Optimized operation control device and method for steam turbine of thermal power plant

Abstract

The invention discloses a thermal power plant steam turbine optimization operation control device and method, and the device comprises a historical data obtaining module which is used for obtaining the historical operation data of a unit; the steady-state working condition judgment module is used for determining a steady-state working condition of stable operation; the thermal economy evaluation module is used for optimal operation main steam pressure of different unit loads; the optimized operation decision module is used for sending out an optimal operation main steam pressure control instruction; and the self-updating module is used for carrying out self-learning updating on the optimal operation main steam pressure. The method solves the problem of uncontrollable errors caused by calculation and correction according to performance tests, design parameters, mathematical models and the like in a traditional method, overcomes the influence of aging and large and small repair of the steam turbine on the optimal operation main steam pressure, enables the steam turbine to be in the optimal operation mode all the time, and is remarkable in energy-saving effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of optimized operation of steam turbines in thermal power plants, and in particular relates to a device and method for controlling optimized operation of steam turbines in thermal power plants. Background Art

[0002] Generally, there are two methods to determine the optimized operating curve of the steam turbine in a large thermal power plant. One is to directly use the sliding pressure heat rate test comparison method. By gradually changing the main steam pressure, the heat rate of the steam turbine under the same load and different main steam pressures is measured, and the main steam pressure and heat rate curve is drawn. The main steam pressure corresponding to the lowest point of the curve is obtained, which is the optimal pressure point for operation under the load; the other is to use the sliding pressure consumption difference analysis method. Under the same load, the main steam pressure is gradually changed, and the corresponding parameters such as high-pressure cylinder efficiency, small steam turbine steam intake or feed water pump motor current change. By analyzing the impact of these important parameter changes on the heat rate, the change in total consumption difference benefit is used as the evaluation basis for sliding pressure optimization. The optimal pressure point for operation under the load can be obtained more easily. Connecting the optimal pressure points for operation under each load and intersecting them with the constant pressure line constitutes the optimized operating curve of the steam turbine.

[0003] The above methods all use the heat rate as a basis for determining the optimal main steam pressure for turbine operation. The calculation involves many parameters, such as condensate flow, main steam pressure and temperature, reheat pressure and temperature, high exhaust pressure and temperature, pressure and temperature of each extraction section, heater inlet and outlet drain temperature, etc. Due to measurement errors in each parameter, the heat rate calculation results have large errors, making it difficult to reflect the impact of main steam pressure changes on the heat rate. Moreover, once the optimized operating curve of the steam turbine is determined, it usually remains unchanged during operation, which cannot reflect the impact of unit aging on the optimized operating curve. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a steam turbine optimized operation control device and method that determines the optimal operating mode of the main steam pressure under the load of each unit based on the heat loss of the steam turbine, and self-learns and updates the optimal operating pressure of the main steam according to the real-time operating conditions of the steam turbine.

[0005] To achieve the above object, the present invention provides a method for optimizing the operation and control of a steam turbine in a thermal power plant, comprising the following steps:

[0006] S1. Obtain historical operating data of the unit, including at least: unit load, main steam pressure, condenser circulating cooling water flow, condenser circulating cooling water inlet temperature, and condenser circulating cooling water outlet temperature;

[0007] S2. Acquire the steady-state operation history data of the steam turbine according to the steady-state criterion, and determine whether the steam turbine is in a steady-state operating condition in the historical operation data of S1;

[0008] S3. Calculate the heat loss of the steam turbine in the steady-state operating state at the same load point and different main steam pressures, and use the main steam pressure corresponding to the lowest heat loss of the steam turbine at each load point as the optimal operating main steam pressure corresponding to the load;

[0009] S4. With the unit load as the horizontal axis and the optimal operating main steam pressure corresponding to each load point in S3 as the vertical axis, a curve of the relationship between the unit load and the main steam pressure is drawn, which is the optimized operation curve of the turbine. The corresponding optimal operating main steam pressure control instruction is issued according to the real-time operating load of the turbine.

[0010] Furthermore, the calculation method of the steam turbine heat loss is:

[0011] Q=D·C·(t2-t1)

[0012] Where: Q is the heat loss of the steam turbine, kJ / / h;

[0013] D is the circulating water flow rate, kg / h;

[0014] C is the mass specific heat capacity of the condenser circulating cooling water, kJ / (kg·℃);

[0015] t2 is the outlet temperature of the condenser circulating cooling water, °C;

[0016] t1 is the condenser circulating cooling water inlet temperature, ℃.

[0017] Furthermore, the steady-state operating condition judgment criterion is: when the fluctuations of five variables, including unit load, main steam flow, main steam pressure, main steam temperature, and reheat steam temperature, are all less than the allowable values within no less than 30 minutes, it indicates that the operating condition is a steady-state condition.

[0018] Furthermore, in S3, the optimal operating main steam pressure at each load point in S3 is fine-tuned. When there is a different main steam pressure that makes the corresponding heat loss smaller than the minimum heat loss in S3, the optimal operating main steam pressure corresponding to the load point in S3 is updated to the fine-tuned value. When there is no different main steam pressure that makes the corresponding heat loss smaller than the minimum heat loss in S3, it remains unchanged.

[0019] Furthermore, under the same unit load and different main steam pressures, the smaller the heat loss of the steam turbine is, the better the thermal economy of the steam turbine operation is.

