Method and system for controlling water quantity of cooling tower in peak regulation operation of thermal power generating unit

Abstract

The invention provides a water volume control method and system for a cooling tower in peak regulation operation of a thermal power generating unit, and the method comprises the steps: constructing a calculation relation model between the evaporation water loss of the cooling tower and the heat load of the tower under different operation conditions of the thermal power generating unit, and predicting the future evaporation water loss of the cooling tower through a prediction model; further, the future evaporation water loss amount of the cooling tower is obtained in combination with the constructed calculation relation model, water is supplemented to the cooling tower, accurate control over the water supplementing amount of the cooling tower is achieved, and therefore the purpose of saving water is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to thermal power units, and particularly relates to a method and system for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit. Background Art

[0002] The statements in this part merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] With the continuous improvement of the power market's requirements for power supply flexibility, frequent peak shaving of thermal power units has become the norm. During the peak shaving process, the steam turbine operates at a low load for a long time, and the amount of steam discharged into the condenser decreases sharply, which leads to significant changes in the operating conditions of the circulating water system. As a result, the heat load entering the cooling tower decreases, causing a significant reduction in the evaporation water loss of the cooling tower. However, the current traditional operation management method of the cooling tower fails to fully consider the water-saving potential brought about by this change and still adopts a relatively fixed water replenishment strategy, resulting in unnecessary consumption of a large amount of water resources during low load periods, increasing the operating cost of thermal power units and also bringing pressure to the sustainable utilization of water resources. Summary of the Invention

[0004] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a method and system for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit, establishing a calculation relationship model between the evaporation water loss of the cooling tower and the heat load entering the tower, and obtaining the future evaporation water loss of the cooling tower based on the predicted future evaporation water loss model of the cooling tower, which can more accurately determine the water replenishment volume, achieve the water-saving effect, and provide a scientific basis for the water-saving management of thermal power plants.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit, including: Based on the historical operation data of the thermal power unit, determining the relationship model between the operating load of the steam turbine and the circulating water volume of the condenser under different operating conditions of the thermal power unit, and the calculation model between the circulating water volume of the condenser and the evaporation water loss of the cooling tower; Based on the load change of the steam turbine during the real-time peak shaving operation of the thermal power unit, adjusting the circulating water volume of the condenser with the minimum evaporation water loss of the cooling tower as the target.

[0006] In a second aspect, the present invention provides a system for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit, characterized by including: A model construction module, which is configured to: based on the historical operation data of the thermal power unit, determine the relationship model between the operating load of the steam turbine and the circulating water volume of the condenser under different operating conditions of the thermal power unit, and the calculation model between the circulating water volume of the condenser and the evaporation water loss of the cooling tower; A regulating module, which is configured to: based on the load change of the steam turbine during the real-time peak shaving operation of the thermal power unit, regulate the circulating water volume of the condenser with the goal of minimizing the evaporation water loss of the cooling tower. In a third aspect, the present invention provides an electronic device, including a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method described in the first aspect is completed.

[0007] In a fourth aspect, the present invention provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the method described in the first aspect is completed.

[0008] In a fifth aspect, the present invention provides a computer program product, including a computer program. When the computer program is executed by a processor, the method described in the first aspect is implemented.

[0009] The above one or more technical solutions have the following beneficial effects: In the present invention, a calculation relationship model between the evaporation water loss of the cooling tower and the incoming heat load under different operating conditions of the thermal power unit is constructed. The prediction model is used to predict the future evaporation water loss of the cooling tower, and then the future evaporation water loss of the cooling tower is obtained by combining the constructed calculation relationship model, and the cooling tower is replenished with water, realizing the precise control of the makeup water volume of the cooling tower, thereby achieving the purpose of water saving.

[0010] The advantages of the additional aspects of the present invention will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0012] Figure 1 It is the overall block diagram of a method for controlling the water volume of a cooling tower during peak shaving operation of a thermal power unit in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0014] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0015] Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0016] Embodiment 1 This embodiment discloses a method for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit, including: Based on the historical operation data of the thermal power unit, determine the relationship model between the operating load of the steam turbine and the circulating water volume of the condenser under different operating conditions of the thermal power unit, as well as the calculation model of the circulating water volume of the condenser and the evaporation water loss of the cooling tower; Based on the load change of the steam turbine during the real-time peak shaving operation of the thermal power unit, adjust the circulating water volume of the condenser with the goal of minimizing the evaporation water loss of the cooling tower.

[0017] The following combines Figure 1 A detailed description of a method for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit proposed in this embodiment is as follows, specifically including: By deploying high-precision and high-reliability sensors, comprehensively collect key parameters such as the steam inlet volume of the steam turbine, the regeneration extraction steam parameters at all levels, the extraction steam parameters for heating (if any), the inlet and outlet temperatures of the circulating water in the condenser, the inlet and outlet water temperatures of the cooling tower, the temperature, humidity, wind speed and wind direction of the air entering the cooling tower. During the data collection process, adopt sensor calibration technology and data filtering algorithms to ensure the accuracy and reliability of the data, providing a solid data foundation for subsequent model calculations.

