Steam generator liquid level control method and related equipment

Abstract

The invention relates to the technical field of nuclear reactor control, in particular to a steam generator liquid level control method and related equipment, and the method is used for feed water flow regulation of a steam generator. And the liquid level deviation, the liquid level deviation change rate, the steam flow, the feed water flow and operation data of the steam generator are obtained. The liquid level deviation and the liquid level deviation change rate serve as input, the water supply flow is adjusted through a liquid level fuzzy controller, and a first output value is obtained; the steam flow and the feed water flow serve as input, and a second output value is obtained through adjustment of a steam-water mismatch flow fuzzy controller; and the steady-state relation deviation between the load and the feed water flow serves as input, a load-flow fuzzy controller is used for adjustment, and a third output value is obtained. And the three output values are synthesized to determine a feed water flow demand value, and the opening degree of a feed water regulating valve is calculated according to the feed water flow demand value so as to regulate the feed water flow. Through cooperative work of the multiple fuzzy controllers, accurate adjustment of the water supply flow of the steam generator is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactor control, and specifically relates to a steam generator liquid level control method and related equipment. Background Art

[0002] As a heat energy device, the steam generator plays a crucial role in many fields such as industrial production, energy utilization, heating systems, and medical and health. In the operation system of nuclear power plants, the liquid level control of the steam generator is particularly critical, and its liquid level must always be stable within a safe range near the program set value to ensure the safe and stable operation of the nuclear power plant.

[0003] Currently, the liquid level control system of nuclear power plant steam generators mainly relies on the cascade PID control strategy. However, with the increasing complexity of the operating conditions of nuclear power plants, especially the frequent changes in load levels, the traditional cascade PID control gradually exposes limitations. During the large-range load change process, the traditional cascade PID control often shows poor control performance, specifically manifested as a large overshoot and a long adjustment time, and it is difficult to quickly respond to load changes, resulting in large fluctuations in the liquid level of the steam generator. More seriously, in the low-power operation state, the traditional cascade PID control even cannot effectively maintain the liquid level stability and can only rely on the manual intervention of operators, which not only increases the burden on operators but also reduces the automation level and operation safety of nuclear power plants.

[0004] In view of the above challenges, in order to improve the economy and safety of nuclear power plant units, achieve rapid and stable adjustment of the steam generator liquid level, reduce the change range of the liquid level during the large-load adjustment process, prevent reactor trip accidents caused by excessive liquid level fluctuations, and at the same time reduce the dependence on manual intervention of personnel and improve the automatic control level of nuclear power plants, it is particularly urgent to carry out research on advanced control algorithms such as fuzzy control. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a steam generator liquid level control method and related equipment for solving the technical problem that the current steam generator control method cannot maintain the liquid level stability in view of the deficiencies in the above-mentioned prior art.

[0006] The object of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a steam generator liquid level control method, including: Obtain the liquid level deviation, liquid level deviation change rate, steam flow rate, feed water flow rate, and operation data of the steam generator; Use the liquid level deviation and liquid level deviation change rate as the input data of the liquid level fuzzy controller, and use the liquid level fuzzy controller to adjust the feed water flow rate to obtain a first output value; Taking the steam flow rate and the feed water flow rate as the input data of the steam-water mismatch flow rate fuzzy controller, adjusting the feed water flow rate to obtain a second output value; Taking the deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate as the input data of the load-flow fuzzy controller, and using the load-flow fuzzy controller to adjust the feed water flow rate to obtain a third output value; Obtaining a feed water flow rate demand value according to the first output value, the second output value, and the third output value, obtaining the opening degree of the feed water regulating valve according to the feed water flow rate demand value, and adjusting the feed water flow rate according to the opening degree.

[0007] As a further improvement of the present invention, the liquid level fuzzy controller, the steam-water mismatch flow rate fuzzy controller, and the load-flow fuzzy controller all include an input layer, an input membership function layer, a fuzzy rule layer, an output membership function layer, and a defuzzification layer; The input layer is used to perform normalization processing on the input data; The input membership function layer uses a triangular function to convert the input data in the input layer into the membership degree of a fuzzy set; the membership degree is obtained according to the membership function, and the membership function is used to define the membership degree value corresponding to different values of the input variable, reflecting the membership relationship between the input variable and the fuzzy set; The fuzzy rule layer includes several nodes, and each node performs fuzzy inference according to the corresponding fuzzy rule to deduce the output fuzzy set from the input fuzzy set; The output membership function layer is used to convert the output fuzzy set into a specific output membership degree value; The defuzzification layer is used to convert the output signal of the output membership function layer into a control quantity.

[0008] As a further improvement of the present invention, the parameter setting of the liquid level fuzzy controller specifically includes: Determining the normalized liquid level deviation domain, the normalized liquid level deviation change rate domain, and the output value domain according to the ranges of the input liquid level deviation and the liquid level deviation change rate variables; According to the selected triangular membership function and in combination with the liquid level characteristics of the steam generator, converting the liquid level deviation domain and the liquid level deviation change rate domain into the membership degrees in the fuzzy set; Performing fuzzy processing on the corresponding membership degrees of the liquid level deviation and the liquid level deviation change rate in the fuzzy set according to the set fuzzy rules; Using the defuzzification rule to convert the fuzzy processed liquid level deviation change rate data into the first output value.

