Method and device for judging air supply opportunity of draft tube of pump turbine

Abstract

The invention relates to a method and device for judging the air supply opportunity of a draft tube of a pump turbine, and belongs to the technical field of hydraulic machinery and engineering equipment monitoring. The method comprises the steps that the real-time flow of the pump turbine is monitored, and a real-time pressure pulsation signal of the draft tube of the pump turbine is collected; performing modal decomposition on the real-time pressure pulsation signal to obtain different modal decomposition quantities; calculating the efficiency variation of the draft tube of the pump turbine; performing correlation analysis on the different modal decomposition quantities and the efficiency variation quantities to obtain correlation coefficients; and when the correlation coefficient is larger than a preset second threshold value, it is judged that the draft tube of the pump turbine supplements air. According to the method, the situation that the vortex strip of the draft tube deviates from the main shaft, so that the air supply valve cannot be opened due to deviation of a low-pressure area, and air supply fails can be overcome, the air supply precision and accuracy are improved, the operation stability of a unit is improved, and a new judgment basis is provided for air supply measures.

Description

Technical Field

[0001] This invention relates to the field of monitoring technology for hydraulic machinery and engineering equipment, and in particular to a method and device for determining the timing of air injection into the tailrace pipe of a water pump turbine. Background Technology

[0002] Pumped storage, as the only energy storage technology currently available for large-scale development, is crucial for the stable operation of the power grid. Due to the unique role of pumped storage units in the grid, the core component, the pump-turbine, experiences frequent starts and operates under suboptimal conditions. When the pump-turbine operates outside its design parameters, vortices are generated in the draft tube as the turbine rotates, causing strong pressure pulsations. When the frequency of these pulsations approaches the unit's natural frequency, resonance can occur, severely compromising the unit's operational stability and adversely affecting the unit, the entire power station, and the powerhouse.

[0003] When the unit operates under suboptimal conditions, the traditional method of relying on pressure to replenish gas may cause the gas replenishment device to fail if the low-pressure area deviates from the replenishment position. Some gas replenishment devices also require manual operation, resulting in low automation. Summary of the Invention

[0004] The purpose of this invention is to propose a method and device for determining the timing of air injection in the tailrace of a pump-turbine to solve the problems existing in the prior art. Based on the influence of the tailrace vortex on the efficiency of the unit, this invention uses the correlation between pressure pulsation signal and efficiency change to determine the appropriate timing of air injection, thereby improving the accuracy and automation of air injection and enhancing the operational stability of the unit.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for determining the timing of air injection into the tailrace pipe of a water pump turbine includes:

[0007] Monitor the real-time flow rate of the pump-turbine and collect the real-time pressure pulsation signal of the pump-turbine tailrace pipe;

[0008] The real-time pressure pulsation signal is subjected to mode decomposition to obtain different mode decomposition quantities;

[0009] Calculate the efficiency change of the water pump turbine tailrace pipe;

[0010] Correlation analysis was performed on the different modal decomposition quantities and efficiency changes to obtain correlation coefficients;

[0011] When the correlation coefficient is greater than a preset second threshold, it is determined that the water pump turbine tailrace pipe is being replenished with air.

[0012] Optionally, monitoring the real-time flow rate of the pump turbine includes:

[0013] Collect the real-time flow rate of the water pump turbine;

[0014] When the real-time flow rate of the water pump turbine is less than the design flow rate of the water pump turbine, the real-time pressure pulsation signal of the tailrace pipe of the water pump turbine is collected.

[0015] Optionally, modal decomposition of the real-time pressure pulsation signal includes:

[0016] S1. Input pressure pulsation signal x(t);

[0017] S2. Calculate the maximum and minimum points of the pressure pulsation signal x(t), and fit the maximum envelope u using a cubic spline function. max (t) and the minimum envelope u min (t);

[0018] S3. Calculate the envelope mean, m(t) = (u min (t)+u max (t)) / 2; where u max Let u(t) be the envelope function of the maximum points. min Let be the envelope function of the minimum points of the function u(t), and m be the average line function;

[0019] S4. Subtract the envelope mean, x k+1 (t)=x k (t)-m(t); where, x k The input signal is x(t) in S1, where m is the envelope function, and x... k+1 For the output signal function;

[0020] S5. Based on the preset first threshold, determine x. k+1 Is it an IMF component?

[0021] S6. Using the new function x k+1 (t) replaces the original function x k (t), repeat S2-S5, calculate each modal component, until x k+1 Until (t) is a monotonic function.

