Method for determining feedwater flow of evaporator of nuclear power plant and related device

Abstract

The application discloses a method for determining feedwater flow of an evaporator of a nuclear power plant and related devices, and relates to the technical field of thermoelectric conversion. The method comprises the following steps: obtaining steam flow at an outlet of the evaporator, secondary loop pressure of the evaporator, feedwater temperature at an inlet of a main feedwater pipe, and nuclear power; using the secondary loop pressure of the evaporator and the feedwater temperature to determine a specific enthalpy coefficient by table lookup, the specific enthalpy coefficient being a ratio of specific enthalpy of steam to specific enthalpy of feedwater; converting the nuclear power into theoretical steam flow, and verifying the steam flow at the outlet of the evaporator by using the theoretical steam flow, if the verification is passed, using the steam flow at the outlet of the evaporator as one of inputs of a feedwater flow soft measurement model; inputting the specific enthalpy coefficient, the steam flow at the outlet of the evaporator and the secondary loop pressure of the evaporator into the feedwater flow soft measurement model to obtain a theoretical feedwater flow. The application realizes high-precision dynamic measurement and calculation of the feedwater flow of the evaporator based on the feedwater flow soft measurement model.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermoelectric conversion, and in particular to a method for determining feedwater flow of a nuclear power plant evaporator and related devices. BACKGROUND

[0002] The water level control system of the nuclear power plant evaporator is one of the key systems to ensure the safe and stable operation of the nuclear power unit. Abnormal fluctuations in the water level of the evaporator can easily cause the reactor to automatically shut down or respond to transient, directly affecting the safety and economy of the nuclear power unit. Currently, the water level of the evaporator needs to be controlled by the feedwater flow of the evaporator.

[0003] The prior art uses a sensor to determine the feedwater flow of the evaporator based on the Venturi tube differential pressure signal. However, under low load conditions, the detection sensitivity of the sensor to the Venturi tube differential pressure signal decreases significantly, resulting in insufficient accuracy of the feedwater flow of the evaporator detected by the sensor, which in turn affects the stability of the water level control and reduces the safety and economy of the nuclear power unit.

[0004] Therefore, there is an urgent need for a technology that can improve the accuracy of obtaining the feedwater flow of the evaporator. SUMMARY

[0005] In view of the above problems, the present application provides a method for determining the feedwater flow of a nuclear power plant evaporator and related devices to improve the accuracy of the feedwater flow of the evaporator. The specific scheme is as follows:

[0006] The first aspect of the present application provides a method for determining the feedwater flow of a nuclear power plant evaporator, comprising:

[0007] Obtaining the steam flow at the outlet of the evaporator, the secondary loop pressure of the evaporator, the feedwater temperature at the inlet of the main feedwater pipe, and the nuclear power;

[0008] Using the secondary loop pressure of the evaporator and the feedwater temperature, a table is consulted to determine the specific enthalpy coefficient, which is the ratio of steam specific enthalpy to feedwater specific enthalpy;

[0009] Convert the nuclear power to a theoretical steam flow, verify the steam flow at the outlet of the evaporator using the theoretical steam flow, and if the verification is passed, use the steam flow at the outlet of the evaporator as one of the inputs of the feedwater flow soft measurement model;

[0010] Input the specific enthalpy coefficient, the steam flow at the outlet of the evaporator, and the secondary loop pressure of the evaporator into the water flow soft measurement model to obtain the theoretical feedwater flow, wherein the water flow soft measurement model is a model pre-constructed based on soft measurement technology, and the water flow soft measurement model has a heat transfer efficiency factor and a heat storage coefficient.

[0011] Optionally, the obtaining process of the heat transfer efficiency factor and the heat storage coefficient comprises:

[0012] obtaining a parameter set comprising at least part of historical operating parameter data of the nuclear power plant;

[0013] constructing a linear relation model about the heat transfer efficiency factor and the heat storage coefficient based on the historical operating parameter data;

[0014] constructing a least square loss function comprising a regularization term based on a regularization factor;

[0015] transforming the linear relation model into a matrix form, solving model parameters of the linear relation model in the matrix form based on the least square loss function, and obtaining an optimal estimated value of the heat transfer efficiency factor and an optimal estimated value of the heat storage coefficient;

[0016] correcting the optimal estimated value of the heat transfer efficiency factor and the optimal estimated value of the heat storage coefficient based on a sliding time window training and anomaly detection mechanism, and obtaining the heat transfer efficiency factor and the heat storage coefficient.

[0017] Optionally, the method further comprises:

[0018] determining a load state of the power generation system;

[0019] if the load state is a low load state, controlling the water level of the evaporator based on the theoretical feedwater flow rate;

[0020] if the load state is a high load state, controlling the water level of the evaporator based on the feedwater flow rate measured by the Venturi tube sensor.

[0021] Optionally, the controlling the water level of the evaporator based on the theoretical feedwater flow rate comprises:

[0022] determining a linearly increasing intervention coefficient according to a time length of a control switching stage from a high load state to a low load state;

[0023] determining a first feedwater flow rate gradually decreasing in the control switching stage based on the linearly increasing intervention coefficient, the theoretical feedwater flow rate and the feedwater flow rate measured by the Venturi tube sensor;

[0024] controlling the water level of the evaporator using the first feedwater flow rate in the control switching stage;

[0025] controlling the water level of the evaporator using the theoretical feedwater flow rate after the control switching stage ends.

[0026] Optionally, the water level of the evaporator is controlled by the sensor-measured feedwater flow rate during the control switching phase from the low load state to the high load state, comprising:

[0027] determining a linearly decreasing intervention coefficient according to the length of the control switching phase from the low load state to the high load state;

[0028] determining a second feedwater flow rate that is gradually increased during the control switching phase based on the linearly decreasing intervention coefficient, the theoretical feedwater flow rate and the sensor-measured feedwater flow rate of the Venturi tube;

[0029] controlling the water level of the evaporator by the second feedwater flow rate during the control switching phase;

[0030] controlling the water level of the evaporator by the sensor-measured feedwater flow rate of the Venturi tube after the control switching phase.

