Method and device for determining air supply timing of water pump water turbine draft tube

Abstract

The present application relates to a kind of water pump water turbine draft tube air supplement opportunity discrimination method and device, belong to the field of hydromechanical and engineering equipment monitoring technique, this method includes: monitoring the real-time flow of water pump water turbine, acquisition water pump water turbine draft tube real-time pressure fluctuation signal;The real-time pressure fluctuation signal is modal decomposition, and different modal decomposition quantity is obtained;The efficiency variation of the water pump water turbine draft tube is calculated;The correlation of different modal decomposition quantity and efficiency variation is analyzed, and correlation coefficient is obtained;When the correlation coefficient is greater than preset second threshold value, the water pump water turbine draft tube air supplement is determined.The present application can overcome the draft tube vortex band deviating from the main shaft, make air supplement valve door deviate from low pressure area and cannot be opened, leading to air supplement failure, improve the precision and accuracy of air supplement, improve the operation stability of unit, provide new determination basis for air supplement measure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic machinery and engineering equipment monitoring, in particular to a water pump water turbine draft tube air supplement timing discrimination method and device. BACKGROUND

[0002] As the only large-scale energy storage technology at present, the stable operation of pumped storage is crucial to the power grid. Because pumped storage units play a special role in the power grid, the core component of pumped storage, the water pump water turbine, is frequently started and operated in non-optimal conditions. When the water pump water turbine operates in non-optimal conditions, the draft tube will generate a vortex band that rotates with the runner, which will cause strong pressure pulsation of the unit. When the generated pulsation frequency is close to the inherent frequency of the unit, resonance will be generated, which will seriously damage the stability of the unit operation and have an adverse effect on the unit and the entire power station and plant.

[0003] When the unit operates in non-optimal conditions, the traditional pressure air supplement method may cause the air supplement device to fail due to the deviation of the low-pressure area from the air supplement position, and some air supplement devices need to be manually operated, which has low automation. SUMMARY

[0004] The purpose of the present application is to provide a water pump water turbine draft tube air supplement timing discrimination method and device to solve the problems of the prior art. According to the influence of the draft tube vortex band on the efficiency of the unit, the correlation between the pressure pulsation signal and the efficiency change is used to determine the appropriate air supplement timing, improve the accuracy and automation of air supplement, and improve the stability of the unit operation.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] A water pump water turbine draft tube air supplement timing discrimination method, comprising:

[0007] monitoring the real-time flow of the water pump water turbine, collecting the real-time pressure pulsation signal of the water pump water turbine draft tube;

[0008] modal decomposition is performed on the real-time pressure pulsation signal to obtain different modal decomposition quantities;

[0009] calculating the efficiency change of the water pump water turbine draft tube;

[0010] correlation analysis is performed on the different modal decomposition quantities and the efficiency change to obtain a correlation coefficient;

[0011] when the correlation coefficient is greater than a preset second threshold value, it is determined that the water pump water turbine draft tube needs to be supplemented with air.

[0012] Optionally, monitoring the real-time flow of the water pump water turbine comprises:

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

[0014] when the real-time flow of the water pump turbine is less than the design flow of the water pump turbine, collecting real-time pressure fluctuation signal of the draft tube of the water pump turbine is started.

[0015] Optionally, the modal decomposition of the real-time pressure fluctuation signal comprises:

[0016] S1. inputting pressure fluctuation signal x(t);

[0017] S2. calculating maximum and minimum points of the pressure fluctuation signal x(t), and fitting maximum envelope line u max (t) and minimum envelope line u min (t) by using cubic spline function;

[0018] S3. calculating envelope average value, m(t) = (u min (t) + u max (t)) / 2; wherein u max is the maximum point envelope line function of function u(t), u min is the minimum point envelope line function of function u(t), and m is the average line function;

[0019] S4. subtracting the envelope average value, x k+1 (t) = x k (t) - m(t); wherein x k is the input signal, i.e. x(t) in S1, m is the envelope function, and x k+1 is the output signal function;

[0020] S5. determining whether x k+1 is an IMF component based on a preset first threshold value;

[0021] S6. replacing the original function x k+1 (t) with a new function x k (t), repeating S2-S5, and calculating each order modal component until x k+1 (t) is a monotonic function.

