How to correct single valve and sequence valve parameters based on DEH valve flow characteristics

Abstract

The present invention relates to a method for correcting single valve and sequence valve parameters according to the DEH valve flow characteristics, which belongs to the technical field of thermal automatic control of thermal power plant. The system is composed of a data collection module, a data processing module, a parameter correction module for each branch high pressure control valve in single valve control mode, and a parameter correction module for each branch high pressure control valve in sequence valve control mode. The present invention provides nonlinear compensation data for the control valve of a steam turbine, and after carrying out the DEH control linear correction, the change in the overall valve position command of the steam turbine after unit load is guaranteed to change linearly corresponding to the generated steam flow rate and unit load, which improves the promptness and stability of unit load control, prevents the occurrence of vibration in unit load control, and has a good promoting effect on improving the control quality of unit AGC and primary frequency modulation, which is of great significance to the safe, stable, economical and reliable operation of thermal power unit.

Description

[Technical Field]

[0001] The present invention relates to the technical field of thermal automatic control of thermal power plants, and particularly to a method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics. [Background technology]

[0002] The proposed "carbon peak and carbon neutral" goal is driving the construction of a new type of power system primarily based on wind and solar power generation. Due to the variability and uncertainty of wind and solar power generation, large-scale grid integration of new energy sources brings many problems, most notably frequency issues. The frequency issues posed by grid integration of wind and solar power generation are caused by their respective output characteristics, variability, and uncertainty, on the one hand, and by the lack of rotational inertia and post-adjustment sag adjustment issues, leading to further frequency deterioration. Thermal power generation units, which are high-quality FM resources, can generally respond to the situation in about 30 seconds and rely on their larger moment of inertia to ensure a higher FM effect.

[0003] Thermal power generation equipment not only plays a key role as the "ballast" of new power systems, but is also an essential part of the current new power system. The valve characteristic curves of most units are based on the characteristic curves established when the turbines were shipped from the factory. Power generation companies do not consider the need for valve overhauls, so valve strokes are adjusted more or less, resulting in changes in valve flow characteristics. Experimental correction of the characteristic curves is not performed, and the original characteristic curves continue to be used. As a result, the valve flow characteristic curves used in DCSs do not match the actual valve flow characteristics. The unit's integrated valve position command exhibits significant nonlinearity with respect to generated steam flow and unit load, significantly affecting the response speed and adjustment effectiveness of the primary FM of thermal power generation units. Rediscovering the flow characteristics of DEH valves and modifying the control parameters of single and sequential valves is of great significance for improving the primary FM capabilities of thermal power generation units and ensuring the safe and stable operation of new power systems. Therefore, how to overcome the shortcomings of existing technology is a key challenge in the field of thermal power plant thermal automation control technology. Summary of the Invention

[0004] The valve flow characteristic curve used in DCS does not match the actual valve flow characteristics, and the unit's overall valve position command change exhibits a large nonlinear relationship with the generated steam flow rate and unit load, affecting the primary frequency modulation response speed and adjustment effect of the thermal power generation unit, and this problem remains unresolved. The objective of this invention is to solve the shortcomings of the prior art by providing a method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics. By analyzing the unit DEH valve flow characteristics through testing, establishing a valve flow characteristic curve, and correcting the control parameters of the single valve and sequence valve, the unit's overall valve position command change exhibits an approximately linear relationship with the generated steam flow rate and unit load.

[0005] To achieve the above objectives, the technical solutions adopted in the present invention are as follows:

[0006] The method to correct single valve and sequence valve parameters based on DEH valve flow characteristics is as follows: Data collection: Switch the unit to DEH valve control mode, switch the unit's primary frequency modulation control, switch the unit's AGC control, switch the machine and furnace coordinated control to manual, switch the unit's automatic fuel, switch the automatic intake oxygen, turn on the automatic unit main steam temperature, automatic feedwater, and automatic furnace pressure. Perform single-step 5% step disturbances on the single high-pressure control valve from 100 to 0% and from 0 to 100%. When a control valve is operating, all other control valves are open. After the operation of the single high-pressure control valve is completed, all control valves are kept fully open. Then, in the reverse order of the sequence valve opening, the control valves are gradually closed in 5% steps until the control valve is kept fully open in the final stage. Record the unit load, main steam pressure before the machine, pressure regulator pressure, main steam temperature, and temperature after the pressure regulator throughout the entire adjustment process. (1) Flow characteristic curve calculation: Step (2) of calculating the flow characteristic curve of each high-pressure control valve according to the Flugel equation using the data obtained in step (1); Parameter correction for each branch high-pressure control valve in single valve control mode: In single valve control mode, calculate the actual single valve normalized relative flow rate, and fit the actual single valve normalized relative flow rate as y and the corresponding valve opening as x, and find the high-order continuous function y = f(x). Find the polygon function currently used by the unit single valve in the DCS, and use the high-order continuous function y = f(x) to correct the overall valve position command or valve opening. (3) Parameter correction for each branch high-pressure control valve in sequence valve control mode: In sequence valve control mode, there are a number of steps from full open to full closed for all control valves. When the valve is fully open, the valves are closed sequentially according to the closing order until the final stage is fully open. The number of inflection points that occur during the process is a-1, and the relative flow rate corresponding to the inflection points is y. m and (4) calculating In the DCS, in the sequence valve control mode, find the polygon function used for each control valve. In this function, Yqi is the discrete integrated valve position command, and Xqi is the corresponding valve opening. The normalized relative flow rate of each high-pressure control valve is y, and the corresponding valve opening is x. Then, the high-order continuous function y i =f i (x), where i is the i-th high-pressure control valve, Relative flow rate y corresponding to the inflection point m And for each high-pressure control valve, the correlation between the overall valve position and the relative flow rate is calculated based on the high-order continuous function y=f(x) and polygon function, and the overall valve position command or valve opening is corrected based on the correlation.

[0007] Furthermore, preferably, in step (1), the recording sampling interval is 1 s during recording.

[0008] Furthermore, preferably, step (2) specifically comprises: When the unit is under the i-th high pressure regulating valve opening degree j, j∈[0, 100%], TIFF0007725723000001.tif21170 Correction is made based on the steam temperature before and after the high-pressure regulating valve. TIFF0007725723000002.tif31170Where, PT ij is the main steam pressure before the machine when the i-th high-pressure control valve is open to j, in MPa. P1 ij is the pressure regulator pressure when the i-th high-pressure control valve is opened to j, in units of MPa. TS ij is the main steam temperature before the machine when the i-th high-pressure control valve is opened to j, in °C. T1 ij is the temperature after the pressure regulator when the i-th high-pressure control valve is at opening degree j, and is expressed in °C.