[0009] As a further improvement of the present invention, the control steps of the steam-water mismatch flow rate fuzzy controller specifically include: Determine the normalized flow deviation domain, output value range, and membership function based on the steam flow and feed water flow; Convert the flow deviation domain into membership degrees in the fuzzy set according to the determined membership function; Perform fuzzy inference on the fuzzy set using the set fuzzy rules; Use the defuzzification rule to convert the flow deviation data after fuzzy processing into a second output value.

[0010] As a further improvement of the present invention, the control steps of the load-flow fuzzy controller specifically include: Determine the corresponding steady-state feed water flow according to different power levels, and determine the feed water flow deviation domain according to different feed water flows; Convert the feed water flow deviation domain into membership degrees in the fuzzy set according to the determined membership function; Perform fuzzy inference on the fuzzy set using the set fuzzy rules; Use the defuzzification rule to convert the flow deviation data after fuzzy processing into a third output value.

[0011] As a further improvement of the present invention, the defuzzification rule in the defuzzification layer is obtained by the centroid method. The centroid method is used to take the area under the membership function curve in the fuzzy set as the basis for weighted averaging, and thus the output after defuzzification can be obtained. The calculation method of the centroid method is as follows:

[0012] In the formula, z is the result of defuzzification; x is the output variable; is the membership function of the fuzzy set.

[0013] As a further improvement of the present invention, the liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller further include adjusting the domain and membership function, specifically including: Obtain the cascade PID control result, and correspondingly adjust the domain and membership function of the liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller according to the cascade PID control result to obtain the optimal output value.

[0014] As a further improvement of the present invention, after obtaining the feed water flow demand value based on the first output value, the second output value, and the third output value, obtain a control command according to the feed water flow demand value. The control command is sent to the actuator, and the actuator adjusts the opening of the valve according to the control command to change the cross-sectional area of the fluid flow path, thereby adjusting the feed water flow until the actual flow matches the set value.

[0015] Second aspect, the present invention provides a steam generator liquid level control system for implementing the above-mentioned steam generator liquid level control method, including: A steam generator data acquisition module that acquires the liquid level deviation, liquid level deviation change rate, steam flow rate, feed water flow rate, and operating data of the steam generator; A liquid level fuzzy control module that uses the liquid level deviation and liquid level deviation change rate as the input data of the liquid level fuzzy controller, and adjusts the feed water flow rate by using the liquid level fuzzy controller to obtain a first output value; A steam-water mismatch flow rate fuzzy control module that uses the steam flow rate and feed water flow rate as the input data of the steam-water mismatch flow rate fuzzy controller, and adjusts the feed water flow rate to obtain a second output value; A load-flow fuzzy control module that uses the deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate as the input data of the load-flow fuzzy controller, and adjusts the feed water flow rate by using the load-flow fuzzy controller to obtain a third output value; A feed water flow rate control module that obtains the feed water flow rate demand value according to the first output value, the second output value, and the third output value, obtains the opening degree of the feed water regulating valve according to the feed water flow rate demand value, and adjusts the feed water flow rate according to the opening degree.

[0016] Third aspect, the present invention provides a computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to execute the above-mentioned steam generator liquid level control method.

[0017] Fourth aspect, the present invention provides a computing device, including: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include steps for executing the above-mentioned steam generator liquid level control method.

[0018] The beneficial effects of the present invention are as follows: The steam generator liquid level control method provided by the present invention realizes the regulation of the feed water flow rate by designing three fuzzy controllers, namely, the liquid level fuzzy controller, the steam-water mismatch flow rate fuzzy controller, and the load-flow fuzzy controller. The liquid level fuzzy controller needs to find the fuzzy relationship between the liquid level deviation, the change rate of the liquid level deviation, and the weight to be changed, and output the feed water flow rate to the feed water flow rate channel. The steam-water mismatch flow rate fuzzy controller needs to find the relationship between the deviation between the steam flow rate and the feed water flow rate and the weight to be changed, and output the feed water flow rate to the feed water flow rate channel. The load-flow fuzzy controller, according to the steady-state correspondence relationship between the load and the feed water flow rate, searches in real time for the feed water flow rate corresponding to the current load, then calculates the deviation from the actual feed water flow rate as the input of the load-flow fuzzy controller, and finds the relationship with the weight to be changed, and outputs the feed water flow rate to the feed water flow rate channel. The flow rate controller helps to maintain the water level of the steam generator within a reasonable range, ensuring the safe and stable operation of the steam generator. When there is a large load change, the load-flow fuzzy controller can find the corresponding steady-state value of the feed water flow rate according to the real-time power level, and then use the deviation between the measured feed water flow rate and the feed water flow rate at steady state as the input of the load-flow fuzzy controller to quickly respond to the change of the liquid level by the power controller, realizing rapid adjustment to maintain the stability of the liquid level.

