Double-back-extraction steam turbine control method based on fuzzy PID

Abstract

The invention aims to provide a double-back-extraction steam turbine control method based on fuzzy PID, and belongs to the field of steam turbines. Comprising the following steps: increasing a high-pressure steam extraction thermal load, taking e1 and e1 as the input of a fuzzy controller, and carrying out fuzzy processing; performing fuzzy logic operation to form fuzzy output; defuzzification processing is carried out on the fuzzy output, Kp, Ki and Kd are input to a PID controller, and the PID controller carries out calculation adjustment on a control signal; the electro-hydraulic control system adjusts the opening degree of the double-seat valve; calculating Kp, Ki and Kd by taking ei and delta ei as input of fuzzy control; and the PID controller outputs to a double-seat valve hydraulic servo-motor, a rotary partition plate hydraulic servo-motor and a main steam adjusting combined valve hydraulic servo-motor to adjust the opening degrees of a double-seat valve, a rotary partition plate and a main steam valve. The PID control parameters Kp, Ki and Kd are adjusted through the error ei and the error change rate delta ei, the control precision is improved, the response time is shortened, and the problems that a double-back-extraction steam turbine control mathematical model is complex and expert system knowledge is difficult to obtain are solved.

Description

Technical Field

[0001] The present invention relates to a steam turbine control method, in particular to a steam turbine heat load control method. Background Art

[0002] A double-extraction back-pressure steam turbine refers to a back-pressure steam turbine with two stages of adjustable extraction. Its characteristic is that it can provide three different parameters of steam for heating users. The extraction pressure is adjusted by rotating the diaphragm or the seat cylinder valve, and the exhaust pressure is adjusted by controlling the steam intake through the main steam regulating combined valve. When the steam demand for a certain parameter changes, it is necessary to adjust the valve opening to the heating pipeline. The adjustment of the valve opening will cause the steam pressure flowing through that position to change. The steam turbine is equipped with a rotating diaphragm or seat cylinder valve to maintain pressure stability by adjusting the flow area at the extraction position. The action of the rotating diaphragm or seat cylinder valve will affect the change in the flow pressure of the entire turbine, which results in changes in the extraction and exhaust pressures of another stage when the extraction volume of one stage is adjusted. The traditional control method adjusts the opening of the rotating diaphragm or the cylinder valve according to the steam pressure, and adjusts the opening of the main steam regulating combined valve according to the exhaust pressure. This control requires multiple adjustments to reach the required target pressure in a double-extraction system where the two-stage extraction pressure and exhaust pressure affect each other. The control operation is cumbersome and the thermal user parameters fluctuate severely. For some chemical production lines that require stable parameters, pressure fluctuations are unacceptable. Summary of the invention

[0003] The object of the present invention is to provide a double-extraction steam turbine control method based on fuzzy PID which can realize static decoupling control of two-stage industrial extraction steam heat load and heating exhaust steam heat load.

[0004] The object of the present invention is achieved in that:

[0005] The double extraction steam turbine control method based on fuzzy PID of the present invention is characterized by comprising the following steps:

[0006] (1) A high-pressure extraction steam heat load increase command is issued, 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 maintained stable, the high-pressure extraction steam pressure set value remains unchanged, and the error between the high-pressure extraction steam pressure set value and the high-pressure extraction steam pressure measured value is e1;

[0007] (2) Taking the error e1 between the high-pressure extraction steam pressure set value and the measured value and the error change rate △e1 as the input of the fuzzy controller, the error e1 and △e1 are fuzzified and the value range of the input variable is converted into the corresponding fuzzy logic language value range;

[0008] (3) Applying fuzzy inference rules, performing fuzzy logic operations on the fuzzified data obtained in step (2) to form fuzzy output;

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

[0010] (5) Step (4) The outputs Kp, Ki and Kd of the fuzzy controller 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 the control signal to the electro-hydraulic control system, and the electro-hydraulic control system adjusts the opening of the double-seat valve;

[0012] (7) After the double-seat valve opening 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. With e1, △e1, e2, △e2, e3, and △e3 as the input of the fuzzy control, the fuzzy controller calculates Kp, Ki, and Kd and outputs them to the PID controller;

[0014] (9) The PID controller outputs to the double-seat valve oil motor, the rotary diaphragm oil motor and the main steam regulating combined valve oil motor to adjust the opening of the double-seat valve, the rotary diaphragm and the main steam valve. The change in the opening will again cause the individual extraction steam pressures to change until the set 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 domain range of e1 as {-1, 1}, and defines the domain range 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 described in step (3) adopt the Mamdani type fuzzy inference method. According to 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,△Kiis 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, Eij are fuzzy sets defined on the domain of error e, error change rate △e and △Kp, △Ki and △Kd.

