Double-extraction back turbine control method based on fuzzy PID

Abstract

The application aims to provide a double-extraction back turbine control method based on fuzzy PID, and belongs to the field of turbine. The method comprises the following steps: increasing the high-pressure extraction heat load, taking e1 and delta e1 as the input of the fuzzy controller, and performing fuzzy processing; performing fuzzy logic operation to form fuzzy output; performing inverse fuzzy processing on the fuzzy output, inputting Kp, Ki and Kd to the PID controller, and the PID controller calculating and adjusting the control signal; adjusting the double-seat valve opening degree by the electro-hydraulic control system; taking e i , delta e i as the input of the fuzzy control, calculating Kp, Ki and Kd; and the PID controller outputting to the double-seat valve oil engine, the rotating baffle oil engine and the main steam regulating joint valve oil engine to adjust the double-seat valve, the rotating baffle and the main steam valve opening degree. The application adjusts the PID control parameters Kp, Ki and Kd through the error e i and the error change rate delta e i , improves the control precision, reduces the response time, and solves the problems of complex control mathematical model and difficult expert system knowledge acquisition of the double-extraction back turbine control.

Description

Technical Field

[0001] The present invention relates to a steam turbine control method, specifically a steam turbine thermal load control method. Background Technology

[0002] A dual-extraction back-pressure steam turbine refers to a back-pressure steam turbine with two adjustable extraction stages, characterized by its ability to provide steam with three different parameters for heating users. Extraction pressure is adjusted by rotating diaphragms or cylinder valves, while exhaust pressure is adjusted by controlling the steam inlet flow through the main steam regulating valve. When the steam demand for a certain parameter changes, the opening of the valve leading to the heating pipeline needs to be adjusted, which causes a change in the steam pressure flowing through that location. The turbine uses rotating diaphragms or cylinder valves to maintain pressure stability by adjusting the flow area at the extraction stage. However, the operation of these diaphragms or cylinder valves affects the overall turbine flow pressure, resulting in changes in the extraction and exhaust pressures of the other stage when the extraction flow of one stage is adjusted. Traditional control methods adjust the opening of the rotary baffle or seat valve based on steam pressure and the opening of the main steam regulating valve based on exhaust pressure. This type of control requires multiple adjustments to achieve the target pressure in a dual-extraction back-end system where the two-stage extraction and exhaust pressures influence each other. The control operation is cumbersome and the heat user parameters fluctuate significantly. For some chemical production lines that require stable parameters, pressure fluctuations are unacceptable. Summary of the Invention

[0003] The purpose of this invention is to provide a fuzzy PID-based control method for a dual-extraction back turbine that enables static decoupling control of two-stage industrial extraction steam heat load and heating exhaust steam heat load.

[0004] The objective of this invention is achieved as follows:

[0005] This invention relates to a dual-extraction back-end steam turbine control method based on fuzzy PID, characterized by the following steps:

[0006] (1) When the high-pressure extraction steam heat load is increased, the opening of the high-pressure extraction steam regulating valve is increased and the high-pressure extraction steam pressure is reduced; the extraction steam pressure is kept stable, the high-pressure extraction steam pressure setpoint remains unchanged, and the error between the high-pressure extraction steam pressure setpoint and the high-pressure extraction steam pressure measurement value is e1.

[0007] (2) Using the error e1 between the given and measured values ​​of the high-pressure extraction steam pressure and the rate of change of the error Δe1 as the input of the fuzzy controller, the error e1 and Δe1 are fuzzified, and the range of values ​​of the input variables is converted to the range of values ​​of the corresponding fuzzy logic language.

[0008] (3) Apply fuzzy inference rules to perform fuzzy logic operations on the fuzzy data obtained in step (2) to form fuzzy output;

[0009] (4) Defuzzify the fuzzy output obtained in step (3) and determine the outputs Kp, Ki and Kd of the fuzzy controller from the fuzzy set of outputs;

[0010] (5) The outputs Kp, Ki and Kd of the fuzzy controller obtained in step (4) are input to the PID controller. The PID controller uses Kp, Ki and Kd as calculation parameters to calculate and adjust the control signal.

