Feedforward-feedback closed-loop control method for sulfur dioxide concentration of desulfurization system

Abstract

The invention discloses a feedforward-feedback closed-loop control method for sulfur dioxide concentration of a desulfurization system. The method comprises the following steps: establishing a steady-state control and energy efficiency characteristic model of a constant-speed slurry circulating pump set through a steady-state characteristic test of a constant-speed slurry circulating pump of the desulfurization system; a variable-frequency slurry circulating pump control dynamic characteristic model is established through a dynamic characteristic test of a desulfurization system variable-frequency slurry circulating pump; on the basis of the established steady-state control and energy efficiency characteristic model of the constant-speed slurry circulating pump set, start-stop feed-forward optimization of the constant-speed slurry circulating pump set is carried out; and on the basis of the established dynamic characteristic model of the variable-frequency slurry circulating pump, closed-loop active-disturbance-rejection control design of the frequency-total discharge port sulfur dioxide concentration process of the variable-frequency slurry circulating pump is carried out, and finally, a feedforward-feedback closed-loop control method is formed. On the premise that sulfur dioxide emission reaches the standard, the energy consumption of the pump set can be remarkably reduced, and the technical problems that sulfur dioxide emission is prone to exceeding the standard and operation energy consumption is high in a traditional control mode are solved.

Description

Technical Field

[0001] This invention belongs to the field of desulfurization control technology for thermal power units, and in particular, it is a feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system. Background Technology

[0002] Thermal power units are one of the main sources of sulfur dioxide (SO2) emissions, which not only have a serious impact on the environment but also pose a threat to human health. Therefore, to meet the growing demands for environmental protection and public health, my country has successively introduced a number of strict pollution emission regulations. Among these, coal-fired power plants are required to implement pollution emission standards for gas turbines (ultra-low emission standards, with SO2 emission limits of 35 mg / Nm³). 3 Therefore, flue gas desulfurization and purification technology has become a key technology for achieving ultra-low SO2 emissions from thermal power units. Among the many power plant desulfurization technologies, wet limestone flue gas desulfurization technology has been widely used in coal-fired power plants in my country due to its mature technology, good reliability, and adaptability.

[0003] Most thermal power unit desulfurization systems were initially designed for extensive emission control, therefore their desulfurization slurry circulation pumps were mostly fixed-speed pumps, controllable only through start-stop operation. In actual operation, the sulfur dioxide concentration at the desulfurization system outlet is often controlled by a combination of automatic adjustment of the limestone slurry valve opening and manual start-stop adjustment of the desulfurization slurry circulation pump. Under ultra-low emission standards, some thermal power unit desulfurization systems have undergone frequency conversion retrofitting of the slurry pumps to achieve continuous adjustment of the circulating slurry. However, under the flexible operation conditions of thermal power units with wide loads, the flue gas flow rate and pollutant concentration change drastically and within a large range; at the same time, various external disturbances, such as changes in coal quality (sulfur content) and combustion instability, can also lead to fluctuations in the sulfur dioxide concentration at the desulfurization system outlet.

[0004] These characteristics lead to frequent exceedances of sulfur dioxide emission concentrations at the desulfurization system outlet under existing control methods, resulting in unnecessary energy consumption for equipment operation. Furthermore, due to the unmeasurable output of each subsystem in the actual desulfurization spray layer and the uncertainty of the sulfur dioxide adsorption chemical reaction, it is difficult to establish a complete dynamic characteristic model of the desulfurization system based on the reaction mechanism. Summary of the Invention

[0005] Technical Problem: The purpose of this invention is to provide a feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system. Through steady-state and dynamic characteristic tests of the slurry circulation pump in the desulfurization system, a dynamic and static characteristic model of the slurry circulation volume versus total outlet sulfur dioxide process in the desulfurization system is obtained. Based on this model, a feedforward-feedback closed-loop control method combining feedforward start / stop of the constant-speed slurry circulation pump and closed-loop active disturbance rejection control of the variable-frequency slurry circulation pump is designed to achieve automatic, flexible, and energy-saving control of the outlet sulfur dioxide concentration in the desulfurization system of thermal power units.

