Carbon Dioxide Capture Control System and Control Method

Abstract

The present disclosure relates to a carbon dioxide capture control system and a control method, belonging to the field of carbon capture. The carbon dioxide capture control system includes a capture subsystem and a control subsystem, and the carbon dioxide capture control system includes a plurality of control loops. The control variables of the carbon dioxide capture control system include the lean liquid flow rate and the steam extraction flow rate of the steam turbine, and the controlled variables include the carbon dioxide capture rate and the reboiler temperature. The target closed-loop transfer function of the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem. The target controller transfer function is determined by sequentially closing a plurality of control loops. The scalar return difference of each subsystem obtained after sequentially closing each control loop satisfies a preset stability condition. The scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system, and the preset stability condition includes: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane.

Description

Technical Field

[0001] The present disclosure relates to the field of carbon capture, and in particular, to a carbon dioxide capture control system and a control method. Background Art

[0002] In the existing CO 2 capture technology for coal-fired power generation systems, the post-combustion CO 2 capture technology based on chemical absorption of monoethanolamine (MEA) is relatively mature. This method directly separates CO 2 from flue gas, and has excellent inheritance for existing generator sets and good technical applicability. Since the CO 2 capture process involves many chemical changes and different equipment, there is strong coupling and great inertia between the variables of the system. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a carbon dioxide capture control system and a control method, which are used to reduce the coupling degree of each control loop while ensuring the stability of the carbon dioxide capture control system.

[0004] According to the first aspect of the embodiments of the present disclosure, a carbon dioxide capture control system is provided. The control variables of the carbon dioxide capture control system include lean liquid flow rate and steam extraction flow rate of the steam turbine, and the controlled variables of the carbon dioxide capture control system include carbon dioxide capture rate and reboiler temperature; the carbon dioxide capture control system includes a capture subsystem and a control subsystem, and the carbon dioxide capture control system includes a plurality of control loops;

[0005] The target closed-loop transfer function corresponding to the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem; the target controller transfer function is determined by sequentially closing the plurality of control loops;

[0006] The scalar return difference of each subsystem obtained after sequentially closing each control loop satisfies a preset stability condition; the scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system, and the preset stability condition includes: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane.

[0007] Optionally, the carbon dioxide capture control system is obtained by the following method:

[0008] Determine the target object transfer function of the capture subsystem;

[0009] Determine the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of each subsystem obtained after sequentially closing each control loop, and each scalar return difference corresponding to the target controller transfer function satisfies the preset stability condition;

[0010] According to the target object transfer function and the target controller transfer function, determine the target closed-loop transfer function to obtain the carbon dioxide capture control system corresponding to the target closed-loop transfer function.

[0011] Optionally, the determining the target object transfer function of the capture subsystem includes:

[0012] Use the step excitation signal corresponding to the sample lean liquid flow rate and the sample steam extraction flow rate of the steam turbine as the input of the capture subsystem to obtain the step response signal corresponding to the sample carbon dioxide capture rate and the sample reboiler temperature;

[0013] According to the step excitation signal and the step response signal, identify the target object transfer function.

[0014] Optionally, the control loop includes: a first control loop and a second control loop. The input of the first control loop is the lean liquid flow rate, the output of the first control loop is the carbon dioxide capture rate, the input of the second control loop is the steam extraction flow rate of the steam turbine, and the output of the second control loop is the reboiler temperature; the determining the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of each subsystem obtained after sequentially closing each control loop includes:

[0015] Determine the first controller transfer function of the first control loop according to the target object transfer function;

[0016] Close the first control loop to obtain a target subsystem, and determine the first closed-loop transfer function of the target subsystem according to the first controller transfer function and the first open-loop transfer function of the first control loop;

[0017] Determine the second controller transfer function of the second control loop according to the target object transfer function;

[0018] Determine the target controller transfer function according to the first controller transfer function and the second controller transfer function.

