WO2024120074A1

WO2024120074A1 - Method for correcting single-valve and sequential-valve parameters on the basis of deh valve flow characteristics

Info

Publication number: WO2024120074A1
Application number: PCT/CN2023/128612
Authority: WO
Inventors: 宋小龙; 刘友宽; 伍阳阳; 文天舒; 袁华宇
Original assignee: 云南电力试验研究院(集团)有限公司
Priority date: 2022-12-08
Filing date: 2023-10-31
Publication date: 2024-06-13
Also published as: CN115857571A

Abstract

The present invention relates to a method for correcting single-valve and sequential-valve parameters on the basis of DEH valve flow characteristics, and belongs to the technical field of controlling thermal automation in thermal power plants. The system comprises a data acquisition module, a data processing module, a parameter correction module for each high control valve in a single-valve control mode, and a parameter correction module for each high control valve in a sequential-valve control mode. The present invention provides control valve non-linear supplemental data for a steam turbine, and following DEH-controlled linearized correction, guarantees a steam turbine comprehensive valve position instruction change after a unit is loaded, and a linear corresponding change to a generated steam flow and the unit load, thereby improving the speed and stability of unit load control, preventing oscillation in unit load control, having the effect of promoting an increase in the control quality of unit AGC and primary frequency modulation, and being of great significance to the safe, stable, economical, and reliable operation of a thermal power generation unit.

Description

Method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics

Technical Field

The invention belongs to the technical field of thermal automation control of thermal power plants, and in particular relates to a method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics.

Background technique

With the proposal of the "dual carbon" goal, a new power system with wind power and photovoltaics as the main body is being constructed. Affected by the volatility and uncertainty of wind power and photovoltaics themselves, large-scale new energy grid connection has brought many problems, the most prominent of which is the frequency problem. The frequency problem caused by wind power and photovoltaic grid connection is caused by their own output characteristics. On the one hand, volatility and uncertainty are, on the other hand, their rotational inertia is insufficient. After adjustment, there is a problem of drooping adjustment, which will cause the frequency to deteriorate further. As a high-quality frequency regulation resource, thermal power units can basically respond in place in about 30 seconds, and can rely on their large rotational inertia to ensure a high frequency regulation effect.

Thermal power units can play a good "ballast stone" role in the new power system, and are also an indispensable part of the current new power system construction. However, the valve characteristic curves of most units have been continued to use the characteristic curves formulated when the turbine leaves the factory. They have not considered that during the overhaul of the unit, each power generation company has overhauled the valves of the turbine, and the valve stroke has been adjusted to some extent, resulting in changes in the flow characteristics of the valve. The characteristic curves have not been tested and corrected, and the original characteristic curves have been continued to be used. This makes the valve flow characteristic curve used in the DCS inconsistent with the actual valve flow characteristic. The comprehensive valve position command changes of the unit and the generated steam flow and unit load show a large nonlinearity, which greatly affects the primary frequency regulation response rate and regulation effect of the thermal power unit. Re-finding the DEH valve flow characteristics and correcting the control parameters in the single valve and sequence valve are of great significance to improving the primary frequency regulation capability of the thermal power unit and thus ensuring the safe and stable operation of the new power system. Therefore, how to overcome the shortcomings of the existing technology is an urgent problem to be solved in the field of thermal automation control technology of thermal power plants.

Summary of the invention

The valve flow characteristic curve used in the DCS is inconsistent with the actual valve flow characteristic. The comprehensive valve position command change of the unit is nonlinear with the generated steam flow and the unit load, which greatly affects the primary frequency regulation response rate and regulation effect of the thermal power unit. This problem has not been solved. The purpose of the present invention is to solve the deficiencies of the prior art and provide a method for correcting the parameters of a single valve and a sequential valve based on the DEH valve flow characteristic. By experimentally analyzing the unit DEH valve flow characteristic, a valve flow characteristic curve is established, and the control parameters in the single valve and the sequential valve are corrected, so that the comprehensive valve position command change of the unit is nearly linear with the generated steam flow and the unit load.

To achieve the above purpose, the technical solution adopted by the present invention is as follows:

A method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics, comprising the following steps:

Step (1), data acquisition: the unit is switched to DEH valve control mode, the primary frequency modulation control of the unit is cut off, the AGC control of the unit is cut off, the machine-boiler coordinated control is switched to manual, the unit fuel is cut off automatically, the air supply oxygen is cut off automatically, the unit main steam temperature is automatically, the water supply is automatically, and the furnace pressure is automatically. A single high-pressure regulating valve is subjected to a single-step 5% step disturbance of 100-0% and 0-100%. When a certain regulating valve is actuated, the other regulating valves are opened. After the single high-pressure regulating valve is actuated, all regulating valves are kept fully open. Then, according to a 5% step, the regulating valves are gradually closed in the reverse order of the sequence valve input until the last stage regulating valve is kept fully open. The unit load, the main steam pressure before the machine, the regulating stage pressure, the main steam temperature and the temperature after the regulating stage are recorded during the entire regulation process.