[0018] Based on the principles of thermodynamics and the law of conservation of mass, construct a calculation model for the operating load of the steam turbine and the steam volume discharged into the condenser. During the construction of the calculation model for the operating load of the steam turbine and the steam volume discharged into the condenser, fully consider the inlet steam parameters of the steam turbine (pressure, temperature, enthalpy value, etc.), the thermodynamic characteristics of the regeneration extraction steam system at all levels (the relationship between the extraction steam pressure, temperature, flow rate and load), and the influence mechanism of the extraction steam for heating (if any). Through a detailed analysis of the internal steam expansion work process of the steam turbine and in combination with classical thermodynamic equations such as the Flügel formula, accurately derive the mathematical relationship expression between the steam volume discharged into the condenser and the load of the steam turbine. During the actual calculation process, according to the real-time collected inlet steam volume and extraction steam volume data, substitute them into the calculation model for the operating load of the steam turbine and the steam volume discharged into the condenser for accurate calculation to ensure the calculation accuracy of the steam flow rate discharged into the condenser.

[0019] Based on the fundamental laws of thermodynamics, especially the laws of conservation of energy and mass, the steam flow rate of the steam turbine is calculated. The expansion work process of steam in the steam turbine follows the first law of thermodynamics, that is, the change in internal energy, kinetic energy, and potential energy of steam is equal to the sum of the heat absorbed from the outside and the work done externally. Under steady flow conditions, it can be simplified to the relationship between enthalpy drop and mechanical work output. According to the law of conservation of mass, the mass flow rate of steam entering the steam turbine is equal to the sum of the extraction steam flow rates at each stage and the steam flow rate discharged into the condenser. These principles provide a fundamental theoretical framework for constructing the steam flow rate calculation model, ensuring the accuracy of the calculation model in terms of physical essence.

[0020] The inlet steam parameters include pressure, temperature, and enthalpy value, which are crucial for steam flow rate calculation. The inlet steam pressure determines the specific volume and density of steam. A higher inlet steam pressure reduces the specific volume of steam, and the mass flow rate will increase correspondingly under the same flow area. The inlet steam temperature affects the enthalpy value and specific entropy of steam, thereby changing the expansion process of steam in the steam turbine. By accurately measuring the inlet steam parameters (using high-precision pressure sensors with an accuracy of ±0.001 MPa and temperature sensors with an accuracy of ±0.5 °C), combined with the thermodynamic property charts of water and steam or precise thermodynamic calculation software (such as the IAPWS - IF97 standard), the inlet steam enthalpy value can be accurately determined, providing a key input for subsequent flow rate calculation.

[0021] The regenerative extraction steam system at each stage plays a key role in steam flow rate distribution. The extraction steam pressure, temperature, and flow rate at different stages have a specific relationship with the steam turbine load. At low loads, to maintain thermal efficiency and system stability, the proportion of regenerative extraction steam relative to the load may increase; at high loads, as the inlet steam flow rate increases, although the extraction steam flow rate increases, the proportion may change. For each stage of extraction steam, the flow rate calculation needs to consider the extraction steam port position, the efficiency of the steam turbine flow passage part, and the mutual influence with adjacent stage extraction steam. Through the analysis and regression of historical operation data, the empirical correlation formula between the extraction steam flow rate at each stage and the steam turbine load under different loads is determined, and it is corrected by combining the real-time monitored extraction steam pressure and temperature to ensure the accuracy of the extraction steam flow rate calculation, thereby accurately obtaining the steam flow rate share discharged into the condenser.

[0022] If there are special considerations for extraction steam for heating: For units with heating tasks, the extraction steam for heating significantly affects steam flow rate distribution. The extraction steam flow rate for heating depends on the heating load demand, and its parameters (pressure, temperature) need to meet the heating process requirements. When calculating the steam flow rate discharged into the condenser, the extraction steam flow rate for heating needs to be deducted from the total inlet steam flow rate. The existence of extraction steam for heating changes the internal steam flow and energy conversion process in the steam turbine, causing the enthalpy drop in different flow passage parts of the steam to be redistributed. By establishing a mathematical model of the extraction steam flow rate for heating, heating load, and steam turbine operation parameters, considering the pressure loss and temperature drop in the heating pipeline network, the impact of extraction steam for heating on the steam flow rate discharged into the condenser is accurately calculated, ensuring the reliability of steam flow rate calculation under heating conditions.

[0023] Based on the above factors and the variable operating condition principle of the steam turbine's flow path section, a calculation model for the steam flow rate discharged into the condenser is derived from the Flügel formula: Let the steam inlet flow rate of the steam turbine be , the extraction steam flow rate of the th stage regenerative extraction be , the extraction steam flow rate for heating be (0 if there is no heating), and the steam flow rate discharged into the condenser be . Then, we have .

[0024] Among them, the extraction steam flow rate of each stage is calculated through an empirical formula related to the load . Among them, is the load of the steam turbine; the extraction steam flow rate for heating is calculated by a function determined by the heating demand and the operating parameters of the steam turbine. Among them, is the extraction steam temperature for heating, and is the extraction steam pressure for heating.