[0011] (6) The PID controller outputs a control signal to the electro-hydraulic control system, which adjusts the opening of the double-seat valve.

[0012] (7) After the opening of the double seat valve is adjusted, the high pressure extraction steam pressure changes, the low pressure extraction steam pressure changes, and the exhaust steam pressure changes.

[0013] (8) The error between the given value and the measured value of the low-pressure extraction steam pressure is e2, and its rate of change is △e2. The error between the given value and the measured value of the exhaust steam pressure is e3, and its rate of change is △e3. e1, △e1, e2, △e2, e3, and △e3 are used as inputs for fuzzy control. Kp, Ki, and Kd are calculated by the fuzzy controller and output to the PID controller.

[0014] (9) The PID controller outputs to the double-seat valve hydraulic actuator, the rotary diaphragm hydraulic actuator and the main steam regulating combined valve hydraulic actuator to adjust the opening of the double-seat valve, the rotary diaphragm and the main steam valve. The change in opening causes the individual extraction steam pressure to change again until the given value of each extraction steam pressure is equal to the measured value.

[0015] The present invention may also include:

[0016] 1. The fuzzy controller described in step (2) adopts a triangular membership function, defines the universe of discourse of e1 as {-1,1}, and defines the universe of discourse of △e1 as {-1,1}. Its fuzzy subsets are all taken as: {NB, NM, NS, ZO, PS, PM, PB}, where N is Negative, P is Positive, B is Big, M is Medium, S is Small, and ZO is Zero. The elements in the corresponding fuzzy subsets represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively.

[0017] 2. The fuzzy inference rules mentioned in step (3) adopt the Mamdani-type fuzzy inference method. Based on the setting of input and output variables and combined with experience, 7*7=49 fuzzy rules are given. The rules take the following form: IF{e is Ai and △e is Bj} THEN{△Kp is Cij, △Kii is Dij, △Kd is Eij}

[0018] i = 1, 2, 3, 4, 5, 6, 7; j = 1, 2, 3, 4, 5, 6, 7, where Ai, Bj, Cij, Dij, and Eij are fuzzy sets defined on the universes of discourse of error e, error rate of change Δe, ΔKp, ΔKi, and ΔKd.

[0019] 3. The defuzzification process described in step (4) takes the fuzzy set obtained in step (3) as input and outputs the PID control parameters Kp, Ki, and Kd as output. The defuzzification process uses the centroid method. Let A be a non-empty fuzzy set, x1, x2, ..., x... m Discretize A into m vertical slices, and take the weighted average of each element in the fuzzy control variable and its corresponding membership degree. Then the centroid of A is: In the formula x A x is the precise value for defuzzification. i For fuzzy variable elements, μ A (x i ) is element x i The degree of membership.

[0020] 4. The control equation of the PID controller in step (5) is: Where e(t) is the error, Kp is the proportional coefficient, Ki is the integral coefficient, and Kd is the differential coefficient.

[0021] 5. In step (6), the controller outputs to the electro-hydraulic control system, which converts the electrical signal into a hydraulic signal. The hydraulic actuator adjusts the opening of the double-seat valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

[0022] 6. Step (9) is as follows: The PID controller outputs to the electro-hydraulic control system, which converts the electrical signal into a hydraulic signal. The double-seat valve hydraulic actuator adjusts the opening of the double-seat valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal. The rotating diaphragm hydraulic actuator adjusts the opening of the rotating diaphragm by moving the lever connected to its cylinder according to the received hydraulic change signal. The main steam regulating valve hydraulic actuator adjusts the opening of the regulating valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

[0023] The advantages of this invention are:

[0024] 1. This invention can precisely control the extraction and exhaust pressures of a dual-extraction back-draft steam turbine;

[0025] 2. It solved the problem of complex mathematical models for the control of dual-extraction back-end steam turbines and the difficulty in acquiring knowledge from expert systems;

[0026] 3. This invention applies a fuzzy PID control system: through error e i and the rate of change of error Δe iAdjusting the PID control parameters Kp, Ki, and Kd improved control accuracy and reduced response time. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the control system of the present invention;

[0028] Figure 2 This is a flowchart of the present invention. Detailed Implementation

[0029] The invention will now be described in more detail with reference to the accompanying drawings:

[0030] Combination Figure 1-2 The present invention provides a dual-extraction back-end steam turbine control method based on fuzzy PID, comprising the following steps:

[0031] Step 1: After the command to increase the high-pressure extraction steam heat load is issued, the opening of the high-pressure extraction steam regulating valve increases, and the high-pressure extraction steam pressure decreases. The turbine needs to maintain a stable extraction steam pressure, so the high-pressure extraction steam pressure setpoint remains unchanged. There is an error e1 between the high-pressure extraction steam pressure setpoint and the measured high-pressure extraction steam pressure.

[0032] Step 2: Using the error e1 between the given and measured high-pressure extraction steam pressure and its rate of change Δe1(de1 / dt) as the input of the fuzzy controller, the error e1 and Δe1 are fuzzified to convert the range of the input variable to the corresponding fuzzy logic language range.

[0033] Step 3: Apply fuzzy inference rules to perform fuzzy logic operations on the fuzzy data obtained in step (2) to form fuzzy output;

[0034] Step 4: Defuzzify the fuzzy output obtained in step (3), and determine the outputs Kp, Ki and Kd of the fuzzy controller from the fuzzy set of the output;

[0035] Step 5: Step (4) obtains the outputs Kp, Ki and Kd of the fuzzy controller and inputs them to the PID controller. The PID controller uses Kp, Ki and Kd as calculation parameters to calculate and adjust the control signal.

[0036] Step 6: The PID controller outputs a control signal to the electro-hydraulic control system, which then adjusts the opening of the double-seat valve.

[0037] Step 7: Due to the adjustment of the double-seat valve opening, the high-pressure extraction steam pressure changes, the low-pressure extraction steam pressure changes, and the exhaust steam pressure changes.

[0038] Step 8: Using the error e1 and the rate of change of the error between the high-pressure extraction steam pressure setpoint and the measured value, the error e2 and the rate of change of the error between the low-pressure extraction steam pressure setpoint and the measured value, and the error e3 and the rate of change of the error between the exhaust steam pressure setpoint and the measured value as inputs to fuzzy control, the fuzzy controller calculates Kp, Ki, and Kd and outputs them to the PID controller.

[0039] Step 9: The PID controller outputs to the double-seat valve hydraulic actuator, the rotary baffle hydraulic actuator, and the main steam regulating combined valve hydraulic actuator to adjust the opening of the double-seat valve, the rotary baffle, and the main steam valve. The change in opening causes a change in the extraction steam pressure again until the set value and the measured value of each extraction steam pressure are equal.

[0040] in:

[0041] In step 2, the fuzzy controller uses a triangular membership function, defining the universe of discourse of e1 as {-1, 1} and the universe of discourse of △e1 as {-1, 1}. Its fuzzy subsets are all taken as: {NB, NM, NS, ZO, PS, PM, PB}. Where N stands for Negative, P for Positive, B for Big, M for Medium, S for Small, and ZO for Zero. The elements in the corresponding fuzzy subsets represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively.

[0042] The inference rules described in step 3 employ the Mamdani-type fuzzy inference method, providing 7*7=49 fuzzy rules based on the input and output variable settings and experience. The rules take the following form: IF{e is Ai and △e is Bj} THEN{△Kp is Cij, △Kii is Dij, △Kd is Eij} i=1,2,3,4,5,6,7; j=1,2,3,4,5,6,7. Here, Ai, Bj, Cij, Dij, and Eij are fuzzy sets defined on the error e, the rate of change of error △e, and the universes of discourse △Kp, △Ki, and △Kd.