[0031] Optionally, the process of controlling the water level of the evaporator comprises:

[0032] determining a first inertia function of valve opening change rate based on a set inertia time;

[0033] controlling the opening of the valve of the main feedwater pipe according to the theoretical feedwater flow rate during the control switching phase from the low load state to the high load state of the power generation system, and limiting the valve opening change rate by the first inertia function, and controlling the opening of the valve of the main feedwater pipe according to the sensor-measured feedwater flow rate of the Venturi tube after the control switching phase of the power generation system;

[0034] controlling the opening of the valve of the main feedwater pipe according to the sensor-measured feedwater flow rate of the Venturi tube during the control switching phase from the high load state to the low load state of the power generation system, and limiting the valve opening change rate by the first inertia function, and controlling the opening of the valve of the main feedwater pipe according to the theoretical feedwater flow rate after the control switching phase of the power generation system.

[0035] The second aspect of the present application provides a device for determining the feedwater flow rate of an evaporator of a nuclear power plant, comprising:

[0036] a data acquisition module configured to acquire the steam flow rate at the outlet of the evaporator, the secondary loop pressure of the evaporator, the feedwater temperature at the inlet of the main feedwater pipe and the nuclear power;

[0037] a table lookup module configured to determine a specific enthalpy coefficient by table lookup using the secondary loop pressure of the evaporator and the feedwater temperature, the specific enthalpy coefficient being the ratio of the specific enthalpy of steam to the specific enthalpy of feedwater;

[0038] a verification module configured to convert the nuclear power into a theoretical steam flow rate, and verify the steam flow rate at the outlet of the evaporator using the theoretical steam flow rate, and if the verification is passed, use the steam flow rate at the outlet of the evaporator as one of the inputs of a feedwater flow rate soft measurement model;

[0039] a data processing module configured to input the specific enthalpy coefficient, the steam flow rate at the outlet of the evaporator, and the evaporator secondary loop pressure into the water flow rate soft measurement model to obtain a theoretical feedwater flow rate, wherein the feedwater flow rate soft measurement model is a model pre-constructed based on a soft measurement technique, and the feedwater flow rate soft measurement model has a heat transfer efficiency factor and a heat storage coefficient.

[0040] The third aspect of the present application provides a computer program product, which comprises computer readable instructions, and when the computer readable instructions are executed on an electronic device, the electronic device implements the method for determining the feedwater flow rate of the evaporator of the nuclear power plant according to the first aspect or any implementation manner of the first aspect.

[0041] The fourth aspect of the present application provides an electronic device, which comprises at least one processor and a memory connected to the processor, wherein:

[0042] The memory is configured to store a computer program;

[0043] The processor is configured to execute the computer program, so that the electronic device can implement the method for determining the feedwater flow rate of the evaporator of the nuclear power plant according to the first aspect or any implementation manner of the first aspect.

[0044] The fifth aspect of the present application provides a computer storage medium, which carries one or more computer programs, and when the one or more computer programs are executed by an electronic device, the electronic device can implement the method for determining the feedwater flow rate of the evaporator of the nuclear power plant according to the first aspect or any implementation manner of the first aspect.

[0045] According to the technical solution, the method for determining the feedwater flow rate of the evaporator of the nuclear power plant and the related device are provided, the specific enthalpy coefficient, the heat transfer efficiency factor, and the heat storage coefficient are introduced, the evaporator outlet steam flow rate, the evaporator secondary loop pressure, the feedwater temperature, and the nuclear power are input into the feedwater flow rate soft measurement model pre-constructed based on the soft measurement technique to realize high-precision soft measurement of the evaporator feedwater flow rate. Compared with the prior art of determining the evaporator feedwater flow rate based on the Venturi tube differential pressure signal, the present application reduces the dependence on the physical flow meter and reduces the measurement error and the maintenance cost. In addition, the theoretical steam flow rate is used to verify the actual steam flow rate in the measurement process, which improves the reliability and robustness of the measurement result, can adapt to the changes of the operating conditions of the nuclear power plant, ensures the stability and accuracy of the feedwater flow rate calculation, and thus improves the safety and economy of the evaporator operation. Attached Figure Description

[0046] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0047] Figure 1 A flowchart illustrating a method for determining the feedwater flow rate of an evaporator in a nuclear power plant, provided in this application;

[0048] Figure 2 A flowchart of a soft measurement model for water supply flow provided in this application;

[0049] Figure 3 A schematic diagram of the structure of a device for determining the feedwater flow rate of an evaporator in a nuclear power plant, provided in this application;

[0050] Figure 4 A schematic block diagram of an electronic device provided in this application. Detailed Implementation

[0051] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.

[0052] The embodiments of this application will now be described with reference to the accompanying drawings. Those skilled in the art will recognize that, with technological advancements and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are equally applicable to similar technical problems.

[0053] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.

[0054] This application provides a method for determining the feedwater flow rate of an evaporator in a nuclear power plant, such as... Figure 1 The method may include the following steps:

[0055] S101: Obtain the steam flow at the outlet of the evaporator, the evaporator secondary loop pressure, the feedwater temperature at the inlet of the main feedwater pipe, and the nuclear power.

[0056] In the present embodiment, the nuclear power plant refers to a power plant that generates heat energy using a nuclear reactor and converts it into electric energy, wherein one of the key devices is an evaporator (also referred to as a steam generator). The evaporator is a vertical, natural circulation, saturated steam generating device. The reactor coolant flows in the heat transfer pipes, transferring heat to the secondary loop water outside the pipes, which is naturally circulated in the evaporator, and a part of the water is changed into saturated steam when it flows through the outside of the heat transfer pipes, to supply the main steam turbine and auxiliary facilities.