[0019] Optionally, the first controller transfer function includes: a first transfer sub-function, a second transfer sub-function, and a third transfer sub-function; the determining the first controller transfer function of the first control loop according to the target object transfer function includes:

[0020] Determine the first transfer sub-function and the second transfer sub-function;

[0021] Determine the first open-loop transfer function of the first control loop according to the target object transfer function, the first transfer sub-function and the second transfer sub-function;

[0022] Determine the third transfer sub-function according to the first open-loop transfer function and the first scalar back-off of the first control loop, and the first scalar back-off corresponding to the third transfer sub-function satisfies the preset stability condition.

[0023] Optionally, the determining the first closed-loop transfer function of the target subsystem according to the first controller transfer function and the first open-loop transfer function of the first control loop includes:

[0024] Determine the first closed-loop transfer function according to the first open-loop transfer function, the third transfer sub-function and the first scalar back-off.

[0025] Optionally, the second controller transfer function includes: a fourth transfer sub-function and a fifth transfer sub-function; the determining the second controller transfer function of the second control loop according to the target object transfer function includes:

[0026] Determine the fourth transfer sub-function;

[0027] Use the first closed-loop transfer function as the second open-loop transfer function of the second control loop;

[0028] Determine the fifth transfer sub-function according to the second open-loop transfer function and the second scalar back-off of the second control loop, and the second scalar back-off corresponding to the fifth transfer sub-function satisfies the preset stability condition.

[0029] Optionally, the determining the target controller transfer function according to the first controller transfer function and the second controller transfer function includes:

[0030] Use the first transfer sub-function as the first target transfer function;

[0031] Use the product of the second transfer sub-function and the fourth transfer sub-function as the second target transfer function;

[0032] Use the diagonal matrix corresponding to the third transfer sub-function and the fifth transfer sub-function as the third target transfer function;

[0033] Use the product of the first target transfer function, the second target transfer function and the third target transfer function as the target controller transfer function.

[0034] Optionally, the method for determining the carbon dioxide capture control system further includes:

[0035] Determining the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function;

[0036] When the coupling degree is greater than a preset threshold, repeatedly execute the steps of determining the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of each subsystem obtained after sequentially closing each control loop until the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function is less than or equal to the preset threshold.

[0037] According to a second aspect of the embodiments of the present disclosure, there is provided a carbon dioxide capture control method, which is applied to the carbon dioxide capture control system described in the first aspect of the present disclosure. The method includes:

[0038] Obtaining the actual carbon dioxide capture rate and the actual reboiler temperature of the capture subsystem of the carbon dioxide capture control system;

[0039] Determining the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine according to the actual carbon dioxide capture rate, the actual reboiler temperature, the preset carbon dioxide capture rate, and the preset reboiler temperature;

[0040] Controlling the lean liquid flow rate and the steam extraction flow rate of the steam turbine of the capture subsystem according to the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine, so that the carbon dioxide capture rate of the capture subsystem is equal to the preset carbon dioxide capture rate, and the reboiler temperature of the capture subsystem is equal to the preset reboiler temperature.

[0041] Through the above technical solution, the carbon dioxide capture control system in the present disclosure includes a capture subsystem and a control subsystem, and the carbon dioxide capture control system includes a plurality of control loops. The control variables of the carbon dioxide capture control system include the lean liquid flow rate and the turbine extraction steam flow rate, and the controlled variables of the carbon dioxide capture control system include the carbon dioxide capture rate and the reboiler temperature. The target closed-loop transfer function corresponding to the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem. The target controller transfer function is determined by sequentially closing a plurality of control loops. The scalar return difference of each subsystem obtained after sequentially closing each control loop satisfies a preset stability condition. The scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system, and the preset stability condition includes: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane. The carbon dioxide capture control system in the present disclosure can reduce the coupling degree of each control system while ensuring stability and response speed, and has stronger setpoint tracking and disturbance rejection capabilities.

[0042] Other features and advantages of the present disclosure will be described in detail in the following specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0044] Figure 1 is a block diagram of a carbon dioxide capture control system shown according to an exemplary embodiment.

[0045] Figure 2 is shown according to an exemplary embodiment zero-pole distribution diagram of.

[0046] Figure 3 is shown according to an exemplary embodiment of t 1 (s) zero-pole distribution diagram.

[0047] Figure 4 is shown according to an exemplary embodiment of t 1 (s) Nyquist locus diagram.