[0019] 3. The defuzzification process described in step (4) uses the fuzzy set obtained in step (3) as input and the PID control parameters Kp, Ki and Kd as output. The defuzzification process adopts the centroid method. Assume that A is a non-empty fuzzy set. 1 , x 2 , …, x m The fuzzy control quantity is discretized into m vertical slices, and the weighted average of each element and its corresponding membership degree in the fuzzy control quantity is taken. Then the centroid of A is: Where x A is the exact value of the defuzzification, x i is the fuzzy variable element, μ A (x i ) is the 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 motor 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 specifically as follows: the PID controller outputs to the electro-hydraulic control system, the electro-hydraulic control system converts the electrical signal into a hydraulic signal, the double-seat valve oil motor adjusts the double-seat valve opening by moving the valve stem connected to its cylinder according to the received hydraulic change signal, the rotating diaphragm oil motor adjusts the rotating diaphragm opening by moving the lever connected to its cylinder according to the received hydraulic change signal, and the main steam regulating combined valve oil motor adjusts the regulating valve opening by moving the valve stem connected to its cylinder according to the received hydraulic change signal.

[0023] The advantages of the present invention are:

[0024] 1. The present invention can accurately control the extraction and exhaust pressure of the double extraction steam turbine;

[0025] 2. Solved the problem of complex mathematical model of double extraction steam turbine control and difficulty in acquiring expert system knowledge;

[0026] 3. The present invention uses a fuzzy PID control system: through the error e i and error change rate Δei Adjusting PID control parameters Kp, Ki and Kd can improve control accuracy and reduce response time. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in more detail below with reference to the accompanying drawings:

[0030] Combination Figure 1-2 The double extraction steam turbine control method based on fuzzy PID of the present invention comprises the following steps:

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

[0032] Step 2: Take the error e1 between the high-pressure extraction steam pressure set value and the measured value and the error change rate △e1 (de1 / dt) as the input of the fuzzy controller, perform fuzzification on the error e1 and △e1, and convert the value range of the input variable into the corresponding fuzzy logic language value range;

[0033] Step 3: Apply fuzzy inference rules to perform fuzzy logic operations on the fuzzified 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 outputs;

[0035] Step 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;

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

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

[0038] Step 8: Take the error e1 between the high-pressure extraction steam pressure set value and the measured value and the error change rate △e1, the error e2 between the low-pressure extraction steam pressure set value and the measured value and the error change rate △e2, and the error e3 between the exhaust steam pressure set value and the measured value and the error change rate △e3 as the input of fuzzy control, calculate Kp, Ki, Kd through the fuzzy controller and output them to the PID controller.

[0039] Step 9: The PID controller outputs to the double-seat valve oil motor, the rotating diaphragm oil motor and the main steam regulating combined valve oil motor to adjust the opening of the double-seat valve, the rotating diaphragm and the main steam valve. The change in the opening will again cause the individual extraction steam pressures to change until the set value of each extraction steam pressure is equal to the measured value.

[0040] in:

[0041] The fuzzy controller in step 2 uses a triangular membership function to define the domain range of e1 as {-1,1}, and the domain range of △e1 as {-1,1}. Its fuzzy subsets are all taken as: {NB, NM, NS, ZO, PS, PM, PB}. Among them, 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 big, negative medium, negative small, zero, positive small, positive medium, and positive big.

[0042] The inference rules described in step 3 adopt the Mamdani type fuzzy inference method, and give 7*7=49 fuzzy rules according to the setting of input and output variables combined with experience. The rules take the following form: IF{e is Ai and △e is Bj}THEN{△Kp is Cij,△Kiis Dij,△Kd is Eij}i=1,2,3,4,5,6,7;j=1,2,3,4,5,6,7. Among them, Ai, Bj, Cij, Dij, Eij are fuzzy sets defined on the domain of error e, error change rate △e and △Kp, △Ki and △Kd.

[0043] The defuzzification process described in step 4 uses the fuzzy set obtained in step (3) as input and the PID control parameters Kp, Ki and Kd as output. The defuzzification process uses the centroid method. Assume A is a non-empty fuzzy set. 1 , x 2 , …, x m The fuzzy control quantity is discretized into m vertical slices, and the weighted average of each element and its corresponding membership degree in the fuzzy control quantity is taken. Then the centroid of A is: Where x A is the exact value of the defuzzification, x i is the fuzzy variable element, μ A (x i ) is the element xi The degree of membership.

