CN111412456A - Secondary reheating main steam temperature cascade control system and control method - Google Patents
Secondary reheating main steam temperature cascade control system and control method Download PDFInfo
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Abstract
A secondary reheating main steam temperature cascade control system relates to the technical field of thermal power generation, and solves the problem of how to improve the control quality when a tertiary superheater adopts water spraying temperature reduction to control the main steam temperature; the secondary superheater, the secondary desuperheater and the tertiary superheater are connected in series by adopting sealed pipelines in sequence; the desuperheating water regulating valve is connected between the secondary superheater and the secondary desuperheater through a three-way sealed pipeline; the auxiliary loop control system is used for controlling the opening degree of the desuperheating water regulating valve to roughly regulate the temperature of main steam at the outlet of the tertiary superheater; the main loop control system is used for controlling the opening degree of the desuperheating water regulating valve to finely regulate the main steam temperature at the outlet of the tertiary superheater, and has high response speed and good control quality; the control method adopts a particle swarm algorithm, so that the PID cascade control setting method is simple and has strong adaptability to the operation condition.
Description
Technical Field
The invention belongs to the technical field of thermal power generation, and relates to a secondary reheating main steam temperature cascade control system and a control method.
Background
With the increasing development of economy and the improvement of living standard of people, the energy resource consumption and the carbon dioxide emission caused by factory electricity and household electricity of residents are increased sharply. Reheating is to lead out the steam which has done part of work in the turbine to be reheated and then lead back to the turbine to do work continuously. Through reasonable reheating, the exhaust steam humidity can be reduced, and the thermodynamic cycle efficiency is improved. The supercritical unit adopting the secondary reheating technology correspondingly reduces the emission of carbon dioxide, nitrogen oxides and the like while improving the overall efficiency of the unit under the same parameters, and is an important future development direction of thermal power units in China. Compared with a single reheating unit with the same capacity, the double reheating thermal power generating unit has larger difference in process structure. If a first-stage reheating system is added on the boiler side, the steam-water flow is increased; the arrangement of the heating surface is more complex, the smoke recirculation is adopted to reduce the heat absorption of the hearth and increase the heat absorption of the convection heating surface, and the like, so that the dynamic and static characteristics of the unit are greatly changed. The configuration of the steam turbine, boiler and its associated systems, particularly in the control of the main steam temperature, is therefore much more complex for a double reheat unit than for a single reheat unit.
The main steam temperature system is a multi-input single-output object, and the main steam temperature is mainly influenced by three factors of steam flow, smoke heat and desuperheating water flow. Wherein the temperature of the main steam is controlled by changing the flow of the desuperheating water, and the adjusting mode is sensitive and precise in adjustment. When the tertiary superheater adopts water spraying temperature reduction to control the main steam temperature, a single-loop control system cannot obtain better control quality due to the fact that an object control channel has larger delay and inertia and has smaller steam temperature control deviation in operation.
Chinese patent application publication No. CN110687778A, entitled "electric heating system cascade control method and main regulator PID parameter setting method" discloses a main regulator self-setting method: initializing parameters and particle swarms, wherein each particle position comprises 3 variables, if the particles meet variation conditions, performing variation operation on the particles and updating the positions of the particles, and if the variation conditions are not met, performing update iteration on the weight, the speed, the positions and the adaptive values of the particles; if the variation condition is met, if the adaptive value of each particle is better than the adaptive value of the optimal position Pi which the particle has experienced, the particle is taken as the current Pi; comparing the adaptive value of each particle with the adaptive value of the optimal position Pg experienced by the whole particle swarm, and if the adaptive value is better than the adaptive value of the optimal position Pg experienced by the whole particle swarm, taking the adaptive value as the current Pg; and taking the optimal position Pg of the current particle swarm as an initial search point, adjusting the Rosenbrock algorithm to perform local search, updating Pi and Pg, and outputting 3 variables of the particles.
Although the invention patent application can improve the response speed of the system, the problems that the inertia delay of a superheated steam temperature control channel is large, the response of the regulated quantity is slow, and the control quality of a single-loop control system is poor when the temperature of the main steam is controlled by the three-level superheater through water spraying and temperature reduction are not solved.
Disclosure of Invention
The invention aims to solve the technical problem of how to improve the control quality when the temperature of the main steam is controlled by the water spraying temperature reduction of the tertiary superheater.