[0025] Precise modeling of the heat balance of the condenser and analysis of the water temperature: Based on the first law of thermodynamics and the principles of heat transfer, a heat balance equation for the heat release of steam, heat transfer, and heat absorption of circulating water in the condenser is constructed. During the process of equation construction, key factors such as the thermodynamic properties of steam (enthalpy value, pressure, temperature, etc.), the structural parameters of the condenser (material of heat exchange tubes, tube diameter, tube length, tube bundle arrangement method, etc.), the heat transfer coefficient (affected by factors such as cooling water flow rate, steam flow rate, fouling thermal resistance, etc.), and the flow rate and specific heat capacity of circulating water are considered in detail. Through comprehensive analysis and mathematical derivation of these factors, a complete heat balance model is established. High-efficiency numerical solution methods such as the Newton - Raphson iteration method are used, combined with an adaptive step size adjustment and error correction mechanism, to solve the inlet temperature of circulating water and ensure that the calculation accuracy meets the requirements of the cooling tower heat load calculation. During the iterative solution process, the model parameters are continuously optimized and adjusted according to the calculation results to improve the accuracy and reliability of the model.

[0026] Thermodynamic basis for heat balance modeling: The thermal balance modeling of the condenser is based on the first law of thermodynamics, i.e., the law of conservation of energy. In the condenser, the steam discharged from the steam turbine releases heat to the circulating water to achieve condensation. This process involves the dynamic balance of the heat released by the steam, the heat transferred by the condenser, and the heat absorbed by the circulating water. The heat released by the steam depends on the enthalpy value, flow rate of the exhaust steam, and the thermodynamic characteristics of the condensation process; the heat transferred by the condenser is restricted by the condenser structure (such as the material of the heat exchange tubes, pipe diameter, pipe length, and the arrangement of the tube bundles), and the heat transfer coefficient (affected by factors such as the flow velocity of the cooling water, steam velocity, and fouling thermal resistance); the heat absorbed by the circulating water is closely related to the flow rate of the circulating water, specific heat capacity, and the inlet and outlet water temperatures. Based on these thermodynamic principles, a thermal balance equation is constructed, providing a theoretical basis for the water temperature analysis.

[0027] Accurate measurement and processing of key parameters: (1)Measurement of steam turbine exhaust parameters: The accurate measurement of steam turbine exhaust parameters is crucial for thermal balance modeling. A high-precision pressure sensor (accuracy up to ±0.001 MPa) is used to monitor the exhaust pressure in real time, and its data is used to determine the steam saturation temperature and enthalpy value. A thermocouple thermometer (accuracy ±0.5 °C) is used to accurately measure the exhaust temperature. Combining the pressure data, the steam enthalpy value can be accurately calculated. For the exhaust humidity, it is measured by a high-precision humidity sensor (accuracy ±2% relative humidity) to comprehensively and accurately grasp the thermodynamic state of the steam and ensure the accuracy of the exhaust heat release calculation. The exhaust flow rate is measured by a high-precision flow meter (accuracy ±0.5%), and its data is an important input for the thermal balance calculation. Any deviation will significantly affect the result accuracy.

[0028] (2)Estimation of circulating water flow rate and inlet temperature: The circulating water flow rate is measured by an electromagnetic flow meter (accuracy ±0.3%) installed on the pipeline. Its stability and accuracy are crucial for the thermal balance. The estimated circulating water inlet temperature is comprehensively estimated based on factors such as the outlet water temperature of the cooling tower, pipeline heat loss, and ambient temperature. Considering the pipeline material, insulation condition, and environmental climate conditions, the initial temperature range is preliminarily determined using the heat conduction theory and empirical formula, providing an initial value for the iterative calculation and being continuously corrected during the subsequent iterative process.

[0029] Construction and solution method of the thermal balance equation: (1)Process of equation construction: Based on the law of conservation of energy, a thermal balance equation is established where the heat released by the steam is equal to the heat transferred by the condenser and the heat absorbed by the circulating water. The specific expression is: , where, is the heat released by the steam, related to the exhaust parameters, and can be calculated through the change in steam enthalpy value and flow rate; is the heat transferred by the condenser, which is a function of the heat transfer coefficient, heat transfer area, and logarithmic mean temperature difference. The heat transfer coefficient needs to be determined by comprehensively considering factors such as the flow velocity of the cooling water, steam velocity, and fouling thermal resistance; The heat absorption of the circulating water depends on the circulating water flow rate, specific heat capacity, and the temperature difference between the inlet and outlet water temperatures. By deriving the heat calculation formulas in detail and substituting the measured and estimated parameters into the equations, a complete mathematical model is formed.

[0030] The heat release of the steam ; The heat transfer amount of the condenser ; The heat absorption of the circulating water . Among them, The latent heat of vaporization of water; is the overall heat transfer coefficient of the condenser; is the heat transfer area of the condenser; is the logarithmic mean temperature difference of the condenser; is the specific heat of water; is the circulating water flow rate; is the temperature difference between the inlet and outlet of the circulating water.