[0006] Technical Solution: This invention provides a feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system. The controlled object is a desulfurization system for a thermal power unit, including a desulfurization tower, a constant-speed slurry circulation pump group, a variable-frequency slurry circulation pump, slurry supply valves, and a flue gas flow channel. The outlets of the constant-speed and variable-frequency slurry circulation pumps are connected to each spray layer of the desulfurization tower. A slurry pool is provided at the bottom of the desulfurization tower. Flue gas enters from the bottom of the desulfurization tower, undergoes spray desulfurization, and is discharged from the main outlet. The variable-frequency slurry circulation pump adjusts the slurry flow rate through frequency regulation, while the constant-speed slurry circulation pump controls the spray slurry flow rate through a start-stop combination. The control method includes the following steps: Step 1: Establish a steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump unit through steady-state characteristic tests of the desulfurization system. Step 2: Establish a dynamic characteristic model for the control of the variable frequency slurry circulation pump by conducting dynamic characteristic tests on the variable frequency slurry circulation pump of the desulfurization system. Step 3: Based on the steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump set established in Step 1, perform feedforward optimization of the start-up and shutdown of the constant-speed slurry circulation pump set. Step 4: Based on the dynamic characteristic model of the variable frequency slurry circulation pump established in Step 2, a closed-loop active disturbance rejection control design is carried out for the process of variable frequency pump frequency-total discharge sulfur dioxide concentration. Finally, a feedforward-feedback closed-loop control combining the feedforward start-stop of the constant speed slurry circulation pump group and the closed-loop active disturbance rejection control of the variable frequency slurry circulation pump is formed.

[0007] in, In step 1, a steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump group is established through steady-state characteristic tests of the desulfurization system, specifically including: Step 1-1: Before the test, adjust the initial setting values ​​of the constant speed slurry circulation pump group, variable frequency slurry circulation pump, and slurry supply valve opening of the desulfurization system. Step 1-2: Under the initial settings of Step 1-1, increase the operating frequency of the variable frequency slurry circulation pump but not above its maximum limit, and run it stably for 10-30 minutes. Record the total sulfur dioxide concentration at the discharge port before and after the frequency change of the variable frequency slurry circulation pump and the energy consumption data of the pump group at this time. Steps 1-3: Following the methods in steps 1-1 and 1-2, perform combined test operations on the constant-speed slurry circulation pump group of the desulfurization system in sequence to obtain the steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump group of the desulfurization system under various load test conditions.

[0008] In step 2, a dynamic characteristic model for the control of the variable frequency slurry circulation pump is established through dynamic characteristic tests of the variable frequency slurry circulation pump in the desulfurization system. Specifically, this includes: Step 2-1: Before the test, adjust the initial setting values ​​of the constant speed slurry circulation pump group, variable frequency slurry circulation pump, and slurry supply valve opening of the desulfurization system. Increase the frequency of the variable frequency slurry circulation pump of the desulfurization system to the rated value, but not higher than its maximum limit. Run it stably for 5-15 minutes and record the key data of variable frequency slurry circulation pump frequency, total outlet sulfur dioxide concentration, and time during the step test. Step 2-2: Based on Step 2-1, use step test data to identify the dynamic model of the transfer function of the pump frequency-total outlet sulfur dioxide concentration process. subscript p Indicates the controlled object, , In the formula, Y ( s )and U ( s ) are the controlled variable in transfer function form, namely the total discharge sulfur dioxide concentration, and the control input, namely the frequency of the variable frequency slurry circulation pump in the desulfurization system; P(s) = K / (1+Ts) For the time-delay-free part of the transfer function model, where K, T , L These are gain, inertia time, and time delay, respectively. s It is the Laplace operator.

[0009] In step 3, based on the steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump group established in step 1, the start-up and shutdown feedforward optimization of the constant-speed slurry pump group is performed, specifically including: On the premise of ensuring that the sulfur dioxide concentration at the total discharge outlet is not higher than the preset value, select a set of constant-speed slurry circulation pumps with the lowest energy consumption from the steady-state characteristic test of the constant-speed slurry circulation pump of the desulfurization system under a given load condition in step 1 above, and ensure that the variable frequency slurry circulation pump has a suitable adjustable range.