[0009] Normalized relative flow rate within the test range of 0-100%: TIFF0007725723000003.tif7170 where FRij% is the relative flow rate when the i-th high-pressure control valve opening is j, F Ri0 is the corrected steam pressure ratio when the i-th high-pressure control valve is at 0% valve opening, F Ri100 is the corrected steam pressure ratio when the i-th high-pressure control valve is 100% open, Based on the obtained relative flow rates, a flow rate characteristic curve of the i-th high-pressure control valve is drawn.

[0010] Furthermore, preferably, in step (3), calculating the actual single-valve normalized relative flow rate specifically includes: TIFF0007725723000004.tif13170 where, TIFF0007725723000005.tif6170 is the actual single-valve normalized relative flow rate, where i is the number of high-pressure regulating valves, j is the high-pressure regulating valve opening, and j∈[0, 100%]. Find the polygon function currently used by the DCS unit single valve, where Yn is the discrete integrated valve position command, Xn is the valve opening corresponding to Yn, and the actual single valve normalized relative flow rate. TIFF0007725723000006.tif7170 is used as y and the corresponding valve opening as x, and a high-order continuous function y=f(x) is obtained. Substitute Xn in the polygon function into the high-order continuous function after fitting to obtain the corrected overall valve position command Yn', or use the inverse function method x=f -1 Using (y), Yn in the polygon function is substituted into the solution of the high-order continuous function to obtain the corrected valve opening Xn'.

[0011] Further, preferably, the method of step (4) specifically comprises: In the sequence valve control mode, there are a number of steps from fully open to fully closed for all control valves, and when a valve is fully open, the number of inflection points that occurs during the process of sequentially closing the valves according to the closing order until the final fully open stage is a-1, the inflection point number corresponding to the first valve that is closed is m=1, the inflection point number corresponding to the second valve that is closed is m=2, and so on, with the final inflection point number being m=a-1; Relative flow rate y corresponding to the inflection point m Calculate In the TIFF0007725723000007.tif12170 formula, P m is the unit load corresponding to the m-th inflection point, and P e is the unit load when the valve is fully open, In the DCS, in the sequence valve control mode, find the polygon function used for each control valve. In this function, Yqi is the discrete integrated valve position command, and Xqi is the corresponding valve opening. Actual normalized relative flow rate F of each high-pressure control valve Rij% The high-order continuous function y is fitted to each high-pressure control valve as y and the corresponding valve opening as x. i =f i (x), where i is the i-th high-pressure control valve, Relative flow rate y corresponding to the inflection point m And each high pressure control valve high order continuous function y=f(x), based on the polygon function, calculate the correlation between the overall valve position and the relative flow rate to obtain, specifically: 1. Determine the overall valve position command and relative flow rate of each inflection point, that is, find the overall valve position command of all inflection points from the polygon function, and correspond to the relative flow rate corresponding to the calculated inflection points; 2. If the overall valve position is within the range of [0, a-1th inflection point corresponding to the overall valve position command], the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, and then calculate the y value of all high-pressure control valves that need to open within this range under that overall valve position. iThe average value of the values is calculated and multiplied by the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position; 3. When the overall valve position is within the range of (the overall valve position command corresponding to the a-1th inflection point, the overall valve position command corresponding to the a-2th inflection point), the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. i the average value is calculated and multiplied by (the relative flow rate corresponding to the (a-2)th inflection point - the relative flow rate corresponding to the (a-1)th inflection point) + the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position, and so on; 4. If the overall valve position is within the range of (the overall valve position command corresponding to the first inflection point, 1), the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. i Average the values and multiply it by (the relative flow rate corresponding to the first inflection point - the relative flow rate corresponding to the second inflection point) + the relative flow rate corresponding to the second inflection point to obtain the actual relative flow rate corresponding to the overall valve position; Then, the overall valve position command or the valve opening is corrected based on the correlation.

[0012] Additionally, the point of greatest deviation from the theoretical curve in the control relationship is preferably corrected.

[0013] The present invention also provides a system for correcting single valve and sequence valve parameters based on the DEH valve flow characteristics, and adopts a method for correcting single valve and sequence valve parameters based on the DEH valve flow characteristics, a data acquisition module configured to collect, during the test process, unit load, main steam pressure before the machine, pressure regulator pressure, main steam flow rate, feedwater flow rate, main steam deheat water flow rate, main steam temperature, reheat steam temperature, steam drum pressure, and steam turbine total energy flow rate; a data processing module configured to calculate a flow characteristic curve for each high-pressure control valve using the Flugel equation based on the data collected by the data collection module; a parameter correction module for each branch high-pressure control valve in the single valve control mode, which is configured to calculate the actual single valve normalized relative flow rate, fit the actual single valve normalized relative flow rate as y and the corresponding valve opening as x to obtain a high-order continuous function y=f(x), find the polygon function currently used for the unit single valve in the DCS, and use the high-order continuous function y=f(x) to correct the overall valve position command or the valve opening; Relative flow rate y corresponding to the inflection point m Calculate the polygon function used by each control valve in the DCS sequence valve control mode, where Yqi is the discrete integrated valve position command and Xqi is the corresponding valve opening. The actual normalized relative flow rate of each high-pressure control valve is y, and the corresponding valve opening is x. Then, for each high-pressure control valve, a high-order continuous function y is fitted. i =f i (x), where i is the ith high-pressure control valve, and the relative flow rate y corresponding to the inflection point m and a parameter correction module for each branch high-pressure control valve in a sequence valve control mode, which is configured to calculate the correlation between the overall valve position and the relative flow rate based on the high-order continuous function y=f(x) and polygon function of each high-pressure control valve, and correct the overall valve position command or valve opening based on the correlation.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The valve flow characteristic curves currently used in DCS (Distributed Control Systems) do not match the actual valve flow characteristics, and the unit's overall valve position command changes have large nonlinearities with the generated steam flow rate and unit load, resulting in serious over- or under-regulation of primary frequency modulation. This causes the coordinated control system to have an adverse regulation effect, ultimately inducing system low-frequency oscillation. This invention proposes a method for correcting single valve and sequence valve parameters based on DEH (Digital Electro-Hydraulic) valve flow characteristics.