[0048] Figure 5 is shown according to an exemplary embodiment of t 2 (s) zero-pole distribution diagram.

[0049] Figure 6 is shown according to an exemplary embodiment of a t 2 (s) Nyquist locus diagram.

[0050] Figure 7 is another Nyquist locus diagram of t 2 (s).

[0051] Figure 8 is a schematic diagram of the unit step response simulation results of four elements of H(s) shown according to an exemplary embodiment.

[0052] Figure 9 is a schematic diagram of the control effect of the output variable under a step change in the carbon dioxide capture rate shown according to an exemplary embodiment.

[0053] Figure 10 is a flowchart of a carbon dioxide capture control method shown according to an exemplary embodiment. Detailed implementation manners

[0054] The following will describe in detail the specific implementation manners of the present disclosure with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0055] Figure 1 is a block diagram of a carbon dioxide capture control system shown according to an exemplary embodiment. As Figure 1 shown, the carbon dioxide capture control system 100 includes a capture subsystem 101 and a control subsystem 102. The carbon dioxide capture control system includes a plurality of control loops. The control variables of the carbon dioxide capture control system include the lean liquid flow rate and the turbine extraction steam flow rate, and the controlled variables of the carbon dioxide capture control system include the carbon dioxide capture rate and the reboiler temperature.

[0056] The target closed-loop transfer function corresponding to the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem. The target controller transfer function is determined by sequentially closing a plurality of control loops. Among them, the target object transfer function and the target controller transfer function can be in matrix form.

[0057] The scalar return difference of each subsystem obtained after sequentially closing each control loop satisfies a preset stability condition.

[0058] Among them, the scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system. The preset stability condition can be the Nyquist stability criterion. The preset stability condition may include: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane, and the complex plane can be understood as the s-plane in the complex frequency domain.

[0059] Exemplarily, the carbon dioxide capture control system in the present disclosure may include a capture subsystem and a control subsystem. Among them, the capture subsystem can be used to capture carbon dioxide in the flue gas emitted from combustion, which belongs to post-combustion carbon dioxide capture. The control subsystem can be used to control the capture subsystem. That is to say, the control subsystem can be the control system of the capture subsystem.

[0060] The carbon dioxide capture control system in the present disclosure can be designed based on the sequential design method. The control variables of the carbon dioxide capture control system may include the lean liquid flow rate and the steam extraction flow rate of the steam turbine. The controlled variables of the carbon dioxide capture control system may include the carbon dioxide capture rate and the reboiler temperature. The carbon dioxide capture control system may include a plurality of control loops. Among them, the plurality of control loops may include a first control loop and a second control loop. The control variable of the first control loop may be the lean liquid flow rate, and the controlled variable of the first control loop may be the carbon dioxide capture rate. The control variable of the second control loop may be the steam extraction flow rate of the steam turbine, and the controlled variable of the second control loop may be the reboiler temperature.

[0061] In some embodiments, the carbon dioxide capture control system can be obtained in the following manner:

[0062] Step A, determine the target object transfer function of the capture subsystem.

[0063] Exemplarily, a step excitation signal corresponding to the sample lean liquid flow rate and the sample steam extraction flow rate of the steam turbine can be used as the input of the capture subsystem to obtain a step response signal corresponding to the sample carbon dioxide capture rate and the sample reboiler temperature. Then, based on the step excitation signal and the step response signal, the target object transfer function is identified.

[0064] Step B, determine the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of each subsystem obtained after sequentially closing each control loop.

[0065] Exemplarily, each control loop can be sequentially closed to obtain the corresponding subsystem, and then the target controller transfer function corresponding to the control subsystem can be determined according to the scalar return difference of each subsystem and the target object transfer function, where each scalar return difference corresponding to the target controller transfer function satisfies the preset stability condition.