[0044] The PID controller control equation described in step 5 is: Where e(t) is the error. The proportional coefficient Kp is used to improve the response speed and adjustment accuracy of the system, the integral coefficient Ki is used to eliminate the steady-state error, and the differential coefficient Kd is used for early prediction and preprocessing to avoid the deviation from changing continuously in the same direction and to suppress the 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 motor 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 the change in the opening of a certain position inside the turbine flow path, and the heat and mass inside the flow path need to be rebalanced, thus causing the pressure in each section to change.

[0047] The high-pressure extraction steam pressure set value and measured value described in step 8 have changed, while the medium-pressure extraction steam and low-pressure extraction steam pressure set values ​​have not changed. The medium-pressure extraction steam and low-pressure extraction steam pressure measured values ​​have changed due to the adjustment of the double-seat valve opening. The error and error change rate of the set value and measured value of each level of extraction (exhaust) steam pressure are used as the input of the fuzzy controller, and the process (2)-(5) is repeated.

[0048] In step 9, the controller outputs to the electro-hydraulic control system, and the electro-hydraulic control system converts the electrical signal into a hydraulic signal. The double-seat valve oil motor 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 oil motor 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 combined valve oil motor 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 double-extraction steam turbine control method based on fuzzy PID is characterized by: The steps include: (1) A high-pressure extraction steam heat load increase command is issued, 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 maintained stable, the high-pressure extraction steam pressure set value remains unchanged, and the error between the high-pressure extraction pressure set value and the high-pressure extraction pressure measured value is e1; (2) The error e1 between the set value and the measured value of the high-pressure extraction steam pressure and the rate of change of the error △e1 are used as the input of the fuzzy controller. The error e1 and △e1 are fuzzified and the value range of the input variable is converted into the corresponding fuzzy logic language value range; (3) Applying fuzzy inference rules, performing fuzzy logic operations on the fuzzified data obtained in step (2) to form fuzzy output; (4) Defuzzifying the fuzzy output obtained in step (3) and determining the outputs Kp, Ki and Kd of the fuzzy controller from the fuzzy set of the outputs; (5) Step (4) The outputs Kp, Ki and Kd of the fuzzy controller 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 the 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. With e1, △e1, e2, △e2, e3, and △e3 as the inputs of the fuzzy control, the fuzzy controller calculates Kp, Ki, and Kd and outputs them to the PID controller. (9) The PID controller outputs to the double-seat valve oil motor, the rotary diaphragm oil motor and the main steam regulating combined valve oil motor to adjust the opening of the double-seat valve, the rotary diaphragm and the main steam valve. The opening change again causes the individual extraction steam pressure changes until the set value of each extraction steam pressure is equal to the measured value.

2. The fuzzy PID-based double-extraction steam turbine control method according to claim 1, characterized in that: The fuzzy controller described in step (2) adopts a triangular membership function, defines the domain range of e1 as {-1, 1}, and defines the domain range 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 Postive, 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 double-extraction steam turbine control method based on fuzzy PID according to claim 1 is characterized in that: The fuzzy inference rules described in step (3) adopt the Mamdani type fuzzy inference method. According to 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,△Kiis 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, Eij are fuzzy sets defined on the domain of error e, error change rate △e and △Kp, △Ki and △Kd.

4. The double-extraction steam turbine control method 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 adopts the centroid method. Assume that A is a non-empty fuzzy set. m Discretize it into m vertical slices, take the weighted average of each element in the fuzzy control quantity and its corresponding membership, then the centroid of A is: Where x A is the exact value of defuzzification, x i is the fuzzy variable element, μ A (x i ) is the element x i The degree of membership.

5. The double-extraction steam turbine control method based on fuzzy PID according to claim 1 is 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 double-extraction steam turbine control method 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 oil motor adjusts the opening of the double-seat valve by moving the valve stem connected to its oil cylinder according to the received hydraulic change signal.

7. The fuzzy PID-based double-extraction steam turbine control method according to claim 1, characterized in that: Step (9) is specifically as follows: the PID controller outputs to the electro-hydraulic control system, the electro-hydraulic control system converts the electrical signal into a hydraulic signal, the double-seat valve oil motor adjusts the double-seat valve opening by moving the valve stem connected to its oil cylinder according to the received hydraulic change signal, the rotary diaphragm oil motor adjusts the rotary diaphragm opening by moving the lever connected to its oil cylinder according to the received hydraulic change signal, and the main steam regulating combined valve oil motor adjusts the regulating valve opening by moving the valve stem connected to its oil cylinder according to the received hydraulic change signal.

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