CN111412456A - A cascade control system and control method for secondary reheat main steam temperature - Google Patents

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 of a tertiary superheater when water spray temperature reduction is used to control the main steam temperature, including a main loop control system, a secondary superheater Loop control system, secondary superheater, secondary desuperheater, tertiary superheater, PID controller, desuperheating water regulating valve; secondary superheater, secondary desuperheater, and tertiary superheater are connected in series by sealed pipes. ; The desuperheating water regulating valve is connected between the secondary superheater and the secondary desuperheater through a three-way sealed pipe; the sub-circuit control system is used to control the opening of the desuperheating water regulating valve to roughen the main steam temperature at the outlet of the tertiary superheater. The main loop control system is used to control the opening of the desuperheater control valve to finely adjust the main steam temperature at the outlet of the three-stage superheater, the system has fast response speed and good control quality; the control method adopts particle swarm algorithm, so that the PID cascade The control setting method is simple and adaptable to the operating conditions.

Description

A cascade control system and control method for secondary reheat main steam temperature

technical field

The invention belongs to the technical field of thermal power generation, and relates to a cascade control system and a control method for the temperature of secondary reheat main steam.

Background technique

With the increasing economic development and the improvement of people's living standards, the consumption of energy resources and carbon dioxide emissions caused by electricity consumption in factories and households have increased sharply. Reheating means that the steam that has done part of the work in the steam turbine is drawn out for reheating, and then led back to the steam turbine to continue doing work. Through reasonable reheating, the humidity of exhaust steam can be reduced and the efficiency of thermal cycle can be improved. Under the same parameters, the super (super) critical unit using the double reheat technology can improve the overall efficiency of the unit and correspondingly reduce the emissions of carbon dioxide and nitrogen oxides, which is an important development direction of my country's thermal power units in the future. Compared with the primary reheat unit of the same capacity, the two-reheat thermal power unit has a big difference in the process structure. For example, the first-stage reheating system is added to the boiler side, and the steam-water flow is increased; the layout of the heating surface is more complicated, and the flue gas recirculation is used to reduce the heat absorption of the furnace and increase the heat absorption of the convection heating surface, which makes the dynamic and static characteristics of the unit better. Big change. Therefore, the configuration of the steam turbine, boiler and related systems of the secondary reheat unit is much more complicated than that of the primary reheat unit, especially in the control of the main steam temperature.

The main steam temperature system is a multi-input and single-output object. The main steam temperature is mainly affected by three factors: steam flow, flue gas heat and desuperheating water flow. The temperature of the main steam is controlled by changing the flow rate of the desuperheating water, which is sensitive and precise. When the three-stage superheater uses water spray to reduce the temperature of the main steam, due to the large delay and inertia of the object control channel and the small steam temperature control deviation required during operation, the single-loop control system often cannot obtain better performance. Control quality.

The Chinese invention patent application with the application publication number CN110687778A, "The Cascade Control Method of the Electric Heating System and the Setting Method of the PID Parameter of the Main Regulator" discloses the Cascade Control Method of the Electric Heating System and the PID Parameter of the Main Regulator Tuning method: Initialize parameters and particle swarm. Each particle position contains 3 variables. If the particle meets the mutation conditions, perform mutation operation on the particle and update the position of the particle. If the particle does not meet the mutation conditions, the weight and speed of the particle are , position and fitness value are updated iteratively; if the mutation condition is met, if the fitness value of each particle is better than the fitness value of the optimal position Pi experienced by the particle, it will be used as the current Pi; for each particle, Compare its fitness value with the fitness value of the optimal position Pg experienced by the entire particle swarm. If its fitness value is better than the fitness value of the optimal position Pg experienced by the entire particle swarm, take it as the current Pg ; Take the optimal position Pg of the current particle swarm as the initial search point, adjust the Rosenbrock algorithm to perform a local search, update Pi and Pg, and output the three variables of the particle.

Although the above-mentioned invention patent application can improve the response speed of the system, it does not solve the problem that the inertial delay of the superheated steam temperature control channel is large and the response of the adjusted quantity is slow. Poor quality problem.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is how to improve the control quality of the three-stage superheater when the temperature of the main steam is controlled by spraying water to reduce the temperature.