The invention solves the technical problems through the following technical scheme.
A secondary reheating main steam temperature cascade control system comprises a main loop control system, an auxiliary loop control system, a secondary superheater (1), a secondary desuperheater (2), a tertiary superheater (4), a PID (proportion integration differentiation) controller (9) and a desuperheating water regulating valve (10); the secondary superheater (1), the secondary desuperheater (2) and the tertiary superheater (4) are sequentially connected in series by adopting sealed pipelines; the desuperheating water regulating valve (10) is connected between the secondary superheater (1) and the secondary desuperheater (2) through a three-way sealed pipeline; the input end of the secondary loop control system is connected between the secondary desuperheater (2) and the tertiary superheater (4) and is used for collecting the steam temperature at the inlet of the tertiary superheater (4); the output end of the auxiliary loop control system is connected with a PID controller (9) and is used for controlling the opening degree of a desuperheating water regulating valve (10) to roughly regulate the temperature of main steam at the outlet of the tertiary superheater (4); the input end of the main loop control system is connected to the outlet of the tertiary superheater (4) and used for collecting the main steam temperature of the outlet of the tertiary superheater (4), and the output end of the main loop control system is connected with the PID controller (9) and used for controlling the opening degree of the desuperheating water regulating valve (10) to finely regulate the main steam temperature of the outlet of the tertiary superheater (4).
The steam temperature at the inlet of the tertiary superheater and the change trend of the main steam temperature at the outlet are consistent, the response speed of the steam temperature at the inlet of the tertiary superheater is obviously higher than that of the main steam temperature at the outlet, the steam temperature at the inlet of the tertiary superheater is added into a control channel of a control object to be used as a parameter of an auxiliary loop control system of the main steam temperature cascade control system, and the auxiliary loop control system is used for controlling the opening degree of the desuperheating water regulating valve to roughly adjust the main steam temperature at the outlet of the tertiary superheater, so that the response speed of the control system is improved, and the control quality of the control system is improved.
As a further improvement of the technical scheme of the invention, the secondary loop control system comprises a first thermocouple temperature sensor (3) and a first temperature transmitter (6); the main loop control system comprises a second thermocouple temperature sensor (5), a second temperature transmitter (7) and a particle swarm intelligent arithmetic unit (8); the first thermocouple temperature sensor (3) is arranged at the output end of the secondary desuperheater (2); the first thermocouple temperature sensor (3) is electrically connected with a first temperature transmitter (6), and the output end of the first temperature transmitter (6) is electrically connected with a PID controller (9); the second thermocouple temperature sensor (5) is arranged at the output end of the tertiary superheater (4); the second thermocouple temperature sensor (5) is electrically connected with a second temperature transmitter (7); the output end of the second temperature transmitter (7) is electrically connected with the particle swarm intelligent arithmetic unit (8); the output end of the particle swarm intelligent arithmetic unit (8) is electrically connected with a PID controller (9); the output end of the PID controller (9) is electrically connected with the control end of the temperature-reducing water regulating valve (10).
As a further improvement of the technical scheme of the invention, the first thermocouple temperature sensor (3) acquires the temperature at the output end of the secondary desuperheater (2), and transmits a temperature signal to the first temperature transmitter (6), and the first temperature transmitter (6) converts the temperature signal into a standard electric signal which is in linear relation with the temperature and transmits the standard electric signal to the PID controller (9); meanwhile, the second thermocouple temperature sensor (5) collects the temperature of the output end of the tertiary superheater (4), the temperature signal is sent to the second temperature transmitter (7), the second temperature transmitter (7) converts the temperature signal into an electromotive force signal and sends the electromotive force signal to the intelligent particle swarm arithmetic unit (8), and the intelligent particle swarm arithmetic unit (8) sends the input standard electric signal to the PID controller (9) after operation; the PID controller (9) controls the opening of the temperature-reducing water regulating valve (10) according to an input signal.