[0022] Optionally, determine x k+1 The method for determining whether something is an IMF component is as follows:

[0023] ;

[0024] Where, x k+1 For the (k+1)th new function, x k For the k-th new function, s d The standard deviation threshold of the signal is given, and T is the signal time interval.

[0025] When S d If x is less than a preset threshold, determine x. k+1 Is it an IMF component?

[0026] Optionally, the efficiency change of the water pump turbine tailrace pipe is:

[0027] ;

[0028] Where, η t+1 For the efficiency at time t+1, η t Let denoted as Δη, and let Δη be the efficiency at time t. The efficiency of the pump-turbine at this location is calculated in real time based on data monitored by instruments, including flow rate, head, main shaft torque, and unit speed.

[0029] Optionally, the method for performing correlation analysis on the different modal decomposition quantities and efficiency changes is as follows:

[0030] ;

[0031] Where, ρ X,Y denoted as the correlation coefficient, X as the modal component of the pulsating signal, Y as the efficiency change, n as the total number of variable values, and i as the i-th data value.

[0032] Optionally, the air supply to the turbine tailrace of the water pump further includes:

[0033] Monitor the change in efficiency Δη; when Δη > 0, continue to replenish gas; when Δη < 0, stop replenishing gas.

[0034] A device for determining the timing of air injection into the tailrace pipe of a water pump turbine includes: a data acquisition module, a monitoring module, a mode decomposition module, an efficiency calculation module, a correlation analysis module, and a determination module;

[0035] The data acquisition module is used to collect the design flow rate and real-time flow rate of the water pump turbine, as well as the efficiency data of the water pump turbine.

[0036] The monitoring module is used to start collecting real-time pressure pulsation signals from the tailrace pipe of the water pump turbine when the real-time flow rate of the water pump turbine is less than the design flow rate of the water pump turbine.

[0037] The mode decomposition module is used to perform mode decomposition on the real-time pressure pulsation signal to obtain different mode decomposition quantities;

[0038] The efficiency calculation module is used to calculate the efficiency change of the water pump turbine tailrace pipe;

[0039] The correlation analysis module is used to perform correlation analysis on the different modal decomposition quantities and efficiency changes to obtain correlation coefficients;

[0040] The determination module is used to determine that the water pump turbine tailrace pipe is replenished with air when the correlation coefficient is greater than a preset second threshold.

[0041] The beneficial effects of this invention are as follows:

[0042] This invention overcomes the shortcomings of traditional methods that rely on pressure judgment for gas replenishment. By monitoring the unit's operating status in real time, when the unit enters unfavorable operating conditions, the monitoring module is activated. Through correlation analysis of unit efficiency and vortex pressure pulsation, the timing of gas replenishment is determined. After gas replenishment, real-time monitoring of efficiency changes determines whether to continue replenishing gas. This achieves precise control over the amount of gas replenishment, improving unit operating efficiency and enhancing the stability of safe production operations. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic flowchart of a method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the device arrangement for a tailwater pipe air supply timing determination method according to an embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] like Figure 1 As shown in the figure, this embodiment proposes a method for determining the timing of air injection into the tailrace pipe of a water pump turbine, including:

[0049] Step 1: Monitor the real-time flow rate of the water pump turbine and collect the real-time pressure pulsation signal of the water pump turbine tailrace pipe;

[0050] Furthermore, monitoring the real-time flow rate of the water pump turbine includes:

[0051] Collect the real-time flow rate of the water pump and turbine;

[0052] When the real-time flow rate of the pump-turbine is less than the design flow rate of the pump-turbine, the real-time pressure pulsation signal of the pump-turbine tailrace pipe is collected.

[0053] Specifically, in this embodiment, the unit flow rate Q and efficiency η are monitored in real time; an electromagnetic flowmeter is used to monitor the flow rate in real time, and the monitoring data is saved; the unit efficiency is monitored in real time, and the monitoring data is saved.

[0054] Calculate the real-time flow rate to determine whether to activate the pressure pulsation monitoring and processing module;

[0055] When Q t = Q design The pressure pulsation monitoring module for the straight section of the tailrace pipe is not activated; when Q t Q design Activate the pressure pulsation monitoring module; Q t —Real-time flow rate of the unit, unit: m³ 3 / s;Q design —Design flow rate, unit: m 3 / s.