[0066] In some other embodiments, first, the first controller transfer function of the first control loop can be determined according to the target object transfer function. Then, the first control loop can be closed to obtain the target subsystem, and the first closed-loop transfer function can be determined according to the first open-loop transfer function, the third transfer sub-function, and the first scalar back-off. In one implementation, the first controller transfer function can include: a first transfer sub-function, a second transfer sub-function, and a third transfer sub-function. First, the first transfer sub-function and the second transfer sub-function can be determined, and the first open-loop transfer function of the first control loop can be determined according to the target object transfer function, the first transfer sub-function, and the second transfer sub-function. Then, according to the first open-loop transfer function and the first scalar back-off of the first control loop, the third transfer sub-function is determined, and the first scalar back-off corresponding to the third transfer sub-function satisfies the preset stability condition.

[0067] For example, taking the matrix G(s) composed of the functions shown in Equations 1-4 as the target object transfer function as an example,

[0068]

[0069]

[0070]

[0071]

[0072] The identity matrix can be used as the first transfer sub-function K a , let K a = I m , that is:

[0073]

[0074] Furthermore, the second transfer sub-function K b1 (s) can be selected, and let:

[0075]

[0076] Correspondingly, the first open-loop transfer function can be calculated by Equation 7:

[0077] Q i-1 (s) = G(s)·K a (s)·K bi (s) (Equation 7)

[0078] where Q i-1 (s) is the open-loop transfer function of the i-th loop. Let i = 1, and the first open-loop transfer function Q 0 (s) can be obtained:

[0079]

[0080] Among them, its zeros and poles are as Figure 2 shown.

[0081] Then, select k c1 (s), and let:

[0082]

[0083] Calculate the first scalar return difference t 1 (s) according to Equation 10:

[0084]

[0085] Measured through simulation experiments, the zeros and poles of t 1 (s) are distributed as Figure 3 shown. The zeros and poles of t 1 (s) are both in the left half-open plane, and its Nyquist locus is as Figure 4 shown. It does not enclose the zeros and does not pass through the origin. It can be determined that the selected k c1 (s) can make the first scalar return difference meet the preset stability condition. Therefore, the rational expression shown in Equation 9 can be used as k c1 (s).

[0086] After closing the first loop, the target subsystem is obtained. The closed-loop transfer function of the target subsystem can be:

[0087]

[0088] Among them, is the first column vector of Q0(s), and q 0(1) (s) is the first row vector of Q0(s).

[0089] In Equation 11, There are no zeros in the right half-plane and there is one pole, but it does not affect the stability of the already closed first loop.

[0090] Furthermore, the second controller transfer function of the second control loop can be determined according to the target object transfer function. In one implementation, the second controller transfer function of the second control loop can include: a fourth transfer sub-function and a fifth transfer sub-function. The fourth transfer sub-function can be determined first, and the first closed-loop transfer function can be used as the second open-loop transfer function of the second control loop. Then, according to the second open-loop transfer function and the second scalar return difference of the second control loop, the fifth transfer sub-function can be determined, and the second scalar return difference corresponding to the fifth transfer sub-function meets the preset stability condition. For example, due to the structural form of the fourth transfer sub-function K b2 (s), only Kb2 (s) = I m , that is:

[0091]

[0092] Then the first closed-loop transfer function can be used as the second open-loop transfer function of the second control loop, that is: Q 1 (s) = G 1 (s),

[0093] Furthermore, k c2 (s) can be selected:

[0094]

[0095] Then t 2 (s) can be calculated according to Equation 14:

[0096]

[0097] Measured through simulation experiments, the zero and pole distributions of t 2 (s) are as shown in Figure 5 , and there is only one pole in the right half-plane. Its Nyquist locus is as shown in Figure 6 and Figure 7 , and it encloses the origin once. According to the extended form of the Nyquist stability criterion, it can be known that it also satisfies the stability condition, and |t i (s)| > 1 within a quite large range. Therefore, the selection of k c2 (s) can make the second scalar return difference meet the preset stability condition.

[0098] Finally, the target controller transfer function is determined according to the first controller transfer function and the second controller transfer function.

[0099] For example, according to the K a , K b1 , K b2 , k c1 , k c2 determined in the above embodiments, the transfer functions of each controller can be:

[0100] K a = I (Equation 15)

[0101]

[0102]

[0103] Finally, the target controller transfer function of the control subsystem can be obtained as:

[0104]

[0105] Step C: Determine the target closed-loop transfer function based on the target object transfer function and the target controller transfer function, so as to obtain a carbon dioxide capture control system corresponding to the target closed-loop transfer function.