As a further improvement of the technical scheme of the invention, when the temperature at the first thermocouple temperature sensor (3) changes, the temperature of main steam at the outlet of the tertiary superheater (4) is coarsely regulated; the coarse concrete is as follows: after the temperature signal is directly operated by a PID controller (9), the flow of the desuperheating water is changed by changing the opening degree of a desuperheating water adjusting valve (10), the steam temperature at the inlet of the tertiary superheater (4) is primarily maintained, and the main steam temperature at the outlet of the tertiary superheater (4) is roughly adjusted; the temperature of main steam at the outlet of the tertiary superheater (4) is finely adjusted; the fine adjustment specifically comprises the following steps: the fine adjustment of the main steam temperature at the outlet of the three-level superheater (4) is controlled by the particle swarm intelligent arithmetic unit (8), and as long as the outlet steam temperature of the three-level superheater (4) does not reach the set value of the main steam temperature, the output of the particle swarm intelligent arithmetic unit (8) is continuously changed, so that the PID controller (9) continuously adjusts the opening degree of the desuperheating water adjusting valve (10) to change the flow of the desuperheating water until the main steam temperature is restored to the set value of the main steam temperature.
As a further improvement of the technical scheme of the invention, the thermocouple temperature sensor adopts a high-temperature K-type thermocouple of Omega company, the K-type thermocouple can directly measure the liquid vapor temperature ranging from 0 ℃ to 1300 ℃, and the model is KQX L-14E-18.
As a further improvement of the technical scheme of the invention, the temperature-reducing water regulating valve (10) adopts a pneumatic valve of Vatak company, and is characterized in that the flow of the system is automatically regulated according to an input signal, so that the automatic control in the running process of the unit is realized.
A control method applied to a double reheat main steam temperature cascade control system comprises the following steps:
step one, a difference is made between a main steam temperature set value r (t) and a system output value y (t) to obtain an error value e (t), and the calculation formula is as follows:
e(t)＝r(t)-y(t) (1)
wherein r (t) is the set value of the main steam temperature, y (t) is the system output value, and e (t) is the error value.
Step two, sending the error value e (t) into a particle swarm intelligent arithmetic unit (8) for operation to obtain a proportionality coefficient KpIntegral coefficient KiDifferential coefficient Kd(ii) a The proportionality coefficient KpIntegral coefficient KiDifferential coefficient KdThe output value u (t) of the controller is obtained by inputting the output value u (t) into a PID controller (9), and the calculation formula of the output value u (t) of the controller is as follows:
wherein, Kp、KiAnd KdRespectively are proportional, integral and differential coefficients, u (t) is the output value of the controller, t is independent variable, and tau is integral intermediate variable;
and thirdly, outputting a system output value y (t) after the controller output value u (t) and the secondary circuit disturbance are input to a control object transfer function together, wherein the system output value y (t) is used for controlling the opening degree of the temperature reduction water regulating valve (10).
As a further improvement of the technical solution of the present invention, the method for performing the operation in the intelligent particle group operator (8) in the second step comprises:
1) initializing a particle swarm, randomly generating the position and the speed of the particle, and determining the optimal position of the particle and the optimal position of the whole particle swarm;
2) comparing the adaptive value of each particle with the optimal position experienced by each particle, and updating the optimal position;
3) comparing the adaptive value of each particle with the optimal position experienced by the whole particle swarm, and updating the optimal position of the whole particle swarm;
4) updating the speed and the position of the particles according to the formula (3) and the formula (4);
5) and if the iteration times and the absolute error time integral meet the requirements, exiting the algorithm to obtain an optimal solution, otherwise, returning to the step 2).
As a further improvement of the technical solution of the present invention, the formula for updating the speed and the position of the particle in step 4) is:
xt+1＝xt+vt+1(4)
wherein v istAnd vt+1Respectively representing the speeds before and after the particle update; x is the number oftAnd xt+1Respectively representing the positions before and after the particle update; c. C1、c2Is an acceleration constant; r is1、r2Is a generated random number; pt bestAnd Gt bestThe individual optimal position and the global optimal position of the particle are respectively, and w is an inertia factor.
As a further improvement of the technical scheme of the invention, the absolute error time integral value in the step 5) is used as a performance evaluation index of the particle swarm intelligent arithmetic unit, and the smaller the value is, the better the system performance is; the calculation formula of the absolute error time integral is as follows:
wherein, JminAbsolute error time integral, e (t) error between output and input, t time;
the iteration number and the absolute error time integral meet the requirement that: the number of iterations reaches a set value of 600 while the absolute error time integral value is less than a set value of 0.1.