Step (2), flow characteristic curve calculation: using the data obtained in step (1), the flow characteristic curve of each high-pressure valve is calculated according to the Flugel formula;

Step (3), parameter correction of each high-pressure valve in the single-valve control mode: Under the single-valve control mode, calculate the actual single-valve normalized relative flow rate; take the actual single-valve normalized relative flow rate as y, and fit it with the corresponding valve opening as x to obtain a high-order continuous function y=f(x); search the broken line function used by the current unit single valve in the DCS; use the high-order continuous function y=f(x) to correct the comprehensive valve position instruction or valve opening;

Step (4), parameter correction of each high-pressure regulating valve in the sequential valve control mode: Under the sequential valve control mode, all regulating valves have a total of a steps from fully closed to fully open; when the valve is fully open, the number of inflection points generated during the process of closing the valves in sequence in accordance with the closing sequence to the last stage of full opening is a-1, and the relative flow _ym corresponding to the inflection point is calculated;

Find the broken line function used by each valve in the sequential valve control mode in the DCS. In this function, Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening;

The normalized relative flow rate of each high-speed valve is y, and the corresponding valve opening is x for fitting, so as to obtain the high-order continuous function of each high-speed valve y _i = _fi (x); i is the ith high-speed valve;

Based on the relative flow _ym corresponding to the inflection point and the high-order continuous function y=f(x) and the broken line function of each high-pressure valve, the comparison relationship between the comprehensive valve position and the relative flow is calculated; based on the comparison relationship, the comprehensive valve position instruction or the valve opening is corrected.

Furthermore, preferably, in step (1), when recording, the recording sampling interval is 1 s.

Further, preferably, step (2) is specifically:

When the opening degree of high pressure regulating valve of unit i is j, j∈[0, 100%], the steam pressure ratio before and after the high pressure regulating valve is ε _ij :

Corrected according to the steam temperature before and after the high-pressure regulating valve, the corrected steam pressure ratio ε'_ij;

Let F _Rij =f(PT _ij ,P1 _ij ,TS _ij ,T1 _ij );

Among them, PT _ij is the main steam pressure in front of the machine when the opening of high-pressure valve No. i is j, in MPa;

P1 _ij is the regulating stage pressure when the opening of high-pressure regulating valve No. i is j, in MPa;

TS _ij is the main steam temperature before the machine when the opening of high-speed control valve No. i is j, in °C;

T1 _ij is the temperature after the adjustment stage when the opening of high-pressure door No. i is j, in ℃.

The relative flow rate within the test range is normalized from 0 to 100%:

F _Rij% = (F _Rij - F _Ri0 ) / (F _Ri100 - F _Ri0 )

Among them, F _Rij% is the relative flow rate when the opening of high-pressure valve No. i is j;

F _Ri0 is the corrected steam pressure ratio of high-pressure regulating valve No. i when the valve opening is 0%;

F _Ri100 is the corrected steam pressure ratio of high-pressure valve No. i when the valve opening is 100%;

Based on the relative flow obtained, draw the flow characteristic curve of high-pressure regulating valve No. i.

Further, preferably, in step (3), the actual single valve normalized relative flow rate is calculated, specifically:

Where _{FR single valve j%} is the actual single valve normalized relative flow rate;

i is the number of high-pressure regulating valves; j is the opening of the high-pressure regulating valve, (j∈[0, 100%]);

Find the broken line function used by the current unit single valve in the DCS. In this function, Yn is the discrete comprehensive valve position instruction, and Xn is the valve opening corresponding to Yn; the actual single valve normalized relative flow F _{R single valve j%} is y, and the corresponding valve opening is x for fitting to obtain the high-order continuous function y=f(x);

Substitute Xn in the broken line function into the fitted high-order continuous function to obtain the corrected comprehensive valve position command Yn'; or substitute Yn in the broken line function into the high-order continuous function through the inverse function method x=f ^-1 (y) to obtain the corrected valve opening Xn'.

Further, preferably, the specific method of step (4) is:

Under the sequential valve control mode, all the control valves have a steps from fully closed to fully open; In this case, the number of inflection points generated during the process of closing the valves in sequence until the last stage of full opening is a-1. The inflection point corresponding to the first closed valve is numbered m=1, the inflection point corresponding to the second closed valve is numbered m=2, and so on. The last inflection point is numbered m=a-1.

Calculate the relative flow y _m corresponding to the inflection point;

Where _Pm is the unit load corresponding to the mth inflection point, and Pe _is the unit load when the valve is fully open.

The actual normalized relative flow rate F _Rij% of each high-speed valve is y, and the corresponding valve opening is x for fitting, so as to obtain the high-order continuous function y _i = _fi (x) of each high-speed valve; i is the ith high-speed valve;

Based on the relative flow _ym corresponding to the inflection point and the high-order continuous function y=f(x) and the broken line function of each high-pressure valve, the comparison relationship between the comprehensive valve position and the relative flow is calculated; specifically:

1. Determine the comprehensive valve position command and relative flow rate of each inflection point, that is, find the comprehensive valve position command of all inflection points from the broken line function, and correspond it with the relative flow rate corresponding to the calculated inflection point;

2. If the comprehensive valve position is within the range of [0, the comprehensive valve position instruction corresponding to the a-1th inflection point], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment valve that needs to be opened within this range to obtain the corresponding _yi value, and then obtain the average of the _yi values of all high-adjustment valves that need to be opened within this range under the comprehensive valve position and multiply it by the relative flow corresponding to the a-1th inflection point, that is, to obtain the actual relative flow corresponding to the comprehensive valve position;