[0010] In step 4, based on the dynamic characteristic model of the variable frequency slurry circulation pump established in step 2, a closed-loop active disturbance rejection control design is performed for the variable frequency pump frequency-total outlet sulfur dioxide concentration process. This ultimately forms a feedforward-feedback closed-loop control combining the feedforward control of the constant speed slurry pump start / stop and the closed-loop active disturbance rejection control of the variable frequency slurry pump, specifically including: Step 4-1: For the optimal energy consumption constant-speed slurry circulation pump group operation combination under a given load condition in Step 3, identify the dynamic model of the corresponding variable frequency slurry circulation pump through a step test. G p ( s The transfer function model of the process of converting the frequency of the variable frequency slurry circulation pump to the sulfur dioxide concentration at the total discharge outlet is used. G p ( s The differential equation of ) is solved, and the extended state observer ESO is designed; Step 4-2: Based on the estimated values ​​from the extended state observer, design a closed-loop active disturbance rejection controller for the process of frequency conversion of the slurry circulation pump frequency versus sulfur dioxide concentration at the total discharge outlet.

[0011] Step 1-1, specifically adjusting the initial setting values ​​of the constant-speed slurry circulation pump group, variable-frequency slurry circulation pump, and slurry supply valve opening of the desulfurization system before the test, is as follows: Under the preset test load conditions, start the preset number of constant-speed slurry circulation pumps and variable-frequency slurry circulation pumps to maintain the minimum safe operating frequency, while maintaining the rated slurry supply valve opening; after stable operation, observe whether the sulfur dioxide concentration at the total discharge port reaches within the preset value and the slurry pH value is basically stable; if the sulfur dioxide concentration at the total discharge port is higher than the preset value, start another constant-speed slurry circulation pump and adjust the frequency of the variable-frequency slurry circulation pump to the minimum safe operating frequency until the sulfur dioxide concentration at the total discharge port is close to the preset value, and run stably for 5-15 minutes to prepare for the steady-state test of the constant-speed slurry circulation pump and record the test data.

[0012] In step 4-1, the transfer function model of the pump frequency-total outlet sulfur dioxide concentration process... G p ( s The differential equation of ) is in the following form: , In the formula , d , These are the control variables (variable frequency pump frequency), external disturbance, and the controlled variable (total sulfur dioxide concentration at the discharge outlet). , t Indicates the time of a dynamic process; Accordingly, the following extended state observer is designed: , , in and These are the estimates of the controlled output and the total disturbance, respectively. , The observer gain is designed using the bandwidth parameter method as follows: , in This represents the observer bandwidth.

[0013] Step 4-2, based on the estimated value from the extended state observer, design the closed-loop active disturbance rejection controller for the process of frequency conversion slurry circulation pump frequency versus total discharge sulfur dioxide concentration as follows: The estimated total disturbance value is compensated in the control channel. ,Right now , in This is a state feedback control law. Through total disturbance compensation, the original controlled system can be approximately simplified to In the formula, the state quantity That is, the controlled output Therefore, the following state feedback control law is designed. , in r The set value for sulfur dioxide concentration at the total discharge outlet. k p For proportional control gain, The controlled variable, namely the outlet sulfur dioxide concentration, is further derived from the disturbance rejection controller as follows: .

[0014] Based on the above technical solutions, this invention achieves closed-loop optimization control of the desulfurization system through the following technical path: Through steady-state and dynamic characteristic tests of the slurry circulation pump in the desulfurization system, a control and energy efficiency characteristic model for the constant-speed pump group and a dynamic control model for the variable-frequency pump are established; the start-stop feedforward strategy of the constant-speed pump group is optimized based on steady-state energy efficiency characteristics to ensure optimal pump group energy consumption and the feasibility of closed-loop control under basic operating conditions; an active disturbance rejection closed-loop controller is designed in conjunction with the dynamic model of the variable-frequency pump, and an extended state observer is used to estimate and compensate for internal and external disturbances in real time; finally, a feedforward-feedback composite control architecture combining the start-stop feedforward of the constant-speed pump and the active disturbance rejection control of the variable-frequency pump is constructed.