[0031] (2) Solution strategy selection: The Newton-Raphson iteration method is used to solve the inlet temperature of the circulating water. This method linearizes the nonlinear equation by using the Taylor series expansion of the function and continuously updates the temperature value in each iteration until the preset convergence accuracy (such as 0.001 °C) is met. During the iteration process, each heat term is calculated based on the current temperature estimate, substituted into the heat balance equation to calculate the residual, and then the temperature value is corrected according to the residual and the Jacobian matrix. At the same time, an adaptive step size adjustment mechanism is introduced to dynamically optimize the step size according to the iteration convergence situation, accelerate the convergence process and enhance the algorithm stability to ensure the accurate solution of the inlet temperature.

[0032] Construction of the key model system of the cooling tower: 1. Accurate model of the heat load entering the tower: Considering comprehensively the outlet temperature and flow rate of the circulating water in the condenser and the inlet air state parameters of the cooling tower (temperature, humidity, wind speed, wind direction, etc.), relying on the heat and mass transfer theory and engineering empirical formulas, an accurate calculation model of the heat load entering the cooling tower is constructed. During the model construction process, an environmental meteorological dynamic factor correction term is introduced to fully consider the influence of environmental factors such as temperature, humidity, and wind speed on the heat and mass transfer process. Through the analysis and fitting of a large amount of actual operation data, the key coefficients and parameters in the model are determined to ensure that the model can accurately reflect the law of the heat load entering the cooling tower changing with the unit operating conditions.

[0033] Theoretical Basis and Consideration of Key Factors: The accurate model of the heat load entering the tower is constructed based on the heat and mass transfer theory, which describes the process of heat and mass transfer between the gas and liquid phases in the cooling tower. The key factors include the outlet temperature and flow rate of the circulating water in the condenser, as well as the temperature, humidity, wind speed and direction of the air entering the tower. The heat carried by the circulating water is an important source of the heat load, and its temperature and flow rate directly determine the absolute value of the heat. A higher outlet temperature and flow rate of the circulating water will significantly increase the heat load entering the tower. The state parameters of the air entering the tower affect the driving force and efficiency of heat and mass transfer. For example, a lower temperature and humidity of the air entering the tower can increase the enthalpy difference between the air and the circulating water, promoting heat transfer; a higher wind speed and direction contribute to enhancing gas-liquid mixing and heat diffusion, improving the heat exchange effect.

[0034] Derivation of the Model Formula and Determination of Parameters: Taking the above factors into comprehensive consideration, the model formula of the heat load entering the tower can be expressed as: +

[0035] Where, is the heat load entering the tower, is the specific heat capacity of the circulating water, is the mass flow rate of the circulating water, is the outlet temperature of the circulating water, is the inlet temperature of the circulating water (which can be estimated initially and corrected iteratively later), is the latent heat of vaporization of water, is the evaporation water volume (related to the state of the air entering the tower and the temperature of the circulating water).

[0036] In practical applications, the specific heat capacity of the circulating water is a known constant. The flow rate and outlet temperature of the circulating water are obtained by real-time measurement using a high-precision flowmeter (with an accuracy of ±0.3%) and a temperature sensor (with an accuracy of ±0.5°C). The calculation of the evaporation water volume needs to combine parameters such as the temperature, humidity, wind speed and direction of the air entering the tower, and is determined through empirical correlation formulas or semi-empirical formulas based on the theory of mass and heat transfer. The parameters of these correlation formulas and formulas are obtained through regression analysis of a large amount of experimental data and calibration with on-site actual operation data to ensure that the model can accurately reflect the change of the heat load under actual working conditions.

[0037] 2. Evaporation Water Loss Model: Based on the heat load entering the tower, multi-dimensional environmental meteorological parameters (temperature, humidity, wind speed, direction, atmospheric pressure, etc.) and the structural characteristics of the cooling tower itself (packing type, tower body geometric parameters, ventilation structure, etc.), a high-precision model of evaporation water loss is established by using the mass transfer coefficient method and empirical correlation formulas, combined with laboratory simulation and on-site test data calibration.

[0038] In the process of deriving the evaporation water loss model, the mass and heat transfer process of steam in the cooling tower is deeply analyzed. According to the principles of thermodynamics and fluid mechanics, the calculation method of the mass transfer coefficient is determined and corrected in combination with actual operation data. Through a large number of experiments and simulation analyses of evaporation water loss under different working conditions, the model structure and parameters are continuously optimized to improve the prediction accuracy of the model.

[0039] Theoretical basis for constructing the evaporation water loss model: The accurate evaporation water loss model is mainly constructed based on the principles of mass and heat transfer and the physical characteristics of the gas-liquid two-phase flow in the cooling tower. In the cooling tower, the circulating water contacts the air, and heat and mass are transferred between the two. The water evaporation process follows the mass transfer law. Heat is transferred from the circulating water to the air, increasing the water vapor partial pressure on the water surface. When the water vapor partial pressure is higher than that in the air, the water will evaporate into the air. This process is closely related to the heat load entering the tower, environmental meteorological parameters (temperature, humidity, wind speed, wind direction, atmospheric pressure, etc.) and the structural characteristics of the cooling tower itself (packing type, tower geometric parameters, ventilation structure, etc.).