3. If the comprehensive valve position is within the range of (comprehensive valve position command corresponding to the a-1th inflection point, comprehensive valve position command corresponding to the a-2th inflection point], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment door that needs to be opened within this range to obtain the corresponding _yi value, except for the high-adjustment door that has been fully opened. Then, the average _yi value of all high-adjustment doors that need to be opened within this range under the comprehensive valve position is obtained and multiplied by (relative flow corresponding to the a-2th inflection point - relative flow corresponding to the a-1th inflection point) + relative flow corresponding to the a-1th inflection point, that is, the actual relative flow corresponding to the comprehensive valve position is obtained. And so on.

4. If the comprehensive valve position is within the range of (comprehensive valve position command corresponding to the first inflection point, 1], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment door that needs to be opened within this range to obtain the corresponding _yi value, except for the high-adjustment door that has been fully opened. Then, the average _yi value of all high-adjustment doors that need to be opened within this range under the comprehensive valve position is obtained and multiplied by (relative flow corresponding to the first inflection point - relative flow corresponding to the second inflection point) + relative flow corresponding to the second inflection point, that is, the comprehensive valve position corresponding to The actual relative flow rate of the response;

Then, based on the comparison relationship, the comprehensive valve position command or the valve opening is corrected.

Furthermore, it is preferred that the point in the control relationship that deviates the most from the theoretical curve be corrected.

The present invention also provides a system for correcting single valve and sequence valve parameters based on DEH valve flow characteristics. The method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics includes:

The data acquisition module is used to collect the unit load, main steam pressure before the unit, regulating stage pressure, main steam flow, feed water flow, main steam desuperheating water flow, main steam temperature, reheat steam temperature, drum pressure and total energy flow of the steam turbine during the test;

A data processing module is used to calculate the flow characteristic curve of each high-pressure valve using the Flugel formula according to the data collected by the data collection module;

The parameter correction module of each high-adjusting valve of the single-valve control mode is used to calculate the actual single-valve normalized relative flow rate; the actual single-valve normalized relative flow rate is y, and the corresponding valve opening is x for fitting to obtain a high-order continuous function y=f(x); the broken line function used by the current unit single valve is searched in the DCS; the comprehensive valve position instruction or valve opening is corrected using the high-order continuous function y=f(x);

The parameter correction module of each high-adjustable valve in the sequential valve control mode is used to calculate the relative flow _ym corresponding to the inflection point; the broken line function used by each adjusting valve in the sequential valve control mode is searched in the DCS, in which Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening; the actual normalized relative flow of each high-adjustable valve is y, and the corresponding valve opening is x for fitting to obtain the high-order continuous function _yi = _fi (x) of each high-adjustable valve; i is the ith high-adjustable valve; based on the relative flow _ym corresponding to the inflection point and the high-order continuous function y = f(x) of each high-adjustable valve, and the broken line function, the comparison relationship between the comprehensive valve position and the relative flow is calculated; based on the comparison relationship, the comprehensive valve position instruction or the valve opening is corrected.

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

Aiming at the problem that the valve flow characteristic curve used in the current DCS (Distributed Control System) is inconsistent with the actual valve flow characteristic, the comprehensive valve position command change of the unit and the generated steam flow and unit load show a large nonlinearity, which causes serious over- or under-regulation of the primary frequency regulation, the coordinated control system produces a reverse regulation effect, and even causes low-frequency oscillation accidents in the power grid, the present invention proposes a method for correcting the parameters of single valves and sequential valves based on the valve flow characteristics of DEH (Digital Electro-Hydraulic, steam turbine digital electro-hydraulic control system)

The method of the present invention is based on field test data, and the results obtained are more targeted and practical, and can well fit the actual situation 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 method used is relative flow calculation method and curve fitting, which is clearer than other methods. It is clear, intuitive, time-saving, and applicable to different thermal power units, with universal applicability.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of the arrangement of the valve nozzles of a steam turbine;

FIG2 is a diagram showing the theoretical and actual corresponding relationship between the normalized integrated valve position command and the relative flow rate;

FIG3 is a schematic diagram of the structure of a system for correcting single valve and sequential valve parameters based on DEH valve flow characteristics according to the present invention; wherein the direction of the arrow is the direction of data or signal.

Detailed ways

The present invention is further described in detail below in conjunction with embodiments.

Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

Example 1

Example 2

Based on the relative flow _ym corresponding to the inflection point and the high-order continuous function y=f(x) and the broken line function of each high-profile gate The numbers are calculated to obtain the comparison relationship between the comprehensive valve position and the relative flow rate; based on the comparison relationship, the comprehensive valve position instruction or the valve opening is corrected.

In step (1), when recording, the recording sampling interval is 1s.