[0016] The method of the present invention is based on field test data, and the obtained results are more targeted and practical, and can well adapt to the actual conditions of the unit. The test time of the method of the present invention is about 2 hours, the test process is simple and easy to operate, and the relative flow meter algorithm and curve fitting method are clearer, more intuitive, and more time-saving than other methods, and can be applied to different thermal power generation units and are universally applicable. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram showing the arrangement of steam turbine valve nozzles. [Figure 2] FIG. 10 is a diagram showing the theoretical and actual correspondence relationship between the normalized total valve position command and the relative flow rate. [Figure 3] 1 is a schematic diagram showing the structure of a system for correcting single valve and sequence valve parameters based on the DEH valve flow characteristics of the present invention, the arrow direction is the data or signal direction. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following the invention will be explained in more detail with reference to examples.

[0019] Those skilled in the art will understand that the following examples are used only for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention. In the examples, if no specific techniques or conditions are specified, they will be in accordance with the techniques, conditions, or product specifications described in the literature in this field. If the manufacturer of the materials or equipment used is not specified, they are conventional products that can be purchased.

[0020] Example 1 The method to correct single valve and sequence valve parameters based on DEH valve flow characteristics is as follows: Data collection: Switch the unit to DEH valve control mode, switch the unit's primary frequency modulation control, switch the unit's AGC control, switch the machine and furnace coordinated control to manual, switch the unit's automatic fuel, switch the automatic intake oxygen, turn on the automatic unit main steam temperature, automatic feedwater, and automatic furnace pressure. Perform single-step 5% step disturbances on the single high-pressure control valve from 100 to 0% and from 0 to 100%. When a control valve is operating, all other control valves are open. After the operation of the single high-pressure control valve is completed, all control valves are kept fully open. Then, in the reverse order of the sequence valve opening, the control valves are gradually closed in 5% steps until the control valve is kept fully open in the final stage. Record the unit load, main steam pressure before the machine, pressure regulator pressure, main steam temperature, and temperature after the pressure regulator throughout the entire adjustment process. (1) Flow characteristic curve calculation: Step (2) of calculating the flow characteristic curve of each high-pressure control valve according to the Flugel equation using the data obtained in step (1); Parameter correction for each branch high-pressure control valve in single valve control mode: In single valve control mode, calculate the actual single valve normalized relative flow rate, and fit the actual single valve normalized relative flow rate as y and the corresponding valve opening as x, and find the high-order continuous function y = f(x). Find the polygon function currently used by the unit single valve in the DCS, and use the high-order continuous function y = f(x) to correct the overall valve position command or valve opening. (3) Parameter correction for each branch high-pressure control valve in sequence valve control mode: In sequence valve control mode, there are a number of steps from full open to full closed for all control valves. When the valve is fully open, the valves are closed sequentially according to the closing order until the final stage is fully open. The number of inflection points that occur during the process is a-1, and the relative flow rate corresponding to the inflection points is y. m and (4) calculating In the DCS, in the sequence valve control mode, find the polygon function used for each control valve. In this function, Yqi is the discrete integrated valve position command, and Xqi is the corresponding valve opening. The normalized relative flow rate of each high-pressure control valve is y, and the corresponding valve opening is x. Then, the high-order continuous function y i =f i (x), where i is the i-th high-pressure control valve, Relative flow rate y corresponding to the inflection point m And for each high-pressure control valve, the correlation between the overall valve position and the relative flow rate is calculated based on the high-order continuous function y=f(x) and polygon function, and the overall valve position command or valve opening is corrected based on the correlation.

[0021] Example 2 The method to correct single valve and sequence valve parameters based on DEH valve flow characteristics is as follows: Data collection: Switch the unit to DEH valve control mode, switch the unit's primary frequency modulation control, switch the unit's AGC control, switch the machine and furnace coordinated control to manual, switch the unit's automatic fuel, switch the automatic intake oxygen, turn on the automatic unit main steam temperature, automatic feedwater, and automatic furnace pressure. Perform single-step 5% step disturbances on the single high-pressure control valve from 100 to 0% and from 0 to 100%. When a control valve is operating, all other control valves are open. After the operation of the single high-pressure control valve is completed, all control valves are kept fully open. Then, in the reverse order of the sequence valve opening, the control valves are gradually closed in 5% steps until the control valve is kept fully open in the final stage. Record the unit load, main steam pressure before the machine, pressure regulator pressure, main steam temperature, and temperature after the pressure regulator throughout the entire adjustment process. (1) Flow characteristic curve calculation: Step (2) of calculating the flow characteristic curve of each high-pressure control valve according to the Flugel equation using the data obtained in step (1); Parameter correction for each branch high-pressure control valve in single valve control mode: In single valve control mode, calculate the actual single valve normalized relative flow rate, and fit the actual single valve normalized relative flow rate as y and the corresponding valve opening as x, and find the high-order continuous function y = f(x). Find the polygon function currently used by the unit single valve in the DCS, and use the high-order continuous function y = f(x) to correct the overall valve position command or valve opening. (3) Parameter correction for each branch high-pressure control valve in sequence valve control mode: In sequence valve control mode, there are a number of steps from full open to full closed for all control valves. When the valve is fully open, the valves are closed sequentially according to the closing order until the final stage is fully open. The number of inflection points that occur during the process is a-1, and the relative flow rate corresponding to the inflection points is y. m and (4) calculating In the DCS, in the sequence valve control mode, find the polygon function used for each control valve. In this function, Yqi is the discrete integrated valve position command, and Xqi is the corresponding valve opening. The normalized relative flow rate of each high-pressure control valve is y, and the corresponding valve opening is x. Then, the high-order continuous function y i =f i (x), where i is the i-th high-pressure control valve, Relative flow rate y corresponding to the inflection point m And for each high-pressure control valve, the correlation between the overall valve position and the relative flow rate is calculated based on the high-order continuous function y=f(x) and polygon function, and the overall valve position command or valve opening is corrected based on the correlation.

[0022] In step (1), the recording sampling interval is 1 s. The unit is under the i-th high pressure regulating valve opening j, j∈[0, 100%], before and after the high pressure regulating valve. TIFF0007725723000008.tif21170 Correction is made based on the steam temperatures before and after the high-pressure regulating valve. TIFF0007725723000009.tif31170Where, PT ij is the main steam pressure before the machine when the i-th high-pressure control valve is open to j, in MPa. P1 ij is the pressure regulator pressure when the i-th high-pressure control valve is opened to j, in units of MPa. TS ij is the main steam temperature before the machine when the i-th high-pressure control valve is opened to j, in °C. T1 ij is the temperature after the pressure regulator when the i-th high-pressure control valve is at opening degree j, and is expressed in °C.