[0040] Influence mechanism of key factors: (1) Dominant role of the heat load entering the tower: The heat load entering the tower is the key driving factor for evaporation water loss. A higher heat load means that more heat is transferred from the circulating water to the air, promoting the increase of the water surface temperature and the acceleration of the water vaporization rate, thus increasing the evaporation water loss. As mentioned above, the heat load entering the tower depends on the outlet temperature and flow rate of the circulating water in the condenser and the air state entering the cooling tower. It has a positive correlation with the evaporation water loss and is one of the core variables in the model. It plays a dominant role in the evaporation process by affecting the energy source of water vaporization.

[0041] (2) Influence of environmental meteorological parameters: The environmental temperature and humidity directly affect the ability of the air to hold water vapor. The higher the temperature, the greater the amount of water vapor the air can hold, and the stronger the driving force for water evaporation; the lower the relative humidity, the greater the water vapor partial pressure difference between the air and the water surface, and the easier the evaporation. The wind speed and wind direction also have an important impact on evaporation. The increase in wind speed improves the air renewal rate in the cooling tower and enhances the ability to carry away water vapor, promoting evaporation; the wind direction affects the flow distribution of air in the tower, and different wind directions will change the gas-liquid contact efficiency, thus affecting the evaporation effect. The atmospheric pressure indirectly affects the evaporation process by influencing the water vapor partial pressure and the boiling point of water. These environmental parameters are all key variables participating in the calculation in the model and interactively affect the evaporation water loss.

[0042] (3)Cooling Tower Structure Characteristics Association: The type of packing in the cooling tower determines the gas-liquid contact area and contact time. Efficient packing can increase the contact area, extend the contact time, promote heat and mass transfer, and increase the evaporation rate. The geometric parameters of the tower body (such as height and diameter) affect the air flow velocity and residence time inside the tower. A taller tower body and appropriate diameter contribute to the uniform distribution of air and sufficient contact with water, facilitating evaporation. The ventilation structure (such as natural ventilation or mechanical ventilation mode, size and position of ventilation openings) determines the air flow rate and velocity. Mechanical ventilation can provide a more stable air flow and enhance the evaporation effect. These structural characteristics are related to the evaporation water loss in the model through specific coefficients or functional relationships, reflecting their impact on the evaporation process.

[0043] Model Formula Derivation and Parameter Determination: Based on the above principles and factors, the evaporation water loss model can be expressed as: , where, is the evaporation water loss, is the mass transfer coefficient, which is a function of the inlet tower heat load , ambient temperature , relative humidity , wind speed , wind direction , atmospheric pressure and the cooling tower structure characteristics , is the effective gas-liquid contact area. The determination of the mass transfer coefficient is the key, which is obtained through the combined calibration of laboratory simulation experiments and on-site multi-condition test data.

[0044] According to the real-time load of the steam turbine and the steam flow rate discharged into the condenser, with the help of a controller with built-in advanced intelligent control algorithms such as a hybrid algorithm based on fuzzy logic and model predictive control, the operation mode of the circulating water system is dynamically determined. In the low-load stage, the controller automatically switches the circulating water pump to low-speed operation or single-pump operation mode according to the preset rules and algorithms, and realizes the refined adjustment of the circulating water flow rate by combining variable frequency speed regulation technology; in the high-load stage, it quickly resumes high-speed or double-pump operation mode to ensure that the circulating water flow rate is closely matched with the steam turbine operating conditions, effectively reducing the inlet tower heat load of the cooling tower. During the control process, the controller real-time monitors the operation status and relevant parameters of the circulating water system, and continuously optimizes the control strategy through the feedback mechanism to ensure the stable operation of the system.

[0045] Specifically, the core of the intelligent control strategy for the circulating water system lies in closely following the load changes of the steam turbine during the peak shaving operation of the thermal power unit, and precisely adjusting the circulating water flow rate and the heat load entering the cooling tower. Its primary goal is to ensure the efficient operation of the circulating water system under different working conditions, achieve water conservation and energy efficiency in the cooling tower, and maintain the stable thermal efficiency and safe operation status of the unit. By real-time monitoring the key parameters of the steam turbine and applying intelligent control algorithms, the operation mode and speed of the circulating water pump are dynamically adjusted to accurately match the circulating water flow rate with the exhaust steam demand of the steam turbine, reduce the fluctuation of the heat load entering the cooling tower, and improve the economy and reliability of the entire thermal power unit operation.

[0046] The adjustment principle of the circulating water system is to minimize the evaporation water loss to ensure the minimum make-up water volume. The method to achieve this principle is as follows: establish a steam turbine exhaust steam volume model, which is actually the condenser inlet steam volume model, and establish a condenser heat transfer model, mainly to evaluate the change of the condenser outlet water temperature under different circulating water volumes, that is, the change model of the heat load entering the cooling tower. In this way, by optimizing the circulating water volume, the circulating water volume of the condenser can be optimized, the heat load entering the cooling tower can be optimized, the evaporation water loss can be minimized, that is, the make-up water volume can be minimized.

