Multi-mode boiler drum liquid level control method and device

Abstract

The embodiment of the invention discloses a control method and device for the liquid level of a multi-mode boiler drum. The control method comprises the steps that the current steam flow value and the current water supply flow value of a target boiler drum are obtained; based on the current steam flow value, determining a current steam flow measurement state of the target boiler drum by utilizing a steam flow theoretical value linear function; determining a current water flow measurement state of the target boiler drum by using a water flow theoretical value linear function based on the current feed water flow value; determining a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state; determining a corresponding preset control algorithm based on the control algorithm selection variable; and regulating and controlling the liquid level of the target boiler drum by using the valve position variable quantity of the feed water flow determined by a preset control algorithm. The technical problem that in the prior art, a traditional three-impulse control method cannot accurately control the liquid level of the boiler drum is solved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of boiler drum control, and in particular to a method and device for controlling the liquid level of a multi-modal boiler drum. Background Art

[0002] The boiler drum level is a key process indicator in the boiler production process and one of the primary conditions for ensuring safe boiler operation. If the drum level is too high, steam will carry liquid, which not only reduces steam production and quality but also causes scaling in the superheater or damage to turbine blades. If the drum level is too low, it can affect the water vapor balance at best and burn the boiler dry at worst, leading to boiler explosions in severe cases. During specific production processes, fluctuations in steam load and changes in feedwater flow often disrupt the equilibrium within the drum, disrupting the drum level and ultimately causing false liquid levels. Boilers are characterized by nonlinearity, large time lags, and strong coupling. Any change in any parameter within the boiler will affect overall operation, causing fluctuations in the unit and making system control difficult.

[0003] Currently, the three-impulse control method is commonly used for boiler drum level. The three-impulse control system is actually a feedforward (steam flow) - cascade (boiler level and feedwater flow cascade) control system. However, in actual application, automatic control is often not implemented. The main reasons are as follows: First, the steam flow meter is not accurate; Second, the water flow meter is not accurate and the cascade cannot be put into use; Third, in the early stages of operation, low steam flow leads to false instrument indications; Fourth, there are problems with the three-impulse configuration in the DCS (Distributed Control System), or the controller parameters are not applicable, which makes it impossible to automatically use the three-impulse control.

[0004] Therefore, it is difficult to solve this type of multivariable system problem using the traditional three-impulse control method, and it is impossible to achieve precise control of the boiler drum liquid level. Summary of the Invention

[0005] The embodiments of the present invention provide a multi-modal boiler drum liquid level control method and device, which solve the technical problem in the prior art that the traditional three-impulse control method cannot achieve precise control of the boiler drum liquid level.

[0006] An embodiment of the present invention provides a multi-modal boiler drum liquid level control method, the control method comprising: Obtain the current steam flow value and current feed water flow value of the target boiler drum; Based on the current steam flow value, determining the current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function, wherein the steam flow theoretical value linear function is a theoretical steam flow measurement model determined in advance based on the feedwater valve position value and the steam flow value of the target boiler drum; Based on the current feedwater flow value, determining the current water flow measurement state of the target boiler drum using a water flow theoretical value linear function, wherein the water flow theoretical value linear function is a theoretical water flow measurement model determined in advance based on the feedwater valve position value and the feedwater flow value of the target boiler drum; determining a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state, wherein one control algorithm selection variable corresponds to a preset control algorithm; Determining the corresponding preset control algorithm based on the control algorithm selection variable; The valve position variation of the feed water flow determined by the preset control algorithm is used to control the liquid level of the target boiler drum.

[0007] Furthermore, based on the current steam flow value, determining the current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function includes: Comparing the current steam flow value with the theoretical steam flow value at the corresponding feedwater valve position in the linear function of the theoretical steam flow value; If the current steam flow rate value is greater than or equal to 95% of the theoretical steam flow rate value, and less than or equal to 105% of the theoretical steam flow rate value, the current steam flow rate measurement state is in the first state; If the current steam flow rate value is greater than or equal to 90% of the theoretical steam flow rate value and less than 95% of the theoretical steam flow rate value, or if the current steam flow rate value is greater than 105% of the theoretical steam flow rate value and less than or equal to 110% of the theoretical steam flow rate value, then the current steam flow rate measurement state is in the second state; If the current steam flow rate value is greater than 110% of the theoretical steam flow rate value, or is less than 90% of the theoretical steam flow rate value, the current steam flow rate measurement state is in the third state.