[0022] Optionally, the method for determining whether x k+1 is an IMF component is:

[0023] ;

[0024] wherein x k+1 is the k+1th new function, x k is the kth new function, s d is the signal standard deviation threshold value, and T is the signal time interval.

[0025] When S d is less than a preset threshold, determining x k+1 is an IMF component.

[0026] Optionally, the efficiency variation of the water pump turbine draft tube is:

[0027] ;

[0028] wherein η t+1 is the efficiency at t+1, η t is the efficiency at t, and Δη is the efficiency variation. The efficiency of the water pump turbine is obtained by real-time calculation of the monitoring data according to the flow rate, head, main shaft torque, and unit speed, etc. monitored by the instrument.

[0029] Optionally, the method for correlation analysis of the different modal decomposition quantities and the efficiency variation is:

[0030] ;

[0031] wherein ρ X,Y is the correlation coefficient, X is the modal component of the fluctuation signal, Y is the efficiency variation, n is the total number of variable values, and i represents the i-th data value.

[0032] Optionally, the air supplementing of the water pump turbine draft tube further comprises:

[0033] monitoring the efficiency variation Δη; when Δη>0, continuing to supplement air; and when Δη<0, stopping air supplementing.

[0034] A water pump turbine draft tube air supplementing timing determination device, comprising: a data acquisition module, a monitoring module, a modal decomposition module, an efficiency calculation module, a correlation analysis module, and a determination module;

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

[0036] The monitoring module is configured to start acquiring the real-time pressure fluctuation signal of the water pump turbine draft tube 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 modal decomposition module is configured to perform modal decomposition on the real-time pressure fluctuation signal to obtain different modal decomposition quantities.

[0038] The efficiency calculation module is configured to calculate the efficiency variation of the water pump turbine draft tube.

[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, monitoring the real-time flow of the water pump turbine, collecting the real-time pressure fluctuation signal of the tail pipe of the water pump turbine;

[0050] Further, the monitoring of the real-time flow of the water pump turbine comprises:

[0051] Collecting the real-time flow of the water pump turbine;

[0052] When the real-time flow of the water pump turbine is less than the design flow of the water pump turbine, the real-time pressure fluctuation signal of the tail pipe of the water pump turbine is collected.

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

[0054] The real-time flow is calculated to determine whether to start the pressure fluctuation monitoring processing module;

[0055] When Q t < Q design , the straight pipe section pressure fluctuation monitoring module of the tail pipe is not started; when Q t < Q design , the pressure fluctuation monitoring module is started; Q t —Real-time flow of the unit, unit: m 3 / s; Q design —Design flow, unit: m 3 / s.

[0056] Step 2, modal decomposition is performed on the real-time pressure fluctuation signal to obtain different modal decomposition quantities;

[0057] Specifically, in this embodiment, the steps of modal decomposition are:

[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 use a cubic spline function to fit the upper and lower envelope curves u max (t) and the minimum envelope curve u min (t);

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

[0061] u max —Function u(t) maximum point envelope function;

[0062] u minThe minimum point envelope function of function u(t)

[0063] The average line function of m

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

[0065] x k The input signal function

[0066] The envelope function of m

[0067] x k+1 The output signal function

[0068] 2.5. Determine whether x k+1 is an IMF component, s d Should be less than 0.2 or 0.3;

[0069]

[0070] x k+1 The k+1 new function

[0071] x k The k new function

[0072] s d The standard deviation

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

[0074] Step 3, calculate the efficiency change of the pump-turbine draft tube

[0075]

[0076] Where, η t+1 is the efficiency at t+1, η t is the efficiency at t, and Δη is the efficiency change.

[0077] Step 4, perform correlation analysis on different modal decomposition quantities and efficiency changes to obtain correlation coefficients

[0078] The method for correlation analysis is:

[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 in the figure, 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] The embodiment discloses a method and device for determining air supplement time of a water pump water turbine tail water pipe, decomposes a vortex band pressure pulsation signal of the tail water pipe by using an empirical mode decomposition method, and determines reasonable air supplement time by correlatively analyzing an efficiency change and mode functions of pressure pulsation signals of different orders.