[0047] Intelligent control algorithms are used for regulation, specifically: (1) Fuzzy logic control mechanism: Fuzzy logic control plays a key role in the regulation of the circulating water system. Based on fuzzy set theory, it fuzzifies key input variables such as the steam turbine load change rate and the steam flow deviation into the condenser, and divides them into fuzzy subsets such as "negative large", "negative small", "zero", "positive small", "positive large", etc.

[0048] According to a large amount of unit operation experience and experimental data, a fuzzy rule base is constructed. For example, "if the load change rate is positive large and the steam flow deviation is positive small, then the speed of the circulating water pump is moderately increased". During the control process, the fuzzy inference engine performs fuzzy inference based on the fuzzy subsets of the input variables and the rule base, obtains the fuzzy output of the circulating water pump speed adjustment, and then converts it into an accurate control instruction through defuzzification. This method can effectively handle the system's nonlinearity and uncertainty, quickly respond to the changes in the steam turbine working conditions, and ensure the stable operation of the circulating water system.

[0049] (2) Model predictive control principle: Model predictive control uses the historical operation data of the unit to construct a dynamic model of the circulating water system. This model comprehensively considers factors such as the resistance characteristics of the circulating water pipeline, the performance curve of the pump, and the thermal performance of the cooling tower, and accurately predicts the future load changes of the steam turbine and the response trend of the circulating water system.

[0050] Within each control cycle, based on the current system state and the prediction model, the system outputs (such as the heat load entering the cooling tower and the circulating water temperature) under different control strategies of the circulating water pump are predicted within the prediction time domain (e.g., 10 - 30 minutes). The optimal control sequence is solved through an optimization algorithm (such as quadratic programming), and the control quantity at the current moment is selected to act on the circulating water pump. The control time domain (e.g., 5 - 10 minutes) specifies the effective time range of the control sequence. As time goes by, it is continuously optimized by rolling, and the control strategy is adjusted in a timely manner to adapt to the dynamic changes of the unit operating conditions, ensuring that the circulating water flow closely tracks the steam turbine load demand and effectively avoiding the degradation of system performance caused by control lag.

[0051] The dynamic adaptation process with the steam turbine load: (1) Data real-time monitoring and transmission link: Through a high-precision sensor network (including flow sensors, temperature sensors, pressure sensors, etc. with an accuracy of up to ±0.05%), key parameters such as the steam inlet volume of the steam turbine, the extraction steam volume of each stage of regenerative extraction, and the extraction steam volume for heating (if any) are collected in real time at a high frequency (3 - 5 times per minute). The collected data is quickly transmitted to the control system via a high-speed communication link. The control system processes and analyzes the data in real time, accurately calculates the real-time load of the steam turbine and the steam volume discharged into the condenser, and monitors its change trend. Once it detects that the load change exceeds the preset threshold, it immediately triggers the adjustment program of the circulating water pump control strategy.

[0052] (2) Operating mode switching and fine adjustment of speed: In the low-load stage, such as when the steam turbine load is lower than 60% of the rated load, the control system makes a decision based on the intelligent algorithm and automatically switches the circulating water pump to the low-speed operation mode or the single-pump operation mode, and finely adjusts the speed in combination with the variable frequency speed regulation technology. For example, when the load drops from 80% to 40%, the speed of the circulating water pump may be reduced by 30% - 50% accordingly to reduce the circulating water flow and the heat load entering the cooling tower.

[0053] In the high-load stage, when the load is higher than 80% of the rated load, it quickly switches to the high-speed mode or the double-pump operation mode to ensure sufficient supply of circulating water, maintain the cooling capacity of the cooling tower, and ensure the efficient operation of the unit. During the dynamic change of the load, the control system continuously tracks the load change rate and the change of the steam flow, and adjusts the speed and operation mode of the circulating water pump in real time to achieve smooth dynamic adaptation of the circulating water flow and the steam turbine load, and avoid system fluctuations and equipment damage caused by improper control.

[0054] The synergistic effect of variable frequency speed regulation technology: (1) Principle and advantages of variable frequency speed regulation: The variable frequency speed regulation technology is based on the linear relationship between the motor speed and the power supply frequency, and adjusts the speed of the circulating water pump by changing the power supply frequency of the motor. Compared with the traditional fixed-speed pump or throttle regulation method, variable frequency speed regulation has significant energy-saving advantages. Reducing the frequency at low loads can reduce the circulating water flow, avoid the ineffective power consumption of the pump, improve the operating efficiency of the pump, reduce pipeline wear and water hammer phenomena, and extend the service life of the equipment.

[0055]

[0056] Among them, is the rotational speed, and is the power supply frequency, is the slip ratio, is the number of pole pairs of the motor.