[0008] Furthermore, based on the current feed water flow value, determining the current water flow measurement state of the target boiler drum using a water flow theoretical value linear function includes: Comparing the current water flow rate value with the theoretical water flow rate value at the corresponding water supply valve position in the water flow rate theoretical value linear function; If the current water flow rate value is greater than or equal to 95% of the theoretical water flow rate value, and less than or equal to 105% of the theoretical water flow rate value, the current water flow rate measurement state is in the fourth state; If the current water flow rate value is greater than 110% of the theoretical water flow rate value, or is less than 90% of the theoretical water flow rate value, the current water flow rate measurement state is in the fifth state.

[0009] Furthermore, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 2, then the preset control method is determined to be the first control algorithm; The first control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller, RG WS is the range of the water flow controller, PV RP is the amount of water replenishment; Based on the set value of the water flow controller, using the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0010] Furthermore, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 1, the preset control method is determined to be the second control algorithm; The second control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, using the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0011] Furthermore, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.4, then determining that the preset control method is the third control algorithm; The third control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, using the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0012] Furthermore, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.1 or 0.05, the preset control method is determined to be the fourth control algorithm; The fourth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of the water flow rate, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller.

[0013] Furthermore, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.02, then the preset control method is determined to be the fifth control algorithm; The fifth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of the water flow, OP LV is the output value of the liquid level controller.

[0014] Further, determining a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state includes: The fuzzy quantity corresponding to the current steam flow measurement state is multiplied by the fuzzy quantity corresponding to the current water flow measurement state to obtain the control algorithm selection variable.

[0015] An embodiment of the present invention further provides a multi-modal boiler drum liquid level control device, the control device comprising: A data acquisition unit, used to obtain the current steam flow value and the current feed water flow value of the target boiler drum; a first state determining unit, configured to determine, based on the current steam flow value, a current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function, wherein the steam flow theoretical value linear function is a theoretical steam flow measurement model determined in advance based on a feedwater valve position value and a steam flow value of the target boiler drum; a second state determination unit, configured to determine, based on the current feedwater flow value, a current water flow measurement state of the target boiler drum using a water flow theoretical value linear function, wherein the water flow theoretical value linear function is a theoretical water flow measurement model determined in advance based on the feedwater valve position value and the feedwater flow value of the target boiler drum; a variable determination unit, configured to determine a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state, wherein one control algorithm selection variable corresponds to a preset control algorithm; an algorithm determining unit, configured to determine the corresponding preset control algorithm based on the control algorithm selection variable; A control unit is used to control the operation of the target boiler drum using the preset control algorithm.

[0016] The embodiment of the present invention discloses a multi-modal boiler drum liquid level control method and device. The control method includes: obtaining a current steam flow rate value and a current feed water flow rate value of a target boiler drum; based on the current steam flow rate value, determining the current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function; based on the current feed water flow rate value, determining the current water flow measurement state of the target boiler drum using a water flow theoretical value linear function; determining a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state; determining a corresponding preset control algorithm based on the control algorithm selection variable; and controlling the liquid level of the target boiler drum using the feed water flow valve position change determined by the preset control algorithm. The present invention solves the technical problem in the prior art that the traditional three-impulse control method cannot achieve precise control of the boiler drum liquid level using the conventional three-impulse control method, achieves the technical effect of improving the control accuracy of the boiler drum liquid level, and ensures the safe and stable operation of the boiler system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a multi-mode boiler drum liquid level control method provided by an embodiment of the present invention; Figure 2 is a control diagram of the first control algorithm provided by an embodiment of the present invention; Figure 3 is a control diagram of the second control algorithm provided by an embodiment of the present invention; Figure 4 is a control diagram of the third control algorithm provided by an embodiment of the present invention; Figure 5 is a control diagram of the fourth control algorithm provided by an embodiment of the present invention; Figure 6 is a control diagram of the fifth control algorithm provided by an embodiment of the present invention; Figure 7 This is a diagram of the change in the drum liquid level of a catalytic device boiler provided in an embodiment of the present invention before the control method provided in the present invention is implemented; Figure 8 This is a feed water flow change diagram of a catalytic device boiler provided by an embodiment of the present invention before the control method provided by the present invention is implemented; Figure 9 This is a diagram showing changes in the drum liquid level of a catalytic device boiler provided by an embodiment of the present invention after the control method provided by the present invention is implemented; Figure 10 This is a diagram showing changes in feed water flow after a catalytic device boiler according to an embodiment of the present invention implements the control method provided by the present invention; Figure 11It is a structural diagram of a multi-modal boiler drum liquid level control device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0019] It should be noted that the terms "first," "second," and so on, in the specification, claims, and drawings of the present invention are used to distinguish different objects, and are not intended to limit a specific order. The following embodiments of the present invention can be implemented independently or in combination with each other, and the present invention does not impose specific limitations on this.