[0023] Normalized relative flow rate within the test range of 0-100%: TIFF0007725723000010.tif7170 where F Rij% is the relative flow rate when the i-th high-pressure control valve opening is j, F Ri0 is the corrected steam pressure ratio when the i-th high-pressure control valve is at 0% valve opening, F Ri100 is the corrected steam pressure ratio when the i-th high-pressure control valve is 100% open, Based on the obtained relative flow rates, a flow rate characteristic curve of the i-th high-pressure control valve is drawn.

[0024] In step (3), calculating the actual single-valve normalized relative flow rate is specifically: TIFF0007725723000011.tif13170 where, TIFF0007725723000012.tif7170 is the actual single-valve normalized relative flow rate, where i is the number of high-pressure regulating valves, j is the high-pressure regulating valve opening, and j∈[0, 100%]. Find the polygon function currently used by the DCS unit single valve, where Yn is the discrete integrated valve position command, Xn is the valve opening corresponding to Yn, and the actual single valve normalized relative flow rate. TIFF0007725723000013.tif7170 is used as y and the corresponding valve opening as x, and a high-order continuous function y=f(x) is obtained. Substitute Xn in the polygon function into the high-order continuous function after fitting to obtain the corrected overall valve position command Yn', or use the inverse function method x=f -1 Using (y), Yn in the polygon function is substituted into the solution of the high-order continuous function to obtain the corrected valve opening Xn'.

[0025] Step (4) Specific method: In the sequence valve control mode, there are a number of steps from fully open to fully closed for all control valves, and when a valve is fully open, the number of inflection points that occurs during the process of sequentially closing the valves according to the closing order until the final fully open stage is a-1, the inflection point number corresponding to the first valve that is closed is m=1, the inflection point number corresponding to the second valve that is closed is m=2, and so on, with the final inflection point number being m=a-1; Relative flow rate y corresponding to the inflection point m Calculate In the TIFF0007725723000014.tif12170 formula, P m is the unit load corresponding to the m-th inflection point, and P e is the unit load when the valve is fully open, In the DCS, in the sequence valve control mode, find the polygon function used for each control valve. In this function, Yqi is the discrete integrated valve position command, and Xqi is the corresponding valve opening. Actual normalized relative flow rate F of each high-pressure control valve Rij% The high-order continuous function y is fitted to each high-pressure control valve as y and the corresponding valve opening as x. i =f i (x), where i is the i-th high-pressure control valve, Relative flow rate y corresponding to the inflection point m And each high pressure control valve high order continuous function y=f(x), based on the polygon function, calculate the correlation between the overall valve position and the relative flow rate to obtain, specifically: 1. Determine the overall valve position command and relative flow rate of each inflection point, that is, find the overall valve position command of all inflection points from the polygon function, and correspond to the relative flow rate corresponding to the calculated inflection points; 2. If the overall valve position is within the range of [0, a-1th inflection point corresponding to the overall valve position command], the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, and then calculate the y value of all high-pressure control valves that need to open within this range under that overall valve position. i The average value of the values is calculated and multiplied by the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position; 3. When the overall valve position is within the range of (the overall valve position command corresponding to the a-1th inflection point, the overall valve position command corresponding to the a-2th inflection point), the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. ithe average value is calculated and multiplied by (the relative flow rate corresponding to the (a-2)th inflection point - the relative flow rate corresponding to the (a-1)th inflection point) + the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position, and so on; 4. If the overall valve position is within the range of (the overall valve position command corresponding to the first inflection point, 1), the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. i Average the values and multiply it by (the relative flow rate corresponding to the first inflection point - the relative flow rate corresponding to the second inflection point) + the relative flow rate corresponding to the second inflection point to obtain the actual relative flow rate corresponding to the overall valve position; Then, the overall valve position command or the valve opening is corrected based on the correlation.

[0026] The point of greatest deviation from the theoretical curve in the control relationship is corrected.

[0027] As shown in Figure 3, the system for correcting single valve and sequence valve parameters based on the DEH valve flow characteristics adopts the method for correcting single valve and sequence valve parameters based on the above-mentioned DEH valve flow characteristics, a data collection module 101 configured to collect, during the test process, unit load, main steam pressure before the machine, pressure regulator pressure, main steam flow rate, feedwater flow rate, main steam deheat water flow rate, main steam temperature, reheat steam temperature, steam drum pressure, and steam turbine total energy flow rate; a data processing module 102 configured to calculate a flow characteristic curve for each high-pressure control valve using the Flugel equation based on the data collected by the data collection module; a parameter correction module 103 for each branch high-pressure control valve in the single valve control mode, which is configured to calculate an actual single-valve normalized relative flow rate, fit the actual single-valve normalized relative flow rate as y and the corresponding valve opening as x to obtain a high-order continuous function y=f(x), find a polygon function currently used for the unit single valve in the DCS, and correct the overall valve position command or the valve opening using the high-order continuous function y=f(x); Relative flow rate y corresponding to the inflection point m Calculate the polygon function used by each control valve in the DCS sequence valve control mode, where Yqi is the discrete integrated valve position command and Xqi is the corresponding valve opening. The actual normalized relative flow rate of each high-pressure control valve is y, and the corresponding valve opening is x. Then, for each high-pressure control valve, a high-order continuous function y is fitted. i =f i (x), where i is the ith high-pressure control valve, and the relative flow rate y corresponding to the inflection point m and a parameter correction module 104 for each branch high-pressure control valve in a sequence valve control mode, which is configured to calculate the correlation between the overall valve position and the relative flow rate based on the high-order continuous function y=f(x) and polygon function of each high-pressure control valve, and correct the overall valve position command or the valve opening based on the correlation.

[0028] Example 3 A method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics includes the following steps: (1) Field test. Set the effective output of the test unit to the load Pe when the valve is fully open, switch the unit to DEH valve control mode, switch the unit's primary frequency modulation control, turn off the unit's AGC control, switch the machine and furnace coordinated control to manual, switch the unit's automatic fuel mode, switch the automatic intake oxygen mode, turn on the automatic main steam temperature, automatic feedwater, and automatic furnace pressure modes, and perform a single high-pressure control valve disturbance from 100 to 0% and 0 to 100% in single steps of 5%. When a control valve is operating, all other control valves are open. After the single high-pressure control valve operation is completed, all control valves are kept fully open, and then gradually close the control valves in reverse order in 5% steps until the control valve is kept fully open in the final stage. During the adjustment process, important parameters such as the unit load P, main steam pressure before the machine PT, pressure regulator pressure P1, main steam temperature TS, and temperature after the pressure regulator T1 are recorded.