[0015] Beneficial effects: This invention has the following innovative features: A control and energy efficiency characteristic model is established through a full-group steady-state test of the constant-speed pump set, providing an optimization basis for the pump set start-stop feedforward control; Dynamic characteristic model is identified using variable-frequency pump step response data, laying the foundation for closed-loop control design; Real-time estimation of the total disturbance of the desulfurization system is achieved through an extended state observer, and a closed-loop active disturbance rejection controller for the variable-frequency pump frequency-outlet sulfur dioxide concentration process is further designed; The start-stop control of the constant-speed pump is organically combined with the continuous adjustment of the variable-frequency pump, balancing the control accuracy of the outlet sulfur dioxide concentration and the operating energy efficiency of the desulfurization system.

[0016] This invention obtains the dynamic and static characteristic parameters of the desulfurization system through field tests and further designs a feedforward-feedback composite control strategy without relying on a precise mechanistic model. The proposed method can effectively cope with large-scale disturbances during the wide-load operation of thermal power units, and can significantly reduce pump energy consumption while ensuring that sulfur dioxide emissions meet standards. It solves the technical problems of easy sulfur dioxide emissions exceeding standards and high operating energy consumption under traditional control methods, and has significant engineering application value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall framework of the present invention; Figure 2 This is a schematic diagram of the desulfurization system and flue gas system of the thermal power unit considered in this invention; Figure 3 This is a schematic diagram of a feedforward-feedback control structure for a desulfurization system provided by the present invention; Figure 4 This is a diagram of an active disturbance rejection control structure for sulfur dioxide at the outlet of a desulfurization system provided by the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] This invention provides a feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system of a thermal power unit, the overall framework of which is shown in the schematic diagram below. Figure 1 As shown, it includes the following steps: S1. Through steady-state characteristic tests of constant-speed slurry circulation pumps in desulfurization systems, a steady-state control and energy efficiency characteristic model of constant-speed slurry pump sets is established. The schematic diagram of the desulfurization system and flue gas system of the thermal power unit considered in this invention is as follows: Figure 2 As shown, the flue gas generated by boiler combustion passes sequentially through a denitrification system and a dry electrostatic precipitator before entering the desulfurization tower. The desulfurized flue gas then passes through a wet electrostatic precipitator and is finally discharged into the atmosphere through a chimney. The flue gas enters from the bottom of the desulfurization tower (above the slurry pool) and flows upwards, contacting and reacting with the limestone slurry sprayed from above. As an example, this embodiment considers five slurry circulation pumps (AE pumps), where pump D is a variable frequency slurry circulation pump.

[0020] Step S1 above specifically includes the following sub-steps: Step 1-1: Adjust the initial set values ​​of the desulfurization slurry circulation pump and slurry supply valve opening before the test. Under the test load condition (e.g., 80% load), start a certain number of constant-speed slurry circulation pumps (e.g., 2 pumps) and variable-frequency slurry circulation pumps to maintain the minimum safe operating frequency (e.g., 40Hz), while maintaining the rated slurry supply valve opening. After stable operation, observe whether the total sulfur dioxide concentration at the discharge port reaches the preset value (e.g., 30mg / Nm³). 3 The sulfur dioxide concentration at the total discharge outlet should be within the preset value, and the pH value of the slurry should be basically stable. If the sulfur dioxide concentration at the total discharge outlet is higher than the preset value, another constant-speed slurry circulation pump should be started, and the frequency of the variable-frequency slurry circulation pump should be adjusted to the lowest safe operating frequency until the sulfur dioxide concentration at the total discharge outlet is close to the preset value. After stable operation for 5 minutes, a steady-state test of the constant-speed slurry circulation pump should be carried out and the test data should be recorded.

[0021] Step 1-2: Under the initial settings of Step 1-1, increase the operating frequency of the variable frequency slurry circulation pump (but not above its maximum limit, such as 50Hz), run it stably for 10 minutes, and record the outlet sulfur dioxide concentration and the energy consumption data of the pump set before and after the frequency change.

[0022] Steps 1-3, following the procedures in steps 1-1 and 1-2, shall be performed sequentially on the desulfurization tower constant-rate slurry circulation pump set (pumps A, B, C, and E): , Using the above method, the steady-state control and energy efficiency characteristic models of the constant-speed slurry pump group of the desulfurization system under various load test conditions can be obtained.