[0020] Figure 1 This is a flow chart of a multi-modal boiler drum liquid level control method provided by an embodiment of the present invention.

[0021] like Figure 1 As shown, the multi-modal boiler drum liquid level control method specifically includes the following steps: S101, obtaining the current steam flow value and the current feed water flow value of the target boiler drum; Specifically, the current steam flow value is measured by a steam measuring instrument set at the steam outlet of the target boiler drum, and the current feed water flow value is measured by a flow meter set at the feed water inlet of the target boiler drum; S102: Based on the current steam flow value, determine the current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function, wherein the steam flow theoretical value linear function is a theoretical steam flow measurement model pre-determined based on the feedwater valve position value and the steam flow value of the target boiler drum; Specifically, the feedwater valve position value is the valve position output value of the feedwater controller in the boiler system, that is, the calculated output value of the feedwater controller, and its value range is 0-100%. Preliminary tests are conducted to measure the feedwater valve position value and steam flow value of the target boiler drum. The acquired data is then used to establish a linear function of the theoretical steam flow value. Once the current steam flow value is obtained, it is compared with the theoretical steam flow value corresponding to the corresponding feedwater valve position in the linear function of the theoretical steam flow value to determine the current steam flow measurement status. This determines whether the steam flow meter's measurement is accurate under the current operating conditions, pending subsequent confirmation of whether the steam volume needs to be used to adjust the feedwater valve position in the boiler system. S103, based on the current feedwater flow value, determine the current water flow measurement state of the target boiler drum using a water flow theoretical value linear function, wherein the water flow theoretical value linear function is a theoretical water flow measurement model pre-determined based on the feedwater valve position value and the feedwater flow value of the target boiler drum; Specifically, a test is conducted in advance to measure the feedwater valve position value and feedwater flow value of the target boiler drum, and then a linear function of the theoretical water flow value is established using the acquired data. After the current feedwater flow value is acquired, it is compared with the theoretical feedwater flow value corresponding to the corresponding feedwater valve position in the linear function of the theoretical water flow value to determine the current water flow measurement state, that is, to determine whether the flow meter is accurately measuring the feedwater flow under the current working conditions, so as to subsequently confirm whether it is necessary to use the make-up water amount to adjust the feedwater valve position in the boiler system; S104, determining a control algorithm selection variable based on a current steam flow measurement state and a current water flow measurement state, wherein one control algorithm selection variable corresponds to one preset control algorithm; Specifically, the current steam flow measurement status can be roughly divided into three states: the first state in which the measurement is accurate, the second state in which the measurement value is inaccurate but the steam flow meter can reflect the changing trend of the steam volume, and the third state in which the measurement is inaccurate. The current water flow measurement status includes two states: the fourth state in which the water flow measurement is accurate, and the fifth state in which the water flow measurement is inaccurate. Each state is assigned a value (i.e., the following fuzzy quantity). Table 1 shows the fuzzy quantity table for the current steam flow measurement state, and Table 2 shows the fuzzy quantity table for the current water flow measurement state. As shown in Tables 1 and 2, the fuzzy quantities corresponding to the current steam flow measurement state and the current water flow measurement state are used to determine the control algorithm selection variables. Obviously, different steam flow states and water flow states represent different current operating conditions of the boiler system, so different control algorithms are required to regulate the feedwater valve position. Table 1. Fuzzy scale of current steam flow measurement status

[0022] Table 2. Fuzzy scale of current water flow measurement status

[0023] S105, determining a corresponding preset control algorithm based on the control algorithm selection variable; Specifically, since one control algorithm selection variable uniquely corresponds to one preset control algorithm, after determining the control algorithm selection variable, the corresponding preset control algorithm can be directly called; S106, using the valve position change of the feedwater flow determined by the preset control algorithm to achieve liquid level control of the target boiler drum; Specifically, the valve position change of the feed water flow is calculated based on the determined preset control algorithm, and the corresponding feed water flow control valve is regulated based on the calculated valve position change to achieve liquid level control of the target boiler liquid drum.