The present invention solves the above technical problems through the following technical solutions.

A secondary reheating main steam temperature cascade control system, comprising a primary loop control system, a secondary loop control system, a secondary superheater (1), a secondary desuperheater (2), a tertiary superheater (4), A PID controller (9), a desuperheating water regulating valve (10); the secondary superheater (1), the secondary desuperheater (2), and the tertiary superheater (4) are connected in series by sealed pipes in sequence; 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 to the secondary desuperheater (2). between the superheater (2) and the tertiary superheater (4), for collecting the steam temperature at the inlet of the tertiary superheater (4); the output end of the secondary loop control system is connected to the PID controller (9) , used to control the opening of the desuperheater (10) to roughly adjust the main steam temperature 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) is used to collect the main steam temperature at the outlet of the tertiary superheater (4), and the output end of the main loop control system is connected to the PID controller (9) for controlling the opening of the desuperheating water regulating valve (10). The main steam temperature at the outlet of the third-stage superheater (4) is finely adjusted.

The steam temperature at the inlet of the tertiary superheater is consistent with the change trend of the main steam temperature at the outlet, and the response speed of the steam temperature at the inlet of the tertiary superheater is significantly faster than that of the main steam temperature at the outlet. The steam temperature at the inlet of the tertiary superheater is used as the parameter of the secondary loop control system of the cascade control system of the main steam temperature, which is used to control the opening of the desuperheating water regulating valve to make a rough adjustment of the main steam temperature at the outlet of the tertiary superheater, which improves the The response speed of the control system improves the control quality of the control system.

As a further improvement of the technical solution of the present invention, the secondary loop control system includes a first thermocouple temperature sensor (3) and a first temperature transmitter (6); the primary loop control system includes a second thermocouple temperature a sensor (5), a second temperature transmitter (7), and an intelligent particle swarm operator (8); the first thermocouple temperature sensor (3) is installed at the output end of the secondary desuperheater (2); The first thermocouple temperature sensor (3) is electrically connected with the first temperature transmitter (6), and the output end of the first temperature transmitter (6) is electrically connected with the PID controller (9); The second thermocouple temperature sensor (5) is installed at the output end of the three-stage superheater (4); the second thermocouple temperature sensor (5) is electrically connected with the second temperature transmitter (7); The output end of the second temperature transmitter (7) is electrically connected with the particle swarm intelligence calculator (8); the output end of the particle swarm intelligence calculator (8) is electrically connected with the PID controller (9) ; The output end of the PID controller (9) is electrically connected with the control end of the desuperheating water regulating valve (10).

As a further improvement of the technical solution of the present invention, the first thermocouple temperature sensor (3) collects the temperature of the output end of the secondary desuperheater (2), and sends the temperature signal to the first temperature transmitter (6), so that the The described first temperature transmitter (6) converts the temperature signal into a standard electrical signal having a linear relationship with the temperature and sends it to the PID controller (9); at the same time, the described second thermocouple temperature sensor (5) ) collects the temperature at the output end of the third-stage superheater (4), sends the temperature signal to the second temperature transmitter (7), and the second temperature transmitter (7) converts the temperature signal into an electromotive force signal and sends it to the particle In the swarm intelligence calculator (8), the particle swarm intelligence calculator (8) sends the input standard electrical signal into the PID controller (9) after calculation; the PID controller (9) controls the subtraction according to the input signal. The opening of the warm water regulating valve (10).

As a further improvement of the technical solution of the present invention, when the temperature of the first thermocouple temperature sensor (3) changes, the main steam temperature at the outlet of the third-stage superheater (4) is firstly adjusted roughly; the roughness is specifically: the temperature After the signal is directly calculated by the PID controller (9), the opening of the desuperheating water regulating valve (10) is changed to change the flow rate of the desuperheating water, and the steam temperature at the inlet of the third-stage superheater (4) is initially maintained. (4) The main steam temperature at the outlet is roughly adjusted; then the main steam temperature at the outlet of the third-stage superheater (4) is finely adjusted; the fine adjustment is specifically: fine adjustment of the main steam temperature at the outlet of the third-stage superheater (4). Controlled by the particle swarm intelligence calculator (8), 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 intelligence calculator (8) changes continuously, making the PID control The device (9) continuously adjusts the opening of the desuperheating water regulating valve (10) to change the flow rate of the desuperheating water until the main steam temperature returns to the set value of the main steam temperature.