[0029] (2) Select an appropriate numerical calculation method for the DEH valve flow characteristics, and calculate the flow rate before and after the i-th high-pressure regulating valve under the opening degree j (j∈[0, 100%]). TIFF0007725723000015.tif21170Different boundary conditions are corrected based on the steam temperatures before and after the high pressure regulating valve. It should be larger than TIFF0007725723000016.tif7170. TIFF0007725723000017.tif24170Where, PT ij is the main steam pressure before the machine when the i-th high-pressure control valve is open to j, in MPa. P1 ij is the pressure regulator pressure when the i-th high-pressure control valve is opened to j, in units of MPa. TS ij is the main steam temperature before the machine when the i-th high-pressure control valve is opened to j, in °C. T1 ij is the temperature after the pressure regulator when the i-th high-pressure control valve is at opening degree j, and is expressed in °C.

[0030] Normalized relative flow rate within the test range of 0-100%: TIFF0007725723000018.tif7170 where F Rij% is the relative flow rate when the i-th high-pressure control valve opening is j, F Ri0 is the corrected steam pressure ratio when the i-th high-pressure control valve is at 0% valve opening, F Ri100 is the corrected steam pressure ratio when the i-th high-pressure control valve is 100% open.

[0031] (3) Correct the parameters of each branch high-pressure control valve in single valve control mode. Under single valve operation mode, steam passes through the high-pressure regulating valve and nozzle chamber and enters the 360°C full-circumference pressure regulating stage vane, which uniformly heats the pressure regulating stage vane and effectively improves the stress distribution of the pressure regulating stage vane, allowing the unit to change load relatively quickly, at which time all regulating valves are partially opened with the same opening (for example, in single valve mode, each valve is opened equally at 50%). In this case, the actual single valve normalized relative flow rate is: TIFF0007725723000019.tif13170, where TIFF0007725723000020.tif6170 is the actual single-valve normalized relative flow rate, i is the number of high-pressure regulating valves, j is the high-pressure regulating valve opening, (j∈[0, 100%]), The polygon function currently used for a single valve in the DCS unit is found, and in this function, the key parameters are the discrete integrated valve position command Yn and the corresponding valve opening Xn, where Yn and Xn are all normalized values.

[0032] In Matlab, call the polyfit and polyval functions to obtain the discretized TIFF0007725723000021.tif7170 is fitted to a high-order continuous function y=f(x). The normalized Xn can be substituted into the fitted function to obtain the corrected overall valve position command Yn'. Alternatively, the inverse function x=f -1Through (y), Yn can be substituted into the solution of the high-order continuous function to obtain the corrected valve opening Xn'.

[0033] (4) Correct the parameters of each branch high-pressure control valve in sequence valve control mode.

[0034] In sequence valve control mode, the regulating valves are opened sequentially according to the preset sequence valve flow characteristic curve of each valve. For example, in a 300MW unit manufactured by the Harbin Steam Turbine Factory with six high-pressure regulating valves, the opening sequence is GV4 and GV5 opened simultaneously → GV6 → GV3 → GV2 → GV1 opened sequentially, and the closing sequence is reversed. Definition: In sequence valve control mode, all control valves have a number of steps from fully open to fully closed, for example, a is 5 in the above example. Based on field testing, when the valve is fully open, it is closed according to the closing sequence until the final fully open stage. The number of inflection points that occur during this process is a-1. If the inflection point number is m, the inflection point number corresponding to the first closed valve is m=1, and the last inflection point number is m=a-1. The calculation formula is as follows: In the TIFF0007725723000022.tif12170 formula, P m is the unit load corresponding to the m-th inflection point, and P e is the unit load when the valve is fully open, In DCS, in the sequence valve control mode, a polygon function is found to be used for each control valve. In this function, the key parameters are the discrete integrated valve position command Yqi and the corresponding valve opening Xqi, where Yqi and Xqi are all normalized values.

[0035] The polyfit and polyval functions are called in Matlab to calculate the normalized relative flow rate F of each high-pressure control valve. Rij% The high-order continuous function y is fitted to each high-pressure control valve as y and the corresponding valve opening as x. i =f i (x), where i is the i-th high-pressure control valve, Relative flow rate y corresponding to the inflection point mAnd each high pressure control valve high order continuous function y=f(x), based on the polygon function, calculate the correlation between the overall valve position and the relative flow rate to obtain, specifically: 1. Determine the overall valve position command and relative flow rate of each inflection point, that is, find the overall valve position command of all inflection points from the polygon function, and correspond to the relative flow rate corresponding to the calculated inflection points; 2. If the overall valve position is within the range of [0, a-1th inflection point corresponding to the overall valve position command], the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, and then calculate the y value of all high-pressure control valves that need to open within this range under that overall valve position. i The average value of the values is calculated and multiplied by the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position; 3. When the overall valve position is within the range of (the overall valve position command corresponding to the a-1th inflection point, the overall valve position command corresponding to the a-2th inflection point), the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. i the average value is calculated and multiplied by (the relative flow rate corresponding to the (a-2)th inflection point - the relative flow rate corresponding to the (a-1)th inflection point) + the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position, and so on; 4. If the overall valve position is within the range of (the overall valve position command corresponding to the first inflection point, 1), the overall valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y i value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. iAverage the values and multiply it by (the relative flow rate corresponding to the first inflection point - the relative flow rate corresponding to the second inflection point) + the relative flow rate corresponding to the second inflection point to obtain the actual relative flow rate corresponding to the overall valve position; Then, the overall valve position command or the valve opening is corrected based on the correlation.

[0036] Application example A method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics includes the following steps: (1) Field test was conducted on a 300MW coal-fired power generation unit as an example. The steam turbine manufacturing factory and model are Dongfang Steam Turbine Factory / N300-16.7 / 537 / 537. The steam turbine valve nozzle layout is as shown in Figure 1. There are a total of four high-pressure control valves. In the sequence valve mode, the opening order is GV1, GV2 open simultaneously → GV3 → GV4.