[0043] The defuzzification process described in step 4 takes the fuzzy set obtained in step (3) as input and outputs the PID control parameters Kp, Ki, and Kd. The defuzzification process uses the centroid method. Let A be a non-empty fuzzy set, x1, x2, ..., x... m Discretize A into m vertical slices, and take the weighted average of each element in the fuzzy control variable and its corresponding membership degree. Then the centroid of A is: In the formula x A x is the precise value for defuzzification. i For fuzzy variable elements, μ A (x i ) is element x i The degree of membership.

[0044] The control equation for the PID controller described in step 5 is as follows: Where e(t) is the error. The proportional coefficient Kp is used to improve the system's response speed and adjustment accuracy, the integral coefficient Ki is used to eliminate steady-state error, and the derivative coefficient Kd is used for early prediction and preprocessing to avoid continuous changes in the same direction of deviation and to suppress deviation in advance.

[0045] Step 6: The controller outputs to the electro-hydraulic control system, which converts the electrical signal into a hydraulic signal. The hydraulic actuator adjusts the opening of the double-seat valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

[0046] The double-seat valve opening adjustment described in step 7 is due to a change in the opening at a certain position inside the turbine flow path. The heat and mass inside the flow path need to be rebalanced, which leads to changes in the pressure of each section.

[0047] In step 8, both the setpoint and measured values ​​of the high-pressure extraction steam pressure changed, while the setpoint values ​​of the medium-pressure and low-pressure extraction steam pressures remained unchanged. However, the measured values ​​of the medium-pressure and low-pressure extraction steam pressures changed due to the adjustment of the double-seat valve opening. The errors and error change rates of the setpoint and measured values ​​of the extraction (exhaust) steam pressures at each stage were used as inputs to the fuzzy controller, and processes (2)-(5) were repeated.

[0048] In step 9, the controller outputs to the electro-hydraulic control system, which converts the electrical signal into a hydraulic signal. The double-seat valve hydraulic actuator adjusts the opening of the double-seat valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal. The rotary diaphragm hydraulic actuator adjusts the opening of the rotary diaphragm by moving the lever connected to its cylinder according to the received hydraulic change signal. The main steam regulating valve hydraulic actuator adjusts the opening of the regulating valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

Claims

1. A control method for a dual-extraction back-end steam turbine based on fuzzy PID, characterized by: Includes the following steps: (1) When the high-pressure extraction steam heat load is increased, the opening of the high-pressure extraction steam regulating valve is increased and the high-pressure extraction steam pressure is reduced; the extraction steam pressure is kept stable, the high-pressure extraction steam pressure setpoint remains unchanged, and the error between the high-pressure extraction steam pressure setpoint and the high-pressure extraction steam pressure measurement value is e1. (2) Using the error e1 between the given and measured values ​​of the high-pressure extraction steam pressure and the rate of change of the error Δe1 as the input of the fuzzy controller, the error e1 and Δe1 are fuzzified, and the range of values ​​of the input variables is converted to the range of values ​​of the corresponding fuzzy logic language. (3) Apply fuzzy inference rules to perform fuzzy logic operations on the fuzzy data obtained in step (2) to form fuzzy output; (4) Defuzzify the fuzzy output obtained in step (3) and determine the outputs Kp, Ki and Kd of the fuzzy controller from the fuzzy set of outputs; (5) The outputs Kp, Ki and Kd of the fuzzy controller obtained in step (4) are input to the PID controller. The PID controller uses Kp, Ki and Kd as calculation parameters to calculate and adjust the control signal. (6) The PID controller outputs a control signal to the electro-hydraulic control system, which adjusts the opening of the double-seat valve. (7) After the opening of the double seat valve is adjusted, the high pressure extraction steam pressure changes, the low pressure extraction steam pressure changes, and the exhaust steam pressure changes. (8) The error between the given value and the measured value of the low-pressure extraction steam pressure is e2, and its rate of change is △e2. The error between the given value and the measured value of the exhaust steam pressure is e3, and its rate of change is △e3. e1, △e1, e2, △e2, e3, and △e3 are used as inputs for fuzzy control. Kp, Ki, and Kd are calculated by the fuzzy controller and output to the PID controller. (9) The PID controller outputs to the double-seat valve hydraulic actuator, the rotary diaphragm hydraulic actuator and the main steam regulating combined valve hydraulic actuator to adjust the opening of the double-seat valve, the rotary diaphragm and the main steam valve. The change in opening causes the individual extraction steam pressure to change again until the given value of each extraction steam pressure is equal to the measured value.