[0095] The above embodiment only describes the preferred mode of the present application, and does not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solution of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for determining the timing of air supply to a draft tube of a pump-turbine, characterized by, The method comprises the following steps: monitoring real-time flow of a water pump turbine, collecting real-time pressure fluctuation signals of a draft tube of the water pump turbine; performing modal decomposition on the real-time pressure fluctuation signals to obtain different modal decomposition quantities; calculating an efficiency variation of the draft tube of the water pump turbine; performing correlation analysis on the different modal decomposition quantities and the efficiency variation to obtain a correlation coefficient; when the correlation coefficient is greater than a preset second threshold, determining that the draft tube of the water pump turbine is aerated.

2. The method of claim 1, wherein The monitoring of the real-time flow of the water pump turbine comprises the following steps: collecting the real-time flow of the water pump turbine; when the real-time flow of the water pump turbine is less than a designed flow of the water pump turbine, starting to collect the real-time pressure fluctuation signals of the draft tube of the water pump turbine.

3. The method of claim 1, wherein The modal decomposition on the real-time pressure fluctuation signals comprises the following steps: S1. inputting pressure fluctuation signals x(t); S2. Calculate the maximum and minimum points of the pressure fluctuation signal x(t) and fit the maximum envelope line u max (t) and the minimum envelope line u min (t); S3. Calculate the envelope average, m(t) = (u min (t) + u max (t)) / 2; where u max is the envelope function of the maximum points of the function u(t), u min is the envelope function of the minimum points of the function u(t), and m is the average line function. S4. Subtract the envelope average, x k+1 (t) = x k (t) - m(t); where x k is the input signal, i.e. x(t) in S1, m is the envelope function, and x k+1 is the output signal function; S5. Determine x based on a preset first threshold k+1 whether it is an IMF component; S6. Use the new function x k+1 (t) instead of the original function x k (t) and repeat S2-S5 to calculate the modal components of each order until x k+1 (t) is a monotonic function.

4. The method of claim 3, wherein the air supply timing of the draft tube of the pump-turbine is determined based on the pressure difference between the pressure of the draft tube and the pressure of the tailrace. determining x k+1 The method for determining whether it is an IMF component is: ； wherein x k+1 is the k+1th new function, x k is the kth new function, s d is the signal standard deviation threshold, T is the signal time interval, and t is the time instant; When S d is less than a preset threshold, it is determined that x k+1 is an IMF component.

5. The method of claim 1, wherein the efficiency variation of the draft tube of the water pump turbine is: ； wherein η t+1 is the efficiency at time t+1, η t is the efficiency at time t, and Δη is the efficiency change.

6. The method of claim 1, wherein the method for performing correlation analysis on the different modal decomposition quantities and the efficiency variation comprises the following steps: ； wherein p X,Y is the correlation coefficient, X is the pulsatile signal modal component, Y is the efficiency variation, n is the total number of variable values, and i represents the i-th data value.

7. The method of claim 5, wherein the air supply timing is determined based on a pressure difference between the pressure in the draft tube and the pressure in the pump chamber. the determination of the aerating time of the draft tube of the water pump turbine further comprises the following steps: monitoring the efficiency variation Δη; when Δη > 0, continuing to aerate; and when Δη < 0, stopping aerating.

8. A device for determining the timing of air injection into the tailrace pipe of a water pump turbine, characterized in that, The device for implementing the method for determining the aerating time of the draft tube of the water pump turbine according to any one of claims 1-7 comprises a data collection module, a monitoring module, a modal decomposition module, an efficiency calculation module, a correlation analysis module and a determination module. The data collection module is configured to collect the designed flow and the real-time flow of the water pump turbine, and efficiency data of the water pump turbine. The monitoring module is configured to start to collect the real-time pressure fluctuation signals of the draft tube of the water pump turbine when the real-time flow of the water pump turbine is less than the designed flow of the water pump turbine. The modal decomposition module is configured to perform modal decomposition on the real-time pressure fluctuation signals to obtain different modal decomposition quantities. The efficiency calculation module is configured to calculate the efficiency variation of the draft tube of the water pump turbine. The correlation analysis module is configured to perform correlation analysis on the different modal decomposition quantities and the efficiency variation to obtain a correlation coefficient. The determination module is configured to determine that the draft tube of the water pump turbine is aerated when the correlation coefficient is greater than a preset second threshold.

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