A method for calculating the linear degree of a steam turbine admission end

Abstract

The application relates to a kind of calculation methods of turbine admission end regulating linearity, the difference of the termination value and initial value of the comprehensive valve position instruction in nearly 5min is calculated, the linearity k basic value of the comprehensive valve position interval to which it belongs is obtained according to the comprehensive valve position instruction value at termination and initial k , how to use linearity to evaluate the overall operation characteristics of high regulating valve is given, and abnormality is found in time to guide operation personnel to handle. The method is simple and reliable, high accuracy, strong practicability, which can be used in online monitoring system of thermal power plant and other digital systems, continuously monitors linearity, reduces the monitoring pressure of operation personnel, and improves work efficiency.

Description

Technical Field

[0001] This invention relates to a method for real-time evaluation of the adjustment linearity of the steam turbine inlet end based on DCS operating data, namely, a method for calculating the adjustment linearity of the steam turbine inlet end. Background Technology

[0002] With the continuous increase in the installed capacity of new energy sources, the stability of the power grid is gradually decreasing. In order to meet the needs of power grid AGC and primary frequency regulation, the frequency and amplitude of load changes in thermal power units, as well as the frequency of primary frequency regulation operations, have increased significantly. The load increase / decrease and primary frequency regulation functions of thermal power units both rely on the flexible operation of the high-voltage regulating valve. With the increasingly frequent primary frequency regulation operations, the failure rate of the high-voltage regulating valve is increasing, such as valve stem detachment, valve core wear, and valve stem vibration.

[0003] Currently, there is a lack of mature methods for identifying and analyzing the linearity of steam turbine inlet control. The current approach relies heavily on long-term tracking of historical data and extensive experience by technical personnel to detect deterioration in turbine control linearity. This method is time-consuming, requires extensive data comparison, and involves a complex analysis process. Given the gradually increasing failure rate of control valves, it is essential to innovate methods and leverage digital and intelligent platforms to achieve rapid monitoring and analysis of steam turbine control linearity. Summary of the Invention

[0004] In view of the above situation and to overcome the defects of the prior art, the purpose of this invention is to provide a method for calculating the adjustment linearity of the steam turbine inlet end, which can monitor the adjustment linearity of the steam turbine in real time and provide guidance and suggestions for the operation and maintenance of the high-pressure regulating valve.

[0005] The technical solution solved by this invention is:

[0006] A method for calculating the linearity of steam turbine inlet adjustment includes the following steps:

[0007] Step 1: Collect historical operating data of the unit at 50%-100% load for the past 180 days. The parameters collected include comprehensive valve position commands, main steam pressure, and regulating stage pressure.

[0008] Step 2: Calculate the corrected regulating stage pressure for each set of data. The calculation formula is as follows:

[0009]

[0010] In the formula, p tjj_xz The corrected regulating stage pressure; p tjj For regulating stage pressure; p0 is the main steam pressure; p 0s To design the main steam pressure;

[0011] Step 3: Using the K-means clustering method (K-means clustering algorithm), with the comprehensive valve position command as the independent variable and the corrected regulating stage pressure as the dependent variable, the historical operating data is clustered to form the turbine regulation linear curve;

[0012] Step 4: Calculate the turbine regulation linearity (i.e., the slope of the combined valve position command and the corrected regulating stage pressure curve). The calculation formula is as follows:

[0013]

[0014] In the formula, k is the linearity, and Δp tjj_xz The corrected change in regulating stage pressure is represented by ΔF, which represents the overall valve position command change.

[0015] Step 5: Divide the integrated valve position into intervals with a step size of 1%, and calculate the linearity k of each integrated valve position for each 1% change in the integrated valve position. This result serves as the baseline value for the turbine regulation linearity over the past 180 days.