[0024] In an embodiment of the present invention, a multi-impulse control method and boiler system for boiler drum level are innovatively proposed. This boiler system is divided into five different operating conditions based on the accuracy of steam flow and feedwater measurement. Each operating condition corresponds to a corresponding control algorithm. When the operating condition changes, the corresponding algorithm automatically switches without disturbance. Ultimately, this ensures precise control of the boiler drum level and guarantees safe and stable operation of the boiler system.

[0025] The present invention determines the current steam flow measurement status and the current water flow measurement status of the boiler drum, and determines the control algorithm selection variables based on them, thereby determining the corresponding preset control algorithm. This solves the technical problem in the prior art that the traditional three-impulse control method cannot achieve precise control of the boiler drum liquid level, achieves the technical effect of improving the control accuracy of the boiler drum liquid level, and ensures the safe and stable operation of the boiler system.

[0026] On the basis of the above technical solutions, S102, based on the current steam flow value, the current steam flow measurement state of the target boiler drum is determined using a linear function of the steam flow theoretical value, specifically including: Compare the current steam flow value with the theoretical steam flow value under the corresponding feed water valve position in the linear function of the theoretical steam flow value; if the current steam flow value is greater than or equal to 95% of the theoretical steam flow value, and less than or equal to 105% of the theoretical steam flow value, then the current steam flow measurement state is in the first state; if the current steam flow value is greater than or equal to 90% of the theoretical steam flow value, and less than 95% of the theoretical steam flow value, or the current steam flow value is greater than 105% of the theoretical steam flow value, and less than or equal to 110% of the theoretical steam flow value, then the current steam flow measurement state is in the second state; if the current steam flow value is greater than 110% of the theoretical steam flow value, or less than 90% of the theoretical steam flow value, then the current steam flow measurement state is in the third state.

[0027] Specifically, the steam flow rate And water supply valve position value OP WS Modeling to obtain the theoretical linear function of steam flow rate After that, the current steam flow value PV ST The theoretical steam flow rate PV at the corresponding feedwater valve position in the linear function of the theoretical steam flow rate STB To compare; if , the steam volume is within this range, and the steam flow measurement can be considered accurate, that is, the current steam flow measurement state is in the first state; if or , the steam volume is within this range, and it can be considered that the steam flow measurement is inaccurate, but the steam measuring instrument can reflect the trend of steam volume changes, that is, the current steam flow measurement state is in the second state; if or , the steam volume is within this range, and it can be considered that the steam flow measurement is inaccurate, that is, the current steam flow measurement state is in the third state.

[0028] On the basis of the above technical solutions, S103, based on the current feed water flow value, the current water flow measurement state of the target boiler drum is determined using a water flow theoretical value linear function, specifically including: Compare the current water flow rate value with the theoretical water flow rate under the corresponding water supply valve position in the linear function of the theoretical water flow rate; if the current water flow rate value is greater than or equal to 95% of the theoretical water flow rate, and less than or equal to 105% of the theoretical water flow rate, then the current water flow measurement state is in the fourth state; if the current water flow rate value is greater than 110% of the theoretical water flow rate, or less than 90% of the theoretical water flow rate, then the current water flow measurement state is in the fifth state.

[0029] Specifically, the water flow rate value And water supply valve position value OP WS Modeling to obtain the theoretical linear function of water flow After that, the current water flow value PV WS Theoretical steam flow rate at the corresponding feedwater valve position in the linear function of the theoretical water flow rate To compare; if , the water flow rate is within this range, and the water flow rate measurement can be considered accurate, that is, the current water flow rate measurement state is in the fourth state; if or , the water flow rate is within this range, and it can be considered that the water flow rate measurement is inaccurate, that is, the current water flow rate measurement state is in the fifth state.

[0030] Based on the above technical solutions, S105, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 2, the preset control method is determined to be the first control algorithm; The first control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller, RG WSis the range of the water flow controller, PV RP is the amount of water replenishment; Based on the set value of the water flow controller, use the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0031] Optionally, S104 determines the control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state, specifically including: multiplying the fuzzy quantity corresponding to the current steam flow measurement state by the fuzzy quantity corresponding to the current water flow measurement state to obtain the control algorithm selection variable.

[0032] Specifically, the fuzzy quantity of the current steam flow measurement state is multiplied by the fuzzy quantity of the current water flow measurement state to obtain the control algorithm selection variable. Table 3 is the fuzzy control table of steam flow value and feed water flow value, and the fuzzy quantity in the table is the control algorithm selection variable.