[0037] Under the test conditions, the load when the valve is fully open is basically stable at about 250MW, the unit is switched to DEH valve control mode, the unit is switched to primary frequency modulation control, the unit is switched to AGC control, the machine and furnace coordinated control is switched to manual, the unit fuel automatic is switched, the intake oxygen automatic is switched, the unit main steam temperature automatic, feedwater automatic, and furnace pressure automatic are turned on, and the single high pressure control valve is subjected to 100-0% and 0-100% single step 5% step disturbance.

[0038] As a result of collecting, PT1=[11.899 11.8343 11.8025 11.7816 11.739 11.7289 11.7083 11.6877 11.6877 11.6701 11.6701 11.6701 11.6814 11.7033 11.7558 11.8018 11.8805 11.9997 12.0799 12.2543, 12.3165 12.3985 12.4289 12.4617 12.4929 12.5034 12.5518 12.5518 12.5518 12.5518 12.5518 12.5518 12.5317 12.5216 12.501 12.48 12.4684 12.4578 12.3699 12.2543].

[0039] P11=[9.9086 9.8544 9.8207 9.7987 9.7775 9.7569 9.732 9.7196 9.7196 9.7013 9.691 9.691 9.68 9.6661 9.6434 9.6075 9.5255 9.3966 9.2201 9.2046 9.3225, 10.2512 10.3149 10.353 10.375 10.4131 10.4131 10.4468 10.4468 10.4468 10.4468 10.4468 10.4321 10.4168 10.3809 10.3289 10.2249 10.0806 9.8572 9.5723 9.4273 9.3225].

[0040] TS1=[533.3653 533.1078 533.3224 533.3224 533.923 534.1805 534.9099 535.6393 536.4116 537.2269 537.5272 538.1709 538.5142 538.9861 539.2436 539.2865 539.2865 539.2865 539.501 539.7156539.9302, 529.847 526.8438 526.5863 526.3718 526.3718 526.8438 527.616 528.3025 529.5038 531.1342 532.4213 533.9659 535.5964 536.8836 538.2138 539.0291 539.501 539.9731 539.9731 539.9302 539.9302].

[0041] T11=[510.0246 510.0246 510.282 510.282 510.6253 511.226 512.0842 512.7278 513.3286 513.8864 514.4442 514.7875 515.1307 515.1307 515.1307 514.6158 513.4144 511.3119 507.879 506.5057 505.8191, 506.8061 503.7591 503.4587 502.9866 502.9866 503.2441 503.7591 504.36 505.2612 506.377 507.8361 508.9518 510.2391 511.5693 512.17 512.213 511.3548 509.3809 506.8061 505.8191 505.8191].

[0042] The above is the data collected using the first high-pressure control valve as an example, and the data collected by the other three high-pressure control valves is similar, so it will not be repeated.

[0043] When the sequence valve is closed in the opposite direction of opening, the unit load changes from 253.86 MW to 237.35 MW to 187.85 MW.

[0044] (2) As a result of calculation using equation F R1j% =[1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 0.986 0.968 0.942 0.890 0.794 0.650 0.416 0.100 0.015 0.000], where j is (100%, 5%, 0), i.e., starting from 100 and decreasing to 0 in intervals of 5, there are 21 numbers: F R2j% =[1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 0.995 0.984 0.945 0.888 0.794 0.639 0.413 0.105 0.023 0.000]. F R3j% =[1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 0.993 0.983 0.959 0.918 0.849 0.697 0.488 0.213 0.032 0.000]. F R4j% =[1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 0.993 0.984 0.962 0.926 0.860 0.756 0.586 0.360 0.094 0.032 0.000].

[0045] (3) Correct the single valve control parameters.

[0046] As a result of calculation from the formula, F R単一バルブj% =[1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 0.998 0.990 0.974 0.943 0.889 0.798 0.643 0.419 0.128 0.026 0.000].

[0047] The original single-valve normalized control parameters found from the DCS are shown in Table 1. TIFF0007725723000023.tif83170 Using the matlab fitting function, for example, a 5th order polynomial function is selected and fitted, and the resulting functional relationship is y=-285.1282x 5 +488.5315x 4 -303.2191x 3 +75.8579x 2 -3.3862x+0.007972.

[0048] For example, if the valve opening is 0.228, the corrected overall valve position command should be 0.73; if the overall valve position command is 0.829, the corrected valve opening should be 0.378; or after finding the functional relationship, the entire polygon function can be modified according to customization.

[0049] According to the above principles, the single valve control parameters can be corrected as needed.

[0050] (4) Correct the sequence valve control parameters.

[0051] According to the test data, there are two inflection points, the first one corresponds to y1=237.35 / 253.86=0.9349, and the second one corresponds to y2=187.35 / 253.86=0.738.

[0052] The currently used sequence valve control normalization parameters found in DCS are shown in Table 2. TIFF0007725723000024.tif161170In Table 2, the actual inflection points are 0.899 for the first and 0.712 for the second, which are close to the situation measured in field tests, where the first inflection point was 0.9349 and the second was 0.738, and the overlap requirement is also met. Therefore, these can continue to be used in accordance with the use of most power plant parameters, and the calculations in this specification can also be used directly, that is, 0.712 in the GV3 overall valve position command column in Table 2 can be replaced with 0.738, and 0.899 in GV4 can be replaced with 0.9349.

[0053] The result of fitting the discrete data obtained in step (2) using Matlab is as follows: y1=-323.0769x1 5 +550.7925x1 4 -339.4231x1 3 +84.6501x1 2 -4.1412x1+0.0095559 y2=-301.0256x2 5 +510.1748x2 4 -315.1288x2 3 +79.1236x2 2 -3.753x2+0.0095332 y3=-393.8462x3 5 +621.958x3 4 -354.9324x3 3 +80.9211x3 2 -2.862x3+0.0025245 y4=-123.5897x4 5 +273.8345x4 4 -205.2558x4 3 +59.2105x4 2 -2.8227x4+0.0099773 Referring to the above table and the inflection point data, each valve opening is substituted into the above formula, and the corresponding relative flow rate is calculated. Furthermore, the comparison table between the relative flow rate and the overall valve position command under the currently used sequence valve parameters is shown in Table 3.

[0054] The specific calculation process is as follows: 1. Determine the overall valve position command and relative flow rate of the two inflection points, i.e., when the overall valve position command is 0.712, the relative flow rate is 0.738, and when the overall valve position command is 0.712, the relative flow rate is 0.9349.