The invention has the advantages that:
(1) the invention aims at the problem that the steam temperature at the inlet of the tertiary superheater and the main steam temperature at the outlet have the same trend, the response speed of the steam temperature at the inlet of the tertiary superheater is obviously higher than that of the main steam at the outlet, the steam temperature at the inlet of the tertiary superheater is added into a control channel of a control object to be used as a parameter of a secondary loop control system of the main steam temperature cascade control system, and the parameter is used for controlling the opening degree of a temperature reduction water regulating valve to roughly adjust the main steam temperature at the outlet of the tertiary superheater, so that the response speed of the control system is improved, and the control quality of the control system is improved.
(2) The main steam temperature cascade control system adopts the particle swarm algorithm, not only has the characteristic of high response speed of the cascade system, but also automatically adjusts the PID parameters of the main loop by combining the intelligent operation of the particle swarm algorithm, so that the PID cascade control adjusting method is simple and has strong adaptability to the operating condition.
Drawings
FIG. 1 is a block diagram of a double reheat main steam temperature cascade control system according to an embodiment of the present invention;
FIG. 2 is a control block diagram of a double reheat main steam temperature cascade control system according to an embodiment of the present invention;
FIG. 3 is a flow chart of a control method for a double reheat main steam temperature cascade control system according to an embodiment of the present invention;
FIG. 4 is a simulation model diagram of a double reheat main steam temperature cascade control system according to an embodiment of the present invention;
FIG. 5 is a diagram of the results of a simulation of a double reheat main steam temperature cascade control system according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical scheme of the invention is further described by combining the drawings and the specific embodiments in the specification:
example one
As shown in fig. 1, a secondary reheating main steam temperature cascade control system comprises a main loop control system, an auxiliary loop control system, a secondary superheater 1, a secondary desuperheater 2, a tertiary superheater 4, a PID controller 9 and a desuperheating water regulating valve 10; the secondary superheater 1, the secondary desuperheater 2 and the tertiary superheater 4 are sequentially connected in series by adopting sealed pipelines; the desuperheating water regulating valve 10 is connected between the secondary superheater 1 and the secondary desuperheater 2 through a three-way sealed pipeline; the input end of the secondary loop control system is connected between the secondary desuperheater 2 and the tertiary superheater 4 and is used for collecting the steam temperature at the inlet of the tertiary superheater 4; the output end of the auxiliary loop control system is connected with a PID controller 9 and is used for controlling the opening degree of a desuperheating water regulating valve 10 to roughly regulate the temperature of main steam at the outlet of the tertiary superheater 4; the input end of the main loop control system is connected to the outlet of the tertiary superheater 4 and used for collecting the main steam temperature of the outlet of the tertiary superheater 4, and the output end of the main loop control system is connected with the PID controller 9 and used for controlling the opening degree of the desuperheating water regulating valve 10 to finely regulate the main steam temperature of the outlet of the tertiary superheater 4.
The steam temperature at the inlet of the tertiary superheater and the change trend of the main steam temperature at the outlet are consistent, the response speed of the steam temperature at the inlet of the tertiary superheater is obviously higher than that of the main steam temperature at the outlet, the steam temperature at the inlet of the tertiary superheater is added into a control channel of a control object to be used as a parameter of an auxiliary loop control system of the main steam temperature cascade control system, and the auxiliary loop control system is used for controlling the opening degree of the desuperheating water regulating valve to roughly adjust the main steam temperature at the outlet of the tertiary superheater, so that the response speed of the control system is improved, and the control quality of the control system is improved.
The secondary loop control system comprises a first thermocouple temperature sensor 3 and a first temperature transmitter 6; the main loop control system comprises a second thermocouple temperature sensor 5, a second temperature transmitter 7 and a particle swarm intelligent arithmetic unit 8; the first thermocouple temperature sensor 3 is arranged at the output end of the secondary desuperheater 2; the first thermocouple temperature sensor 3 is electrically connected with a first temperature transmitter 6, and the output end of the first temperature transmitter 6 is electrically connected with a PID controller 9; the second thermocouple temperature sensor 5 is arranged at the output end of the tertiary superheater 4; the second thermocouple temperature sensor 5 is electrically connected with a second temperature transmitter 7; the output end of the second temperature transmitter 7 is electrically connected with the particle swarm intelligent arithmetic unit 8; the output end of the particle swarm intelligent arithmetic unit 8 is electrically connected with a PID controller 9; the output end of the PID controller 9 is electrically connected with the control end of the temperature-reducing water regulating valve 10.