[0106] Exemplarily, the target closed-loop transfer function of the carbon dioxide system can be:

[0107]

[0108] In some other embodiments, the method for determining the carbon dioxide capture control system may further include:

[0109] Step D: Determine the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function.

[0110] Step E: When the coupling degree is greater than a preset threshold, repeatedly execute the steps from determining the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of each subsystem obtained after sequentially closing each control loop to determining the target closed-loop transfer function based on the target object transfer function and the target controller transfer function, until the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function is less than or equal to the preset threshold.

[0111] Exemplarily, after obtaining the target closed-loop transfer function, the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function can be tested. If the coupling degree of multiple control loops is greater than the preset threshold, it can be determined that the designed carbon dioxide capture control system meets the preset standard and can, on the premise of ensuring system stability, reduce the coupling of each control loop as much as possible.

[0112] If the coupling degree of multiple control loops is greater than the preset threshold, steps B and C can be repeatedly executed until the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function is less than or equal to the preset threshold.

[0113] Measured by simulation experiments, the unit step response simulation results of the four elements h 11 (s), h 12 (s), h 21 (s), h 22 (s) in the target closed-loop transfer function obtained according to Equations 1 to 19 are as Figure 8 shown, and it can be seen that the strong coupling between the first control loop and the second control loop can be improved to a certain extent. The control curves of the control variables (lean liquid flow rate and turbine extraction steam flow rate) and the controlled variables (carbon dioxide capture rate and reboiler temperature) in the carbon dioxide capture control system are as Figure 9As shown, when the capture rate undergoes a step change, the controller can maintain the reboiler temperature constant by adjusting the lean liquid flow rate and the reboiler steam extraction flow rate, verifying the effectiveness of the proposed post-combustion carbon dioxide capture control system based on the sequential design method.

[0114] In summary, the carbon dioxide capture control system in the present disclosure includes a capture subsystem and a control subsystem, and the carbon dioxide capture control system includes multiple control loops. The control variables of the carbon dioxide capture control system include the lean liquid flow rate and the steam extraction flow rate of the steam turbine, and the controlled variables of the carbon dioxide capture control system include the carbon dioxide capture rate and the reboiler temperature. The target closed-loop transfer function corresponding to the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem. The target controller transfer function is determined by sequentially closing multiple control loops. The scalar return difference of each subsystem obtained after sequentially closing each control loop satisfies a preset stability condition. The scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system, and the preset stability condition includes: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane. The carbon dioxide capture control system in the present disclosure can reduce the coupling degree of each control system while ensuring stability and response speed, and has stronger setpoint tracking and disturbance rejection capabilities.

[0115] Figure 10 is a flowchart of a carbon dioxide capture control method shown according to an exemplary embodiment. As Figure 10 shown, applied to the above carbon dioxide capture control system, the method includes:

[0116] Step 201, obtain the actual carbon dioxide capture rate and the actual reboiler temperature of the capture subsystem of the carbon dioxide capture control system.

[0117] Step 202, determine the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine according to the actual carbon dioxide capture rate and the actual reboiler temperature, as well as the preset carbon dioxide capture rate and the preset reboiler temperature.

[0118] Step 203, control the lean liquid flow rate and the steam extraction flow rate of the steam turbine of the capture subsystem according to the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine, so that the carbon dioxide capture rate of the capture subsystem is equal to the preset carbon dioxide capture rate, and the reboiler temperature of the capture subsystem is equal to the preset reboiler temperature.

[0119] Exemplarily, the control subsystem of the carbon dioxide capture control system is used to control the capture subsystem. The control subsystem can utilize the PID control method to control the controlled variables (lean liquid flow rate and steam extraction flow rate of the steam turbine) of the capture subsystem, so as to control the controlled quantities (carbon dioxide capture rate and reboiler temperature) of the capture subsystem, and keep the carbon dioxide capture rate of the capture subsystem at the preset carbon dioxide capture rate and the reboiler temperature at the preset reboiler temperature.