[0033] Table 3. Fuzzy control table for steam flow and feed water flow

[0034] When the control algorithm selects variable 2, it indicates that both the steam flow rate and feedwater flow rate are accurately measured, indicating normal operating conditions. A three-impulse control strategy is then adopted, with the primary impulse being the drum level and the auxiliary impulses being the steam flow rate and feedwater flow rate. The drum level is both the primary and controlled variable, serving as the primary process indicator reflecting the boiler drum's operating status and a necessary indicator for ensuring safe boiler operation. The steam flow rate is introduced as a feedforward signal to overcome the effects of steam flow fluctuations on the drum level and effectively mitigate control system malfunctions caused by false liquid levels. The feedwater flow rate is introduced as a secondary variable, leveraging the rapidity with which the secondary loop in the cascade control system can overcome interference to promptly mitigate the effects of feedwater pressure changes on the drum level.

[0035] Under ideal operating conditions, the drum liquid level is maintained at 50%. Figure 2 is a control diagram of the first control algorithm provided by an embodiment of the present invention. Figure 2The input of the calculation block in the system is the output of the drum liquid level controller LC (Liquid Level Controller), the steam flow value measurement and the water supply, and the output of the calculation block is the set value SV of the feedwater flow controller FC (Feedwater Flow Controller) WS The valve position change of the water flow is obtained through the PID (Proportional-Integral-Derivative Controller) calculation of the water flow controller FC. .

[0036] In short, according to the formula and formula Calculate the valve position change for: .

[0037] Based on the above technical solutions, S105, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 1, the preset control method is determined to be the second control algorithm; The second control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, use the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0038] Specifically, when the control algorithm selects the variable as 1, it indicates that the steam flow value is not accurately measured, but the steam measuring instrument can reflect the changing trend of the steam flow, and the current feed water measurement is accurate. Figure 3 is a control diagram of the second control algorithm provided by an embodiment of the present invention, such as Figure 3As shown in Figure 1, a three-impulse control strategy is employed, using a cascade connection between the drum level controller LC and the feedwater flow controller FC, with the steam flow measurement used as the feedforward variable. Although steam measuring instruments cannot accurately measure steam load, they can reflect changes in steam load. When the steam load increases, the feedforward signal indicates an increase in water flow; when the steam load decreases, the feedforward signal indicates a decrease in water flow.

[0039] Set value SW of water flow controller FC WS The calculation method is: , the valve position change of the water flow is obtained through the PID calculation of the water flow controller FC for: .

[0040] Based on the above technical solutions, S105, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.4, the preset control method is determined to be the third control algorithm; The third control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, use the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0041] Specifically, when the control algorithm selects the variable as 0.4, it indicates that the steam flow is unstable and the steam measuring instrument cannot reflect the trend of steam volume changes. However, the feed water volume measurement is accurate at this time, so the current stage is the initial start-up of the boiler system. Figure 4 is a control diagram of the third control algorithm provided by an embodiment of the present invention, such as Figure 4 As shown, the drum level controller LC and the feed water flow controller FC are connected in cascade, and the two-impulse control strategy is adopted. The change of steam load is not considered. The set value of the feed water flow controller FC is the output OP of the drum level controller. LV , the set value SW of the water flow controller FC WS The calculation method is: , the valve position change of the water flow is obtained through the PID calculation of the water flow controller FC for: .

[0042] Based on the above technical solutions, S105, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.1 or 0.05, the preset control method is determined to be the fourth control algorithm; The fourth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of the water flow rate, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller.

[0043] Specifically, when the control algorithm selects the variable as 0.1 or 0.05, it indicates that the feedwater measurement is inaccurate and the steam flow measurement is accurate. Figure 5 is a control diagram of the fourth control algorithm provided by an embodiment of the present invention, such as Figure 5 As shown in the figure, a two-impulse control strategy is adopted in which the steam flow measurement value is used as the feedforward value. The steam drum level controller LC directly controls the feedwater flow valve and can adjust the feedwater flow according to the steam load. It is suitable for situations where the feedwater flow measurement is inaccurate. The valve position OP of the feedwater flow WS Calculated as: .

[0044] Based on the above technical solutions, S105, determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.02, the preset control method is determined to be the fifth control algorithm; The fifth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of water flow, OP LV is the output value of the liquid level controller.