As a further improvement of the technical solution of the present invention, the thermocouple temperature sensor adopts a high-temperature K-type thermocouple from Omega Company. The K-type thermocouple can directly measure the temperature of liquid vapor in the range of 0°C to 1300°C, and the model is KQXL-14E -18.

As a further improvement of the technical solution of the present invention, the desuperheating water regulating valve (10) adopts the pneumatic valve of Vatak Company. Automatic control.

A control method applied to a secondary reheat main steam temperature cascade control system, comprising the following steps:

Step 1, make the difference between the main steam temperature set value r(t) and the system output value y(t) to obtain the error value e(t), the calculation formula is:

e(t)=r(t)-y(t) (1)

Among them, r(t) is the main steam temperature set value, y(t) is the system output value, and e(t) is the error value.

In step 2, the error value e(t) is sent to the particle swarm intelligent calculator (8) for operation, and the proportional coefficient K _p , the integral coefficient K _i , and the differential coefficient K _d are obtained; the proportional coefficient K _p , the integral coefficient K _i , the differential coefficient K _d is input into the PID controller (9) to obtain the controller output value u(t), and the calculation formula of the controller output value u(t) is:

Among them, K _p , K _i and K _d are proportional, integral and differential coefficients, respectively, u(t) is the output value of the controller, t is the independent variable, and τ is the intermediate variable of integration;

In step 3, the controller output value u(t) and the disturbance of the secondary loop are jointly input to the control object transfer function device and then output the system output value y(t) to control the opening of the desuperheating water regulating valve (10).

As a further improvement of the technical solution of the present invention, the computing method in the particle swarm intelligence calculator (8) in the second step is:

1) Initialize the particle swarm, randomly generate the position and velocity of the particle, and determine the optimal position of the particle and the optimal position of the entire particle swarm;

2) Compare the fitness value of each particle with its optimal position, and update the optimal position;

3) Compare the fitness value of each particle with the optimal position experienced by the entire particle swarm, and update the optimal position of the entire particle swarm;

4) According to formula (3) and formula (4), update the speed and position of the particle;

5) If the number of iterations and the absolute error time integral meet the requirements, exit the algorithm and obtain the optimal solution, otherwise return to step 2).

As a further improvement of the technical solution of the present invention, the formula of the speed and position of the updated particles in the step 4) is:

x _t+1 = x _t +v _t+1 (4)

Among them, v _t and v _t+1 represent the velocities before and after the particle update respectively; x _t and x _t+1 represent the position before and after the particle update respectively; c ₁ , c ₂ are acceleration constants; r ₁ , r ₂ is the generated random number; P _t ^best and G _t ^best are the individual optimal position and the global optimal position of the particle, respectively, and w is the inertia factor.

As a further improvement of the technical solution of the present invention, the absolute error time integral value in the step 5) is used as the performance evaluation index of the particle swarm intelligence calculator, and the smaller the value is, the better the performance of the system; the absolute error time integral value is described. The calculation formula is:

Among them, J _min is the absolute error time integral value, e(t) is the error between the output and the input, and t is the time;

The number of iterations and the time integral of absolute error meeting the requirements means that the number of iterations reaches the set value of 600, while the time integral value of the absolute error is less than the set value of 0.1.

The advantages of the present invention are:

(1) The present invention is consistent with the change trend of the steam temperature at the inlet of the third-stage superheater and the main steam temperature at the outlet, and the response speed of the steam temperature at the inlet of the third-stage superheater is obviously faster than that of the main steam temperature at the outlet. The steam temperature at the inlet of the tertiary superheater is added to the control channel of the 3-stage superheater as a parameter of the secondary loop control system of the cascade control system of the main steam temperature, which is used to control the opening of the desuperheater control valve to the main steam temperature at the outlet of the tertiary superheater. The rough adjustment improves the response speed of the control system and improves the control quality of the control system.

