Method and device for evaluating performance trend of pump for nuclear power station

Abstract

The invention relates to the field of pump performance evaluation, in particular to a performance trend evaluation method and device for a pump for a nuclear power station. The method comprises the following steps: establishing an input and output model of inlet and outlet pressure of the pump in an ideal operation state; according to an established input and output model of inlet and outlet pressure, the minimum variance standard # imgabs0 # of the pump is calculated, the output variance # imgabs1 # is calculated according to actual output data on site, the minimum variance standard of the pump in an ideal operation state is compared with the actual output variance, and the performance index # imgabs2 # of the pump is calculated according to the change trend of the performance index eta of the pump along with time; and the performance change trend of the pump is judged. The device comprises an ideal state calculation module; an actual variance acquisition module; and a comparative judgment module. The system is low in cost and high in monitoring precision.

Description

Technical Field

[0001] The present invention relates to the field of pump performance evaluation, and particularly to a method and device for evaluating the performance trend of pumps used in nuclear power plants. Background Art

[0002] At present, the performance evaluation of pump systems mainly focuses on the analysis of steady-state operating conditions. A vibration sensor is added to the pump shaft to collect vibration acceleration data of a centrifugal pump in a stable operating state and calculate its effective value and other data for performance evaluation. This evaluation method mainly adds vibration sensors and corresponding transmission cables, which is too costly for most pumps and cannot be implemented in actual use. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and device for evaluating the performance trend of pumps used in nuclear power plants, with low cost and high monitoring accuracy.

[0004] The present invention provides a method for evaluating the performance trend of pumps used in nuclear power plants, including the following steps:

[0005] Step 1: Establish an input-output model of the inlet and outlet pressures of the pump under ideal operating conditions;

[0006] The input-output model of the inlet and outlet pressures is:

[0007]

[0008] f d is the impulse response coefficient of the disturbance signal transfer function, and a t is the white noise of the disturbance signal at time t;

[0009] Step 2: Calculate the minimum variance reference of the pump according to the established input-output model of the inlet and outlet pressures

[0010] Step 3: Calculate the output variance according to the actual output data on site

[0011] Step 4: Compare the minimum variance reference of the pump in the ideal operating state with the actual output variance, and calculate the performance index of the pump Judge the performance change trend of the pump according to the change trend of the performance index η of the pump over time.

[0012] In a specific embodiment of the present invention, Step 1 specifically includes:

[0013] Step 1-1: Estimate the process time delay of the closed-loop control loop

[0014] Step 1-2: Collect the time series (t, y of the outlet pressure parameters of the pumpt ) Using the moving average model structure, the output signal a is obtained from the disturbance end t to the control output signal y t between the expressions;

[0015]

[0016] Step 1-3: Expand the disturbance signal transfer function N of the expression (1) and perform tail residual deletion processing to establish an input-output model of the inlet and outlet pressures;

[0017]

[0018] In a specific embodiment of the present invention, the specific steps of step 2 include:

[0019] Step 2-1: Calculate the variance of the outlet pressure value according to the established input-output model of the inlet and outlet pressures;

[0020] Step 2-2: Delete the tail residual to obtain the minimum variance benchmark

[0021]

[0022] E[y t a t is the mathematical expectation of the product of the outlet pressure y of the pump t and the disturbance signal white noise a t ;

[0023] In a specific embodiment of the present invention, in step 3,

[0024] Take the actual outlet pressure sequence of the pump continuously measured for a calculation period to obtain m data points, and the pressure data of each data point is y i , i = number of measurement points m; calculate the output variance

[0025] where E(y) is the mathematical expectation of y, that is, the average value of the pressure data of the measured data points;

[0026] E(y 2 ) is the expectation of the square of the pressure data;

[0027] In a specific embodiment of the present invention, the standard for the performance change trend of the pump is:

[0028] When the performance index η of the pump is closer to 1, it indicates better pump performance; when the performance index η of the pump is closer to 0, it indicates worse pump performance;

[0029] When the performance index η of the pump shows a significant downward trend in the short term, it is necessary to check the pump status to see if there are any defects; when the performance index η of the pump shows a downward trend in the long term, it is necessary to check the pump status and plan for preventive maintenance in the next maintenance cycle.

[0030] In a specific embodiment of the present invention, the significant downward trend of the performance index η of the pump in the short term means that (η at the previous time point - η at the current time point) / η at the previous time point > 10%;

[0031] The long-term downward trend of the performance index η of the pump means that (η of the previous 100 time points - η at the current time point) / η of the previous 100 time points > 10%.

[0032] The present invention provides a device for evaluating the performance trend of a pump for a nuclear power plant, including:

[0033] An ideal state calculation module for calculating the minimum variance benchmark of the pump according to the input-output model of the inlet and outlet pressure model;

[0034] An actual variance acquisition module for acquiring the pressure variance value output during actual operation;

[0035] A comparison and judgment module for comparing the minimum variance benchmark of the pump in the ideal state with the actually acquired pressure variance value and judging the state of the pump.

[0036] In a specific embodiment of the present invention, the ideal state calculation module includes an input-output model of the inlet and outlet pressure and a minimum variance controller model.