Step (2) is specifically as follows:

Let F _Rij =f(PT _ij ,P1 _ij ,TS _ij ,T1 _ij );

The relative flow rate within the test range is normalized from 0 to 100%:
F _Rij% = (F _Rij - F _Ri0 ) / (F _Ri100 - F _Ri0 )

In step (3), the actual single valve normalized relative flow rate is calculated as follows:

Find the broken line function used by the current unit single valve in the DCS. In this function, Yn is the discrete integrated valve position instruction, and Xn is the valve opening corresponding to Yn. The actual single valve normalized relative flow rate F _{R single valve j%} is y, and the corresponding valve opening is fitted as x to obtain a high-order continuous function y = f(x);

The specific method of step (4) is:

Under the sequential valve control mode, there are a total of a steps for all valves from fully closed to fully open. When the valve is fully open, the number of inflection points generated during the process of closing the valves in sequence until the last stage of full opening is a-1. The inflection point corresponding to the first closed valve is numbered m=1, the inflection point corresponding to the second closed valve is numbered m=2, and so on. The last inflection point is numbered m=a-1.

Calculate the relative flow y _m corresponding to the inflection point;

Find the broken line function used by each valve in the sequential valve control mode in DCS. In this function, Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening;

3. If the comprehensive valve position is within the range of (comprehensive valve position command corresponding to the a-1th inflection point, comprehensive valve position command corresponding to the a-2th inflection point], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment valve that needs to be opened within this range to obtain the corresponding _yi value, except for the high-adjustment valve that has been fully opened. Then, the average _yi value of all high-adjustment valves that need to be opened within this range under the comprehensive valve position is obtained and multiplied by (relative flow corresponding to the a-2th inflection point - relative flow corresponding to the a-1th inflection point) + relative flow corresponding to the a-1th inflection point The corresponding relative flow rate is obtained, that is, the actual relative flow rate corresponding to the comprehensive valve position is obtained; and so on;

4. If the comprehensive valve position is within the range of (comprehensive valve position command corresponding to the first inflection point, 1], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment valve that needs to be opened within this range to obtain the corresponding _yi value, except for the high-adjustment valve that has been fully opened. Then, the average _yi value of all high-adjustment valves that need to be opened within this range under the comprehensive valve position is obtained and multiplied by (relative flow corresponding to the first inflection point - relative flow corresponding to the second inflection point) + relative flow corresponding to the second inflection point, that is, the actual relative flow corresponding to the comprehensive valve position is obtained.

Correct the point in the control relationship that deviates the most from the theoretical curve.

As shown in FIG3 , a system for correcting single valve and sequential valve parameters based on DEH valve flow characteristics adopts the method for correcting single valve and sequential valve parameters based on DEH valve flow characteristics, including:

The data acquisition module 101 is used to collect the unit load, main steam pressure before the unit, regulating stage pressure, main steam flow, feed water flow, main steam desuperheating water flow, main steam temperature, reheat steam temperature, drum pressure and total energy flow of the steam turbine during the test;

The data processing module 102 is used to calculate the flow characteristic curve of each high-pressure valve using the Flugel formula according to the data collected by the data collection module;

The parameter correction module 103 of each high-pressure valve of the single valve control mode is used to calculate the actual single valve normalized relative flow rate; the actual single valve normalized relative flow rate is y, and the corresponding valve opening is x for fitting to obtain a high-order continuous function y=f(x); the broken line function used by the current unit single valve is searched in the DCS; the comprehensive valve position instruction or valve opening is corrected using the high-order continuous function y=f(x);

The parameter correction module 104 of each high-adjustable valve in the sequential valve control mode is used to calculate the relative flow _ym corresponding to the inflection point; the broken line function used by each adjusting valve in the sequential valve control mode is searched in the DCS, in which Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening; the actual normalized relative flow of each high-adjustable valve is y, and the corresponding valve opening is x for fitting to obtain the high-order continuous function _yi = _fi (x) of each high-adjustable valve; i is the ith high-adjustable valve; based on the relative flow _ym corresponding to the inflection point and the high-order continuous function y = f(x) of each high-adjustable valve, and the broken line function, the comparison relationship between the comprehensive valve position and the relative flow is calculated; based on the comparison relationship, the comprehensive valve position instruction or the valve opening is corrected.

Example 3

(I) Conduct field tests. Bring the active output of the test unit to a load of Pe when the valve is fully open, switch the unit to DEH valve control mode, cut off the primary frequency modulation control of the unit, and cut off the AGC control of the unit. The coordinated control of the machine and boiler is switched to manual, the unit fuel is automatically cut off, the air supply oxygen is automatically cut off, the unit main steam temperature is automatically put into operation, the water supply is automatically put into operation, and the furnace pressure is automatically put into operation. A single high-pressure regulating valve is subjected to a single-step 5% step disturbance of 100-0% and 0-100%. When a certain regulating valve is actuated, the other regulating valves are opened. After the action of a single high-pressure regulating valve is completed, all regulating valves are kept fully open, and then the regulating valves are gradually closed according to the reverse order of the sequence valve input according to the 5% step until the last stage of the regulating valve is kept fully open. Important parameters such as unit load P, main steam pressure before the machine PT, regulating stage pressure P1, main steam temperature TS, and temperature after the regulating stage T1 during the adjustment process are recorded.

(II) Select a numerical calculation method suitable for the flow characteristics of the DEH valve, and take the steam pressure ratio ε _ij before and after the high-pressure regulating valve when the unit is at the opening j (j∈[0, 100%]) of the high-pressure regulating valve No. i:

Different boundary conditions should be corrected according to the steam temperature before and after the high-pressure regulating valve, and the corrected steam pressure ratio is ε' _ij .