[0045] Specifically, when the control algorithm selects the variable as 0.02, it indicates that the feed water measurement is inaccurate and the steam flow measurement is also inaccurate. Figure 6 is a control diagram of the fifth control algorithm provided by an embodiment of the present invention, such as Figure 6As shown in the figure, a single impulse control strategy of single loop control of drum level controller LC is adopted. Drum level controller LC directly controls the feed water flow valve, and no longer uses steam load and feed water flow as impulses. It is suitable for the situation where both steam flow value and feed water flow value are measured inaccurately. The valve position OP of feed water flow value WS Calculated as: .

[0046] In summary, in the embodiments of the present invention, the multi-modal boiler drum liquid level control method provided by the embodiments of the present invention has the following advantages: (1) Using existing modules on the DCS to establish a multi-impulse control system for the boiler drum level, the control system was configured and connected, and the control language and control logic were compiled, fully utilizing the operational potential of the DCS; (2) In combination with the process operation characteristics and requirements of the boiler, the algorithm of the boiler drum level multi-impulse control system is selected according to the measurement accuracy of the on-site steam load and feed water flow to ensure that the drum level is automatically controlled, reduce the operator's manual operation workload, and ensure the smooth operation of the boiler; (3) The multi-impulse control system for the boiler drum liquid level includes five control algorithms that match different operating conditions. The control method of each algorithm is different. When the operating conditions change, the corresponding algorithm will automatically switch without disturbance, ensuring safe, stable and automatic control of the boiler drum liquid level under all operating conditions, with strong versatility.

[0047] The following describes a specific embodiment to illustrate the technical effects of the multi-modal boiler drum liquid level control method provided by the embodiment of the present invention.

[0048] For example, taking a catalytic device boiler as an example, the boiler liquid level value is LIC11002, and the feed water flow value is FIC11002. The functional relationship between the feed water flow value and the valve position is , the functional relationship between steam flow value and valve position is .

[0049] Figure 7 This is a diagram showing the change in the drum liquid level of a catalytic device boiler provided in an embodiment of the present invention before the control method provided in the present invention is implemented. Figure 8 This is a feed water flow change diagram of a catalytic device boiler provided by an embodiment of the present invention before the control method provided by the present invention is implemented. Figure 9 This is a diagram showing the change in the drum liquid level of a catalytic device boiler provided by an embodiment of the present invention after the control method provided by the present invention is implemented. Figure 10 This is a diagram showing changes in feed water volume after a catalytic device boiler according to an embodiment of the present invention implements the control method according to the present invention.

[0050] like Figure 7-10As shown in the figure, before the implementation of the multi-impulse control of the boiler drum liquid level, the operating conditions changed greatly, the steam consumption load was variable, resulting in unstable steam flow, the original design automatic control could not achieve precise control, the feed water flow and liquid level fluctuated greatly, and the boiler drum liquid level fluctuation range was 36%-50%; after the implementation of the boiler drum liquid level multi-impulse control system, the corresponding algorithm was automatically selected according to the fluctuation range of the steam flow and feed water flow, the liquid level control became more precise and stable, and the boiler drum liquid level fluctuation range was reduced to 39%-42%, ensuring the safe operation of the boiler.

[0051] Figure 11 It is a structural diagram of a multi-modal boiler drum liquid level control device provided by an embodiment of the present invention.

[0052] like Figure 11 As shown, the multi-modal boiler drum liquid level control device specifically includes: The data acquisition unit 111 is used to obtain the current steam flow rate value and the current feed water flow rate value of the target boiler drum; a first state determination unit 112 for determining a current steam flow measurement state of a target boiler drum based on a current steam flow value and using a steam flow theoretical value linear function, wherein the steam flow theoretical value linear function is a theoretical steam flow measurement model determined in advance based on a feedwater valve position value and a steam flow value of the target boiler drum; a second state determining unit 113 for determining a current water flow measurement state of a target boiler drum based on the current feedwater flow value and using a water flow theoretical value linear function, wherein the water flow theoretical value linear function is a theoretical water flow measurement model determined in advance based on the feedwater valve position value and the feedwater flow value of the target boiler drum; a variable determination unit 114 for determining a control algorithm selection variable based on a current steam flow measurement state and a current water flow measurement state, wherein one control algorithm selection variable corresponds to one preset control algorithm; An algorithm determination unit 115 is configured to determine a corresponding preset control algorithm based on a control algorithm selection variable; The control unit 116 is used to control the operation of the target boiler drum using a preset control algorithm.