[0056] Step 2: Perform mode decomposition on the real-time pressure pulsation signal to obtain different mode decomposition quantities;

[0057] Specifically, in this embodiment, the steps for performing mode decomposition are as follows:

[0058] 2.1. Input signal function x(t);

[0059] 2.2. For a given function x(t), calculate the maximum and minimum points of the function, and fit the upper and lower envelope curves u using a cubic spline function. max (t) and the minimum envelope u min (t);

[0060] 2.3. Calculate the envelope mean, m(t) = (u min (t)+u max (t)) / 2;

[0061] u max —The envelope function of the maximum point of the function u(t);

[0062] u min—The envelope function of the minimum point of the function u(t);

[0063] m — Average line function;

[0064] 2.4. Subtract the envelope mean, x k+1 (t)=x k (t)-m(t);

[0065] x k —Input signal function;

[0066] m — envelope function;

[0067] x k+1 — Output signal function;

[0068] 2.5. Determine x k+1 Is it an IMF component, s d It should be less than 0.2 or 0.3;

[0069]

[0070] x k+1 —The (k+1)th new function;

[0071] x k —The kth new function;

[0072] s d —Standard deviation;

[0073] 2.6. Using the new function x k+1 (t) replaces the original x k (t), repeat steps 2.2-2.5 to calculate the modal components of each order until x k+1 Until (t) is a monotonic function.

[0074] Step 3: Calculate the change in efficiency of the water pump turbine tailrace pipe;

[0075]

[0076] Where, η t+1 For the efficiency at time t+1, η t Let be the efficiency at time t, and Δη be the change in efficiency.

[0077] Step 4: Perform correlation analysis on different modal decomposition quantities and efficiency changes, and obtain the correlation coefficients;

[0078] The method for conducting correlation analysis is as follows:

[0079] ;

[0080] Where, ρ X,Ydenoted as the correlation coefficient, X as the modal component of the pulsating signal, Y as the efficiency change, n as the total number of variable values, and i as the i-th data value.

[0081] Step 5: When the correlation coefficient is greater than the preset second threshold, determine that the water pump turbine tailrace pipe is being replenished with air.

[0082] Furthermore, determining whether air supply to the turbine tailrace pipe of the pump-turbine also includes:

[0083] Monitor the change in efficiency Δη; when Δη > 0, continue to replenish gas; when Δη < 0, stop replenishing gas.

[0084] Specifically, in this embodiment, a gas replenishment determination is performed when ρ X,Y A value > 0.8 indicates a high correlation between vortex pressure pulsation and efficiency, prompting the issuance of a gas replenishment signal for gas replenishment.

[0085] The system monitors the change in efficiency Δη to determine whether to continue gas supply. If Δη > 0, gas supply continues; if Δη < 0, a stop gas supply signal is sent to stop gas supply.

[0086] Step 6: Repeat the above steps to perform real-time monitoring.

[0087] like Figure 2 As shown, this embodiment also proposes a device for determining the timing of air injection into the tailrace pipe of a water pump turbine, including: a data acquisition module, a monitoring module, a mode decomposition module, an efficiency calculation module, a correlation analysis module, and a determination module;

[0088] The data acquisition module is used to collect the design flow rate and real-time flow rate of the water pump turbine, as well as the efficiency data of the water pump turbine;

[0089] The monitoring module is used to collect real-time pressure pulsation signals from the tailrace pipe of the water pump turbine when the real-time flow rate of the water pump turbine is less than the design flow rate of the water pump turbine.

[0090] The mode decomposition module is used to perform mode decomposition on real-time pressure pulsation signals and obtain different mode decomposition quantities.

[0091] The efficiency calculation module is used to calculate the efficiency change of the water pump turbine tailrace pipe;

[0092] The correlation analysis module is used to perform correlation analysis on different modal decomposition quantities and efficiency changes to obtain correlation coefficients.

[0093] The determination module is used to determine the air supply to the tailrace pipe of the water pump turbine when the correlation coefficient is greater than the preset second threshold.

[0094] This embodiment discloses a method and apparatus for determining the timing of air injection in the draft tube of a pump-turbine. The method involves empirical mode decomposition of the pressure pulsation signal in the draft tube vortex band, and correlation analysis of efficiency changes and mode functions of pressure pulsation signals of different orders to determine a reasonable air injection timing. This invention overcomes the problem of air injection failure caused by the draft tube vortex band deviating from the main axis, preventing the air injection valve from opening due to low-pressure zone deviation. It improves the precision and accuracy of air injection, enhances the unit's operational stability, and provides a new basis for determining air injection measures.