The first thermocouple temperature sensor 3 collects the temperature of the output end of the secondary desuperheater 2 and sends a temperature signal to the first temperature transmitter 6, and the first temperature transmitter 6 converts the temperature signal into a standard electric signal which is in a linear relation with the temperature and sends the standard electric signal to the PID controller 9; meanwhile, the second thermocouple temperature sensor 5 collects the temperature of the output end of the tertiary superheater 4, and sends a temperature signal to the second temperature transmitter 7, the second temperature transmitter 7 converts the temperature signal into an electromotive force signal and sends the electromotive force signal to the particle swarm intelligent arithmetic unit 8, and the particle swarm intelligent arithmetic unit 8 sends an input standard electric signal to the PID controller 9 after operation; the PID controller 9 controls the opening degree of the temperature-decreasing water regulating valve 10 based on the input signal.
When the temperature of the first thermocouple temperature sensor 3 changes, the temperature of main steam at the outlet of the tertiary superheater 4 is roughly adjusted; the coarse concrete is as follows: after the temperature signal is directly operated by a PID controller 9, the flow of the desuperheating water is changed by changing the opening degree of the desuperheating water adjusting valve 10, the steam temperature at the inlet of the tertiary superheater 4 is primarily maintained, and the main steam temperature at the outlet of the tertiary superheater 4 is roughly adjusted; the temperature of main steam at the outlet of the tertiary superheater 4 is finely adjusted; the fine adjustment specifically comprises the following steps: the fine adjustment of the main steam temperature at the outlet of the tertiary superheater 4 is controlled by the particle swarm intelligent arithmetic unit 8, and as long as the outlet steam temperature of the tertiary superheater 4 does not reach the set value of the main steam temperature, the output of the particle swarm intelligent arithmetic unit 8 is continuously changed, so that the PID controller 9 continuously adjusts the opening degree of the desuperheating water adjusting valve 10 to change the flow of the desuperheating water until the main steam temperature is restored to the set value of the main steam temperature.
The thermocouple temperature sensor adopts a high-temperature K-type thermocouple of Omega company, the K-type thermocouple can directly measure the liquid vapor temperature ranging from 0 ℃ to 1300 ℃, and the type is KQX L-14E-18.
The temperature-reducing water regulating valve 10 adopts a pneumatic valve of Vatak company, and is characterized in that the flow of a system is automatically regulated according to an input signal, and the automatic control in the running process of a unit is realized.
The particle swarm intelligent arithmetic unit 8 sends the input standard electric signal into the PID controller 9 after operation; the PID controller 9 controls the opening degree of the temperature-decreasing water regulating valve 10 based on the input signal.
As shown in fig. 2, the method for inputting the standard electrical signal into the PID controller 9 after the particle swarm intelligent arithmetic unit 8 performs arithmetic operation includes the following steps:
step one, a difference is made between a main steam temperature set value r (t) and a system output value y (t) to obtain an error value e (t), and the calculation formula is as follows:
e(t)＝r(t)-y(t) (1)
wherein r (t) is the set value of the main steam temperature, y (t) is the system output value, and e (t) is the error value.
Step two, sending the error value e (t) into a particle swarm intelligent arithmetic unit 8 for operation to obtain a proportionality coefficient KpIntegral coefficient KiDifferential coefficient Kd(ii) a The proportionality coefficient KpIntegral coefficient KiDifferential coefficient KdThe output value u (t) is input into a PID controller 9 to obtain a controller output value u (t), and the calculation formula of the controller output value u (t) is as follows:
wherein, Kp、KiAnd KdRespectively are proportional, integral and differential coefficients, u (t) is the output value of the controller, t is independent variable, and tau is integral intermediate variable;
and step three, outputting a system output value y (t) after the controller output value u (t) and the secondary circuit disturbance are input to a control object transfer function together, and controlling the opening degree of the temperature reduction water regulating valve 10.