[0037] Compared with the prior art, the method and device for evaluating the performance trend of a pump for a nuclear power plant of the present invention have the following beneficial effects:

[0038] (1) The present invention does not require adding special test equipment or additional measuring points and transmission lines. It can be achieved only by using the existing measuring points in the system: the inlet pressure and outlet pressure of the pump, so the measurement cost is low;

[0039] (2) The present invention judges the working stability of the pump by comparing the correlation of the inlet and outlet pressures of the pump, thereby judging the operating condition of the pump. Therefore, the monitoring accuracy after measurement is high, and the compliance with the actual pump system is strong;

[0040] (3) The present invention can monitor the operating performance of the pump in the actual working pump system, that is, obtain the pump performance index value in real time, reducing the measurement time;

[0041] (4) The present invention does not require adding other equipment, does not affect the normal operating state of the system, and can perform continuous measurement;

[0042] (5) The present invention can be implemented by a computer program and realizes automatic supervision and alarm;

[0043] (6) Since the pump model is obtained from input and output parameters, it is applicable to the performance monitoring of various types of pumps;

[0044] (7) There is no need to know the process model and the disturbance model, which does not affect the normal operation state of the system and does not require an additional excitation signal. Detailed implementation manners

[0045] To further understand the present invention, the implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the present invention.

[0046] An embodiment of the present invention discloses a method for evaluating the performance trend of a pump used in a nuclear power plant, including the following steps:

[0047] Step 1-1: Estimate the process time delay of the closed-loop control loop

[0048] Use the correlation analysis algorithm, that is, analyze the correlation between the control output signal y t and the control signal u t to obtain the process time delay of the system:

[0049]

[0050] is the estimated value of the time delay of the control loop, d is the number of steps moved forward along the time axis in a time series segment; y t is the control output signal at time t, which is actually the output pressure value; u t is the control input signal at time t, and u t-d is the control input signal at time t-d.

[0051] Step 1-2: Collect the time series (t, y t ) of the outlet pressure parameters of the pump and establish an input-output model of the inlet and outlet pressures;

[0052] Specifically:

[0053] Adopt a moving average model structure to obtain the expression from the disturbance end to the output end:

[0054]

[0055] Q is the minimum variance controller model;

[0056] q -dTQ is the transfer function expression of the input-output model of the inlet and outlet pressures of the pump; the control output signal is the outlet pressure of the pump;

[0057] Among them, using Diophantine to expand the disturbance signal transfer function N, we get:

[0058]

[0059] Among them, fx(t) is the impulse response coefficient of the disturbance signal transfer function, x = 1,..., d - 1; R(q -d ) is the remaining rational and proper transfer function of N(q -d ), and can also be written as q -d R.q -a denotes the backward shift operator, which shifts the observed values in the time series backward by a time units, and the value range of a is 1 to d;

[0060] Substituting N into Equation (1), we get:

[0061]

[0062] Among them: L is the remainder of N and can be omitted. Therefore:

[0063]

[0064] The minimum variance controller model is The moving average model is:

[0065]

[0066] Among them: the value of d is equal to the time delay of the control loop Deleting the tail residuals, finally, establishing the time series expression of the input-output model of the inlet and outlet pressures:

[0067] f d is the impulse response coefficient of the disturbance signal transfer function, and a t is the white noise of the disturbance signal at time t.

[0068] Step 2: Calculate the minimum variance reference of the pump according to the established input-output model of the inlet and outlet pressures

[0069] According to the input-output model of the inlet and outlet pressures, calculate the variance of the outlet pressure value,

[0070]

[0071] Deleting the tail residuals, obtaining the minimum variance reference of the pump;

[0072]

[0073] E[y t a t is the mathematical expectation of the outlet pressure y of the pump t multiplied by the disturbance signal white noise a t .

[0074] Among them,

[0075]

[0076]

[0077]

[0078] Step 3: Calculate the output variance according to the actual output data on site

[0079] Take the actual outlet pressure sequence of the pump measured continuously for a calculation time period to obtain m data points, and the pressure data of each data point is y i , i = the number of measurement points m; calculate the output variance

[0080] where E(y) is the mathematical expectation of y, that is, the average value of the pressure data of the measured data points;

[0081] E(y 2 ) is the expectation of the square of the pressure data;

[0082] Step 4: Compare the minimum variance benchmark of the pump in the ideal operating state with the actual output variance to calculate the performance index of the pump According to the changing trend of the pump performance index η over time, judge the changing trend of the pump performance.

[0083] When the pump performance index η is closer to 1, it indicates that the pump performance is better; when the pump performance index η is closer to 0, it indicates that the pump performance is worse. When the pump performance index η has a significant downward trend in the short term, it is necessary to check the pump status to see if there are any defects. When the pump performance index η has a downward trend in the long term, it is necessary to check the pump status and plan preventive maintenance in the next maintenance cycle.

[0084] The significant downward trend of the pump performance index η in the short term means (η at the previous time point - η at the current time point) / η at the previous time point > 10%;

[0085] The long-term downward trend of the pump performance index η means (η of the previous 100 time points - η at the current time point) / η of the previous 100 time points > 10%.