[0057] (2) Seamless integration with intelligent control: In the intelligent control strategy of the circulating water system, the variable frequency speed regulation device works closely with the control system. When the intelligent control algorithm determines that the circulating water flow needs to be adjusted, such as when the steam turbine load decreases, the control system sends a command to reduce the frequency to the variable frequency speed regulator, and the variable frequency speed regulator smoothly reduces the motor speed according to the command to achieve stepless adjustment of the circulating water flow. At the same time, the variable frequency speed regulation device has a feedback function, which real-time feeds back parameters such as the actual speed, current, and power of the pump to the control system, facilitating the control system for closed-loop control and fault diagnosis, ensuring the stable and reliable operation of the entire circulating water system, and effectively improving the operating performance and water-saving and energy-saving effects of the cooling tower during the peak shaving operation of thermal power units.

[0058] Water-saving and accurate determination model of water-saving amount: Under high and low load conditions respectively, use the evaporation water loss model to calculate the evaporation water volume of the cooling tower, and combine the actual makeup water records. According to the water-saving amount calculation formula: water-saving amount = (makeup water volume corresponding to the optimized circulating water volume before - makeup water volume corresponding to the optimized circulating water volume after), accurately determine the water-saving amount.

[0059] Basis and principle of model construction: The water-saving and accurate determination model of water-saving amount is based on the accurate analysis of the evaporation water loss amount and actual makeup water records of the cooling tower under high and low load conditions. Its core principle is to quantify the water-saving amount by comparing the water loss characteristics before and after the optimization of the circulating water volume and using the internal relationship between the evaporation water loss amount and the makeup water volume. During the peak shaving process of thermal power units, the change in the steam volume discharged into the condenser caused by the change in the steam turbine load leads to significant changes in the heat load entering the cooling tower and the evaporation water loss amount. By optimizing the circulating water volume, with the principle of minimizing the evaporation water loss under the premise of meeting the cooling efficiency of the cooling tower, a water-saving amount calculation model is constructed to achieve accurate evaluation of the water-saving amount.

[0060] Determine the water saving amount in combination with the actual water replenishment record: The actual water replenishment record is one of the key bases for determining the water saving amount. During the operation of the unit, the water replenishment operation of the cooling tower is recorded in detail, including information such as the water replenishment time and the water replenishment volume. When recording, in addition to meeting the evaporation water loss, other minor water losses in the system (such as sewage discharge, leakage, etc., set as) need to be considered. To ensure the accuracy of the data, a strict data quality assessment is carried out on the water replenishment record, checking the integrity, consistency, and accuracy of the data, and excluding the influence of abnormal data on the calculation results.

[0061] Embodiment 2 The purpose of this embodiment is to provide a water volume control system for a cooling tower during the peak shaving operation of a thermal power unit, including: A determination module, which is configured to: obtain the historical operation data of the thermal power unit, and determine the calculation relationship model between the evaporation water loss of the cooling tower and the inlet tower heat load under different operating conditions of the thermal power unit based on the historical operation data of the thermal power unit; A prediction module, which is configured to: based on the resistance characteristics of the circulating water pipeline, the performance curve of the pump, and the thermal performance of the cooling tower, optimize the circulating water volume under different operating conditions through a prediction model, and determine the future heat load of the cooling tower; A calculation module, which is configured to: according to the predicted future heat load of the cooling tower, obtain the future evaporation water loss of the cooling tower according to the calculation relationship model corresponding to the working condition; A control module, which is configured to: control the water replenishment volume of the cooling tower according to the future evaporation water loss of the cooling tower.

[0062] In more embodiments, there is also provided: An electronic device, including a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method described in Embodiment 1 is completed. For the sake of brevity, it will not be elaborated here.

[0063] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor, or the processor may also be any conventional processor, etc.

[0064] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A part of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0065] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the method described in Embodiment 1.

[0066] The method in Embodiment 1 can be directly implemented by a hardware processor or by a combination of hardware and software modules in the processor. The software modules can be located in mature storage media in the art such as random access memory, flash memory, read-only memory, programmable read-only memory, or electrically erasable programmable memory, registers, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method. To avoid repetition, it will not be described in detail here.

[0067] A computer program product, including a computer program, which, when executed by a processor, implements the method described in Embodiment 1.

[0068] The present invention also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as instructions included in program modules, which are executed in a device on a target real or virtual processor to perform the processes / methods described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or divided as needed. The machine-executable instructions for program modules can be executed within a local or distributed device. In a distributed device, program modules can be located in local and remote storage media.

[0069] The computer program code for implementing the method of the present invention can be written in one or more programming languages. These computer program codes can be provided to the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing devices, such that when the program code is executed by the computer or other programmable data processing devices, the functions / operations specified in the flowchart and / or block diagram are implemented. The program code can be executed entirely on the computer, partially on the computer, as an independent software package, partially on the computer and partially on a remote computer, or entirely on a remote computer or server.

[0070] In the context of the present invention, the computer program code or related data can be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc. Examples of signals can include electrical, optical, radio, acoustic, or other forms of propagated signals, such as carrier waves, infrared signals, etc.

[0071] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in conjunction with this embodiment can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0072] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for controlling the water volume of a cooling tower during the peak shaving operation of a thermal power unit, characterized in that, Including: Based on the historical operation data of thermal power units, determine the relationship model between the operation load of the steam turbine and the circulating water volume of the condenser under different operation conditions of the thermal power unit, as well as the calculation model of the circulating water volume of the condenser and the evaporation water loss of the cooling tower; Based on the load change of the steam turbine during the real-time peak shaving operation of the thermal power unit, adjust the circulating water volume of the condenser with the goal of minimizing the evaporation water loss of the cooling tower.