(2) The main steam temperature cascade control system of the present invention adopts the particle swarm algorithm, which not only has the characteristics of fast response speed of the cascade system, but also combines the intelligent operation of the particle swarm algorithm to automatically adjust the PID parameters of the main loop, so that the PID The cascade control setting method is simple and adaptable to operating conditions.

Description of drawings

1 is a structural diagram of a cascade control system for secondary reheat main steam temperature according to an embodiment of the present invention;

Fig. 2 is the control block diagram of the cascade control system of secondary reheat main steam temperature according to the embodiment of the present invention;

Fig. 3 is the control method flow chart of the secondary reheat main steam temperature cascade control system of the embodiment of the present invention;

Fig. 4 is the simulation model diagram of the secondary reheat main steam temperature cascade control system according to the embodiment of the present invention;

FIG. 5 is a simulation result diagram of a cascade control system for the temperature of the secondary reheat main steam according to an embodiment of the present invention.

Detailed ways

In order to make the purposes, 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 in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The technical solutions of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments:

Example 1

As shown in Figure 1, a secondary reheat main steam temperature cascade control system includes a primary loop control system, a secondary loop control system, a secondary superheater 1, a secondary desuperheater 2, a tertiary superheater 4, The PID controller 9, the desuperheating water regulating valve 10; the secondary superheater 1, the secondary desuperheater 2, and the tertiary superheater 4 are connected in series by sealed pipes in sequence; the desuperheating water regulating valve 10 is connected by a three-way The sealed pipeline is connected between the secondary superheater 1 and the secondary desuperheater 2; the input end of the secondary loop control system is connected between the secondary desuperheater 2 and the tertiary superheater 4 for collecting three The steam temperature at the inlet of the stage superheater 4; the output end of the secondary loop control system is connected with the PID controller 9, which is used to control the opening of the desuperheating water regulating valve 10 to roughen the main steam temperature at the outlet of the third stage superheater 4. The input end of the main loop control system is connected to the outlet of the tertiary superheater 4 for collecting the main steam temperature at the outlet of the tertiary superheater 4, and the output end of the main loop control system is connected to the PID controller 9 It is used to control the opening of the desuperheating water regulating valve 10 to finely adjust the main steam temperature at the outlet of the three-stage superheater 4 .

The steam temperature at the inlet of the tertiary superheater is consistent with the change trend of the main steam temperature at the outlet, and the response speed of the steam temperature at the inlet of the tertiary superheater is significantly faster than that of the main steam temperature at the outlet. The steam temperature at the inlet of the tertiary superheater is used as the parameter of the secondary loop control system of the cascade control system of the main steam temperature, which is used to control the opening of the desuperheating water regulating valve to make a rough adjustment of the main steam temperature at the outlet of the tertiary superheater, which improves the The response speed of the control system improves the control quality of the control system.

The secondary loop control system includes a first thermocouple temperature sensor 3 and a first temperature transmitter 6; the primary loop control system includes a second thermocouple temperature sensor 5, a second temperature transmitter 7, a particle swarm Intelligent calculator 8; the first thermocouple temperature sensor 3 is installed at the output end of the secondary desuperheater 2; the first thermocouple temperature sensor 3 is electrically connected with the first temperature transmitter 6, the The output end of the first temperature transmitter 6 is electrically connected with the PID controller 9; the second thermocouple temperature sensor 5 is installed at the output end of the three-stage superheater 4; the second thermocouple temperature sensor 5 is electrically connected with the second temperature transmitter 7; the output end of the second temperature transmitter 7 is electrically connected with the particle swarm intelligence calculator 8; the output end of the particle swarm intelligence calculator 8 is connected with the PID controller 9 is electrically connected; the output end of the PID controller 9 is electrically connected to the control end of the desuperheating water regulating valve 10 .