[0057] The steam flow at the outlet of the evaporator refers to the mass flow rate of steam output from the evaporator to the steam turbine, which can be kg / s or t / h, and is a core parameter for judging the evaporation efficiency and system operating load, which can be collected in real time by a mass flow meter installed on the outlet pipe of the evaporator. The evaporator secondary loop refers to the inner water side of the evaporator, and the evaporator secondary loop pressure affects the saturation temperature of the water and the steam enthalpy, which can be measured by a high-precision pressure transmitter and transmitted to the control system in real time. The feedwater temperature at the inlet of the main feedwater pipe refers to the temperature of the main feedwater entering the evaporator at the inlet of the pipe, which can be expressed in degrees Celsius, and is a key input parameter for the feedwater enthalpy table lookup. The temperature can be collected by a temperature sensor or a thermocouple, and the enthalpy of the feedwater can be determined in combination with the pressure. The nuclear power refers to the total heat power released by the nuclear reactor per unit time, which is in units of MW (megawatt), and is calculated by the reactor I&C system according to the neutron flux and other parameters. The nuclear power determines the heat supply, which indirectly affects the steam production. By combining multiple source parameters such as the steam flow at the outlet of the evaporator, the secondary loop pressure, the feedwater temperature, and the nuclear power, the dependence on a single sensor is avoided, and the accuracy and reliability of the feedwater flow measurement soft measurement are improved.

[0058] S102: Use the evaporator secondary loop pressure and the feedwater temperature to look up the specific enthalpy coefficient, which is the ratio of the steam specific enthalpy to the feedwater specific enthalpy.

[0059] In the present embodiment, specific enthalpy is a basic parameter in thermodynamics, which is used to represent the heat energy possessed by unit mass of fluid, usually expressed in units of kJ / kg. The specific enthalpy value is an important basis for judging the energy change of fluid in the heat energy conversion process, and is of great significance for the analysis and modeling of the thermal system of the nuclear power plant.

[0060] Specifically, the specific enthalpy of steam refers to the thermal energy contained in unit mass of steam at a specific pressure and temperature. Since the steam in a nuclear power plant is generated from the heating process of feedwater in the evaporator, the specific enthalpy of steam generally represents the heat transfer capacity of the evaporator to the secondary loop water. The specific value of the specific enthalpy of steam depends on the thermodynamic state of the steam, especially the pressure condition. In this embodiment, the working pressure of the evaporator secondary loop can be used as a lookup input parameter to obtain the specific enthalpy value of the saturated steam at the corresponding pressure by consulting the thermodynamic property table of water and steam.

[0061] The specific enthalpy of feedwater refers to the thermal energy contained in unit mass of feedwater before it enters the evaporator. In a nuclear power system, the temperature of the main feedwater is usually low, but its enthalpy value also changes with temperature.

[0062] In this embodiment, the specific enthalpy value of the feedwater corresponding to the temperature at constant pressure can be obtained by measuring the temperature at the inlet of the main feedwater pipe and combining the standard thermodynamic property table. It should be noted that in the thermodynamic property table, the enthalpy value is generally listed according to the constant pressure process.

[0063] Specifically, in this method, the lookup strategy is as follows: given the evaporator secondary loop pressure, find the specific enthalpy value of the saturated steam at that pressure , given the feedwater temperature, assume its pressure is much lower than the saturation pressure, find the specific enthalpy value of liquid water at that temperature . Through the above two operations, the specific enthalpy of steam and the specific enthalpy of feedwater can be obtained, and the specific enthalpy coefficient can be calculated, and the calculation formula is: specific enthalpy coefficient This ratio is used to measure the relative thermal energy required for unit mass of feedwater to be evaporated into steam. Generally, this value is usually greater than 1, indicating that the thermal content of steam is significantly higher than that of liquid feedwater. The higher the specific enthalpy coefficient, the greater the heat conversion capacity required by the evaporator at this operating condition. The specific enthalpy coefficient is one of the important input parameters of the subsequent soft measurement model in this embodiment, reflecting the change trend of the heat transfer efficiency of the system under the current thermal state, which helps to dynamically correct the estimated value of the feedwater flow and improve the response accuracy of the soft measurement model and the real-time performance of the system control.

[0064] S103: Convert the nuclear power into theoretical steam flow, verify the steam flow at the outlet of the evaporator using the theoretical steam flow, and if the verification is passed, use the steam flow at the outlet of the evaporator as one of the inputs of the feedwater flow soft measurement model.

[0065] In the present embodiment, the theoretical steam flow rate refers to the steam mass flow rate that should be generated by the secondary loop under the current nuclear reactor released heat power condition, assuming that the heat transfer process of the evaporator is ideal and there is no heat loss in each link. This parameter is a calculation result derived based on the thermodynamic energy conservation principle and can be used to verify the rationality of the actually measured steam flow rate, thereby improving the reliability of the measurement data.

[0066] The calculation formula of the theoretical steam flow rate is , wherein is the theoretical steam flow rate, is the nuclear power, is the evaporator thermal efficiency, which represents the efficiency of the evaporator in converting the heat energy of the primary loop coolant into the heat energy of the secondary loop steam, and the value range can be 0.85-0.95. The specific value can be obtained by regression analysis or long-term statistics based on the historical operation data of the nuclear power plant to ensure the calculation accuracy.

[0067] Specifically, the calculated theoretical steam flow rate can be compared with the actually measured steam flow rate . If the deviation between the two is within the set allowable range (such as ±2%), the measurement value is considered to be reliable; if the deviation is out of limit, an abnormal detection mechanism can be triggered to prompt that there may be problems such as sensor drift, blockage or data distortion. When the verification is passed, the measured steam flow rate at the outlet of the evaporator is used as one of the input parameters of the feedwater flow rate soft measurement model; if the verification is not passed, the measurement point data can be temporarily excluded, and the model predicted value or other redundant measurement signals are used instead to ensure the effectiveness of the soft measurement model input. By continuously comparing the theoretical value with the measured value, the change trend of the heat transfer efficiency of the evaporator can also be evaluated, helping the operation and maintenance personnel to find potential problems such as fouling, dirt deposition, heat exchange tube blockage, etc., so as to perform maintenance in advance.