2. The water volume control method of a cooling tower during peak shaving operation of a thermal power unit according to claim 1, wherein, Based on the historical operation data of thermal power units, determine the relationship model between the operation load of the steam turbine and the circulating water volume of the condenser under different operation conditions of the thermal power unit, specifically: Considering the steam inlet parameters of the steam turbine and the thermodynamic characteristics of each stage of the regenerative extraction steam system, construct a steam volume model discharged into the condenser; According to the constructed steam volume model discharged into the condenser, construct a heat balance model of the steam heat release, heat transfer of the condenser, and heat absorption of the circulating water; According to the constructed steam volume model discharged into the condenser and the heat balance model, determine the relationship model between the operation load of the steam turbine and the circulating water volume of the condenser.

3. The water volume control method of a cooling tower during peak shaving operation of a thermal power unit according to claim 1, characterized in that, The construction of the calculation model of the circulating water volume of the condenser and the evaporation water loss of the cooling tower is specifically: Specifically: Based on the outlet temperature of the condenser circulating water, the mass flow rate of the circulating water, the inlet temperature of the circulating water, and the inlet air state parameters of the cooling tower, construct a heat load model for the cooling tower inlet; Based on the heat load at the inlet of the cooling tower, multi-dimensional environmental meteorological parameters, and the structural characteristics of the cooling tower itself, combined with the mass transfer coefficients under different working conditions, construct a calculation relationship model between the evaporation water loss of the cooling tower and the heat load at the inlet under different working conditions, and then determine the calculation model of the circulating water volume of the condenser and the evaporation water loss of the cooling tower under different working conditions.

4. The water volume control method of a cooling tower during peak shaving operation of a thermal power unit according to claim 3, characterized in that, Based on the outlet temperature, flow rate of the condenser circulating water, and the inlet air state parameters of the cooling tower, construct a heat load model for the cooling tower inlet, specifically: According to the specific heat capacity of the circulating water, the mass flow rate of the circulating water, the outlet temperature of the circulating water, the inlet temperature of the circulating water, the latent heat of vaporization of water, and the evaporation water volume, construct a primary heat load model for the cooling tower inlet; Based on the dynamic change characteristics of environmental factors, introduce a correction coefficient to correct the primary heat load model for the cooling tower inlet to obtain the final heat load model for the cooling tower inlet.

5. The water volume control method of a cooling tower during peak shaving operation of a thermal power unit according to claim 3, characterized in that, Based on the heat load at the inlet of the cooling tower, multi-dimensional environmental meteorological parameters, and the structural characteristics of the cooling tower itself, combined with the mass transfer coefficients under different working conditions, construct a calculation relationship model between the evaporation water loss of the cooling tower and the heat load at the inlet under different working conditions, specifically: Build an experimental model of the cooling tower, simulate different heat loads at the inlet, environmental parameters, and the structure of the cooling tower respectively, and obtain the evaporation water loss of the cooling tower; Use the regression analysis method to determine the relationship between the mass transfer coefficient and each variable under different working conditions, and determine the calculation relationship model between the evaporation water loss of the cooling tower and the heat load at the inlet under different working conditions.

6. The water volume control method of a cooling tower during peak load regulation operation of a thermal power unit according to claim 3, wherein The determination of the inlet temperature of the circulating water is specifically: Based on the first law of thermodynamics and the principles of heat transfer, construct a heat balance equation for the steam heat release, heat transfer, and heat absorption of the circulating water in the condenser; Solve the constructed heat balance equation to obtain the inlet temperature of the circulating water.

7. The water volume control method of a cooling tower during peak shaving operation of a thermal power unit according to claim 1, characterized in that, Based on the load change of the steam turbine during the real-time peak shaving operation of the thermal power unit, aiming at minimizing the evaporation water loss of the cooling tower, the circulating water volume of the condenser is adjusted, specifically as follows: According to the change of the outlet water temperature of the condenser under different circulating water volumes, optimize the circulating water volume of the condenser to minimize the evaporation water loss of the cooling tower.

8. A water volume control system for a cooling tower during peak load regulation operation of a thermal power unit, characterized in that, It includes: A model construction module, which is configured to: based on the historical operation data of the thermal power unit, determine the relationship model between the operation load of the steam turbine and the circulating water volume of the condenser under different operation conditions of the thermal power unit, and the calculation model of the circulating water volume of the condenser and the evaporation water loss of the cooling tower; An adjustment module, which is configured to: based on the load change of the steam turbine during the real-time peak shaving operation of the thermal power unit, aiming at minimizing the evaporation water loss of the cooling tower, adjust the circulating water volume of the condenser.

9. An electronic device, characterized in that, It includes a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method described in any one of claims 1-7 is completed.

10. A computer-readable storage medium, characterized in that, For storing computer instructions, when the computer instructions are executed by the processor, the method described in any one of claims 1-7 is completed.

Images