[0019] Furthermore, the present invention adopts normalization processing and fuzzy inference, enabling the fuzzy controller to adapt to different working conditions and environmental changes, with strong robustness and adaptability. Through the fuzzy rule layer for fuzzy inference, the output fuzzy set is derived from the input fuzzy set, thus simulating the human reasoning and decision-making process and being able to handle complex control problems. The triangular function is used to convert the input data into the membership degree of the fuzzy set, enabling the input data to be fuzzified. This method can effectively process uncertain, non-linear, and fuzzy information. Brief Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0021] Figure 1 It is the flow chart of the steam generator liquid level control method in the embodiment of the present invention; Figure 2 It is the corresponding curve graph of the load-flow fuzzy controller in the embodiment of the present invention; Figure 3 is a schematic diagram comparing the simulation results when the power of the embodiment of the present invention rises from 30% to 100% again and the power recovers to 100% when running to 4600 s, using this method and the cascade control method; (a) is a curve comparison diagram corresponding to the steam generator liquid level; (b) is a curve comparison diagram corresponding to the feed water flow rate; (c) is a curve comparison diagram corresponding to the steam space pressure; (d) is a curve comparison diagram corresponding to the steam main pipe pressure; (e) is a curve comparison diagram corresponding to the power; (f) is a curve comparison diagram corresponding to the pressurizer pressure; (g) is a curve comparison diagram corresponding to the average coolant temperature; (h) is a curve comparison diagram corresponding to the pressurizer liquid level; Figure 4 is a schematic diagram comparing the simulation results when the load set value of the embodiment of the present invention is load-shed from 100% to 30%, using this method and the cascade control method; (a) is a curve comparison diagram corresponding to the steam generator liquid level; (b) is a curve comparison diagram corresponding to the feed water flow rate; (c) is a curve comparison diagram corresponding to the steam space pressure; (d) is a curve comparison diagram corresponding to the steam main pipe pressure; (e) is a curve comparison diagram corresponding to the power; (f) is a curve comparison diagram corresponding to the pressurizer pressure; (g) is a curve comparison diagram corresponding to the average coolant temperature; (h) is a curve comparison diagram corresponding to the pressurizer liquid level; Figure 5 It is a schematic diagram of the structure of an electronic device in the embodiment of the present invention. Specific embodiments

[0022] In order to make the purpose and technical solutions of the present invention clearer and easier to understand. The following further describes the present invention in detail with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Among them, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0024] Embodiment 1 This embodiment provides a steam generator liquid level control method. Through the set liquid level fuzzy controller, steam-water mismatch flow rate fuzzy controller and load-flow fuzzy controller, considering several aspects such as liquid level deviation, liquid level deviation change rate, steam-water mismatch and operation data, the liquid level of the steam generator is adjusted comprehensively to be stable, so that when the steam generator is subjected to large-range load changes, the amplitude of liquid level change and the time of liquid level adjustment are reduced. The following are the specific implementation manners.

[0025] First, a liquid level fuzzy controller, a steam-water mismatch flow fuzzy controller, and a load-flow fuzzy controller are set up. Among them, the liquid level fuzzy controller adjusts the feed water flow rate based on the liquid level deviation and the deviation change rate; the steam-water mismatch flow fuzzy controller adjusts the feed water flow rate based on the deviation between the steam flow rate and the feed water flow rate; the load-flow fuzzy controller adjusts the feed water flow rate based on the deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate.

[0026] Among them, the liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller in this embodiment all include an input layer, an input membership function layer, a fuzzy rule layer, an output membership function layer, and a defuzzification layer. The input layer is used to normalize the input data; the input membership function layer uses a triangular function to convert the input data in the input layer into the membership degree of a fuzzy set; the fuzzy rule layer includes several nodes, and each node performs fuzzy reasoning according to the corresponding fuzzy rule, deriving an output fuzzy set from the input fuzzy set; the output membership function layer is used to convert the output fuzzy set into a specific output membership degree value; the defuzzification layer is used to convert the output signal of the output membership function layer into a control quantity.

[0027] Among them, the membership degree is obtained according to the membership function, and the membership function is used to define the membership degree value corresponding to the input variable under different values, reflecting the membership relationship between the input variable and the fuzzy set.

[0028] In this embodiment, the input layer of the liquid level fuzzy controller includes the normalized liquid level deviation and the normalized liquid level change rate. The input layer of the steam-water mismatch flow fuzzy controller is the normalized deviation between the steam flow rate and the feed water flow rate. The input layer of the load-flow fuzzy controller is the normalized deviation between the steady-state feed water flow rate and the actual feed water flow rate.

[0029] Both the input membership function layer and the output membership function layer use triangular functions, and the center and width of the triangular functions are updated according to the simulation results.

[0030] The fuzzy rule layer of the liquid level fuzzy controller contains 49 nodes, the fuzzy rule layer of the steam-water mismatch flow fuzzy controller contains 7 nodes, and the fuzzy rule base of the load-flow fuzzy controller contains 7 nodes. Each node corresponds to a fuzzy rule.

[0031] The output layers of the liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller are all the normalized feed water flow rate demand values.

[0032] Therefore, when collecting data of the steam generator in this embodiment, the liquid level deviation, the liquid level deviation change rate, the steam flow rate, the feed water flow rate, and the operation data are mainly collected. The operation data in this embodiment is the load data of the steam generator.

[0033] Secondly, a liquid level fuzzy controller, a steam-water mismatch flow fuzzy controller, and a load-flow fuzzy controller are respectively used to adjust the feed water flow rate.

[0034] Specifically, the liquid level deviation and the change rate of the liquid level deviation are used as the input data of the liquid level fuzzy controller, and the liquid level fuzzy controller is used to adjust the feed water flow rate to obtain a first output value.