Let F _Rij =f(PT _ij ,P1 _ij ,TS _ij ,T1 _ij ).

F _Ri100 is the corrected steam pressure ratio of high-pressure regulating valve No. i when the valve opening is 100%.

(III) Parameter correction of each high-pressure regulating valve in the single valve control mode. In the single valve operation mode, steam passes through the high-pressure regulating valve and the nozzle chamber and enters the regulating stage moving blades at 360°C. The regulating stage blades are heated evenly, which effectively improves the stress distribution of the regulating stage blades, allowing the unit to change the load more quickly. At this time, all regulating valves are partially opened with the same opening (for example, the opening of each valve in the single valve mode is the same, all 50%). In this case, the actual single valve standardized relative flow is:

Where _{FR single valve j%} is the actual single valve normalized relative flow rate; i is the number of high-pressure regulating valves; j is the opening of the high-pressure regulating valve, (j∈[0, 100%]);

Find the broken line function used by the current single valve of the unit in the DCS. In this function, the important parameters are the discrete comprehensive valve position command Yn and its corresponding valve opening Xn. Here, Yn and Xn are both normalized values.

In Matlab, call the polyfit function and the polyval function to fit the discrete _{FR single valve j%} into a high-order continuous function y=f(x). Substitute the normalized Xn into the above fitted function to obtain the corrected comprehensive valve position command Yn'. Alternatively, through the inverse function method x=f ^-1 (y), substitute Yn into the solution of the high-order continuous function to obtain the corrected valve opening Xn'.

(IV) Modify the parameters of each high-pressure valve controlled by the sequential valve.

Under the sequential valve control mode, the regulating valves are opened in sequence according to the pre-set sequential valve flow characteristic curves of each valve. For example, the 300MW unit produced by Harbin Steam Turbine Plant is equipped with 6 high-pressure regulating valves: the opening sequence is GV4 and GV5 open at the same time → GV6 → GV3 → GV2 → GV1 open one by one, and the closing sequence is opposite. Definition: Under the sequential valve control mode, all regulating valves have a total of a steps from fully closed to fully open. For example, a in the above example is 5. Combined with the field test, when the valve is fully open, the valves are closed in sequence according to the closing sequence until the last stage of full opening. In this process, the number of inflection points generated is a-1. Define the inflection point number m, the first closed valve corresponds to the inflection point number m=1, and the last inflection point number is m=a-1. Calculate the following formula:

In the DCS, find the broken line function of each regulating valve under the sequential valve control mode. In this function, the important parameters are the discrete comprehensive valve position command Yqi and its corresponding valve opening Xqi. Here, Yqi and Xqi are both normalized values.

In Matlab, the polyfit function and the polyval function are called, and the actual normalized relative flow F _Rij% of each high-pressure valve is y, and the corresponding valve opening is x for fitting, so as to obtain the high-order continuous function y _i = _fi (x) of each high-pressure valve; i is the ith high-pressure valve;

Based on the relative flow _ym corresponding to the inflection point and the high-order continuous function y=f(x) and the broken line function of each high-profile gate Calculate and obtain the relationship between the comprehensive valve position and relative flow rate; specifically:

Applications

(I) Carry out field tests. Take a 300MW coal-fired unit as an example. The turbine manufacturer and model are Dongfang Steam Turbine Factory/N300-16.7/537/537. The arrangement of the turbine valve nozzle is shown in Figure 1. There are 4 high-pressure valves. The opening sequence in the valve sequence mode is GV1 and GV2 are opened at the same time → GV3 → GV4.

Under the test conditions, the load is basically stable at about 250MW when the valve is fully open. The unit is switched to DEH valve control mode, the primary frequency modulation control of the unit is cut off, the AGC control of the unit is cut off, the boiler-machine coordination control is switched to manual, the unit fuel automatic control is cut off, the air supply oxygen automatic control is cut off, the unit main steam temperature automatic control, water supply automatic control, furnace pressure automatic control are put into operation, and a single high-pressure valve is subjected to a single-step 5% step disturbance of 100-0% and 0-100%.

The collected data is as follows: PT ₁ = [11.899 11.8343 11.8025 11.7816 11.739 11.7289 11.7083 11.6877 11.6877 11.6701 11.6701 11.6701 11.6701 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].

P1 ₁ = [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 10.4321 10.4168 10.3809 10.3289 10.2249 10.0806 9.8572 9.5723 9.4273 9.3225].

_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].

T1 ₁ = [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].

The above is the data collected using high-profile door No. 1 as an example. The data collected by the other three high-profile doors are similar and will not be repeated here.

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

(ii) By using the formula, we can obtain _FR1j% = [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., it starts from 100 and decreases to 0 at intervals of 5, with a total of 21 numbers, and the following are similar. _FR2j% ＝[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].

_FR3j% ＝[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]. _FR4j% ＝[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].

(III) Correct the single valve control parameters.

_{The FR single valve j%} is calculated by the formula: [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].

See Table 1 for the standardized control parameters of the original single valve in the DCS.