[0016] Step 6: Execute once every 5 minutes to collect historical operating data of the past 5 minutes in real time. The collected data includes comprehensive valve position command, main steam pressure, and regulating stage pressure. Take the average value of the most recent 10 time points as the termination value and take the average value of the first 10 time points as the initial value.

[0017] Step 7: Calculate the difference between the termination value and the initial value of the integrated valve position command in the past 5 minutes. If the difference is less than 1%, the data collected this time is invalid. If the difference is greater than 1%, calculate the corrected regulating stage pressure at the termination and initial time according to the method in Step 2. Then, calculate the linearity k in the past 5 minutes according to Step 4. Based on the integrated valve position command value at the termination and initial time, obtain the basic value of the linearity k of the integrated valve position interval to which it belongs.

[0018] Step 8: Compare the relative deviation δ of the linearity k over the past 5 minutes with the baseline value of linearity k. k The calculation formula is as follows:

[0019]

[0020] Perform fault diagnosis:

[0021] If δ k If the rate is >50%, it indicates that the high-pressure regulating valve is loose. The high-pressure regulating valve should be isolated and repaired.

[0022] If δ k If the rate is >100%, it indicates that the high-pressure valve has detached and the machine needs to be stopped for inspection.

[0023] If δ k <50% indicates normal linearity of adjustment;

[0024] Step 9: After 5 minutes, perform the next judgment;

[0025] Step 10: After executing continuously for 180 days, if no abnormalities occur within the next 180 days, repeat steps 1-5 to obtain the basic linearity value again.

[0026] With increasingly frequent deep peak shaving by thermal power units, on the one hand, the units experience frequent load changes, and on the other hand, the number of primary frequency regulation actions is gradually increasing. This places higher demands on the quality of turbine regulation. In addition to control system parameters, the linearity of turbine inlet regulation is a crucial factor determining the load change rate and the quality of primary frequency regulation. The structural characteristics of the turbine high-pressure regulating valve and the degree of matching between the high-pressure regulating valve management curve and the high-pressure regulating valve flow characteristics determine the linearity of turbine regulation. Since high-pressure regulating valves mostly operate in a sequential valve mode, the identification and characterization of the overall flow characteristics of the high-pressure regulating valve are key to evaluating the linearity of turbine regulation.

[0027] Furthermore, once the physical profile of the turbine high-pressure control valve is determined, it generally remains largely unchanged. However, if the control valve experiences malfunctions such as valve stem detachment or valve core wear, the flow characteristics of the high-pressure control valve will change, resulting in alterations in the control linearity. Therefore, monitoring the linearity can also be used to identify high-pressure control valve malfunctions.

[0028] This invention proposes a linearity characterization method based on monitored section pressure, and demonstrates how to use linearity to evaluate the overall operating characteristics of high-pressure regulating valves, enabling timely detection of anomalies and guiding operators in handling them. This method is simple, reliable, highly accurate, and practical. It can be used in digital systems such as online monitoring systems in thermal power plants to continuously monitor linearity, reducing the stress on operators, improving work efficiency, and offering significant social and economic benefits. Attached Figure Description

[0029] Figure 1 The graph shows the turbine regulation linearity curves before and after clustering processing, which is an application example of the present invention. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and application examples.

[0031] An application example is the 660MW ultra-supercritical turbine unit at Xuchang Power Plant, which experienced a sudden 50MW load drop in 2022 due to a high-pressure regulating valve malfunction. During this period, parameters such as regulating stage pressure and main steam pressure showed significant changes. Under the power closed-loop control, the overall valve position increased. The contradiction between the sudden load drop and the increase in the overall valve position posed challenges to fault diagnosis. The method of this invention is now used to monitor the turbine regulating linearity, with the following steps:

[0032] Step 1: Collect historical operating data of the unit at 50%-100% load for the past 180 days. Collect parameters including comprehensive valve position commands, main steam pressure, and regulating stage pressure, and obtain their historical values.