As shown in fig. 3, the method for performing the operation in the particle swarm intelligent operator 8 in the second step includes:
1) initializing a particle swarm, randomly generating the position and the speed of the particle, and determining the optimal position of the particle and the optimal position of the whole particle swarm;
2) comparing the adaptive value of each particle with the optimal position experienced by each particle, and updating the optimal position;
3) comparing the adaptive value of each particle with the optimal position experienced by the whole particle swarm, and updating the optimal position of the whole particle swarm;
4) updating the speed and the position of the particles according to the formula (3) and the formula (4);
the formula for updating the speed and the position of the particles is as follows:
xt+1＝xt+vt+1(4)
wherein v istAnd vt+1Respectively representing the speeds before and after the particle update; x is the number oftAnd xt+1Respectively representing the positions before and after the particle update; c. C1、c2Is an acceleration constant; r is1、r2Is a generated random number; pt bestAnd Gt bestThe individual optimal position and the global optimal position of the particle are respectively, and w is an inertia factor.
5) And if the iteration times and the absolute error time integral meet the requirements, exiting the algorithm to obtain an optimal solution, otherwise, returning to the step 2).
The absolute error time integral value is used as a performance evaluation index of the particle swarm intelligent arithmetic unit, and the smaller the absolute error time integral value is, the better the system performance is; the calculation formula of the absolute error time integral is as follows:
wherein, JminAbsolute error time integral, e (t) is the error between the output and the input, t is time.
The step five that the iteration number and the absolute error time integral meet the requirements refers to: the number of iterations reaches a set value of 600 while the absolute error time integral value is less than a set value of 0.1.
As shown in fig. 4, the control method is tested through a simulation experiment, a PSO algorithm program is written on a simulation analysis Matlab, and a PID model file is built in a Simulink system;
entering a Simulink modeling interface to construct a model, wherein the set initial parameters of the standard particle swarm algorithm are as follows: particle number pop of 40; the maximum number of iterations is 100; kp，Ki，KdThe location search range of the three parameters is [0, 100 ]]Speed range of [ -1, 1 [)](ii) a Learning factor c1 ═ c2 ═ 1.49; the inertial weight decreases linearly from 0.9 to 0.3; setting the simulation time to be 500s according to the control characteristics of the main steam temperature of the industrial site; PID setting is carried out by utilizing a particle swarm optimization algorithm, and the following results can be obtained:
Kp＝22.5632，Ki＝0.1704，Kd＝98.4566；
as shown in fig. 5, simulation results show that after the optimization by the particle swarm optimization, the system output is immediately reduced and tends to be stable after the first oscillation is generated, the stabilization time is 60s, and the control performance of the main regulating loop is remarkably improved.
Example two
As shown in fig. 3, a control method applied to the double reheat main steam temperature cascade control system includes the following steps:
step one, a difference is made between a main steam temperature set value r (t) and a system output value y (t) to obtain an error value e (t), and the calculation formula is as follows:
e(t)＝r(t)-y(t) (1)
wherein r (t) is the set value of the main steam temperature, y (t) is the system output value, e (t) is the error value;
step two, sending the error value e (t) into a particle swarm intelligent arithmetic unit 8 for operation to obtain a proportionality coefficient KpIntegral coefficient KiDifferential coefficient Kd(ii) a The proportionality coefficient KpIntegral coefficient KiDifferential coefficient KdThe output value u (t) is input into a PID controller 9 to obtain a controller output value u (t), and the calculation formula of the controller output value u (t) is as follows:
wherein, Kp、KiAnd KdRespectively are proportional, integral and differential coefficients, u (t) is the output value of the controller, t is independent variable, and tau is integral intermediate variable;
the transfer function formula obtained according to formula (2) is:
wherein, TiTo integrate the time constant, TdIs a differential time constant;
the method for performing the operation in the particle swarm intelligent operator 8 in the second step comprises the following steps:
1) initializing a particle swarm, randomly generating the position and the speed of the particle, and determining the optimal position of the particle and the optimal position of the whole particle swarm;
2) comparing the adaptive value of each particle with the optimal position experienced by each particle, and updating the optimal position;
3) comparing the adaptive value of each particle with the optimal position experienced by the whole particle swarm, and updating the optimal position of the whole particle swarm;
4) updating the speed and the position of the particles according to the formula (3) and the formula (4);
the formula for updating the speed and the position of the particle in the step 4) is as follows:
xt+1＝xt+vt+1(4)
wherein v istAnd vt+1Respectively representing the speeds before and after the particle update; x is the number oftAnd xt+1Respectively representing the positions before and after the particle update; c. C1、c2Is an acceleration constant; r is1、r2Is a generated random number; pt bestAnd Gt bestThe individual optimal position and the global optimal position of the particle are respectively, and w is an inertia factor.