Table 1

Through the matlab fitting function, for example, a 5th-order polynomial function is selected for fitting, and the functional relationship is obtained as follows:
y=-285.1282x ⁵ +488.5315x ⁴ -303.2191x ³ +75.8579x ² -3.3862x+0.007972.

For example, when the valve opening is 0.228, the corrected integrated valve position instruction should be 0.73; or when the integrated valve position instruction is 0.829, the corrected valve opening should be 0.378; or after finding the functional relationship, the entire broken line function can also be modified according to customization.

Based on the above principles, the single valve control parameters can be modified as needed.

(IV) Correction of the control parameters of the sequential valve.

According to the experimental data, there are two inflection points. The first inflection point corresponds to y1=237.35/253.86=0.9349, and the second inflection point corresponds to y2=187.35/253.86=0.738.

Find the normalized parameters of the sequential valve control currently used in the DCS, see Table 2.

Table 2

In Table 2, the first inflection point actually used is 0.899, and the second is 0.712, which are close to the inflection points measured in the field test, that is, the first inflection point is 0.9349, and the second is 0.738. They also meet the overlap requirements and can continue to be used. They are also in line with the parameter usage of most power plants. They can also be directly adopted by the calculation in this paper, that is, replace 0.712 in the GV3 comprehensive valve position instruction column in Table 2 with 0.738, and replace 0.899 in GV4 with 0.9349.

The discrete data of step (2) is fitted by MATLAB and obtained as follows:
y ₁ = -323.0769x ₁ ⁵ +550.7925x ₁ ⁴ -339.4231x ₁ ³ +84.6501x ₁ ² -4.1412x ₁ +0.0095559
y ₂ = -301.0256x ₂ ⁵ +510.1748x ₂ ⁴ -315.1288x ₂ ³ +79.1236x ₂ ² -3.753x ₂ +0.0095332
y ₃ = -393.8462x ₃ ⁵ +621.958x ₃ ⁴ -354.9324x ₃ ³ +80.9211x ₃ ² -2.862x ₃ +0.0025245
y ₄ =-123.5897x ₄ ⁵ +273.8345x ₄ ⁴ -205.2558x ₄ ³ +59.2105x ₄ ² -2.8227x ₄ +0.0099773

Referring to the above table and the inflection point data, the opening of each valve is substituted into the above formula to calculate the corresponding relative flow rate, and then the comparison table between the relative flow rate and the comprehensive valve position instruction under the currently used sequential valve parameters can be obtained as shown in Table 3.

The specific calculation process is as follows:

1. Determine the comprehensive valve position command and relative flow rate of the two inflection points, that is, when the comprehensive valve position command is 0.712, the relative flow rate is 0.738, and when the comprehensive valve position command is 0.712, the relative flow rate is 0.9349.

2. When the comprehensive valve position is less than or equal to 0.712, take the comprehensive valve position instruction of 0.585 as an example. In the original parameter setting, the openings of GV1 and GV2 are both 0.319. Substitute the two y values into the above function relationship to obtain 0.9207 and 0.923 respectively. The average of the two values is multiplied by 0.738, and the actual relative flow rate under this parameter can be calculated to be 0.68. The remaining values are calculated for reference.

3. When the comprehensive valve position is greater than 0.712 and less than or equal to 0.899, take the comprehensive valve position of 0.835 as an example. In the original parameter setting, the opening of GV3 is 0.206. Substituting the above function relationship into the y value is 0.718. In this case, GV1 and GV2 are fully open, so the value 0.718 is multiplied by (0.9349-0.738) and then added to 0.738, and the actual relative flow rate under this parameter can be calculated to be 0.879. The remaining values are calculated for reference.

4. When the comprehensive valve position is greater than 0.899, take the comprehensive valve position of 0.960 as an example. In the original parameter setting, the opening of GV4 is 0.206. Substituting the above function relationship, the y value is 0.594. In this case, GV1, GV2, and GV3 are fully open, so the value 0.594 is multiplied by (1-0.9349) and then added to 0.9349 to calculate The actual relative flow rate under this parameter is 0.974, and the remaining values are calculated for reference.

table 3

Theoretically, after normalization, the integrated valve position command and relative flow rate should be in the relationship of y=x, x∈[0,1]. The theoretical function and the actual curve are plotted on the same graph, as shown in Figure 2.

For example, after comparison, it is found that the valve opening corresponding to the integrated valve position of 0.585 needs to be corrected, because the relative flow rate calculated by the parameters currently used in Table 3 is 0.68. In theory, the relative flow rate and the integrated valve position instruction should be in direct proportion, so in theory it should be 0.585 and needs to be corrected. From Table 2, it can be seen that when the integrated valve position instruction is 0.585, only the No. 1 and No. 2 high-adjustment gates are actuated, so the No. 1 and No. 2 high-adjustment gates need to be corrected. The inverse function method can be used to solve that the valve opening of the No. 1 and No. 2 high-adjustment gates should be corrected from 0.319 to 0.25. The correction method of the valve opening corresponding to other integrated valve position instructions is similar.

Strictly speaking, all points can be corrected as long as they are not on the theoretical curve, that is, the proportional relationship curve. However, on site, corrections are generally made within the minimum range, that is, corrections are made only when there is a significant deviation from the points on the theoretical curve. Therefore, the point with the largest deviation is used for demonstration in the example.