[0035] Among them, the control steps of the liquid level fuzzy controller specifically include: determining the normalized liquid level deviation domain, the normalized liquid level deviation change rate domain, and the output value domain according to the ranges of the input liquid level deviation and liquid level deviation change rate variables; according to the selected triangular membership function and combining the liquid level characteristics of the steam generator, converting the liquid level deviation domain and the liquid level deviation change rate domain into membership degrees in the fuzzy set; performing fuzzy processing on the corresponding membership degrees of the liquid level deviation and liquid level deviation change rate in the fuzzy set according to the set fuzzy rules; using the defuzzification rule to convert the fuzzy processed liquid level deviation change rate data into a first output value.

[0036] The steam flow rate and the feed water flow rate are used as the input data of the steam-water mismatch flow fuzzy controller to adjust the feed water flow rate to obtain a second output value.

[0037] The control steps of the steam-water mismatch flow fuzzy controller specifically include: determining the normalized flow deviation domain, the output value domain, and the membership function according to the steam flow rate and the feed water flow rate; converting the flow deviation domain into membership degrees in the fuzzy set according to the determined membership function; performing fuzzy inference on the fuzzy set using the set fuzzy rules; using the defuzzification rule to convert the fuzzy processed flow deviation data into a second output value.

[0038] The deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate is used as the input data of the load-flow fuzzy controller, and the load-flow fuzzy controller is used to adjust the feed water flow rate to obtain a third output value; The control steps of the load-flow fuzzy controller specifically include: determining the corresponding steady-state feed water flow rate according to different power levels, and determining the feed water flow rate deviation domain according to different feed water flow rates; converting the feed water flow rate deviation domain into membership degrees in the fuzzy set according to the determined membership function; performing fuzzy inference on the fuzzy set using the set fuzzy rules; using the defuzzification rule to convert the fuzzy processed flow deviation data into a third output value.

[0039] Finally, obtain the feed water flow demand value based on the first output value, the second output value, and the third output value. Obtain the opening degree of the feed water regulating valve according to the feed water flow demand value, and adjust the feed water flow according to the opening degree. Specifically, the sum of the first output value, the second output value, and the third output value is the demand value of the feed water flow. The opening degree of the feed water regulating valve is calculated by the feed water flow controller to adjust the feed water flow.

[0040] In addition, in this embodiment, fuzzy rules are written based on empirical knowledge and the operation results of the steam generator, and the relationships between the controlled quantity, the disturbing quantity, and the output quantity need to be found. The liquid level fuzzy controller uses the liquid level deviation and the change rate of the liquid level deviation as input signals. When the liquid level deviation is in a positive or negative state, it is impossible to determine whether to increase or decrease the feed water flow based on this quantity alone. Therefore, the change rate of the liquid level deviation also needs to be combined to determine the state of the liquid level change. When the liquid level is low, the feed water flow will be increased. When the liquid level reaches the set value, the size of the feed water flow will also be adjusted according to the change rate of the liquid level deviation to avoid the problem of excessive overshoot.

[0041] The steam-water mismatch flow fuzzy controller takes the deviation between the steam flow and the feed water flow as input. This signal can quickly adjust the feed water flow according to the deviation of the steam-water flow to restore the steam-water balance, thereby suppressing the deviation of the steam generator liquid level from the set value. In this way, the flow controller helps to maintain the water level of the steam generator within a reasonable range and ensure the safe and stable operation of the steam generator.

[0042] When there is a large load change, the load-flow fuzzy controller can find the corresponding steady-state value of the feed water flow according to the real-time power level, and then use the deviation between the measured feed water flow and the feed water flow at steady state as the input of the load-flow fuzzy controller to quickly respond to the change of the liquid level by the power controller and achieve rapid adjustment to maintain the stability of the liquid level.

[0043] In addition, in this embodiment, the defuzzification rules in the defuzzification layer are obtained by the centroid method. The centroid method is used to take the area under the membership function curve in the fuzzy set as the basis for weighted averaging, and the defuzzified output can be obtained therefrom. The calculation method of the centroid method is as follows:

[0044] In the formula, z is the result of defuzzification; x is the output variable; is the membership function of the fuzzy set.

[0045] During the entire adjustment process, the flow controller first monitors the actual flow rate of the fluid in real time through sensors, then compares this data with the preset flow rate target value, calculates the required adjustment amount based on the deviation, and then the controller issues a command to the actuator. The actuator immediately adjusts the opening of the valve, changing the cross-sectional area of the fluid flow path, thereby finely adjusting the flow rate until the actual flow rate matches the set value, ensuring that the fluid flows stably according to the predetermined flow rate.

[0046] Embodiment 2 As a preferred implementation of Embodiment 1, this embodiment specifically includes: The liquid level fuzzy controller takes the liquid level deviation LE and the deviation change rate CL as input signals, which are passed through fuzzification, fuzzy inference, and defuzzification to the output layer, obtaining the water supply flow rate demand value of the fuzzy controller according to the liquid level of the steam generator (i.e., the first output value) CA1 , and then based on the deviation between the water supply flow rate and the steam flow rate of the steam generator FE2 as the input of the steam-water mismatch fuzzy controller, and then through fuzzification, fuzzy inference, and defuzzification to the output layer, obtaining the water supply flow rate demand value of the fuzzy controller according to the steam-water mismatch deviation (i.e., the second output value) CA2 . On the basis of the original adjustment in only two aspects of liquid level and steam-water mismatch, it is increased to find the corresponding steady-state water supply flow rate according to the actual power level, and the deviation from the actual water supply flow rate is used as the input value FE3 , realizing a more direct adjustment of the water supply flow rate. Finally, through fuzzification, fuzzy inference, and defuzzification to the output layer, obtaining the water supply flow rate demand value of the steam generator for the load level CA3 .