[0068] S104: input the specific enthalpy coefficient, the steam flow rate at the outlet of the evaporator and the evaporator secondary loop pressure into the water flow rate soft measurement model to obtain the theoretical feedwater flow rate, wherein the feedwater flow rate soft measurement model is a model pre-constructed based on the soft measurement technology, and the feedwater flow rate soft measurement model has a heat transfer efficiency factor and a heat storage coefficient.

[0069] In the present embodiment, the soft measurement model of the present embodiment is a method for estimating process variables that cannot be directly measured or are difficult to accurately measure based on the mathematical relationship between observable variables. Unlike traditional hardware measurement methods, soft measurement technology relies on a mathematical model established based on historical operation data, process mechanism model or both, rather than on direct measurement of the target variable by physical sensors. The soft measurement model is as shown in Figure 2 .

[0070] Specifically, based on the law of conservation of energy, i.e. the steam output energy is equal to the feedwater input energy and the change of system energy storage, a feedwater flow soft measurement calculation method is established, and the formula is: wherein is the theoretical feedwater flow calculated in real time, is the secondary circuit pressure, represents the instantaneous change rate of time t, is a thermal efficiency factor, is a heat storage coefficient. and can be obtained by training historical data. Through the soft measurement model, the embodiment can realize continuous, real-time and accurate estimation of the main feedwater flow without relying on high-cost hardware flow meters. This technical solution effectively improves the regulation accuracy of the control system for the water level of the evaporator, and enhances the fault tolerance of the system to sensor failures, significantly reducing maintenance costs and downtime risks. In addition, by introducing the heat transfer efficiency factor and the heat storage coefficient, the model can accurately correct the inertia effect of the evaporator under dynamic load changes, further improving the estimation accuracy during non-steady state operation such as start-stop and power-up / down, and providing a strong guarantee for the stability and reliability of system operation.

[0071] In one embodiment, the process of obtaining the heat transfer efficiency factor and the heat storage coefficient includes:

[0072] obtaining a parameter set including at least part of the historical operating parameter data of the nuclear power plant;

[0073] constructing a linear relationship model of the heat transfer efficiency factor and the heat storage coefficient based on the historical operating parameter data;

[0074] based on the regularization factor, constructing a least squares loss function containing a regularization term;

[0075] transforming the linear relationship model into a matrix form, solving the model parameters of the matrix form of the linear relationship model based on the least squares loss function, and obtaining the optimal estimated value of the heat transfer efficiency factor and the optimal estimated value of the heat storage coefficient;

[0076] based on the sliding time window training and anomaly detection mechanism, correcting the optimal estimated value of the heat transfer efficiency factor and the optimal estimated value of the heat storage coefficient to obtain the heat transfer efficiency factor and the heat storage coefficient.

[0077] wherein the parameter set includes at least part of the historical operating parameter data of the nuclear power plant, which can be obtained through the digital I&C system of the nuclear power plant, and the stable working condition period is selected for sampling with a sampling period ≤1s. The parameter list is shown in Table 1.

[0078] Secondly, the acquired data is pre-processed, which can eliminate the start-stop pile and load mutation period, and finally the data is normalized. In this method, the theoretical heat balance flow is defined as: where the parameters in the brackets are optional parameters, is the feedwater temperature, which can increase the accuracy of the calculation, but will increase the complexity of the algorithm, and needs to be judged according to the real-time situation. Based on the above parameters, a linear relationship model of heat transfer efficiency factor and heat storage coefficient can be established as follows: where represents the secondary side pressure change rate, which reflects the transient effect caused by the system dynamic process such as load change, valve opening and closing, etc.

[0079] Table 1 Parameter list

[0080]

[0081] To improve the identification reliability and suppress the overfitting of parameters, the least square loss with a quadratic regularization term is used as the objective function.

[0082] The least square loss function is as follows: ,

[0083] The loss consists of two parts: one is the average square error between the measured data and the model prediction, which is used to ensure the fitting of the model to the observed data, where is the average square error between the observed value and the model prediction value, which is used to approximate the actual reference feedwater flow , minimizing this part can make the model fit better on the training data, where is the number of data points, representing the total number of data samples, is the data index, indicating that the current calculation is the th sample, represents the change of the secondary circuit pressure of the th sample relative to time . The second is the quadratic penalty term for the to-be-identified parameters, which can be quadratic penalty for the size of the parameters, the purpose of which is to suppress the parameters from becoming too large or unstable, thereby reducing overfitting, improving generalization ability, and enhancing numerical stability, especially when there is multicollinearity between independent variables or insufficient samples. The parameter determines the penalty strength, the larger the value, the more the parameter is shrunk to 0, and vice versa, which is closer to the ordinary least squares. In this application, the parameter is 0.01 by default to prevent overfitting. The partial derivative of the loss with respect to the parameter can be set to zero to obtain the normal equation: , therefore the closed-form solution is: where , The optimal estimated value of the heat transfer efficiency factor and the optimal estimated value of the heat storage coefficient can be obtained, wherein is a unit matrix, is is a transition matrix. For the case of device aging or internal structure of the evaporator, the application adopts a sliding time window training to automatically recalculate the heat transfer efficiency factor and the heat storage coefficient with the latest data to ensure their accuracy. For the case that the deviation between the continuous 3-hour soft measurement value and the reference flow is > 2%, the retraining mode is triggered immediately to recalculate the heat transfer efficiency factor and the heat storage coefficient.

[0084] From the above, it can be concluded that the heat transfer efficiency factor and the heat storage coefficient obtained through the above process not only can reflect the real running state of the evaporator, but also can be self-adaptively adjusted under different loads, temperatures and pressures. Compared with the fixed parameter model, the method can significantly reduce the estimation error of the feedwater flow in long-term operation, and improve the stability and safety of the water level control of the evaporator.