[0023] Step S2: Establish a dynamic characteristic model for the control of the variable frequency slurry circulation pump by conducting dynamic characteristic tests on the variable frequency slurry circulation pump of the desulfurization system. Step S2 above specifically includes the following sub-steps: Step 2-1: In Step 1-2 above, increase the frequency of the variable frequency slurry circulation pump D of the desulfurization tower to the rated value (e.g., 10Hz), run it stably for 5 minutes, and record key data such as pump frequency, outlet sulfur dioxide concentration and time during the step test.

[0024] Step 2-2: Based on Step 2-1, use the step test data to identify the dynamic model of the transfer function of the pump frequency-outlet sulfur dioxide concentration process. subscript p Indicates the controlled object, , In the formula, Y ( s )and U ( s ) are the controlled variable (outlet sulfur dioxide concentration) and the control input (variable frequency pump frequency) in transfer function form, respectively. P(s) = K / (1+Ts) For the time-delay-free part of the transfer function model, where K, T , L These are gain, inertia time, and time delay, respectively.

[0025] A schematic diagram of a feedforward-feedback control structure for a desulfurization system provided by this invention is shown below. Figure 3 As shown, the feedforward and feedback control design is explained in detail below.

[0026] Step S3: Based on the steady-state control and energy efficiency characteristic model of the constant-speed slurry pump group established in step S1, perform feedforward optimization of the start-up and shutdown of the constant-speed slurry pump group. Step S3 above specifically includes: On the premise of ensuring that the sulfur dioxide concentration at the total discharge outlet is not higher than the preset value, select a set of constant-speed slurry circulation pumps with the lowest energy consumption from the test operation scheme under a given load condition in step S1 above, and ensure that the variable frequency slurry pump has a suitable adjustable range.

[0027] Step S4: Based on the dynamic characteristic model of the variable frequency slurry circulation pump established in step S2, a closed-loop active disturbance rejection control design for the variable frequency pump frequency-outlet sulfur dioxide concentration process is carried out, and finally a feedforward-feedback closed-loop control method combining the feedforward of the constant speed slurry pump start-stop and the closed-loop active disturbance rejection control of the variable frequency slurry pump is formed.

[0028] The structure diagram of the sulfur dioxide self-disturbance control structure at the outlet of the desulfurization system provided by this invention is as follows: Figure 4 As shown.

[0029] Step S4 above specifically includes the following sub-steps: Step 4-1: For the optimal energy consumption constant-speed slurry circulation pump group operation combination under a given load condition in step S3, identify the dynamic model of the corresponding variable frequency pump step test. G p ( s The equations are transformed into differential equations, and an extended state observer (ESO) is designed.

[0030] Transfer function model of pump frequency-outlet sulfur dioxide concentration process G p ( s The differential equation of ) is in the following form: , In the formula , d , These are the control variable (variable frequency pump frequency), external disturbance, and controlled variable (outlet sulfur dioxide concentration), respectively. .

[0031] Accordingly, the following extended state observer can be designed: , , in and These are the estimates of the controlled output and the total disturbance, respectively. , The observer gain, according to the bandwidth parameter method, can be designed as follows: , in This represents the observer bandwidth.

[0032] Step 4-2: Based on the extended state observer estimate, design a closed-loop active disturbance rejection controller for the pump frequency-outlet sulfur dioxide concentration process.

[0033] The estimated total disturbance is compensated in the control channel. ,Right now , in This is a state feedback control law. Through total disturbance compensation, the original controlled system can be approximately simplified to... In the formula, the state quantity That is, the controlled output Therefore, the following state feedback control law can be designed. , in r Set a value for the sulfur dioxide concentration at the export site. k p This is the proportional control gain. Further, the disturbance rejection controller can be obtained as follows: .