[0033] (1) Collect historical operating data for nearly 180 days to obtain historical values ​​of integrated valve position, main steam pressure, and regulating stage pressure;

[0034] Step 2: Calculate the corrected regulating stage pressure for each set of data. The calculation formula is as follows:

[0035]

[0036] In the formula, p tjj_xz The corrected regulating stage pressure; p tjj For regulating stage pressure; p0 is the main steam pressure; p 0s To design the main steam pressure;

[0037] Some of the data is listed in Table 1 below:

[0038] Table 1. Original data and corrected regulating stage pressure

[0039] Serial Number Main steam pressure Regulating pressure Integrated valve position command Corrected regulating stage pressure 1 22.15 10.94 60.49 11.95 … … … … … 15552000 20.19 16.47 99.47 19.73

[0040] Step 3: Using K-means clustering, with the comprehensive valve position command as the independent variable and the corrected regulating stage pressure as the dependent variable, historical operating data is clustered to form a turbine regulation linear curve, such as... Figure 1 As shown;

[0041] Step 4: Calculate the turbine regulation linearity (i.e., the slope of the combined valve position command and the corrected regulating stage pressure curve). The calculation formula is as follows:

[0042]

[0043] In the formula, k is the linearity, and Δp tjj_xz The corrected change in regulating stage pressure is represented by ΔF, which represents the overall valve position command change.

[0044] Step 5: Divide the integrated valve position into intervals of 1%, such as 50%, 51%, 52%...100%. Calculate the linearity k of each integrated valve position for every 1% change. This result serves as the baseline value for the turbine regulation linearity over the past 180 days, as shown in Table 2 below:

[0045] Table 2. Linearity k-baseline values ​​for each comprehensive valve position range over the past 180 days.

[0046] Integrated valve position % linearity k Integrated valve position % linearity k 61 0.1900 81 0.193 62 0.1950 82 0.193 63 0.1970 83 0.200 64 0.1940 84 0.200 65 0.1980 85 0.197 66 0.1940 86 0.199 67 0.1920 87 0.172 68 0.1950 88 0.181 69 0.1990 89 0.194 70 0.1960 90 0.198 71 0.1910 91 0.181 72 0.1900 92 0.195 73 0.1950 93 0.195 74 0.1930 94 0.199 75 0.1920 95 0.197 76 0.1950 96 0.194 77 0.1920 97 0.195 78 0.2000 98 0.2 79 0.1940 99 0.195 80 0.1990 100 0.194

[0047] Step 6: Execute once every 5 minutes to collect historical operating data of the past 5 minutes in real time. The collected data includes comprehensive valve position command, main steam pressure, and regulating stage pressure. Take the average value of the most recent 10 time points as the termination value and take the average value of the first 10 time points as the initial value.

[0048] Step 7: Calculate the difference between the termination value and the initial value of the integrated valve position command in the past 5 minutes. If the difference is less than 1%, the data collected this time is invalid. If the difference is greater than 1%, calculate the corrected regulating stage pressure at the termination and initial times according to the method in Step 2. Then, calculate the linearity k in the past 5 minutes according to Step 4. Based on the integrated valve position command value at the termination and initial times, obtain the basic value of the linearity k of the integrated valve position interval to which it belongs, as shown in Table 3 below.

[0049] Table 3 Initial and final values ​​over the past 5 minutes

[0050] project Integrated valve position Main steam pressure Regulating pressure Corrected regulating stage pressure unit ％ MPa MPa MPa 5min initial value 73 15.53 9.31 14.50 5-minute final value 75 14.55 9.00 14.89

[0051] According to the table, the linearity k for 73%-75% is calculated to be 0.195;

[0052] Step 8: Compare the relative deviation δ of the linearity k over the past 5 minutes with the baseline value of linearity k. k The average value of the linearity k-baseline for the 73%-75% integrated valve position in Table 2 is 0.193. Based on the linearity k-baseline values ​​over the past 5 minutes, the deviation between the two values ​​is calculated as follows:

[0053]

[0054] δ k <50%, linearity adjustment is normal.