[0085] In one embodiment, the method for determining the feedwater flow of the evaporator of the nuclear power plant further comprises:

[0086] determining the load state of the power generation system;

[0087] if the load state is a low load state, controlling the water level of the evaporator based on the theoretical feedwater flow;

[0088] if the load state is a high load state, controlling the water level of the evaporator based on the feedwater flow measured by the Venturi tube sensor.

[0089] The load state refers to the ratio of the current power output level of the nuclear power unit to the design rated power, which can be generally divided into a low load state and a high load state. In the present application, the low load state can be 30% of the standard power, and the rest of the time is the high load state. In the low load state, since the nuclear power is low and the steam production fluctuation is relatively small, and the flow rate in the feedwater pipeline is low, the measurement accuracy of the Venturi flowmeter can be affected by factors such as too low Reynolds number and weak pressure difference, and thus the present embodiment preferably adopts a water level control strategy based on the theoretical feedwater flow.

[0090] In the high load state, the steam production of the unit is large and the feedwater flow rate is high, and the differential pressure signal of the Venturi flowmeter is stable and much higher than the lower limit of the instrument range, so its measurement accuracy can meet the operation requirements. Therefore, the present embodiment preferably adopts a water level control strategy based on the measurement of the Venturi tube sensor.

[0091] From the above, it can be concluded that the control strategy solves the precision degradation problem of a single measurement mode in the full working condition by intelligently switching the measurement mode under different load conditions, improves the stability and safety of water level control, optimizes the operation economy, and realizes precise, rapid and safe closed-loop control of the water level of the evaporator in the full working condition range of the nuclear power plant.

[0092] In one embodiment, the water level of the evaporator is controlled based on a theoretical feedwater flow rate, including:

[0093] determining a linearly increasing intervention coefficient according to the duration of the control switching stage from the high load state to the low load state;

[0094] determining a first feedwater flow rate that gradually decreases within the control switching stage based on the linearly increasing intervention coefficient, the theoretical feedwater flow rate, and the sensor measured feedwater flow rate of the Venturi tube;

[0095] controlling the water level of the evaporator using the first feedwater flow rate during the control switching stage;

[0096] controlling the water level of the evaporator using the theoretical feedwater flow rate after the control switching stage ends.

[0097] Wherein, when the nuclear power plant power generation system switches from a high load state to a low load state, in order to ensure the stability of the water level adjustment process of the evaporator and avoid water level fluctuations caused by sudden changes in the control signal, the method introduces a linearly increasing intervention coefficient for control smooth transition. Specifically, the start time of the control switching stage can be determined by the following two methods:

[0098] 1) Nuclear power signal determination:

[0099] When the nuclear power decreases from greater than the set high load threshold to and below the low load threshold, the system determines that it enters the switching stage from high load to low load.

[0100] 2) Operation mode signal determination:

[0101] When the unit operation mode switches from full power generation mode to peak shaving or low power operation mode, the switching control is automatically triggered. The duration of the control switching stage can be set according to historical operation data or engineering experience, for example, 30-120 seconds, to ensure smooth adjustment.

[0102] Specifically, the linearly increasing intervention coefficient is defined as: , In the linearly increasing control strategy, the linearly increasing intervention coefficient increases linearly from 0 to 1, which is used to gradually introduce the theoretical feedwater flow control signal, wherein, a time period of a control switching stage from the high load state to the low load state has run, a total time length of the control switching stage from the high load state to the low load state. For example, when the control is completely dependent on the measurement value of the Venturi tube, when the control is completely dependent on the theoretical feedwater flow value. When the first feedwater flow is adopted, which is defined as: wherein is the theoretical feedwater flow, is the sensor measured feedwater flow of the Venturi tube.

[0103] It can be concluded from the above that the control strategy proposed in the present application can realize smooth switching of the high and low load measurement modes through linearly increasing intervention coefficients, which not only retains the high response speed of the Venturi tube in the early stage of switching, but also gradually introduces the low load precision advantage of the soft measurement model, forming an optimal signal combination in all working conditions. The water level stability in the load switching process is improved, and the robustness of the control system to power fluctuations, signal abnormalities and other disturbances is enhanced, which ensures nuclear safety while taking into account equipment protection and long-term operation economy.

[0104] In one embodiment, the water level of the evaporator is controlled based on the sensor measured feedwater flow of the Venturi tube, comprising:

[0105] determining a linearly decreasing intervention coefficient according to a time length of a control switching stage from the low load state to the high load state;

[0106] determining a second feedwater flow that gradually increases in the control switching stage based on the linearly decreasing intervention coefficient, the theoretical feedwater flow and the sensor measured feedwater flow of the Venturi tube;

[0107] controlling the water level of the evaporator using the second feedwater flow in the control switching stage;

[0108] controlling the water level of the evaporator using the sensor measured feedwater flow of the Venturi tube after the control switching stage ends.

[0109] Specifically, the linearly decreasing intervention coefficient is defined as: , in the linearly decreasing control strategy, the linearly decreasing intervention coefficient linearly decreases from 1 to 0, which is used to gradually introduce the sensor measured feedwater flow of the Venturi tube, wherein is a time period of a control switching stage from the low load state to the high load state has run, is a total time length of the control switching stage from the low load state to the high load state. For example, when When the control is fully dependent on the theoretical feedwater flow value, when When the control is fully dependent on the measurement of the Venturi tube. When The second feedwater flow is used, which is defined as: Wherein is the theoretical feedwater flow, is the feedwater flow measured by the sensor of the Venturi tube.

[0110] It can be concluded from the above that the control strategy in the application realizes the non-impact switching from low load to high load through a linearly decreasing intervention coefficient, can suppress disturbances by using the theoretical flow in the early stage, and combines the Venturi tube for rapid response in the later stage, giving consideration to both accuracy and dynamic performance. The linearly increasing strategy for high-low load switching forms a symmetrical logic, simplifying system implementation and maintenance. The water level is kept within a safe range throughout the process, avoiding the risks of full water and dryness, and improving the operation safety and stability of the unit.