[0034] The above embodiments provide a feedforward-feedback closed-loop control method for sulfur dioxide concentration in a thermal power unit desulfurization system. Through steady-state and dynamic characteristic tests of the slurry circulation pump in the desulfurization system, a control and energy efficiency characteristic model for the constant-speed pump group and a dynamic control model for the variable-frequency pump are established. Based on the steady-state energy efficiency characteristics, the start-stop feedforward strategy of the constant-speed pump group is optimized to ensure optimal pump group energy consumption and the feasibility of closed-loop control under basic operating conditions. An active disturbance rejection closed-loop controller is designed in conjunction with the dynamic model of the variable-frequency pump, and an extended state observer is used to estimate and compensate for internal and external disturbances in real time. Finally, a feedforward-feedback composite control architecture combining the start-stop feedforward of the constant-speed pump and the active disturbance rejection control of the variable-frequency pump is constructed. This invention has the following innovative features: A control and energy efficiency characteristic model is established through a full-group steady-state test of the constant-speed pump unit, providing an optimization basis for the pump unit's start-stop feedforward control; the dynamic characteristic model is identified using the step response data of the variable-frequency pump, laying the foundation for closed-loop control design; the total disturbance of the desulfurization system is estimated in real time through an extended state observer, and a closed-loop active disturbance rejection controller for the variable-frequency pump frequency-outlet sulfur dioxide concentration process is further designed; the start-stop control of the constant-speed pump is organically combined with the continuous adjustment of the variable-frequency pump, balancing the control accuracy of the outlet sulfur dioxide concentration with the operating energy efficiency of the desulfurization system.

[0035] This invention obtains the dynamic and static characteristic parameters of the desulfurization system through field tests and further designs a feedforward-feedback composite control strategy without relying on a precise mechanistic model. The proposed method can effectively cope with large-scale disturbances during the wide-load operation of thermal power units, and can significantly reduce pump energy consumption while ensuring that sulfur dioxide emissions meet standards. It solves the technical problems of easy sulfur dioxide emissions exceeding standards and high operating energy consumption under traditional control methods, and has significant engineering application value.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system, characterized in that... The controlled object is the desulfurization system of a thermal power unit, including a desulfurization tower, a constant-speed slurry circulation pump set, a variable-frequency slurry circulation pump, slurry supply valves, and flue gas flow channels. The outlets of the constant-speed slurry circulation pump and the variable-frequency slurry circulation pump are connected to each spray layer of the desulfurization tower. A slurry pool is provided at the bottom of the desulfurization tower. Flue gas enters from the bottom of the desulfurization tower, is sprayed and desulfurized, and is discharged from the main outlet. The variable-frequency slurry circulation pump adjusts the slurry flow rate by frequency, and the constant-speed slurry circulation pump controls the spray slurry flow rate by start-stop combination. The control method includes the following steps: Step 1: Establish a steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump unit through steady-state characteristic tests of the desulfurization system. Step 2: Establish a dynamic characteristic model for the control of the variable frequency slurry circulation pump by conducting dynamic characteristic tests on the variable frequency slurry circulation pump of the desulfurization system. Step 3: Based on the steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump set established in Step 1, perform feedforward optimization of the start-up and shutdown of the constant-speed slurry circulation pump set. Step 4: Based on the dynamic characteristic model of the variable frequency slurry circulation pump established in Step 2, a closed-loop active disturbance rejection control design is carried out for the process of variable frequency pump frequency-total discharge sulfur dioxide concentration. Finally, a feedforward-feedback closed-loop control combining the feedforward start-stop of the constant speed slurry circulation pump group and the closed-loop active disturbance rejection control of the variable frequency slurry circulation pump is formed.

2. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 1, characterized in that: Step 1 specifically includes: Step 1-1: Before the test, adjust the initial setting values ​​of the constant speed slurry circulation pump group, variable frequency slurry circulation pump, and slurry supply valve opening of the desulfurization system. Step 1-2: Under the initial settings of Step 1-1, increase the operating frequency of the variable frequency slurry circulation pump but not above its maximum limit, and run it stably for 10-30 minutes. Record the total sulfur dioxide concentration at the discharge port before and after the frequency change of the variable frequency slurry circulation pump and the energy consumption data of the pump group at this time. Steps 1-3: Following the methods in steps 1-1 and 1-2, perform combined test operations on the constant-speed slurry circulation pump group of the desulfurization system in sequence to obtain the steady-state control and energy efficiency characteristic model of the constant-speed slurry circulation pump group of the desulfurization system under various load test conditions.

3. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 1 or 2, characterized in that: Step 2 specifically includes: Step 2-1: Before the test, adjust the initial setting values ​​of the constant speed slurry circulation pump group, variable frequency slurry circulation pump, and slurry supply valve opening of the desulfurization system. Increase the frequency of the variable frequency slurry circulation pump of the desulfurization system to the rated value, but not higher than its maximum limit. Run it stably for 5-15 minutes and record the key data of variable frequency slurry circulation pump frequency, total outlet sulfur dioxide concentration, and time during the step test. Step 2-2: Based on Step 2-1, use step test data to identify the dynamic model of the transfer function of the pump frequency-total outlet sulfur dioxide concentration process. subscript p Indicates the controlled object, ， In the formula, Y ( s )and U ( s ) are the controlled variable in transfer function form, namely the total discharge sulfur dioxide concentration, and the control input, namely the frequency of the variable frequency slurry circulation pump in the desulfurization system; P(s) = K / (1+Ts) For the time-delay-free part of the transfer function model, where K, T , L These are gain, inertia time, and time delay, respectively. s It is the Laplace operator.

4. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 1, characterized in that: Step 3 specifically includes: on the basis of ensuring that the sulfur dioxide concentration at the total discharge outlet is not higher than the preset value, in the steady-state characteristic test of the constant-speed slurry circulation pump of the desulfurization system under given load conditions, selecting a set of constant-speed slurry circulation pumps with the lowest energy consumption and ensuring that the variable frequency slurry circulation pump has a suitable adjustable range.

5. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 1, characterized in that: Step 4 specifically includes: Step 4-1: For the optimal energy consumption constant-speed slurry circulation pump unit operation combination under a given load condition, identify the dynamic model of the corresponding variable frequency slurry circulation pump through a step test. G p ( s The transfer function model of the process of converting the frequency of the variable frequency slurry circulation pump to the sulfur dioxide concentration at the total discharge outlet is used. G p ( s The differential equation of ) is solved, and the extended state observer ESO is designed; Step 4-2: Based on the ESO estimate from the extended state observer, design a closed-loop active disturbance rejection controller for the process of frequency conversion of slurry circulation pump frequency versus total outlet sulfur dioxide concentration.

6. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 2, characterized in that: Step 1-1, specifically adjusting the initial setting values ​​of the constant-speed slurry circulation pump group, variable-frequency slurry circulation pump, and slurry supply valve opening of the desulfurization system before the test, is as follows: Under the preset test load conditions, start the preset number of constant-speed slurry circulation pumps and variable-frequency slurry circulation pumps to maintain the minimum safe operating frequency, while maintaining the rated slurry supply valve opening; after stable operation, observe whether the sulfur dioxide concentration at the total discharge port reaches within the preset value and the slurry pH value is basically stable; if the sulfur dioxide concentration at the total discharge port is higher than the preset value, start another constant-speed slurry circulation pump and adjust the frequency of the variable-frequency slurry circulation pump to the minimum safe operating frequency until the sulfur dioxide concentration at the total discharge port is close to the preset value, and run stably for 5-15 minutes to prepare for the steady-state test of the constant-speed slurry circulation pump and record the test data.

7. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 5, characterized in that: In step 4-1, the transfer function model of the pump frequency-total outlet sulfur dioxide concentration process... G p ( s The differential equation of ) is in the following form: ， In the formula , d , These are the control variables (variable frequency pump frequency), external disturbance, and the controlled variable (total sulfur dioxide concentration at the discharge outlet). , K, T , L These are gain, inertia time, and time delay, respectively. t Indicates the time of a dynamic process; Accordingly, the following extended state observer is designed: ， ， in and These are the estimated values ​​of the controlled output and the total disturbance, respectively. , The observer gain is designed using the bandwidth parameter method as follows: ， in This represents the observer bandwidth.

8. The feedforward-feedback closed-loop control method for sulfur dioxide concentration in a desulfurization system as described in claim 5 or 7, characterized in that: Step 4-2: Based on the ESO estimate from the extended state observer, design the closed-loop active disturbance rejection controller (ADRC) for the frequency-to-total discharge sulfur dioxide concentration process of the variable frequency slurry circulation pump as follows: The total disturbance estimate is compensated in the control channel. ,Right now ， in This is a state feedback control law. Through total disturbance compensation, the original controlled system is simplified to In the formula, the state quantity That is, the controlled output ; Therefore, the following state feedback control law is designed. , in r The set value for sulfur dioxide concentration at the total discharge outlet. k p For proportional control gain, The controlled variable, namely the outlet sulfur dioxide concentration, is further derived from the disturbance rejection controller as follows: 。

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