[0053] Optionally, the first state determining unit 112 is specifically configured to: Compare the current steam flow value with the theoretical steam flow value at the corresponding feedwater valve position in the linear function of the theoretical steam flow value; If the current steam flow rate value is greater than or equal to 95% of the theoretical steam flow rate value, and less than or equal to 105% of the theoretical steam flow rate value, the current steam flow rate measurement state is in the first state; If the current steam flow rate value is greater than or equal to 90% of the theoretical steam flow rate value and less than 95% of the theoretical steam flow rate value, or the current steam flow rate value is greater than 105% of the theoretical steam flow rate value and less than or equal to 110% of the theoretical steam flow rate value, then the current steam flow rate measurement state is in the second state; If the current steam flow rate value is greater than 110% of the theoretical steam flow rate value, or is less than 90% of the theoretical steam flow rate value, the current steam flow rate measurement state is in the third state.

[0054] Optionally, the second state determining unit 113 is specifically configured to: Compare the current water flow rate value with the theoretical water flow rate value at the corresponding water flow valve position in the linear function of the theoretical water flow rate; If the current water flow rate value is greater than or equal to 95% of the theoretical water flow rate value, and less than or equal to 105% of the theoretical water flow rate value, the current water flow measurement state is in the fourth state; If the current water flow rate value is greater than 110% of the theoretical water flow rate value, or is less than 90% of the theoretical water flow rate value, the current water flow rate measurement state is in the fifth state.

[0055] Optionally, the algorithm determination unit 115 is specifically configured to: If the control algorithm selection variable is 2, the preset control method is determined to be the first control algorithm; The first control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller, RG WS is the range of the water flow controller, PV RP is the amount of water replenishment; Based on the set value of the water flow controller, use the formula The valve position change of the water flow is calculated, where: is the valve position change, Kc is the gain coefficient of the water flow controller, Ti is the integral time of the flow controller, Td is the differential time of the water flow controller, s is the Laplace transformation factor, and PVWS represents the water flow rate.

[0056] Optionally, the algorithm determination unit 115 is further configured to: If the control algorithm selection variable is 1, the preset control method is determined to be the second control algorithm; The second control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, use the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0057] Optionally, the algorithm determination unit 115 is further configured to: If the control algorithm selection variable is 0.4, the preset control method is determined to be the third control algorithm; The third control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, use the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

[0058] Optionally, the algorithm determination unit 115 is further configured to: If the control algorithm selection variable is 0.1 or 0.05, the preset control method is determined to be the fourth control algorithm; The fourth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of the water flow rate, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller.

[0059] Optionally, the algorithm determination unit 115 is further configured to: If the control algorithm selection variable is 0.02, the preset control method is determined to be the fifth control algorithm; The fifth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of water flow, OP LV is the output value of the liquid level controller.

[0060] Optionally, the variable determination unit 114 is specifically configured to: The fuzzy quantity corresponding to the current steam flow measurement state is multiplied by the fuzzy quantity corresponding to the current water flow measurement state to obtain the control algorithm selection variable.

[0061] The multimodal boiler drum liquid level control device provided in the embodiment of the present invention has the same technical features as the multimodal boiler drum liquid level control method provided in the above embodiment, so it can also solve the same technical problems and achieve the same technical effects.

[0062] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0063] Finally, it should be noted that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A multi-mode boiler drum liquid level control method, characterized in that: The control method includes: Obtain the current steam flow value and current feed water flow value of the target boiler drum; Based on the current steam flow value, determining the current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function, wherein the steam flow theoretical value linear function is a theoretical steam flow measurement model determined in advance based on the feedwater valve position value and the steam flow value of the target boiler drum; Based on the current feedwater flow value, determining the current water flow measurement state of the target boiler drum using a water flow theoretical value linear function, wherein the water flow theoretical value linear function is a theoretical water flow measurement model determined in advance based on the feedwater valve position value and the feedwater flow value of the target boiler drum; determining a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state, wherein one control algorithm selection variable corresponds to a preset control algorithm; Determining the corresponding preset control algorithm based on the control algorithm selection variable; The valve position variation of the feed water flow determined by the preset control algorithm is used to control the liquid level of the target boiler drum.

2. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining the current steam flow measurement state of the target boiler drum based on the current steam flow value using a steam flow theoretical value linear function includes: Comparing the current steam flow value with the theoretical steam flow value at the corresponding feedwater valve position in the linear function of the theoretical steam flow value; If the current steam flow rate value is greater than or equal to 95% of the theoretical steam flow rate value, and less than or equal to 105% of the theoretical steam flow rate value, the current steam flow rate measurement state is in the first state; If the current steam flow rate value is greater than or equal to 90% of the theoretical steam flow rate value and less than 95% of the theoretical steam flow rate value, or if the current steam flow rate value is greater than 105% of the theoretical steam flow rate value and less than or equal to 110% of the theoretical steam flow rate value, then the current steam flow rate measurement state is in the second state; If the current steam flow rate value is greater than 110% of the theoretical steam flow rate value, or is less than 90% of the theoretical steam flow rate value, the current steam flow rate measurement state is in the third state.

3. The multi-mode boiler drum liquid level control method according to claim 2, characterized in that: Determining the current water flow measurement state of the target boiler drum based on the current feed water flow value using a water flow theoretical value linear function includes: Comparing the current water flow rate value with the theoretical water flow rate value at the corresponding water supply valve position in the water flow rate theoretical value linear function; If the current water flow rate value is greater than or equal to 95% of the theoretical water flow rate value, and less than or equal to 105% of the theoretical water flow rate value, the current water flow rate measurement state is in the fourth state; If the current water flow rate value is greater than 110% of the theoretical water flow rate value, or is less than 90% of the theoretical water flow rate value, the current water flow rate measurement state is in the fifth state.

4. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 2, then the preset control method is determined to be the first control algorithm; The first control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller, RG WS is the range of the water flow controller, PV RP is the amount of water replenishment; Based on the set value of the water flow controller, the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

5. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 1, the preset control method is determined to be the second control algorithm; The second control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

6. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.4, then determining that the preset control method is the third control algorithm; The third control algorithm includes: Using the formula Calculate the set value of the water flow controller, where SV WS is the set value of the water flow controller, OP LV is the output value of the liquid level controller; Based on the set value of the water flow controller, the formula The valve position change of the water flow is calculated, where: is the valve position change, K c is the gain coefficient of the water flow controller, T i is the integral time of the flow controller, T d is the differential time of the water flow controller, s is the Laplace transformation factor, PV WS Indicates the water flow rate.

7. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.1 or 0.05, the preset control method is determined to be the fourth control algorithm; The fourth control algorithm includes: Using the formula Calculate the valve position of the water flow, where OP WS is the valve position of the water flow rate, PV ST is the steam flow rate, CF is the fixed parameter in the steam flow measurement process, OP LV is the output value of the liquid level controller.

8. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining the corresponding preset control algorithm based on the control algorithm selection variable includes: If the control algorithm selection variable is 0.02, then the preset control method is determined to be the fifth control algorithm; The fifth control algorithm includes: Use formula OP WS =OP LV Calculate the valve position of the water flow, where OP WS is the valve position of the water flow, OP LV is the output value of the liquid level controller.

9. The multi-mode boiler drum liquid level control method according to claim 1, characterized in that: Determining a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state includes: The fuzzy quantity corresponding to the current steam flow measurement state is multiplied by the fuzzy quantity corresponding to the current water flow measurement state to obtain the control algorithm selection variable.

10. A multi-mode boiler drum liquid level control device, characterized in that: The control device comprises: A data acquisition unit, used to obtain the current steam flow value and the current feed water flow value of the target boiler drum; a first state determining unit, configured to determine, based on the current steam flow value, a current steam flow measurement state of the target boiler drum using a steam flow theoretical value linear function, wherein the steam flow theoretical value linear function is a theoretical steam flow measurement model determined in advance based on a feedwater valve position value and a steam flow value of the target boiler drum; a second state determination unit, configured to determine, based on the current feedwater flow value, a current water flow measurement state of the target boiler drum using a water flow theoretical value linear function, wherein the water flow theoretical value linear function is a theoretical water flow measurement model determined in advance based on the feedwater valve position value and the feedwater flow value of the target boiler drum; a variable determination unit, configured to determine a control algorithm selection variable based on the current steam flow measurement state and the current water flow measurement state, wherein one control algorithm selection variable corresponds to a preset control algorithm; an algorithm determining unit, configured to determine the corresponding preset control algorithm based on the control algorithm selection variable; A control unit is used to control the operation of the target boiler drum using the preset control algorithm.

Images