[0095] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for determining the timing of air injection into the tailrace pipe of a water pump turbine, characterized in that, include: Monitor the real-time flow rate of the water pump turbine and collect the real-time pressure pulsation signal of the water pump turbine tailrace pipe; The real-time pressure pulsation signal is subjected to mode decomposition to obtain different mode decomposition quantities; Calculate the efficiency change of the water pump turbine tailrace pipe; Correlation analysis was performed on the different modal decomposition quantities and efficiency changes to obtain correlation coefficients; When the correlation coefficient is greater than a preset second threshold, it is determined that the water pump turbine tailrace pipe is being replenished with air.

2. The method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to claim 1, characterized in that, Monitoring the real-time flow rate of the water pump turbine includes: Collect the real-time flow rate of the water pump turbine; When the real-time flow rate of the water pump turbine is less than the design flow rate of the water pump turbine, the real-time pressure pulsation signal of the tailrace pipe of the water pump turbine is collected.

3. The method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to claim 1, characterized in that, Modal decomposition of the real-time pressure pulsation signal includes: S1. Input pressure pulsation signal x(t); S2. Calculate the maximum and minimum points of the pressure pulsation signal x(t), and fit the maximum envelope u using a cubic spline function. max (t) and the minimum envelope u min (t); S3. Calculate the envelope mean, m(t) = (u min (t)+u max (t)) / 2; where u max Let u(t) be the envelope function of the maximum points. min Let be the envelope function of the minimum points of the function u(t), and m be the average line function; S4. Subtract the envelope mean, x k+1 (t)=x k (t)-m(t); where, x k The input signal is x(t) in S1, where m is the envelope function, and x... k+1 For the output signal function; S5. Based on a preset first threshold, determine x. k+1 Is it an IMF component? S6. Using the new function x k+1 (t) replaces the original function x k (t), repeat S2-S5, calculate each modal component, until x k+1 Until (t) is a monotonic function.

4. The method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to claim 3, characterized in that, Determine x k+1 The method for determining whether something is an IMF component is as follows: ； Where, x k+1 For the (k+1)th new function, x k For the k-th new function, s d The standard deviation threshold of the signal is given by T, where T is the signal time interval and t is the time interval. When S d If x is less than a preset threshold, determine x. k+1 Is it an IMF component? 5. The method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to claim 1, characterized in that, The efficiency change of the water pump turbine tailrace pipe is: ； Where, η t+1 For the efficiency at time t+1, η t Let be the efficiency at time t, and Δη be the change in efficiency.

6. The method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to claim 1, characterized in that, The method for correlation analysis of the different modal decomposition quantities and efficiency changes is as follows: ； Where, ρ X,Y denoted as the correlation coefficient, X as the modal component of the pulsating signal, Y as the efficiency change, n as the total number of variable values, and i as the i-th data value.

7. The method for determining the timing of air injection into the tailrace pipe of a water pump turbine according to claim 5, characterized in that, The air supply to the tailrace pipe of the water pump turbine also includes: Monitor the change in efficiency Δη; when Δη > 0, continue to replenish gas; when Δη < 0, stop replenishing gas.

8. A device for determining the timing of air injection into the tailrace pipe of a water pump turbine, characterized in that, The device is used to implement the method for determining the timing of air injection into the tailrace pipe of a water pump turbine as described in any one of claims 1-7. The device includes: a data acquisition module, a monitoring module, a mode decomposition module, an efficiency calculation module, a correlation analysis module, and a determination module. The data acquisition module is used to collect the design flow rate and real-time flow rate of the water pump turbine, as well as the efficiency data of the water pump turbine. The monitoring module is used to start collecting real-time pressure pulsation signals from the tailrace pipe of the water pump turbine when the real-time flow rate of the water pump turbine is less than the design flow rate of the water pump turbine. The mode decomposition module is used to perform mode decomposition on the real-time pressure pulsation signal to obtain different mode decomposition quantities; The efficiency calculation module is used to calculate the efficiency change of the water pump turbine tailrace pipe; The correlation analysis module is used to perform correlation analysis on the different modal decomposition quantities and efficiency changes to obtain correlation coefficients; The determination module is used to determine that the water pump turbine tailrace pipe is replenished with air when the correlation coefficient is greater than a preset second threshold.

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