The first thermocouple temperature sensor 3 collects the temperature of 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 The standard electrical signal whose temperature is in a linear relationship is sent to the PID controller 9; at the same time, the second thermocouple temperature sensor 5 collects the temperature of the output end of the third-stage superheater 4, and sends the temperature signal to the second temperature transmitter The second temperature transmitter 7 converts the temperature signal into an electromotive force signal and sends it to the particle swarm intelligent calculator 8, and the particle swarm intelligent calculator 8 calculates the input standard electrical signal and sends it to the PID control In the device 9; the PID controller 9 controls the opening of the desuperheating water regulating valve 10 according to the input signal.

When the temperature of the first thermocouple temperature sensor 3 changes, the main steam temperature at the outlet of the third-stage superheater 4 is roughly adjusted first; Adjust the opening of the valve 10 to change the flow rate of the desuperheating water, initially maintain the steam temperature at the inlet of the tertiary superheater 4, and make rough adjustments to the main steam temperature at the outlet of the tertiary superheater 4; The temperature is finely adjusted; the fine adjustment is specifically: the fine adjustment of the main steam temperature at the outlet of the third-stage superheater 4 is controlled by the particle swarm intelligent calculator 8, as long as the outlet steam temperature of the third-stage superheater 4 does not reach the main steam temperature setting When the value is fixed, the output of the particle swarm intelligence calculator 8 will change continuously, so that the PID controller 9 will continuously adjust the opening of the desuperheating water regulating valve 10 to change the flow rate of the desuperheating water until the main steam temperature returns to the main steam temperature setting. value up to.

The thermocouple temperature sensor uses a high-temperature K-type thermocouple from Omega Company. The K-type thermocouple can directly measure the temperature of liquid vapor in the range of 0°C to 1300°C, and the model is KQXL-14E-18.

The desuperheating water regulating valve 10 adopts the pneumatic valve of Vatak Company. The characteristic of the pneumatic desuperheating water regulating valve is to automatically adjust the flow rate of the system according to the input signal, so as to realize the automatic control during the operation of the unit.

The particle swarm intelligence calculator 8 sends the input standard electrical signal into the PID controller 9 after calculation; the PID controller 9 controls the opening of the desuperheating water regulating valve 10 according to the input signal.

As shown in FIG. 2 , the method for the particle swarm intelligence calculator 8 to send the input standard electrical signal into the PID controller 9 after calculation includes the following steps:

Step 1, make the difference between the main steam temperature set value r(t) and the system output value y(t) to obtain the error value e(t), the calculation formula is:

e(t)=r(t)-y(t) (1)

Among them, r(t) is the main steam temperature set value, y(t) is the system output value, and e(t) is the error value.

In step 2, the error value e(t) is sent to the particle swarm intelligent calculator 8 for operation, and the proportional coefficient K _p , the integral coefficient K _i , and the differential coefficient K _d are obtained; the proportional coefficient K _p , the integral coefficient K _i , the differential coefficient K The coefficient K _d is input into the PID controller 9 to obtain the controller output value u(t), and the calculation formula of the controller output value u(t) is:

Among them, K _p , K _i and K _d are proportional, integral and differential coefficients, respectively, u(t) is the output value of the controller, t is the independent variable, and τ is the intermediate variable of integration;

Step 3: The controller output value u(t) and the disturbance of the secondary loop are jointly input to the control object transfer function device and output the system output value y(t) to control the opening of the desuperheating water regulating valve 10 .

As shown in FIG. 3 , the method for computing in the particle swarm intelligence calculator 8 in the second step is:

1) Initialize the particle swarm, randomly generate the position and velocity of the particle, and determine the optimal position of the particle and the optimal position of the entire particle swarm;

2) Compare the fitness value of each particle with its optimal position, and update the optimal position;

3) Compare the fitness value of each particle with the optimal position experienced by the entire particle swarm, and update the optimal position of the entire particle swarm;

4) According to formula (3) and formula (4), update the speed and position of the particle;

The formulas for updating the speed and position of particles are:

x _t+1 = x _t +v _t+1 (4)

Among them, v _t and v _t+1 represent the velocities before and after the particle update respectively; x _t and x _t+1 represent the position before and after the particle update respectively; c ₁ , c ₂ are acceleration constants; r ₁ , r ₂ is the generated random number; P _t ^best and G _t ^best are the individual optimal position and the global optimal position of the particle, respectively, and w is the inertia factor.