[0086] The embodiment of the present invention also provides a device for evaluating the performance trend of a pump for a nuclear power plant, including:

[0087] An ideal state calculation module, configured to calculate the minimum variance benchmark of the pump according to the input-output model of the inlet and outlet pressure model;

[0088] An actual variance acquisition module, configured to acquire the pressure variance value output during actual operation;

[0089] A comparison and judgment module, configured to compare the minimum variance benchmark of the pump in the ideal state with the actually acquired pressure variance value, and judge the state of the pump.

[0090] The ideal state calculation module includes an input-output model of the inlet and outlet pressure and a minimum variance controller model.

[0091] The input-output model of the outlet pressure controlled by the minimum variance controller model is the operating state of the ideal pump. Its control process is as follows:

[0092] The error signal obtained by subtracting the outlet pressure value required to reach by the pump design from the output pressure value of the pump under the actual outlet minimum variance control enters the minimum variance controller model. The minimum variance controller model outputs a control signal according to the error value to control the input-output model of the inlet and outlet pressure. The output value of the input-output model of the inlet and outlet pressure is added to the disturbance signal to obtain the output pressure value under the minimum variance control;

[0093] The function of the added minimum variance controller model is to obtain the minimum variance reached by the pump output under the best control as the reference variance, and then obtain the performance index of the pump according to the output variance calculated from the on-site actual measurement output data.

[0094] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0095] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the performance trend of a pump used in a nuclear power plant, characterized in that It includes the following steps: Step 1: Establish an input-output model of the inlet and outlet pressures of the pump under ideal operating conditions; The input-output model of the inlet and outlet pressures is: f d is the impulse response coefficient of the disturbance signal transfer function, a t is the white noise of the disturbance signal at time t; Step 2: Calculate the minimum variance reference of the pump according to the established input-output model of the import and export pressures Step 3: Calculate the output variance based on the actual on-site output data Step 4: Compare the minimum variance benchmark of the pump in the ideal operating state with the actual output variance, and calculate the performance index of the pump Judge the changing trend of the pump's performance according to the changing trend of the pump's performance index η over time 2. The performance trend evaluation method of the pump for nuclear power plants according to claim 1, characterized in that Specifically, Step 1 includes: Step 1-1: Estimate the process time delay of the closed-loop control loop Step 1-2: Collect the time series (t, y t ) of the outlet pressure parameter of the pump, and use the moving average model structure to obtain the expression between the output signal a t from the disturbance end to the control output signal y t ; Step 1-3: Expand the disturbance signal transfer function N of the expression (1) and perform tail residual deletion processing to establish the input-output model of the inlet and outlet pressures; 3. The performance trend evaluation method of the pump for nuclear power plants according to claim 2, characterized in that Specifically, Step 2 includes: Step 2-1: Calculate the variance of the outlet pressure value according to the established input-output model of the inlet and outlet pressures; Step 2-2: Delete the trailing residuals to obtain the minimum variance benchmark E[y t a t is the mathematical expectation of the outlet pressure y t of the pump multiplied by the disturbance signal white noise a t .

4. The performance trend evaluation method for the pump used in nuclear power plants according to claim 1, wherein In Step 3, The pump continuously measures the actual outlet pressure sequence for a calculation time period to obtain m data points, and the pressure data of each data point is y i , i = the number of measurement points m; Calculate the output variance where E(y) is the mathematical expectation of y, that is, the mean value of the pressure data of the measured data points; E(y 2 ) is the expectation of the square of the pressure data.

5. The performance trend evaluation method for the pump used in a nuclear power plant according to claim 1, characterized in that, The standard for the performance change trend of the pump is: The closer the performance index η of the pump is to 1, the better the pump performance; the closer the performance index η of the pump is to 0, the worse the pump performance; When the performance index η of the pump has a significant downward trend in the short term, it is necessary to check the pump status to see if there are any defects; when the performance index η of the pump has a downward trend in the long term, it is necessary to check the pump status and plan for preventive maintenance in the next maintenance cycle.

6. The performance trend evaluation method for the pump used in nuclear power plants according to claim 5, characterized in that The significant downward trend of the performance index η of the pump in the short term means that (η at the previous time point - η at the current time point) / η at the previous time point > 10%; The downward trend of the performance index η of the pump in the long term means that (η of the previous 100 time points - η at the current time point) / η of the previous 100 time points > 10%.

7. A performance trend evaluation device for a pump used in a nuclear power plant, characterized in that, It includes: An ideal state calculation module for calculating the minimum variance benchmark of the pump according to the input-output model of the inlet and outlet pressure model; An actual variance acquisition module for acquiring the pressure variance value output during actual operation; A comparison and judgment module for comparing the minimum variance benchmark of the pump under the ideal state with the actually acquired pressure variance value and judging the status of the pump.

8. The performance trend evaluation device for the pump used in a nuclear power plant according to claim 7, wherein The ideal state calculation module includes the input-output model of the inlet and outlet pressures and the minimum variance controller model.

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