[0047] Determine the universes of discourse of the input and output according to the ranges of the input variables, and set the relevant parameters in the liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller.

[0048] 1. The relevant parameter settings in the liquid level fuzzy controller are as follows: 1-1) The basic universes of discourse of the input and output: The universe of discourse of the normalized liquid level deviation LE is [-0.1, 0.1], the universe of discourse of the normalized liquid level deviation change rate CL is [-0.02, 0.02], and the value range of the output CA1 is [-0.6, 0.6]; Among them, the liquid level controller, based on the step change of the liquid level set value at ±5% / s at the 100% power level, the load ±10%, and the load rejection to the 30% power level according to the traditional cascade control, lays the foundation for the confirmation of the input universe of discourse and the membership function of the liquid level fuzzy controller.

[0049] 1-2) Fuzzy subsets and membership functions: The input liquid level deviation change rate CL is set to {NB, NS, ZO, PS, PB}, and the input liquid level deviation LE and the output CA1 are both set to {NB, NM, NS, ZO, PS, PM, PB}. The triangular membership function (trimf) type is selected for the membership function because its formula design is simple and convenient for online operation. Since the steam generator object is affected by the false liquid level, the membership function needs to be slightly adjusted.

[0050] 1-3) Compile fuzzy rules: According to the liquid level characteristics of the steam generator, combined with the control and adjustment characteristics, and combined with the logic followed by the above fuzzy rules, the fuzzy rules are formulated as shown in Table 1: Table 1 Fuzzy Rules of the Liquid Level Fuzzy Controller

[0051] Among them, the meanings corresponding to the variables in the fuzzy set are: NB (Negative Big): Negative big, indicating that the deviation change is significantly negative. This means that the liquid level deviation is rapidly decreasing, that is, the liquid level is rapidly dropping.

[0052] NM (Negative Medium): Negative medium, indicating that the deviation change is a medium negative value.

[0053] NS (Negative Small): Negative small, indicating that the deviation change is slightly negative. This means that the liquid level deviation is slowly decreasing, that is, the liquid level is slowly dropping.

[0054] ZO (Zero): Zero, indicating that the deviation change is close to zero. This means that the liquid level deviation hardly changes, that is, the liquid level remains stable.

[0055] PS (Positive Small): Positive small, indicating that the deviation change is slightly positive. This means that the liquid level deviation is slowly increasing, that is, the liquid level is slowly rising.

[0056] PM (Positive Medium): Positive medium, indicating that the deviation change is a medium positive value.

[0057] PB (Positive Big): Positive big, indicating that the deviation change is significantly positive. This means that the liquid level deviation is rapidly increasing, that is, the liquid level is rapidly rising.

[0058] 1-4) Defuzzification is performed using the centroid method: The centroid method uses the area under the membership function curve in the fuzzy set as the basis for weighted averaging, obtaining a definite value as the output after defuzzification. Therefore, the centroid method is not only simple and intuitive, but also can handle multiple fuzzy rules well. Moreover, the output inference is smoother compared to other methods and is more sensitive to small signals. In an actual system, the implementation of the centroid method is relatively easy because its calculation process is intuitive and simple.

[0059] 2. The relevant parameters of the steam-water mismatch flow fuzzy controller are set as follows: 2-1) Input and output basic universes: The universe of discourse of the flow deviation FE2 is [-0.5, 0.5], and the value range of the output CA2 is [-0.38, 0.38]; Among them, the input of the flow fuzzy controller determines the deviation universe of discourse and membership function of the flow fuzzy controller by finding the deviation range between the feed water flow and the steam flow according to four working conditions: the liquid level set value at ±5% / s under 100% power level, 100%-110% step-up load, 100%-90% step-down load, and 100% load rejection to 30%.

[0060] 2-2) Fuzzy subsets and membership functions: The input flow deviation change rate FE2 is set to {NB, NM, NS, ZO, PS, PM, PB}, and the output CA2 is also set to {NB, NM, NS, ZO, PS, PM, PB}. The triangular membership function (trimf) type is selected for the membership function because its formula design is simple and convenient for on-line operation. Since the steam generator object is affected by the false liquid level, the membership function needs to be slightly adjusted: 2-3) Compile fuzzy rules: According to the liquid level characteristics of the steam generator, combined with the control adjustment characteristics and the logic followed by the above fuzzy rules, the fuzzy rules are formulated as shown in Table 2: Table 2 Fuzzy rules of the steam-water mismatch flow fuzzy controller

[0061] 2-4) Defuzzification is performed using the centroid method: The centroid method uses the area under the membership function curve in the fuzzy set as the basis for weighted averaging, obtaining a definite value as the output after defuzzification. Therefore, the centroid method is not only simple and intuitive, but also can handle multiple fuzzy rules well. Moreover, the output inference is smoother compared to other methods and is more sensitive to small signals. In an actual system, the implementation of the centroid method is relatively easy because its calculation process is intuitive and simple.