[0111] In one embodiment, the process of controlling the water level of the evaporator includes:

[0112] A first-order inertia function is determined based on a set inertia time to determine the valve opening change rate;

[0113] In the control switching stage of the power generation system from a low load state to a high load state, the opening of the valve of the main feedwater pipe is controlled according to the theoretical feedwater flow, and the valve opening change rate is limited by using a first-order inertia function;

[0114] After the control switching stage of the power generation system ends, the opening of the valve of the main feedwater pipe is controlled according to the feedwater flow measured by the sensor of the Venturi tube.

[0115] In the control switching stage of the power generation system from a high load state to a low load state, the opening of the valve of the main feedwater pipe is controlled according to the feedwater flow measured by the sensor of the Venturi tube, and the valve opening change rate is limited by using a first-order inertia function;

[0116] After the control switching stage of the power generation system ends, the opening of the valve of the main feedwater pipe is controlled according to the theoretical feedwater flow.

[0117] Wherein, in order to avoid the rapid opening and closing and water level impact caused by the direct action of the control signal on the valve, the first-order inertia function is defined in this embodiment, which is defined as follows Wherein is the inertia time. Wherein, When the value is large, the valve action is relatively smooth, and is suitable for large inertia and large capacity systems; when The response speed is faster when the value is smaller, but water level fluctuation can be introduced. It is preferable to take 30s to balance the control response speed and system stability, and s is a Laplace operator. For example, when the nuclear power plant power generation system is switched from a high load state to a low load state, the control signal adopts the theoretical feedwater flow. Before a first-order inertia link is added, the control signal directly controls the valve opening, which can easily lead to a large water level fluctuation in the evaporator. At this time, a first-order inertia link is introduced to smooth the control signal before inputting it to the valve. The flow required for high load operation is gradually established in the transition stage, while the water level fluctuation caused by sudden load increase is avoided.

[0118] When the nuclear power plant power generation system is switched from a high load state to a low load state, the control signal adopts the measured feedwater flow of the Venturi tube. After the signal is processed by a first-order inertia link, the output value of the valve can maintain the rapid response capability in the high flow condition in the transition stage, while preventing the water level from suddenly dropping or overshooting caused by directly switching to the theoretical flow.

[0119] As can be seen from the above, the control strategy in the present application realizes smooth adjustment of the valve opening through a first-order inertia function, can suppress water level fluctuation, and ensure stable transition in the load switching process. The system has bidirectional adaptive capability and can maintain stable water level during high and low load switching. The valve speed limit protects the actuator, reduces mechanical impact, and prolongs the service life of the equipment.

[0120] The above introduces a method for determining the feedwater flow of a nuclear power plant evaporator provided by the embodiments of the present application. The following will introduce a device for determining the feedwater flow of a nuclear power plant evaporator.

[0121] Please refer to Figure 3 , Figure 3 The structure diagram of the device for determining the feedwater flow of a nuclear power plant evaporator provided by the embodiments of the present application. As Figure 3 shown, the device for determining the feedwater flow of a nuclear power plant evaporator comprises:

[0122] A data acquisition module 301 is configured to acquire the steam flow at the outlet of the evaporator, the secondary loop pressure of the evaporator, the feedwater temperature at the inlet of the main feedwater pipe, and the nuclear power;

[0123] A table lookup module 302 is configured to use the secondary loop pressure of the evaporator and the feedwater temperature to determine the specific enthalpy coefficient by table lookup. The specific enthalpy coefficient is the ratio of the specific enthalpy of steam to the specific enthalpy of feedwater;

[0124] A verification module 303 is configured to convert the nuclear power into a theoretical steam flow, verify the steam flow at the outlet of the evaporator using the theoretical steam flow, and use the steam flow at the outlet of the evaporator as one of the inputs of the feedwater flow soft measurement model if the verification is passed;

[0125] The data processing module 304 is configured to input the specific enthalpy coefficient, the steam flow at the outlet of the evaporator, and the evaporator secondary loop pressure into a water flow soft measurement model to obtain a theoretical feedwater flow, wherein the water flow soft measurement model is a model pre-constructed based on a soft measurement technique, and the water flow soft measurement model has a heat transfer efficiency factor and a heat storage coefficient.

[0126] In one embodiment, the data acquisition module 301 is specifically configured to:

[0127] obtain a parameter set, the parameter set including at least partial historical operation parameter data of the nuclear power plant;

[0128] construct a linear relationship model about the heat transfer efficiency factor and the heat storage coefficient based on the historical operation parameter data;

[0129] construct a least square loss function including a regularization term based on a regularization factor;

[0130] convert the linear relationship model into a matrix form, solve model parameters of the linear relationship model in the matrix form based on the least square loss function, and obtain an optimal estimated value of the heat transfer efficiency factor and an optimal estimated value of the heat storage coefficient;

[0131] correct the optimal estimated value of the heat transfer efficiency factor and the optimal estimated value of the heat storage coefficient based on a sliding time window training and anomaly detection mechanism, and obtain the heat transfer efficiency factor and the heat storage coefficient.

[0132] In one embodiment, the data processing module 304 is specifically configured to:

[0133] determine a load state of the power generation system;

[0134] if the load state is a low load state, control the water level of the evaporator based on the theoretical feedwater flow;

[0135] if the load state is a high load state, control the water level of the evaporator based on the feedwater flow measured by the sensor of the Venturi tube.

[0136] In one embodiment, the data processing module 304 is specifically configured to:

[0137] determine a linearly increasing intervention coefficient according to a time length of a control switching stage in which the high load state changes to the low load state;

[0138] determine a first feedwater flow that gradually decreases in the control switching stage based on the linearly increasing intervention coefficient, the theoretical feedwater flow, and the feedwater flow measured by the sensor of the Venturi tube;

[0139] control the water level of the evaporator by using the first feedwater flow in the control switching stage;

[0140] After the end of the control switching phase, the water level of the evaporator is controlled by using the theoretical feedwater flow.