So far, a method for correcting the control parameters of a sequential valve has been given.

The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

A method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics, characterized in that it comprises the following steps:

Step (1), data acquisition: the unit is switched to DEH valve control mode, the primary frequency modulation control of the unit is cut off, the AGC control of the unit is cut off, the machine-boiler coordinated control is switched to manual, the unit fuel is cut off automatically, the air supply oxygen is cut off automatically, the unit main steam temperature is automatically, the water supply is automatically, and the furnace pressure is automatically. A single high-pressure regulating valve is subjected to a single-step 5% step disturbance of 100-0% and 0-100%. When a certain regulating valve is actuated, the other regulating valves are opened. After the single high-pressure regulating valve is actuated, all regulating valves are kept fully open. Then, according to a 5% step, the regulating valves are gradually closed in the reverse order of the sequence valve input until the last stage regulating valve is kept fully open. The unit load, the main steam pressure before the machine, the regulating stage pressure, the main steam temperature and the temperature after the regulating stage are recorded during the entire regulation process.

Step (2), flow characteristic curve calculation: using the data obtained in step (1), the flow characteristic curve of each high-pressure valve is calculated according to the Flugel formula;

Step (3), parameter correction of each high-pressure valve in the single-valve control mode: Under the single-valve control mode, calculate the actual single-valve normalized relative flow rate; take the actual single-valve normalized relative flow rate as y, and fit it with the corresponding valve opening as x to obtain a high-order continuous function y=f(x); search the broken line function used by the current unit single valve in the DCS; use the high-order continuous function y=f(x) to correct the comprehensive valve position instruction or valve opening;

Step (4), parameter correction of each high-pressure regulating valve in the sequential valve control mode: Under the sequential valve control mode, all regulating valves have a total of a steps from fully closed to fully open; when the valve is fully open, the number of inflection points generated during the process of closing the valves in sequence in accordance with the closing sequence to the last stage of full opening is a-1, and the relative flow ym corresponding to the inflection point is calculated;

Find the broken line function used by each valve in the sequential valve control mode in the DCS. In this function, Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening;

The normalized relative flow rate of each high-speed valve is y, and the corresponding valve opening is x for fitting, so as to obtain the high-order continuous function of each high-speed valve y i = fi (x); i is the ith high-speed valve;

Based on the relative flow ym corresponding to the inflection point and the high-order continuous function y=f(x) and the broken line function of each high-pressure valve, the comparison relationship between the comprehensive valve position and the relative flow is calculated; based on the comparison relationship, the comprehensive valve position instruction or the valve opening is corrected.
The method for correcting single valve and sequential valve parameters based on DEH valve flow characteristics according to claim 1 is characterized in that, in step (1), when recording, the recording sampling interval is 1s.
The method for correcting single valve and sequential valve parameters based on DEH valve flow characteristics according to claim 1 is characterized in that step (2) specifically comprises:

When the opening degree of high pressure regulating valve of unit i is j, j∈[0,100％], the steam before and after the high pressure regulating valve is Steam pressure ratio ε ij :

Corrected according to the steam temperature before and after the high-pressure regulating valve, the corrected steam pressure ratio ε'ij;

Let F Rij =f(PT ij ,P1 ij ,TS ij ,T1 ij );

Among them, PT ij is the main steam pressure in front of the machine when the opening of high-pressure valve No. i is j, in MPa;

P1 ij is the regulating stage pressure when the opening of high-pressure regulating valve No. i is j, in MPa;

TS ij is the main steam temperature before the machine when the opening of high-speed control valve No. i is j, in °C;

T1 ij is the temperature after the adjustment stage when the opening of high-pressure door No. i is j, in ℃.

The relative flow rate within the test range is normalized from 0 to 100%:
F Rij% = (F Rij - F Ri0 ) / (F Ri100 - F Ri0 )

Among them, F Rij% is the relative flow rate when the opening of high-pressure valve No. i is j;

F Ri0 is the corrected steam pressure ratio of high-pressure regulating valve No. i when the valve opening is 0%;

F Ri100 is the corrected steam pressure ratio of high-pressure valve No. i when the valve opening is 100%;

Based on the relative flow obtained, draw the flow characteristic curve of high-pressure regulating valve No. i.
The method for correcting single valve and sequential valve parameters based on DEH valve flow characteristics according to claim 3 is characterized in that, in step (3), the actual single valve normalized relative flow is calculated, specifically:

Where FR single valve j% is the actual single valve normalized relative flow rate; i is the number of high-pressure regulating valves; j is the opening of the high-pressure regulating valve, j∈[0, 100%];

Find the broken line function used by the current unit single valve in the DCS. In this function, Yn is the discrete comprehensive valve position instruction, and Xn is the valve opening corresponding to Yn; the actual single valve normalized relative flow F R single valve j% is y, and the corresponding valve opening is x for fitting to obtain the high-order continuous function y=f(x);

Substitute Xn in the broken line function into the fitted high-order continuous function to obtain the corrected comprehensive valve position command Yn'; or substitute Yn in the broken line function into the high-order continuous function through the inverse function method x=f -1 (y) to obtain the corrected valve opening Xn'.
The method for correcting single valve and sequential valve parameters based on DEH valve flow characteristics according to claim 3 is characterized in that the specific method of step (4) is:

Under the sequential valve control mode, there are a total of a steps for all valves from fully closed to fully open. When the valve is fully open, the number of inflection points generated during the process of closing the valves in sequence until the last stage of full opening is a-1. The inflection point corresponding to the first closed valve is numbered m=1, the inflection point corresponding to the second closed valve is numbered m=2, and so on. The last inflection point is numbered m=a-1.