[0062] 3. The relevant parameters in the load-flow fuzzy controller are set as follows: 3-1) Input and output basic universe of discourse: The universe of discourse of the flow deviation FE3 is [-0.1, 0.1], and the value range of the output CA3 is [-0.02, 0.02]; The load-flow fuzzy controller determines different steady-state feedwater flows according to power levels of 110%, 100%, 90%, 80%, 70%, 60%, 50%, 40%, and 30%, and establishes a linear correspondence based on this relationship, such as Figure 2 , and then uses the deviation from the actual feedwater flow as the input for power fuzzy control, thereby laying the foundation for the universe of discourse and membership function of the power fuzzy controller.

[0063] 3-2) Fuzzy subsets and membership functions: Set the change rate FE3 of the deviation between the flow corresponding to the input power and the actual flow to {NB, NS, ZO, PS, PB}, and set the output CA3 to {NB, NM, NS, ZO, PS, PM, PB}. The triangular membership function (trimf) type is selected for the membership function because its formula design is simple and convenient for online operation. Since the steam generator object is affected by false liquid levels, the membership function needs to be slightly adjusted: 3-3) Write fuzzy rules. According to the liquid level characteristics of the steam generator, combined with the control and adjustment characteristics, and combined with the logic followed by the above fuzzy rules, the fuzzy rules are formulated as shown in Table 3: Table 3 Fuzzy rules of the load-flow fuzzy controller

[0064] 3-4) Defuzzification using the centroid method: The centroid method uses the area under the membership function curve in the fuzzy set as the basis for weighted averaging, and thus obtains a determined value as the output after defuzzification. Therefore, the centroid method is not only simple and intuitive, but also can handle multiple fuzzy rules well, and the output inference is smoother than other methods and more sensitive to small signals. In an actual system, the implementation of the centroid method is also relatively easy because its calculation process is intuitive and simple.

[0065] According to the designed fuzzy controller, simulation tests are carried out on the steam generator under two working conditions: linear load change from 100% - 30% - 100% and load rejection change from 100% - 30%.

[0066] Example 3 As a further preferred embodiment of this method, when performing a 100%-30%-100% linear load change, a disturbance of linearly decreasing load will be introduced at 600 s, causing the load set value to linearly decrease from 100% to 30%, with other set values remaining unchanged. When running to 1000 s, the power is stabilized at the 30% level. At 4200 s, a linearly increasing disturbance is introduced, causing the power to rise from 30% back to 100%. When running to 4600 s, the power returns to 100%, with other set values remaining unchanged. It is defined that when the steam generator liquid level reaches within the range of 49.95 - 50.05, it is considered to reach a steady state. The simulation results can be obtained as shown in Figure 3.

[0067] Table 4 Deviation and adjustment time of steam generator liquid level

[0068] During the test of the 100%-30%-100% load linear change condition, since the control system of the primary loop did not change, there was no obvious difference in the effects of using a PID controller and fuzzy control. For the secondary loop, since there are three fuzzy controllers in the fuzzy steam generator liquid level control system for compensation, as can be seen from Figure 3(a), the control of the steam generator liquid level has been significantly improved after using the fuzzy controller. During the power reduction process, the maximum deviation of the traditional control is 2.2%, and the adjustment time is 2994 s; the maximum deviation of the fuzzy control is 1.9%, and the adjustment time is 595 s; during the power increase process, the maximum deviation of the traditional control is 2.3%, and the adjustment time is 2041 s; the maximum deviation of the fuzzy control is 1.8%, and the adjustment time is 495 s. It can be seen that the fuzzy controller has obvious improvements both in the power reduction condition and the power increase condition. Therefore, the control performance of the fuzzy control is better than that of the cascade PID controller.

[0069] Example 4 As a further preferred embodiment of this method, when performing a load rejection change from 100% to 30%, a disturbance of load decrease is introduced at 100 s, causing the load set value to be load rejected from 100% to 30%, with other set values remaining unchanged. It is defined that when the steam generator liquid level reaches within the range of 49.95 - 50.05, it is considered to reach a steady state. The simulation results can be obtained as shown in Figure 4.

[0070] Table 5 Deviation and adjustment time of steam generator liquid level

[0071] During the test of the load rejection condition from 100% to 30%, since the control system of the primary loop did not change, there was no obvious difference between the PID controller and the fuzzy control effect. For the secondary loop, since there are three fuzzy controllers for compensation in the fuzzy steam generator liquid level control system, it can be seen from Figure 4(a) that the control of the steam generator liquid level has been significantly improved after using the fuzzy controller. The maximum deviation of the traditional control is 4.7%, and the adjustment time is 2269 s; the maximum deviation of the fuzzy control is 3.4%, and the adjustment time is 1032 s. The deviation of the fuzzy control has been significantly improved in both cases, proving that the control performance of the fuzzy control is better than that of the PID controller.

[0072] Therefore, compared with the traditional cascade PID control, the present invention can significantly reduce the maximum deviation and adjustment time of the steam generator liquid level, significantly improve the efficiency of the nuclear power plant, increase the profit of the nuclear power plant, and enhance the market competitiveness of the nuclear power plant.