[0141] In one embodiment, the data processing module 304 is specifically configured to:

[0142] determine a linearly decreasing intervention coefficient according to a time length of the control switching phase from the low load state to the high load state;

[0143] determine a second feedwater flow that is gradually increased within the control switching phase based on the linearly decreasing intervention coefficient, the theoretical feedwater flow and the sensor measured feedwater flow of the Venturi tube;

[0144] In the control switching phase, the water level of the evaporator is controlled by using the second feedwater flow;

[0145] After the end of the control switching phase, the water level of the evaporator is controlled by using the sensor measured feedwater flow of the Venturi tube.

[0146] In one embodiment, the data processing module 304 is specifically configured to:

[0147] determine a first inertia function of the valve opening change rate based on a set inertia time;

[0148] In the control switching phase from the low load state to the high load state of the power generation system, the opening of the valve of the main feedwater pipe is controlled according to the theoretical feedwater flow, and the first inertia function is used to limit the valve opening change rate;

[0149] After the end of the control switching phase of the power generation system, the opening of the valve of the main feedwater pipe is controlled according to the sensor measured feedwater flow of the Venturi tube.

[0150] In the control switching phase from the high load state to the low load state of the power generation system, the opening of the valve of the main feedwater pipe is controlled according to the sensor measured feedwater flow of the Venturi tube, and the first inertia function is used to limit the valve opening change rate;

[0151] After the end of the control switching phase of the power generation system, the opening of the valve of the main feedwater pipe is controlled according to the theoretical feedwater flow.

[0152] The embodiments of the present application also provide an electronic device. Referring to FIG. 1, which shows a structural schematic diagram of an electronic device suitable for implementing the method for determining the feedwater flow of the evaporator of the nuclear power plant in the embodiments of the present application. The electronic device in the embodiments of the present application can include but is not limited to fixed terminals such as mobile phones, notebook computers, PDAs (Personal Digital Assistants), PADs (Tablet Personal Computers), desktop computers and the like. Figure 4 Figure 4 ​The electronic device shown is merely one example, and should not be taken as limiting the functionality or use of embodiments of the application.

[0153] As shown in Figure 4 The electronic device can include a processing device (e.g., a central processing unit, a graphics processing unit, etc.) 601 that can perform various appropriate actions and processes according to programs stored in a read-only memory (ROM) 602 or loaded into a random access memory (RAM) 603 from a storage device 608. In a state where the electronic device is powered on, various programs and data required for operation of the electronic device are also stored in the RAM 603. The processing device 601, the ROM 602, and the RAM 603 are connected to each other through a bus 604. An input / output (I / O) interface 605 is also connected to the bus 604.

[0154] Generally, the following devices can be connected to the I / O interface 605: input devices 606 including, for example, a touch screen, a touch pad, a keyboard, a mouse, a camera, a microphone, an accelerometer, a gyroscope, etc.; output devices 607 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; storage devices 608 including, for example, a memory card, a hard disk, etc.; and communication devices 609. The communication devices 609 can allow the electronic device to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 4 An electronic device having various devices is shown, but it is understood that all of the shown devices are not required to be implemented or present. More or fewer devices can alternatively be implemented or present.

[0155] The embodiments of the present application also provide a computer program product, including computer readable instructions, which, when executed on an electronic device, cause the electronic device to implement any of the methods for determining feedwater flow of a nuclear power plant evaporator provided by the embodiments of the present application.

[0156] The embodiments of the present application also provide a computer readable storage medium, which carries one or more computer programs, which, when executed by an electronic device, can cause the electronic device to implement any of the methods for determining feedwater flow of a nuclear power plant evaporator provided by the embodiments of the present application.

[0157] It should be noted that the apparatus embodiments described above are merely illustrative, and the units described as separate units can or can not be physically separate, and the units displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed to multiple network units. Part or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment. In addition, the connection relationship between the modules in the apparatus embodiment provided in the present application indicates that there is a communication connection between them, which can be implemented as one or more communication buses or signal lines.

[0158] Through the description of the above embodiments, those skilled in the art can clearly understand that the present application can be realized by means of software and the necessary general hardware, and of course can also be realized by special hardware including special integrated circuits, special CPUs, special memories, special components, etc. Generally, functions completed by computer programs can be easily realized by corresponding hardware, and the specific hardware structure for realizing the same function can also be various, such as analog circuit, digital circuit or special circuit, etc. However, for the present application, software program implementation is a better embodiment. Based on this understanding, the technical solutions of the present application can be embodied in the form of software products, which are stored in readable storage media, such as computer floppy disks, U disks, mobile hard disks, ROM, RAM, magnetic or optical disks, etc., including a plurality of instructions for making a computer device (which can be a personal computer, a training device, or a network device, etc.) execute the methods described in various embodiments of the present application.

[0159] In the above embodiments, all or part can be realized by software, hardware, firmware or any combination thereof. When realized by software, it can be realized in the form of a computer program product in whole or in part.

[0160] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transmitted from one website, computer, training device or data center to another website, computer, training device or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be stored by the computer or a data storage device such as a training device, a data center, etc. integrated with one or more available media sets. The available media can be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium (for example, a solid state disk (SSD)), etc.

Claims

1. A method of determining the feedwater flow of an evaporator of a nuclear power plant, characterized in that, The method comprises: acquiring steam flow at the outlet of the evaporator, evaporator secondary loop pressure, feedwater temperature at the inlet of the main feedwater pipe, and nuclear power; using the evaporator secondary loop pressure and the feedwater temperature, looking up a specific enthalpy coefficient, which is the ratio of steam specific enthalpy to feedwater specific enthalpy; converting the nuclear power into theoretical steam flow, verifying the steam flow at the outlet of the evaporator using the theoretical steam flow, and using the steam flow at the outlet of the evaporator as one of the inputs of a feedwater flow soft measurement model if the verification is passed; inputting the specific enthalpy coefficient, steam flow at the outlet of the evaporator, and evaporator secondary loop pressure into the water flow soft measurement model to obtain theoretical feedwater flow, wherein the water flow soft measurement model is a model pre-constructed based on soft measurement technology, and the water flow soft measurement model has a heat transfer efficiency factor and a heat storage coefficient.