2. The control method for a dual-extraction back-end steam turbine based on fuzzy PID according to claim 1, characterized in that: The fuzzy controller described in step (2) adopts a triangular membership function, defines the universe of discourse of e1 as {-1,1}, and defines the universe of discourse of △e1 as {-1,1}. Its fuzzy subsets are all taken as: {NB, NM, NS, ZO, PS, PM, PB}, where N is Negative, P is Positive, B is Big, M is Medium, S is Small, and ZO is Zero. The elements in the corresponding fuzzy subsets represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively.

3. The control method for a dual-extraction back-end steam turbine based on fuzzy PID according to claim 1, characterized in that: The fuzzy inference rules described in step (3) adopt the Mamdani-type fuzzy inference method. Based on the setting of input and output variables and combined with experience, 7*7=49 fuzzy rules are given. The rules take the following form: IF{e is Ai and △e is Bj}THEN{△Kp is Cij, △Kii is Dij, △Kd is Eij}i=1,2,3,4,5,6,7;j=1,2,3,4,5,6,7, where Ai, Bj, Cij, Dij, and Eij are fuzzy sets defined on the universes of discourse of error e, error rate of change △e, and △Kp, △Ki, and △Kd.

4. The control method for a dual-extraction back-end steam turbine based on fuzzy PID according to claim 1, characterized in that: The defuzzification process described in step (4) takes the fuzzy set obtained in step (3) as input and outputs the PID control parameters Kp, Ki, and Kd. The defuzzification process uses the centroid method. Let A be a non-empty fuzzy set, x1, x2, ..., x... m Discretize A into m vertical slices, and take the weighted average of each element in the fuzzy control variable and its corresponding membership degree. Then the centroid of A is: In the formula x A x is the precise value for defuzzification. i For fuzzy variable elements, μ A (x i ) is element x i The degree of membership.

5. The control method for a dual-extraction back-end steam turbine based on fuzzy PID according to claim 1, characterized in that: The control equation of the PID controller in step (5) is: Where e(t) is the error, Kp is the proportional coefficient, Ki is the integral coefficient, and Kd is the differential coefficient.

6. The control method for a dual-extraction back-end steam turbine based on fuzzy PID according to claim 1, characterized in that: In step (6), the controller outputs to the electro-hydraulic control system, which converts the electrical signal into a hydraulic signal. The hydraulic actuator adjusts the opening of the double-seat valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

7. The control method for a dual-extraction back-end steam turbine based on fuzzy PID according to claim 1, characterized in that: Step (9) specifically involves: the PID controller outputs to the electro-hydraulic control system, which converts the electrical signal into a hydraulic signal. The double-seat valve hydraulic actuator adjusts the opening of the double-seat valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal. The rotary diaphragm hydraulic actuator adjusts the opening of the rotary diaphragm by moving the lever connected to its cylinder according to the received hydraulic change signal. The main steam regulating valve hydraulic actuator adjusts the opening of the regulating valve by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

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