[0073] Example 5 This embodiment provides a steam generator liquid level control system for implementing the steam generator liquid level control method in the above-mentioned Embodiments 1 to 4. The system includes: A steam generator data acquisition module that acquires the liquid level deviation, liquid level deviation change rate, steam flow rate, feed water flow rate, and operating data of the steam generator; A liquid level fuzzy control module that uses the liquid level deviation and liquid level deviation change rate as the input data of the liquid level fuzzy controller, and adjusts the feed water flow rate using the liquid level fuzzy controller to obtain a first output value; A steam-water mismatch flow rate fuzzy control module that uses the steam flow rate and feed water flow rate as the input data of the steam-water mismatch flow rate fuzzy controller, and adjusts the feed water flow rate to obtain a second output value; A load-flow fuzzy control module that uses the deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate as the input data of the load-flow fuzzy controller, and adjusts the feed water flow rate using the load-flow fuzzy controller to obtain a third output value; A feed water flow rate control module that obtains the feed water flow rate demand value according to the first output value, the second output value, and the third output value, obtains the opening degree of the feed water regulating valve according to the feed water flow rate demand value, and adjusts the feed water flow rate according to the opening degree.

[0074] Example 6 In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory). This storage medium is a memory device in a terminal device and is used to store programs and data. It should be noted that the computer-readable storage medium here not only includes the built-in storage medium of the terminal device, but also can include the extended storage medium supported by the terminal device. It can be any tangible medium that can contain or store programs, and these programs can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides a storage space for storing the operating system of the terminal. In addition, one or more instructions suitable for the processor to load and execute are stored in this storage space, and these instructions can be one or more computer programs (including program code).

[0075] More specifically, examples (non-exhaustive list) of computer-readable storage media include: electrical connections with one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above.

[0076] The computer-readable storage medium can also include a data signal propagated in a baseband or as part of a carrier wave, which carries readable program code. Such a propagated data signal can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than the readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the readable storage medium can be transmitted by any suitable medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0077] The program code for performing the operations of the present invention can be written in any combination of one or more programming languages, including object-oriented programming languages (such as Java, C++ etc.) and conventional procedural programming languages (such as the "C" language or similar programming languages). The program code can be executed entirely on the user's computing device, partially on the user's device, executed as an independent software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device can be connected to the user's computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (for example, through an Internet service provider using an Internet connection).

[0078] The processor can load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the steam generator liquid level control method in the above embodiments. The specific steps are as follows: Obtain the liquid level deviation, liquid level deviation change rate, steam flow rate, feed water flow rate, and operation data of the steam generator; Use the liquid level deviation and liquid level deviation change rate as the input data of the liquid level fuzzy controller, and use the liquid level fuzzy controller to adjust the feed water flow rate to obtain a first output value; Use the steam flow rate and feed water flow rate as the input data of the steam-water mismatch flow rate fuzzy controller, and adjust the feed water flow rate to obtain a second output value; Use the deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate as the input data of the load-flow fuzzy controller, and use the load-flow fuzzy controller to adjust the feed water flow rate to obtain a third output value; Obtain the required value of the feed water flow rate according to the first output value, the second output value, and the third output value, obtain the opening degree of the feed water regulating valve according to the required value of the feed water flow rate, and adjust the feed water flow rate according to the opening degree.

[0079] Embodiment 7 As Figure 5 shown, another embodiment provided by the present invention provides a terminal device, specifically a computer device 60. Its main components include: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. The processor 61 is responsible for executing the computer program to implement the steam generator liquid level control method in Embodiment 1. The memory 62 is used to store the computer program and other programs and data required for the operation of the device. The computer program 63 runs on the processor 61 to implement the steam generator liquid level control method in Embodiment 1. To avoid repetition, details are not described here one by one.

[0080] The computer device 60 can be various forms of computing devices, including but not limited to: desktop computers, notebooks, palm computers, cloud servers, and other computing devices.

[0081] The processor 61 can be a Central Processing Unit (CPU), or other general-purpose processors, central processors, graphics processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, data processing logics based on quantum computing, discrete hardware components, etc. The general-purpose processor is an unprivileged processor or any conventional processor.

[0082] The memory 62 can be an internal storage unit of the computer device 60, such as the hard disk or memory of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc., equipped on the computer device 60. The memory 62 is not only used to store computer programs, but also used to store other programs and data required for the operation of the device, as well as temporarily store the data that has been output or will be output.

[0083] Any reference to a memory, database, or other medium used in the embodiments provided in this application may include at least one of non-volatile and volatile memories. The non-volatile memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. The volatile memory may include Random Access Memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), etc.

Claims

1. A method for controlling the liquid level of a steam generator, characterized in that Including: Obtain the liquid level deviation, liquid level deviation change rate, steam flow rate, feed water flow rate, and operating data of the steam generator; Use the liquid level deviation and liquid level deviation change rate as the input data of the liquid level fuzzy controller, and use the liquid level fuzzy controller to adjust the feed water flow rate to obtain a first output value; Use the steam flow rate and feed water flow rate as the input data of the steam-water mismatch flow rate fuzzy controller to adjust the feed water flow rate to obtain a second output value; Use the deviation between the steady-state relationship between the load and the feed water flow rate and the actual feed water flow rate as the input data of the load-flow fuzzy controller, and use the load-flow fuzzy controller to adjust the feed water flow rate to obtain a third output value; Obtain the feed water flow rate demand value according to the first output value, the second output value, and the third output value, obtain the opening degree of the feed water regulating valve according to the feed water flow rate demand value, and adjust the feed water flow rate according to the opening degree.