Calculate the relative flow y m corresponding to the inflection point;

Where Pm is the unit load corresponding to the mth inflection point, and Pe is the unit load when the valve is fully open.

Find the broken line function used by each valve in the sequential valve control mode in the DCS. In this function, Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening;

The actual normalized relative flow rate F Rij% of each high-speed valve is y, and the corresponding valve opening is x for fitting, so as to obtain the high-order continuous function y i = fi (x) of each high-speed valve; i is the ith high-speed valve;

Based on the relative flow ym corresponding to the inflection point and the high-order continuous function y=f(x) and broken line function of each high-pressure valve, the comparison relationship between the comprehensive valve position and the relative flow is calculated; specifically:

1. Determine the comprehensive valve position command and relative flow rate of each inflection point, that is, find the comprehensive valve position command of all inflection points from the broken line function, and correspond it with the relative flow rate corresponding to the calculated inflection point;

2. If the comprehensive valve position is within the range of [0, the comprehensive valve position instruction corresponding to the a-1th inflection point], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment valve that needs to be opened within this range to obtain the corresponding yi value, and then obtain the average of the yi values of all high-adjustment valves that need to be opened within this range under the comprehensive valve position and multiply it by the relative flow corresponding to the a-1th inflection point, that is, to obtain the actual relative flow corresponding to the comprehensive valve position;

3. If the comprehensive valve position is within the range of (comprehensive valve position command corresponding to the a-1th inflection point, comprehensive valve position command corresponding to the a-2th inflection point], substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment door that needs to be opened within this range to obtain the corresponding yi value, except for the high-adjustment door that has been fully opened. Then, the average yi value of all high-adjustment doors that need to be opened within this range under the comprehensive valve position is obtained and multiplied by (relative flow corresponding to the a-2th inflection point - relative flow corresponding to the a-1th inflection point) + relative flow corresponding to the a-1th inflection point, that is, the actual relative flow corresponding to the comprehensive valve position is obtained. And so on.

4. If the comprehensive valve position is within the range of (the comprehensive valve position command corresponding to the first inflection point, 1], then substitute the comprehensive valve position as x into the high-order continuous function of each high-adjustment valve that needs to be opened within this range, and obtain Take the corresponding yi value, except for the high-pressure valve that has been fully opened; then find the average of the yi values of all high-pressure valves that need to be opened within this range under the comprehensive valve position and multiply it by (the relative flow corresponding to the first inflection point - the relative flow corresponding to the second inflection point) + the relative flow corresponding to the second inflection point, that is, to obtain the actual relative flow corresponding to the comprehensive valve position;

Then, based on the comparison relationship, the comprehensive valve position command or the valve opening is corrected.
The method for correcting single valve and sequential valve parameters based on DEH valve flow characteristics according to claim 5 is characterized in that the point in the control relationship with the largest deviation from the theoretical curve is corrected.
A system for correcting single valve and sequence valve parameters based on DEH valve flow characteristics, adopting a method for correcting single valve and sequence valve parameters based on DEH valve flow characteristics as described in any one of claims 1 to 4, characterized in that it includes:

The data acquisition module is used to collect the unit load, main steam pressure before the unit, regulating stage pressure, main steam flow, feed water flow, main steam desuperheating water flow, main steam temperature, reheat steam temperature, drum pressure and total energy flow of the steam turbine during the test;

A data processing module is used to calculate the flow characteristic curve of each high-pressure valve using the Flugel formula according to the data collected by the data collection module;

The parameter correction module of each high-adjusting valve of the single-valve control mode is used to calculate the actual single-valve normalized relative flow rate; the actual single-valve normalized relative flow rate is y, and the corresponding valve opening is x for fitting to obtain a high-order continuous function y=f(x); the broken line function used by the current unit single valve is searched in the DCS; the comprehensive valve position instruction or valve opening is corrected using the high-order continuous function y=f(x);

The parameter correction module of each high-adjustable valve in the sequential valve control mode is used to calculate the relative flow ym corresponding to the inflection point; the broken line function used by each adjusting valve in the sequential valve control mode is searched in the DCS, in which Yqi is the discrete comprehensive valve position instruction, and Xqi is the corresponding valve opening; the actual normalized relative flow of each high-adjustable valve is y, and the corresponding valve opening is x for fitting to obtain the high-order continuous function yi = fi (x) of each high-adjustable valve; i is the ith high-adjustable valve; based on the relative flow ym corresponding to the inflection point and the high-order continuous function y = f(x) of each high-adjustable valve, and the broken line function, the comparison relationship between the comprehensive valve position and the relative flow is calculated; based on the comparison relationship, the comprehensive valve position instruction or the valve opening is corrected.