[0055] Step 9: After 5 minutes, data was collected again, yielding nearly 5 minutes of data, as follows:

[0056] project Integrated valve position Main steam pressure Regulating pressure Corrected regulating stage pressure unit ％ MPa MPa MPa 5min initial value 88 22.49 16.17 17.40 5-minute final value 90 20.03 13.54 16.36

[0057] According to the table, the linearity k for 88%-90% is calculated to be -0.52;

[0058] The average value of the linearity k baseline for the 88%-90% integrated valve position in Table 2 is 0.191. Based on the linearity k values ​​over the past 5 minutes, the deviation between the two values ​​is calculated as follows:

[0059]

[0060] δ kThe failure rate was >100%, indicating a valve stem detachment fault in the high-pressure regulating valve, requiring shutdown and repair. Further inspection revealed that the valve's connecting sleeve had become loose from the valve stem, causing the anti-rotation pin to be subjected to alternating stress over a long period. This ultimately led to the anti-rotation pin breaking, the valve stem detaching, and the high-pressure regulating valve becoming ineffective for regulation.

[0061] The present invention has achieved good technical results in practical applications, as detailed below:

[0062]

Claims

1. A method for calculating the linearity of the steam turbine inlet adjustment, characterized in that, Includes the following steps: Step 1: Collect historical operating data of the unit at 50%-100% load for 180 days. The parameters collected include comprehensive valve position commands, main steam pressure, and regulating stage pressure. Step 2: Calculate the corrected regulating stage pressure for each set of data. The calculation formula is as follows: In the formula, p tjj_xz The corrected regulating stage pressure; p tjj For regulating stage pressure; p0 is the main steam pressure; p 0s To design the main steam pressure; Step 3: Using the K-means clustering method, with the comprehensive valve position command as the independent variable and the corrected regulating stage pressure as the dependent variable, the historical operating data is clustered to form the turbine regulation linear curve; Step 4: Calculate the turbine regulating linearity. The calculation formula is as follows: In the formula, k is the linearity, and Δp tjj_xz The corrected change in regulating stage pressure is represented by ΔF, which represents the overall valve position command change. Step 5: Divide the integrated valve position into intervals with a step size of 1%, and calculate the linearity k of each integrated valve position for each 1% change in the integrated valve position. This result is used as the base value of the turbine regulation linearity over the past 180 days. Step 6: Execute once every 5 minutes to collect historical operating data of the past 5 minutes in real time. The collected data includes comprehensive valve position command, main steam pressure, and regulating stage pressure. Take the average value of the most recent 10 time points as the termination value and take the average value of the first 10 time points as the initial value. Step 7: Calculate the difference between the termination value and the initial value of the integrated valve position command over the past 5 minutes. If the difference is less than 1%, the data collected this time is invalid. If the difference is greater than 1%, calculate the corrected regulating stage pressure at the termination and initial values ​​according to the method in Step 2. Then, calculate the linearity k over the past 5 minutes according to Step 4. Based on the integrated valve position command values ​​at the termination and initial values, obtain the basic value of the linearity k of the integrated valve position range to which it belongs. Step 8: Compare the relative deviation δ of the linearity k over the past 5 minutes with the baseline value of linearity k. k The calculation formula is as follows: Perform fault diagnosis: If δ k If the rate is >50%, it indicates that the high-pressure regulating valve is loose. The high-pressure regulating valve should be isolated and repaired. If δ k If the percentage is >100%, it indicates that the high-pressure regulating valve has detached and the machine needs to be stopped for inspection. If δ k <50% indicates normal linearity of adjustment; Step 9: After 5 minutes, perform the next judgment; Step 10: After executing continuously for 180 days, if no abnormality occurs within 180 days, repeat steps 1-5 to obtain the basic linearity value again.

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