[0055] 2. When the overall valve position is below 0.712, take the overall valve position command as an example: when the overall valve position command is 0.585, the openings of GV1 and GV2 in the original parameter settings are all 0.319, and the two y values obtained by substituting them into the above functional relationships are 0.9207 and 0.923, respectively. The average of the two values is multiplied by 0.738 to calculate the actual relative flow rate under these parameters: 0.68. Other values can be referenced.

[0056] 3. When the overall valve position is greater than 0.712 and less than or equal to 0.899, take the case where the overall valve position is 0.835 as an example. In the original parameter settings, the opening of GV3 is 0.206, and the y value obtained by substituting it into the above functional relationship is 0.718. In this case, GV1 and GV2 are fully open, so this value 0.718 is multiplied by (0.9349-0.738) and then 0.738 is added to calculate, and the actual relative flow rate under these parameters is 0.879. Other values can be referenced.

[0057] 4. When the total valve position is greater than 0.899, take the case where the total valve position is 0.960 as an example. In the original parameter setting, the opening of GV4 is 0.206, and the y value obtained by substituting it into the above functional relationship is 0.594. In this case, GV1, GV2, and GV3 are fully open, so this value 0.594 is multiplied by (1-0.9349) and then 0.9349 is added to calculate, and the actual relative flow rate under these parameters is 0.974. Other values can be referenced. TIFF0007725723000025.tif76170Theoretically, the total valve position command and relative flow rate after normalization are TIFF0007725723000026.tif6170, and the theoretical function and the actual curve are plotted on the same graph, see Figure 2.

[0058] For example, a comparison shows that when the overall valve position is 0.585, the corresponding valve opening needs to be corrected. As can be seen from Table 3, the relative flow rate obtained using the currently used parameter calculation is 0.68. Since the relative flow rate and the overall valve position command should theoretically be directly proportional to each other, the theoretical value is 0.585 and needs to be corrected. As can be seen from Table 2, when the overall valve position command is 0.585, only the first and second high-pressure control valves are in operation, so the first and second high-pressure control valves need to be corrected. Using the inverse function method, the first and second high-pressure control valve openings need to be corrected from 0.319 to 0.25. The correction methods for valve openings corresponding to other overall valve position commands are similar.

[0059] Strictly speaking, correction is possible as long as all points are not on the theoretical curve, i.e., the curve of direct proportionality. However, in practice, correction is generally made according to the minimum range, i.e., only points that deviate significantly from the theoretical curve are corrected. Therefore, in this embodiment, the point with the greatest deviation will be described as an example.

[0060] So far, the method for correcting sequence valve control parameters has been described.

[0061] The basic principles, main features, and advantages of the present invention have been shown and described above. Those skilled in the art will understand that the present invention is not limited by the above examples, and that the above examples and the description in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the present invention, and all such changes and modifications are included within the scope of the present invention that is intended to be protected. The scope that is intended to be protected by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for switching a coal-fired power generation unit from a sequence valve control mode that sequentially opens multiple high-pressure control valves to a valve control mode of a digital electro-hydraulic control system for a steam turbine, shutting off the primary frequency modulation control and AGC control of said coal-fired power generation unit, switching the coordinated control of said coal-fired power generation unit and furnace to manual, shutting off the automatic operation of fuel and automatic operation of oxygen supply of said coal-fired power generation unit, automatically operating the main steam temperature, feedwater and furnace pressure of said coal-fired power generation unit, and switching a single high-pressure control valve from 100 to 0% and 0 to 100% in single steps of 5%. a step disturbance is performed, and when one of the high pressure control valves is operating, all of the other high pressure control valves are open; after the operation of one of the high pressure control valves is completed, all of the high pressure control valves are kept fully open; then, in the final stage, the high pressure control valves are gradually closed in a reverse order to the way in which they are opened in the sequence valve mode in 5% steps until the high pressure control valve is fully opened; and the load, main steam pressure, pressure at the pressure adjustment stage, main steam temperature, and temperature after the pressure adjustment stage of the coal-fired power generation unit are recorded during the entire adjustment process; Step (2) of calculating the flow characteristic curve of each high-pressure control valve according to the Flugel equation using the data obtained in step (1); (3) in single valve control mode, calculate the normalized relative flow rate of the actual single valve, and fit the normalized relative flow rate of the actual single valve as y and the corresponding valve opening as x to obtain a high-order continuous function y=f(x); find the polygon function used in the single valve of said coal-fired power generation unit in the distributed control system; and use the high-order continuous function y=f(x) to correct the overall valve position command or valve opening; In the sequence valve control mode, there are a number of steps from full open to full closed for all high pressure control valves, and when the high pressure control valve is fully open, the number of inflection points that occurs in the process of sequentially closing the high pressure control valve in accordance with the closing order until the final fully open stage is a-1, and the relative flow rate y corresponding to the inflection points is ｍ and (4) calculating In the sequence valve control mode of the distributed control system, find the polygon function used for each high-pressure control valve, where Yqi is the discrete integrated valve position command and Xqi is the corresponding valve opening; The actual normalized relative flow rate of each high-pressure control valve is y, the corresponding valve opening is x, and a high-order continuous function y ｉ = f ｉ (x), where i is the i-th high pressure control valve; Relative flow rate y corresponding to the inflection point ｍ A method for correcting single valve and sequence valve parameters based on valve flow characteristics of a digital electro-hydraulic control system, comprising: calculating a correlation between the overall valve position and the relative flow rate based on the high-order continuous function y=f(x) of each high-pressure control valve and a polygon function; and correcting the overall valve position command or valve opening based on the correlation.

2. A method for correcting single valve and sequence valve parameters based on the valve flow characteristics of a digital electro-hydraulic control system as described in claim 1, characterized in that in step (1), during recording, the recording sampling interval is 1 s.

3. Specifically, step (2) comprises: The coal-fired power generation unit is under the i-th high pressure regulating valve opening degree j, j∈[0, 100%], and Correction is made based on the steam temperature before and after the high pressure regulating valve. Here, PT ｉｊ is the main steam pressure when the i-th high pressure control valve opening degree j, and is expressed in MPa. P1 ｉｊ is the pressure at the pressure adjustment stage when the i-th high pressure control valve opening degree j is reached, in units of MPa. TS ｉｊ is the main steam temperature when the i-th high pressure control valve is opened to j, in °C. T1 ｉｊ is the temperature after the pressure adjustment stage when the i-th high pressure control valve opening degree j, and is expressed in °C. Normalize the relative flow rate within the test range from 0 to 100%: Here, F Ｒｉｊ％ is the relative flow rate when the i-th high-pressure control valve opening degree is j, F Ｒｉ０ is the corrected steam pressure ratio when the i-th high-pressure control valve is at 0% valve opening, F Ｒｉ１００ is the corrected steam pressure ratio when the i-th high pressure control valve is 100% open, The method for correcting single valve and sequence valve parameters based on valve flow characteristics of a digital electro-hydraulic control system as claimed in claim 1, further comprising: drawing an ith high-pressure control valve flow characteristic curve based on the obtained relative flow rate.