5) And if the iteration times and the absolute error time integral meet the requirements, exiting the algorithm to obtain an optimal solution, otherwise, returning to the step 2).
The absolute error time integral value in the step 5) is used as a performance evaluation index of the particle swarm intelligent arithmetic unit, and the smaller the value is, the better the system performance is; the calculation formula of the absolute error time integral is as follows:
wherein, JminAbsolute error time integral, e (t) error between output and input, t time;
the iteration number and the absolute error time integral meet the requirement that: the number of iterations reaches a set value of 600 while the absolute error time integral value is less than a set value of 0.1.
And thirdly, outputting a system output value y (t) after the controller output value u (t) and the secondary circuit disturbance are input to a control object transfer function together, wherein the system output value y (t) is used for controlling the opening degree of the temperature reduction water regulating valve (10).
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A secondary reheating main steam temperature cascade control system is characterized by comprising a main loop control system, an auxiliary loop control system, a secondary superheater (1), a secondary desuperheater (2), a tertiary superheater (4), a PID controller (9) and a desuperheating water regulating valve (10); the secondary superheater (1), the secondary desuperheater (2) and the tertiary superheater (4) are sequentially connected in series by adopting sealed pipelines; the desuperheating water regulating valve (10) is connected between the secondary superheater (1) and the secondary desuperheater (2) through a three-way sealed pipeline; the input end of the secondary loop control system is connected between the secondary desuperheater (2) and the tertiary superheater (4) and is used for collecting the steam temperature at the inlet of the tertiary superheater (4); the output end of the auxiliary loop control system is connected with a PID controller (9) and is used for controlling the opening degree of a desuperheating water regulating valve (10) to roughly regulate the temperature of main steam at the outlet of the tertiary superheater (4); the input end of the main loop control system is connected to the outlet of the tertiary superheater (4) and used for collecting the main steam temperature of the outlet of the tertiary superheater (4), and the output end of the main loop control system is connected with the PID controller (9) and used for controlling the opening degree of the desuperheating water regulating valve (10) to finely regulate the main steam temperature of the outlet of the tertiary superheater (4).
2. A double reheat main steam temperature cascade control system as claimed in claim 1, wherein said secondary loop control system comprises a first thermocouple temperature sensor (3), a first temperature transmitter (6); the main loop control system comprises a second thermocouple temperature sensor (5), a second temperature transmitter (7) and a particle swarm intelligent arithmetic unit (8); the first thermocouple temperature sensor (3) is arranged at the output end of the secondary desuperheater (2); the first thermocouple temperature sensor (3) is electrically connected with a first temperature transmitter (6), and the output end of the first temperature transmitter (6) is electrically connected with a PID controller (9); the second thermocouple temperature sensor (5) is arranged at the output end of the tertiary superheater (4); the second thermocouple temperature sensor (5) is electrically connected with a second temperature transmitter (7); the output end of the second temperature transmitter (7) is electrically connected with the particle swarm intelligent arithmetic unit (8); the output end of the particle swarm intelligent arithmetic unit (8) is electrically connected with a PID controller (9); the output end of the PID controller (9) is electrically connected with the control end of the temperature-reducing water regulating valve (10).
3. The double reheat main steam temperature cascade control system as claimed in claim 2, wherein the first thermocouple temperature sensor (3) collects the temperature at the output end of the secondary desuperheater (2) and sends the temperature signal to the first temperature transmitter (6), and the first temperature transmitter (6) converts the temperature signal into a standard electrical signal which is in a linear relation with the temperature and sends the standard electrical signal to the PID controller (9); meanwhile, the second thermocouple temperature sensor (5) collects the temperature of the output end of the tertiary superheater (4), the temperature signal is sent to the second temperature transmitter (7), the second temperature transmitter (7) converts the temperature signal into an electromotive force signal and sends the electromotive force signal to the intelligent particle swarm arithmetic unit (8), and the intelligent particle swarm arithmetic unit (8) sends the input standard electric signal to the PID controller (9) after operation; the PID controller (9) controls the opening of the temperature-reducing water regulating valve (10) according to an input signal.
