics and operating condition changes, the oscillation amplitude, oscillation frequency and target damping are updated in real time; When the oscillation amplitude or frequency changes significantly, the table lookup process is entered again and a new instruction is issued to adjust the telescopic height of each damping rod.

Images