2. The method of determining the feedwater flow rate of a nuclear power plant evaporator according to claim 1, characterized in that, The process of obtaining the heat transfer efficiency factor and the heat storage coefficient comprises: acquiring a parameter set, the parameter set including at least part of historical operating parameter data of the nuclear power plant; constructing a linear relationship model about the heat transfer efficiency factor and the heat storage coefficient based on the historical operating parameter data; constructing a least square loss function containing a regularization term based on a regularization factor; transforming the linear relationship model into a matrix form, solving model parameters of the linear relationship model in the matrix form based on the least square loss function, and obtaining an optimal estimated value of the heat transfer efficiency factor and an optimal estimated value of the heat storage coefficient; correcting the optimal estimated value of the heat transfer efficiency factor and the optimal estimated value of the heat storage coefficient based on a sliding time window training and anomaly detection mechanism, and obtaining the heat transfer efficiency factor and the heat storage coefficient.

3. The method of determining the feedwater flow rate of a nuclear power plant evaporator as claimed in claim 1, characterized in that, The method further comprises: determining a load state of the power generation system; if the load state is a low load state, controlling the water level of the evaporator based on the theoretical feedwater flow; if the load state is a high load state, controlling the water level of the evaporator based on the feedwater flow measured by the sensor of the Venturi tube.

4. The method of determining the feedwater flow rate of a boiler of a nuclear power plant according to claim 3, characterized in that, The controlling of the water level of the evaporator based on the theoretical feedwater flow comprises: determining a linearly increasing intervention coefficient according to the length of a control switching stage from a high load state to a low load state; determining a first feedwater flow that gradually decreases in the control switching stage based on the linearly increasing intervention coefficient, the theoretical feedwater flow, and the feedwater flow measured by the sensor of the Venturi tube; controlling the water level of the evaporator using the first feedwater flow in the control switching stage; controlling the water level of the evaporator using the theoretical feedwater flow after the control switching stage ends.

5. The method of determining the feedwater flow rate of a nuclear power plant evaporator as claimed in claim 3, characterized in that, The controlling of the water level of the evaporator based on the feedwater flow measured by the sensor of the Venturi tube comprises: determining a linearly decreasing intervention coefficient according to the length of a control switching stage from a low load state to a high load state; determining a second feedwater flow that gradually increases in the control switching stage based on the linearly decreasing intervention coefficient, the theoretical feedwater flow, and the feedwater flow measured by the sensor of the Venturi tube; In the control switching stage, the water level of the evaporator is controlled by the second feedwater flow rate; After the end of the control switching stage, the water level of the evaporator is controlled by the feedwater flow rate measured by the sensor of the Venturi tube.

6. The method of determining the feedwater flow rate of a boiler of a nuclear power plant according to claim 3, characterized in that, The process of controlling the water level of the evaporator comprises: determining a first-order inertia function of the valve opening rate based on a set inertia time; In the control switching stage when the power generation system changes from a low load state to a high load state, the opening of the valve of the main feedwater pipe is controlled according to the theoretical feedwater flow rate, and the first-order inertia function is used to limit the valve opening rate, and after the end of the control switching stage of the power generation system, the opening of the valve of the main feedwater pipe is controlled according to the feedwater flow rate measured by the sensor of the Venturi tube; In the control switching stage when the power generation system changes from a high load state to a low load state, the opening of the valve of the main feedwater pipe is controlled according to the feedwater flow rate measured by the sensor of the Venturi tube, and the first-order inertia function is used to limit the valve opening rate, and after the end of the control switching stage of the power generation system, the opening of the valve of the main feedwater pipe is controlled according to the theoretical feedwater flow rate.

7. A device for determining the feedwater flow of an evaporator of a nuclear power plant, characterized in that Comprise: a data acquisition module for acquiring the steam flow rate at the outlet of the evaporator, the secondary loop pressure of the evaporator, the feedwater temperature at the inlet of the main feedwater pipe, and the nuclear power; a table lookup module for determining a specific enthalpy coefficient by table lookup using the secondary loop pressure of the evaporator and the feedwater temperature, the specific enthalpy coefficient being the ratio of the specific enthalpy of steam to the specific enthalpy of feedwater; a verification module for converting the nuclear power into a theoretical steam flow rate, verifying the steam flow rate at the outlet of the evaporator using the theoretical steam flow rate, and using the steam flow rate at the outlet of the evaporator as one of the inputs of the feedwater flow rate soft measurement model if the verification is passed; a data processing module for inputting the specific enthalpy coefficient, the steam flow rate at the outlet of the evaporator, and the secondary loop pressure of the evaporator into the water flow rate soft measurement model to obtain a theoretical feedwater flow rate, wherein the water flow rate soft measurement model is a model pre-constructed based on soft measurement technology, and the water flow rate soft measurement model has a heat transfer efficiency factor and a heat storage coefficient.

8. A computer program product, characterised in that, The computer readable instructions, when executed on an electronic device, cause the electronic device to implement the method for determining the feedwater flow rate of the evaporator of the nuclear power plant according to any one of claims 1 to 6.

9. An electronic device, comprising: The memory is configured to store computer programs, and the processor is configured to execute the computer programs to enable the electronic device to implement the method for determining the feedwater flow rate of the evaporator of the nuclear power plant according to any one of claims 1 to 6. The storage medium carries one or more computer programs, and when the one or more computer programs are executed by an electronic device, the electronic device can implement the method for determining the feedwater flow rate of the evaporator of the nuclear power plant according to any one of claims 1 to 6. ​ 10. A computer storage medium, characterized in that, ​

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