4. In the step (3), calculating the actual normalized relative flow rate of the single valve specifically includes: where: is the actual normalized relative flow rate of a single valve, i is the number of high-pressure regulating valves, j is the high-pressure regulating valve opening, j∈[0, 100%], Find a polygon function used by a single valve of the coal-fired power generation unit in the distributed control system, in which Yn is a discrete integrated valve position command, Xn is a valve opening corresponding to Yn, and the actual normalized relative flow rate of the single valve is fitted as y and the corresponding valve opening as x to obtain a high-order continuous function y = f(x), Xn in the polygon function is substituted into the high-order continuous function after fitting to obtain the corrected overall valve position command Yn', or by the inverse function method x=f －１ 4. The method for correcting single valve and sequence valve parameters based on the valve flow characteristics of a digital electro-hydraulic control system according to claim 3, wherein Yn in the polygon function is substituted into a high-order continuous function according to (y) to obtain the corrected valve opening Xn'.

5. The method of step (4) specifically includes: In the sequence valve control mode, there are a number of steps from fully open to fully closed for all high pressure control valves, and when the high pressure control valve is fully open, the number of inflection points that occurs in the process of sequentially closing the high pressure control valves in the closing order until the final fully open stage is a-1, the inflection point number corresponding to the first high pressure control valve to be closed is m=1, the inflection point number corresponding to the second high pressure control valve to be closed is m=2, and so on, with the final inflection point number being m=a-1; Relative flow rate y corresponding to the inflection point ｍ Calculate In the formula, P ｍ is the load of the coal-fired power generation unit corresponding to the m-th inflection point, and P ｅ is the load of the coal-fired power generation unit when the high-pressure control valve is fully open, In the sequence valve control mode of the distributed control system, find the polygon function used for each high-pressure control valve, where Yqi is the discrete integrated valve position command and Xqi is the corresponding valve opening; Actual normalized relative flow rate F of each high pressure control valve Ｒｉｊ％ The high-order continuous function y ｉ = f ｉ (x), where i is the i-th high pressure control valve; Relative flow rate y corresponding to the inflection point ｍ ,According to the high-order continuous function y=f(x) of each high-pressure control valve and the polygon function, the correlation between the overall valve position and the relative flow rate is calculated and obtained, specifically:

1. Determine the overall valve position command and relative flow rate of each inflection point, i.e., find the overall valve position command of all inflection points from the polygon function, and match it with the relative flow rate corresponding to the calculated inflection point; 2. If the total valve position is within the range of [total valve position command corresponding to 0, a-1th inflection point], the total valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y ｉ value of all high pressure control valves that need to open within this range under that overall valve position. ｉ the average value is calculated and multiplied by the relative flow rate corresponding to the (a-1)th inflection point to obtain the actual relative flow rate corresponding to the total valve position; 3. If the total valve position is within the range of (total valve position command corresponding to the (a-1)th inflection point, total valve position command corresponding to the (a-2)th inflection point), the total valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y ｉ value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. ｉ the average value is calculated and multiplied by (the relative flow rate corresponding to the (a-2) inflection point - the relative flow rate corresponding to the (a-1) inflection point) + the relative flow rate corresponding to the (a-1) inflection point to obtain the actual relative flow rate corresponding to that overall valve position, and so on; 4. If the total valve position is within the range of (total valve position command corresponding to the first inflection point, 1), the total valve position is set as x and substituted into the high-order continuous function of each high-pressure control valve that needs to be opened within this range, and the corresponding y ｉ value, excluding the fully open high-pressure control valve, and then calculating the y value of all high-pressure control valves that need to be open within this range under that overall valve position. ｉ Average the values and multiply by (the relative flow rate corresponding to the first inflection point - the relative flow rate corresponding to the second inflection point) + the relative flow rate corresponding to the second inflection point to obtain the actual relative flow rate corresponding to the overall valve position; The method for correcting single valve and sequence valve parameters based on valve flow characteristics of a digital electro-hydraulic control system according to claim 3, characterized in that the overall valve position command or valve opening is then corrected based on the correlation.

6. A method for correcting single valve and sequence valve parameters based on the valve flow characteristics of a digital electro-hydraulic control system described in Claim 5, characterized in that the point in the contrast relationship where the deviation from the theoretical curve is greatest is corrected.

7. A data collection module configured to collect load, main steam pressure, pressure at pressure control stage, main steam flow rate, feedwater flow rate, main steam deheat water flow rate, main steam temperature, reheat steam temperature, steam drum pressure, and steam turbine total energy flow rate of a coal-fired power generation unit; a data processing module configured to calculate a flow characteristic curve of each high-pressure control valve using the Flugel equation based on the data collected by the data collection module; a parameter correction module for each high-pressure control valve in a single valve control mode, configured to calculate the normalized relative flow rate of the actual single valve, fit the normalized relative flow rate of the actual single valve as y and the corresponding valve opening as x, obtain a high-order continuous function y=f(x), find a polygon function to be used for the single valve of the coal-fired power generation unit in a distributed control system, and correct the overall valve position command or the valve opening using the high-order continuous function y=f(x); Relative flow rate y corresponding to the inflection point ｍ Calculate the polygon function used for each high-pressure control valve in the sequence valve control mode of the distributed control system, where Yqi is the discrete integrated valve position command, Xqi is the corresponding valve opening, and fit the actual normalized relative flow rate of each high-pressure control valve as y and the corresponding valve opening as x, and calculate the high-order continuous function y for each high-pressure control valve. ｉ = f ｉ (x), where i is the i-th high-pressure control valve, and the relative flow rate y corresponding to the inflection point ｍ and a parameter correction module for each high-pressure control valve in a sequence valve control mode, the parameter correction module being configured to calculate a correlation between the overall valve position and the relative flow rate based on a high-order continuous function y=f(x) and a polygon function for each high-pressure control valve, and to correct the overall valve position command or the valve opening based on the correlation.

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