[0120] In some embodiments, the control subsystem can obtain the actual carbon dioxide capture rate and the actual reboiler temperature of the capture subsystem in real time, and then determine the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine according to the differences between the actual carbon dioxide capture rate and the actual reboiler temperature and the preset carbon dioxide capture rate and the preset reboiler temperature set in advance. Further, the lean liquid flow rate of the capture subsystem can be controlled to be the target lean liquid flow rate, and the steam extraction flow rate of the steam turbine can be controlled to be the target steam extraction flow rate, so that the carbon dioxide capture rate of the capture subsystem is equal to the preset carbon dioxide capture rate, and the reboiler temperature of the capture subsystem is equal to the preset reboiler temperature. Since the coupling degree of the two control loops in the carbon dioxide capture control system is relatively low, the carbon dioxide capture control system can control the carbon dioxide capture rate and the reboiler temperature more accurately and flexibly, effectively improving the stability and response speed of the post-combustion carbon dioxide capture control system, and having stronger setpoint tracking and anti-interference capabilities.

[0121] In summary, the carbon dioxide capture control system in the present disclosure includes a capture subsystem and a control subsystem, and the carbon dioxide capture control system includes multiple control loops. The control variables of the carbon dioxide capture control system include the lean liquid flow rate and the steam extraction flow rate of the steam turbine, and the controlled quantities of the carbon dioxide capture control system include the carbon dioxide capture rate and the reboiler temperature. The target closed-loop transfer function corresponding to the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem. The target controller transfer function is determined by sequentially closing multiple control loops. The scalar return difference of each subsystem obtained after sequentially closing each control loop satisfies the preset stability condition. The scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system, and the preset stability condition includes: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane. The carbon dioxide capture control system in the present disclosure can reduce the coupling degree of each control system while ensuring stability and response speed, and has stronger setpoint tracking and anti-disturbance capabilities.

[0122] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0123] In addition, it should be noted that, for the various specific technical features described in the above specific embodiments, without conflict, they can be combined in any appropriate manner. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination manners.

[0124] Furthermore, any combinations can be made among the various different embodiments of the present disclosure, as long as they do not violate the idea of the present disclosure, and they should also be regarded as the content disclosed by the present disclosure.

Claims

1. A carbon dioxide capture control system, characterized in that, the control variables of the carbon dioxide capture control system include lean liquid flow rate and steam extraction flow rate of the steam turbine, and the controlled variables of the carbon dioxide capture control system include carbon dioxide capture rate and reboiler temperature; the carbon dioxide capture control system includes a capture subsystem and a control subsystem, and the carbon dioxide capture control system includes a plurality of control loops; the target closed-loop transfer function corresponding to the carbon dioxide capture control system is determined according to the target object transfer function corresponding to the capture subsystem and the target controller transfer function corresponding to the control subsystem; the target controller transfer function is determined by sequentially closing the plurality of control loops; the scalar return difference of the capture subsystem and the control subsystem obtained after sequentially closing each of the control loops satisfies a preset stability condition; the scalar return difference is related to the return difference matrix corresponding to the carbon dioxide capture control system, and the preset stability condition includes: the Nyquist locus of the scalar return difference does not enclose or pass through the origin of the complex plane.

2. The carbon dioxide capture control system according to claim 1, characterized in that, the carbon dioxide capture control system is obtained by the following method: determining the target object transfer function of the capture subsystem; determining the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of the capture subsystem and the control subsystem obtained after sequentially closing each of the control loops, and each scalar return difference corresponding to the target controller transfer function satisfies the preset stability condition; determining the target closed-loop transfer function according to the target object transfer function and the target controller transfer function to obtain the carbon dioxide capture control system corresponding to the target closed-loop transfer function.

3. The carbon dioxide capture control system according to claim 2, characterized in that, the determining of the target object transfer function of the capture subsystem includes: using the step excitation signals corresponding to the sample lean liquid flow rate and the sample steam extraction flow rate of the steam turbine as the input of the capture subsystem to obtain the step response signals corresponding to the sample carbon dioxide capture rate and the sample reboiler temperature; identifying the target object transfer function according to the step excitation signals and the step response signals.