2. The steam generator liquid level control method according to claim 1, characterized in that, The liquid level fuzzy controller, the steam-water mismatch flow rate fuzzy controller, and the load-flow fuzzy controller all include an input layer, an input membership function layer, a fuzzy rule layer, an output membership function layer, and a defuzzification layer; The input layer is used to perform normalization processing on the input data; The input membership function layer uses a triangular function to convert the input data in the input layer into the membership degree of a fuzzy set; the membership degree is obtained according to the membership function, and the membership function is used to define the membership degree value corresponding to different values of the input variable, reflecting the membership relationship between the input variable and the fuzzy set; The fuzzy rule layer includes several nodes, and each node performs fuzzy reasoning according to the corresponding fuzzy rule to deduce the output fuzzy set from the input fuzzy set; The output membership function layer is used to convert the output fuzzy set into a specific output membership degree value; The defuzzification layer is used to convert the output signal of the output membership function layer into a control quantity.

3. The steam generator liquid level control method according to claim 2, wherein The control steps of the liquid level fuzzy controller specifically include: Determine the normalized liquid level deviation domain, the normalized liquid level deviation change rate domain, and the output value domain according to the ranges of the input liquid level deviation and liquid level deviation change rate variables; According to the selected triangular membership function and combined with the liquid level characteristics of the steam generator, convert the liquid level deviation domain and the liquid level deviation change rate domain into the membership degrees in the fuzzy set; Perform fuzzy processing on the corresponding membership degrees of the liquid level deviation and liquid level deviation change rate in the fuzzy set according to the set fuzzy rules; Use the defuzzification rule to convert the fuzzy processed liquid level deviation change rate data into a first output value.

4. The steam generator liquid level control method according to claim 2, wherein, The control steps of the steam-water mismatch flow rate fuzzy controller specifically include: Determine the normalized flow rate deviation domain, the output value domain, and the membership function according to the steam flow rate and the feed water flow rate; Convert the flow rate deviation domain into the membership degree in the fuzzy set according to the determined membership function; Perform fuzzy reasoning on the fuzzy set using the set fuzzy rules; use the defuzzification rule to convert the fuzzy processed flow rate deviation data into a second output value.

5. The steam generator liquid level control method according to claim 2, characterized in that, The control steps of the load-flow fuzzy controller specifically include: Determine the corresponding steady-state feed water flow rate according to different power levels, and determine the feed water flow rate deviation domain according to different feed water flow rates; Convert the domain of the feed water flow deviation into the membership degrees in the fuzzy set according to the determined membership function; Perform fuzzy inference on the fuzzy set using the set fuzzy rules; adopt the defuzzification rule to convert the flow deviation data after fuzzy processing into the third output value.

6. The method for controlling the liquid level of a steam generator according to any one of claims 3 to 5, characterized in that, The defuzzification rule in the defuzzification layer is obtained by the centroid method. The centroid method is used to take the area under the curve of the membership function in the fuzzy set as the basis for weighted averaging, and thus the output after defuzzification can be obtained. The calculation method of the centroid method is as follows: In the formula, z is the result of defuzzification; x is the output variable; is the membership function of the fuzzy set.

7. The method for controlling the liquid level of a steam generator according to any one of claims 3 to 5, characterized in that, The liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller also include adjusting the domain and the membership function, specifically including: Obtain the cascade PID control result, and correspondingly adjust the domain and the membership function of the liquid level fuzzy controller, the steam-water mismatch flow fuzzy controller, and the load-flow fuzzy controller according to the cascade PID control result to obtain the optimal output value.

8. The steam generator liquid level control method according to claim 1, characterized in that, After obtaining the feed water flow demand value based on the first output value, the second output value, and the third output value, obtain the control instruction according to the feed water flow demand value. The control instruction is sent to the actuator, and the actuator adjusts the opening of the valve according to the control instruction to change the cross-sectional area of the fluid flow path, thereby adjusting the feed water flow until the actual flow matches the set value.

9. A steam generator liquid level control system for implementing the steam generator liquid level control method according to any one of claims 1 to 8, characterized in that, Including: A steam generator data acquisition module that acquires the liquid level deviation, the liquid level deviation change rate, the steam flow, the feed water flow, and the operation data of the steam generator; A liquid level fuzzy control module that uses the liquid level deviation and the liquid level deviation change rate as the input data of the liquid level fuzzy controller, and adjusts the feed water flow using the liquid level fuzzy controller to obtain the first output value; A steam-water mismatch flow fuzzy control module that uses the steam flow and the feed water flow as the input data of the steam-water mismatch flow fuzzy controller, and adjusts the feed water flow to obtain the second output value; A load-flow fuzzy control module that uses the deviation between the steady-state relationship between the load and the feed water flow and the actual feed water flow as the input data of the load-flow fuzzy controller, and adjusts the feed water flow using the load-flow fuzzy controller to obtain the third output value; A feed water flow control module that obtains the feed water flow demand value according to the first output value, the second output value, and the third output value, obtains the opening of the feed water regulating valve according to the feed water flow demand value, and adjusts the feed water flow according to the opening.

10. A computer-readable storage medium storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to execute the steam generator liquid level control method according to any one of claims 1 to 8.

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