5) If the number of iterations and the absolute error time integral meet the requirements, exit the algorithm and obtain the optimal solution, otherwise return to step 2).

The absolute error time integral value is used as the performance evaluation index of the particle swarm intelligence calculator, and the smaller the value, the better the performance of the system; the calculation formula of the absolute error time integral is:

Among them, J _min is the absolute error time integral value, e(t) is the error between the output and the input, and t is the time.

The number of iterations and the time integral of the absolute error in the step 5 meet the requirements means that the number of iterations reaches the set value of 600, while the time integral value of the absolute error is less than the set value of 0.1.

As shown in Figure 4, the described control method is tested through simulation experiments, the PSO algorithm program is written on the simulation analysis Matlab, and the PID model file is built in the Simulink system at the same time;

Enter the Simulink modeling interface to build the model, and set the initial parameters of the standard particle swarm algorithm as follows: the number of particles pop is 40; the maximum number of iterations is 100; the location search range of the three parameters K _p , K _i , K _d is [0, 100], the speed range is [-1, 1]; the learning factor c1=c2=1.49; the inertia weight decreases linearly from 0.9 to 0.3; according to the control characteristics of the main steam temperature in the industrial site, the simulation time is set to 500s; Particle swarm optimization algorithm performs PID tuning, and can get:

Kp=22.5632, Ki=0.1704, Kd=98.4566;

As shown in Figure 5, the simulation results show that after the optimization of the particle swarm algorithm, the system output decreases and tends to be stable immediately after the first oscillation occurs. The stabilization time is 60s, and the control performance of the main regulation loop is significantly improved.

Embodiment 2

As shown in Figure 3, a control method applied to the described secondary reheat main steam temperature cascade control system includes the following steps:

Step 1, make the difference between the main steam temperature set value r(t) and the system output value y(t) to obtain the error value e(t), the calculation formula is:

e(t)=r(t)-y(t) (1)

Among them, r(t) is the main steam temperature set value, y(t) is the system output value, and e(t) is the error value;

In step 2, the error value e(t) is sent to the particle swarm intelligent calculator 8 for operation, and the proportional coefficient K _p , the integral coefficient K _i , and the differential coefficient K _d are obtained; the proportional coefficient K _p , the integral coefficient K _i , the differential coefficient K The coefficient K _d is input into the PID controller 9 to obtain the controller output value u(t), and the calculation formula of the controller output value u(t) is:

Among them, K _p , K _i and K _d are proportional, integral and differential coefficients, respectively, u(t) is the output value of the controller, t is the independent variable, and τ is the intermediate variable of integration;

According to formula (2), the transfer function formula obtained is:

Among them, T _i is the integral time constant, T _d is the differential time constant;

The method for computing in the particle swarm intelligence calculator 8 in the second step is:

1) Initialize the particle swarm, randomly generate the position and velocity of the particle, and determine the optimal position of the particle and the optimal position of the entire particle swarm;

2) Compare the fitness value of each particle with its optimal position, and update the optimal position;

3) Compare the fitness value of each particle with the optimal position experienced by the entire particle swarm, and update the optimal position of the entire particle swarm;

4) According to formula (3) and formula (4), update the speed and position of the particle;

The formula of the speed and position of the described update particle in the described step 4) is:

x _t+1 = x _t +v _t+1 (4)

Among them, v _t and v _t+1 represent the velocities before and after the particle update respectively; x _t and x _t+1 represent the position before and after the particle update respectively; c ₁ , c ₂ are acceleration constants; r ₁ , r ₂ is the generated random number; P _t ^best and G _t ^best are the individual optimal position and the global optimal position of the particle, respectively, and w is the inertia factor.

5) If the number of iterations and the absolute error time integral meet the requirements, exit the algorithm and obtain the optimal solution, otherwise return to step 2).