4. The double reheat main steam temperature cascade control system as claimed in claim 3, wherein when the temperature at the first thermocouple temperature sensor (3) changes, the temperature of the main steam at the outlet of the three-level superheater (4) is roughly adjusted; the coarse concrete is as follows: after the temperature signal is directly operated by a PID controller (9), the flow of the desuperheating water is changed by changing the opening degree of a desuperheating water adjusting valve (10), the steam temperature at the inlet of the tertiary superheater (4) is primarily maintained, and the main steam temperature at the outlet of the tertiary superheater (4) is roughly adjusted; the temperature of main steam at the outlet of the tertiary superheater (4) is finely adjusted; the fine adjustment specifically comprises the following steps: the fine adjustment of the main steam temperature at the outlet of the three-level superheater (4) is controlled by the particle swarm intelligent arithmetic unit (8), and as long as the outlet steam temperature of the three-level superheater (4) does not reach the set value of the main steam temperature, the output of the particle swarm intelligent arithmetic unit (8) is continuously changed, so that the PID controller (9) continuously adjusts the opening degree of the desuperheating water adjusting valve (10) to change the flow of the desuperheating water until the main steam temperature is restored to the set value of the main steam temperature.
5. The double reheat main steam temperature cascade control system of claim 4, wherein the thermocouple temperature sensor is an Omega high temperature K thermocouple, model KQX L-14E-18.
6. A double reheat main steam temperature cascade control system as claimed in claim 5, wherein the desuperheating water adjusting valve (10) is a Vatak pneumatic valve.
7. A control method applied to the double reheat main steam temperature cascade control system of any one of claims 2-6 comprises the following steps:
step one, a difference is made between a main steam temperature set value r (t) and a system output value y (t) to obtain an error value e (t), and the calculation formula is as follows:
e(t)＝r(t)-y(t) (1)
wherein r (t) is the set value of the main steam temperature, y (t) is the system output value, e (t) is the error value;
step two, sending the error value e (t) into a particle swarm intelligent arithmetic unit (8) for operation to obtain a proportionality coefficient KpIntegral coefficient KiDifferential coefficient Kd(ii) a The proportionality coefficient KpIntegral coefficient KiDifferential coefficient KdThe output value u (t) of the controller is obtained by inputting the output value u (t) into a PID controller (9), and the calculation formula of the output value u (t) of the controller is as follows:
wherein, Kp、KiAnd KdProportional, integral respectivelyAnd a differential coefficient, u (t) is the controller output value, t is the independent variable, and tau is the integral intermediate variable;
and thirdly, outputting a system output value y (t) after the controller output value u (t) and the secondary circuit disturbance are input to a control object transfer function together, wherein the system output value y (t) is used for controlling the opening degree of the temperature reduction water regulating valve (10).
8. The control method of a double reheat main steam temperature cascade control system according to claim 7, wherein the method of performing the operation in the intelligent particle group operator (8) in the second step is:
1) initializing a particle swarm, randomly generating the position and the speed of the particle, and determining the optimal position of the particle and the optimal position of the whole particle swarm;
2) comparing the adaptive value of each particle with the optimal position experienced by each particle, and updating the optimal position;
3) comparing the adaptive value of each particle with the optimal position experienced by the whole particle swarm, and updating the optimal position of the whole particle swarm;
4) updating the speed and the position of the particles according to the formula (3) and the formula (4);
5) and if the iteration times and the absolute error time integral meet the requirements, exiting the algorithm to obtain an optimal solution, otherwise, returning to the step 2).
9. The method as claimed in claim 8, wherein the formula for updating the velocity and position of the particles in step 4) is as follows:
xt+1＝xt+vt+1(4)
wherein v istAnd vt+1Respectively representing the speeds before and after the particle update; x is the number oftAnd xt+1Respectively representing the positions before and after the particle update; c. C1、c2Is an acceleration constant; r is1、r2Is a generated random number; pt bestAnd
the individual optimal position and the global optimal position of the particle are respectively, and w is an inertia factor.
10. The control method of a double reheat main steam temperature cascade control system according to claim 8, wherein the absolute error time integral value in the step 5) is used as a performance evaluation index of a particle swarm intelligent operator, and the smaller the value, the better the system performance; the calculation formula of the absolute error time integral is as follows:
wherein, JminAbsolute error time integral, e (t) error between output and input, t time;
the iteration number and the absolute error time integral meet the requirement that: the number of iterations reaches a set value of 600 while the absolute error time integral value is less than a set value of 0.1.
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