4. The carbon dioxide capture control system according to claim 3, characterized in that, The control loop includes: a first control loop and a second control loop. The input of the first control loop is the lean liquid flow rate, and the output of the first control loop is the carbon dioxide capture rate. The input of the second control loop is the extraction steam flow rate of the steam turbine, and the output of the second control loop is the reboiler temperature. Determining the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of the capture subsystem and the control subsystem obtained after sequentially closing each control loop includes: determining the first controller transfer function of the first control loop according to the target object transfer function; closing the first control loop to obtain a target subsystem, and determining the first closed-loop transfer function of the target subsystem according to the first controller transfer function and the first open-loop transfer function of the first control loop; determining the second controller transfer function of the second control loop according to the target object transfer function; and determining the target controller transfer function according to the first controller transfer function and the second controller transfer function.

5. The carbon dioxide capture control system according to claim 4, wherein, the first controller transfer function includes: a first transfer sub-function, a second transfer sub-function, and a third transfer sub-function. Determining the first controller transfer function of the first control loop according to the target object transfer function includes: determining the first transfer sub-function and the second transfer sub-function; determining the first open-loop transfer function of the first control loop according to the target object transfer function, the first transfer sub-function, and the second transfer sub-function; and determining the third transfer sub-function according to the first open-loop transfer function and the first scalar return difference of the first control loop, and the first scalar return difference corresponding to the third transfer sub-function satisfies the preset stability condition.

6. The carbon dioxide capture control system according to claim 5, wherein, determining the first closed-loop transfer function of the target subsystem according to the first controller transfer function and the first open-loop transfer function of the first control loop includes: determining the first closed-loop transfer function according to the first open-loop transfer function, the third transfer sub-function, and the first scalar return difference.

7. The carbon dioxide capture control system according to claim 6, wherein, the second controller transfer function includes: a fourth transfer sub-function and a fifth transfer sub-function. Determining the second controller transfer function of the second control loop according to the target object transfer function includes: determining the fourth transfer sub-function; using the first closed-loop transfer function as the second open-loop transfer function of the second control loop; and determining the fifth transfer sub-function according to the second open-loop transfer function and the second scalar return difference of the second control loop, and the second scalar return difference corresponding to the fifth transfer sub-function satisfies the preset stability condition.

8. The carbon dioxide capture control system according to claim 7, wherein, Determining the target controller transfer function according to the first controller transfer function and the second controller transfer function includes: taking the first transfer sub-function as the first target transfer function; taking the product of the second transfer sub-function and the fourth transfer sub-function as the second target transfer function; taking the diagonal matrix corresponding to the third transfer sub-function and the fifth transfer sub-function as the third target transfer function; and taking the product of the first target transfer function, the second target transfer function, and the third target transfer function as the target controller transfer function.

9. The carbon dioxide capture control system according to any one of claims 2-8, wherein, the method for determining the carbon dioxide capture control system further includes: determining the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function; and when the coupling degree is greater than a preset threshold, repeatedly executing the steps of determining the target controller transfer function corresponding to the control subsystem according to the target object transfer function and the scalar return difference of the capture subsystem and the control subsystem obtained after sequentially closing each control loop to determining the target closed-loop transfer function according to the target object transfer function and the target controller transfer function until the coupling degree of multiple control loops in the carbon dioxide capture control system corresponding to the target closed-loop transfer function is less than or equal to the preset threshold.

10. A carbon dioxide capture control method, wherein, applied to the carbon dioxide capture control system according to any one of claims 1-9, the method includes: obtaining the actual carbon dioxide capture rate and the actual reboiler temperature of the capture subsystem of the carbon dioxide capture control system; determining the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine according to the actual carbon dioxide capture rate, the actual reboiler temperature, a preset carbon dioxide capture rate, and a preset reboiler temperature; and controlling the lean liquid flow rate and the steam extraction flow rate of the steam turbine of the capture subsystem according to the target lean liquid flow rate and the target steam extraction flow rate of the steam turbine, so that the carbon dioxide capture rate of the capture subsystem is equal to the preset carbon dioxide capture rate, and the reboiler temperature of the capture subsystem is equal to the preset reboiler temperature.

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