The absolute error time integral value in the described step 5) is used as the performance evaluation index of the particle swarm intelligence calculator, and the smaller the value, the better the performance of the system; the calculation formula of the absolute error time integral is:

Among them, J _min is the absolute error time integral value, e(t) is the error between the output and the input, and t is the time;

The number of iterations and the time integral of absolute error meeting the requirements means that the number of iterations reaches the set value of 600, while the time integral value of the absolute error is less than the set value of 0.1.

In step 3, the controller output value u(t) and the disturbance of the secondary loop are jointly input to the control object transfer function device and then output the system output value y(t) to control the opening of the desuperheating water regulating valve (10).

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A secondary reheating main steam temperature cascade control system, characterized in that it comprises a main loop control system, a secondary loop control system, a secondary superheater (1), a secondary desuperheater (2), a three-stage desuperheater (2), a A superheater (4), a PID controller (9), and a desuperheater (10); the secondary superheater (1), the secondary desuperheater (2), and the tertiary superheater (4) are sequentially used The sealing pipes are connected in series; the desuperheating water regulating valve (10) is connected between the secondary superheater (1) and the secondary desuperheater (2) through a three-way sealing pipe; the input of the secondary loop control system The end is connected between the secondary desuperheater (2) and the tertiary superheater (4), and is used to collect the steam temperature at the inlet of the tertiary superheater (4); the output end of the secondary loop control system is connected to the PID The controller (9) is connected to control the opening of the desuperheating water regulating valve (10) to roughly adjust the main steam temperature at the outlet of the third-stage superheater (4); the input end of the main loop control system is connected to the third-stage superheater (4). The outlet of the superheater (4) is used to collect the main steam temperature at the outlet of the third-stage superheater (4). 10) to finely adjust the main steam temperature at the outlet of the third-stage superheater (4). 2. A secondary reheat main steam temperature cascade control system according to claim 1, characterized in that the secondary loop control system comprises a first thermocouple temperature sensor (3), a first temperature transmitter device (6); the main loop control system includes a second thermocouple temperature sensor (5), a second temperature transmitter (7), and a particle swarm intelligence calculator (8); the first thermocouple temperature The sensor (3) is installed at the output end of the secondary desuperheater (2); the first thermocouple temperature sensor (3) is electrically connected with the first temperature transmitter (6), and the first temperature changes The output end of the transmitter (6) is electrically connected with the PID controller (9); the second thermocouple temperature sensor (5) is installed at the output end of the three-stage superheater (4); the second thermocouple The temperature sensor (5) is electrically connected with the second temperature transmitter (7); the output end of the second temperature transmitter (7) is electrically connected with the particle swarm intelligent calculator (8); the particle swarm The output end of the intelligent calculator (8) is electrically connected with the PID controller (9); the output end of the PID controller (9) is electrically connected with the control end of the desuperheating water regulating valve (10). 3. A secondary reheating main steam temperature cascade control system according to claim 2, characterized in that the first thermocouple temperature sensor (3) collects the temperature of the output end of the secondary desuperheater (2). temperature, the temperature signal is sent to the first temperature transmitter (6), and the first temperature transmitter (6) converts the temperature signal into a standard electrical signal that has a linear relationship with the temperature and sends it to the PID controller (9) ); at the same time, the second thermocouple temperature sensor (5) collects the temperature at the output end of the third-stage superheater (4), and sends the temperature signal into the second temperature transmitter (7), and the first 2. The temperature transmitter (7) converts the temperature signal into an electromotive force signal and sends it to the particle swarm intelligent calculator (8), and the particle swarm intelligent calculator (8) calculates the input standard electrical signal and sends it to the PID controller In (9); the PID controller (9) controls the opening of the desuperheating water regulating valve (10) according to the input signal. 4. A kind of secondary reheating main steam temperature cascade control system according to claim 3, it is characterized in that, when the temperature at the first thermocouple temperature sensor (3) changes, first the three-stage superheater ( 4) The main steam temperature at the outlet is roughly adjusted; the rough details are: after the temperature signal is directly calculated by the PID controller (9), the opening of the desuperheating water regulating valve (10) is changed to change the flow rate of the desuperheating water, and the initial maintenance The steam temperature at the inlet of the third-stage superheater (4) is roughly adjusted for the main steam temperature at the outlet of the third-stage superheater (4); and the main steam temperature at the outlet of the third-stage superheater (4) is finely adjusted; The adjustment is as follows: the fine adjustment of the main steam temperature at the outlet of the third-stage superheater (4) is controlled by the particle swarm intelligent calculator (8). As long as the outlet steam temperature of the third-stage superheater (4) does not reach the set value of the main steam temperature, The output of the particle swarm intelligence calculator (8) changes continuously, so that the PID controller (9) continuously adjusts the opening of the desuperheating water regulating valve (10) to change the flow rate of the desuperheating water until the main steam temperature returns to the main steam temperature. temperature setting value. 5. a kind of secondary reheat main steam temperature cascade control system according to claim 4, is characterized in that, the high temperature K type thermocouple of Omega company that the described thermocouple temperature sensor adopts, model is KQXL-14E -18. 6 . The secondary reheat main steam temperature cascade control system according to claim 5 , wherein the desuperheating water regulating valve ( 10 ) adopts a pneumatic valve of Vatak Company. 7 . 7. A control method applied to the secondary reheat main steam temperature cascade control system described in any one of claims 2-6, comprising the following steps: Step 1, make the difference between the main steam temperature set value r(t) and the system output value y(t) to obtain the error value e(t), the calculation formula is: e(t)=r(t)-y(t) (1) Among them, r(t) is the main steam temperature set value, y(t) is the system output value, and e(t) is the error value; In step 2, the error value e(t) is sent to the particle swarm intelligent calculator (8) for operation, and the proportional coefficient K _p , the integral coefficient K _i , and the differential coefficient K _d are obtained; the proportional coefficient K _p , the integral coefficient K _i , the differential coefficient K _d is input into the PID controller (9) to obtain the controller output value u(t), and the calculation formula of the controller output value u(t) is:

Among them, K _p , K _i and K _d are proportional, integral and differential coefficients, respectively, u(t) is the output value of the controller, t is the independent variable, and τ is the intermediate variable of integration; In step 3, the controller output value u(t) and the disturbance of the secondary loop are jointly input to the control object transfer function device and then output the system output value y(t) to control the opening of the desuperheating water regulating valve (10). 8 . The control method for a secondary reheat main steam temperature cascade control system according to claim 7 , wherein the method for computing in the particle swarm intelligence calculator (8) in the second step for: 1) Initialize the particle swarm, randomly generate the position and velocity of the particle, and determine the optimal position of the particle and the optimal position of the entire particle swarm; 2) Compare the fitness value of each particle with its optimal position, and update the optimal position; 3) Compare the fitness value of each particle with the optimal position experienced by the entire particle swarm, and update the optimal position of the entire particle swarm; 4) According to formula (3) and formula (4), update the speed and position of the particle; 5) If the number of iterations and the absolute error time integral meet the requirements, exit the algorithm and obtain the optimal solution, otherwise return to step 2). 9. the control method of a kind of secondary reheat main steam temperature cascade control system according to claim 8, is characterized in that, described step 4) the described formula of updating particle speed and position is:

x _t+1 = x _t +v _t+1 (4) Among them, v _t and v _t+1 represent the velocities before and after the particle update respectively; x _t and x _t+1 represent the position before and after the particle update respectively; c ₁ , c ₂ are acceleration constants; r ₁ , r ₂ is the random number generated; P _t ^best and

are the individual optimal position and the global optimal position of the particle, respectively, and w is the inertia factor. 10. The control method of a secondary reheating main steam temperature cascade control system according to claim 8, wherein the absolute error time integral value in the step 5) is used as the value of the particle swarm intelligence calculator. Performance evaluation index, the smaller the value, the better the performance of the system; the calculation formula of the absolute error time integral is:

Among them, J _min is the absolute error time integral value, e(t) is the error between the output and the input, and t is the time; The number of iterations and the time integral of absolute error meeting the requirements means that the number of iterations reaches the set value of 600, while the time integral value of the absolute error is less than the set value of 0.1.

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