[0020] Furthermore, a thermal power plant steam turbine optimized operation control device implementing the above-mentioned method includes:

[0021] A historical data acquisition module is used to obtain historical operating data of the unit, including at least: unit load, main steam pressure, condenser circulating cooling water flow, condenser circulating cooling water inlet temperature, and condenser circulating cooling water outlet temperature;

[0022] a steady-state operating condition judgment module, which determines, according to a steady-state operating condition judgment criterion, that the steam turbine in the historical data acquisition module is in a steady-state operating condition;

[0023] A thermal economic evaluation module is used to evaluate the heat loss of the steam turbine in steady-state operation at the same unit load point and different main steam pressures. The main steam pressure corresponding to the lowest heat loss of the steam turbine at each load point and the load are stored in this module as reference values.

[0024] an optimization operation decision module, which forms a turbine optimization operation curve by connecting each main steam pressure point based on the reference value stored in the thermal economy evaluation module, with the unit load as the horizontal axis and the main steam pressure as the vertical axis, and issues a main steam pressure control instruction according to the real-time operating load of the turbine;

[0025] A self-update module fine-tunes the main steam pressure at each load point in the thermal economy evaluation module, and when the heat loss corresponding to a different main steam pressure is smaller than the minimum heat loss value of the thermal economy evaluation module, updates the main steam pressure corresponding to the load point in the thermal economy evaluation module to the fine-tuned main steam pressure value.

[0026] Compared with existing technologies, the present invention has the following advantages and effects: The present invention determines the optimal operating main steam pressure based on the magnitude of the turbine's heat loss. This determination requires only five parameters, reducing calculation errors and workload. Furthermore, the present invention determines the optimal operating mode for the main steam pressure under various loads based on the turbine's actual operating history data, resolving the problem of uncontrollable errors caused by traditional methods based on performance testing, design parameters, mathematical model calculations, and corrections. Furthermore, the present invention uses real-time turbine operating data to self-learn and update the optimal main steam operating pressure, overcoming the effects of turbine aging and major or minor repairs on its performance. This ensures that the main steam pressure is always in the optimal operating mode that matches the turbine's actual conditions, resulting in significant energy savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the operation diagram of the steam turbine optimized operation control device of the present invention.

[0028] Figure 2 This is a flow chart of the steam turbine optimized operation control method of the present invention. DETAILED DESCRIPTION

[0029] In order to better understand the purpose of the present invention, the data processing mode and function of the control device, and the control method, the present invention is further described in detail below with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

[0030] During the operation of a steam turbine, under the same unit load, different main steam pressures correspond to different turbine efficiencies. The traditional method determines the optimal operating value of the main steam pressure based on the minimum value of the turbine heat rate under different main steam pressures. This method requires a large amount of calculation and is not very accurate. In essence, after the steam turbine absorbs heat from the boiler, part of the heat is converted into mechanical energy through the steam turbine and transmitted to the generator to generate electrical energy, which is the energy that truly generates benefits for the power plant; the other part of the heat is absorbed by the condenser circulating cooling water and then discharged into the atmosphere in the cooling tower, which is lost energy. According to the law of conservation of energy, the less energy is lost to the atmosphere, the higher the efficiency of the steam turbine. The present invention determines the optimal operating value of the main steam pressure based on the amount of heat loss. Under different main steam pressures under the same unit load, the main steam pressure corresponding to the minimum energy loss of the steam turbine is the optimal operating main steam pressure.

[0031] like Figure 1 As shown, the steam turbine optimization operation control device of the present invention is located in the steam turbine generator distributed control system (DCS), and includes: a historical data acquisition module, which is nested in the DCS and is used to obtain historical operation data from the steam turbine generator and condenser, including at least: unit load, main steam pressure, condenser circulating cooling water flow, condenser circulating cooling water inlet temperature, and condenser circulating cooling water outlet temperature, which is used to provide basic data for the operation control device.

[0032] Since thermal power steam turbines adjust their load based on grid-side power demand during actual operation, their load fluctuates. Unstable operating conditions make it difficult to accurately determine thermal economy. The steady-state operating condition determination module determines, based on steady-state operating condition determination criteria, that the steam turbine is in a steady-state operating condition, indicating stable operation. This embodiment defines the unit steady-state operating condition for engineering applications based on GB / T 8117.1-2008, Steam Turbine Thermal Performance Acceptance Test Procedure, and in conjunction with actual operating conditions: within 30 minutes, when the difference between the maximum and minimum values of the five variables described in Table 1 is less than twice the absolute value of the fluctuation, the unit is considered to have reached a stable state.

[0033] Table 1 Steady-state operating condition judgment criteria

[0034] Serial number variable Fluctuation value 1 Main steam flow ±2.5％ 2 Main steam pressure ±0.25% of absolute pressure 3 Main steam temperature ±4℃ 4 Reheat steam temperature ±4℃ 5 Unit load ±0.25％

[0035] After acquiring several stable operating conditions from historical data, these data are transmitted to the thermal economic evaluation module. This module calculates the heat loss of the steam turbine under these steady-state conditions, with the same unit load and different main steam pressures. For example, a 600MW steam turbine is an N600-16.7 / 538 / 538 subcritical, reheated, impulse, single-shaft, three-cylinder, four-exhaust condensing turbine. Its main technical parameters are listed in Table 2.

[0036] Table 2 Main technical parameters of steam turbine

[0037]

[0038]

[0039] Retrieving the past three years of historical operating data and statistically analyzing the unit load and main steam pressure in the steady-state operating condition judgment module revealed that the unit load ranged from 200MW to 600MW, and the main steam pressure ranged from 9 to 17MPa. The historical data was clustered, with each 50MW increase in unit load as a new operating point. Consequently, the historical data was divided into nine operating conditions based on unit load: 200MW, 250MW, 300MW, 350MW, 400MW, 450MW, 500MW, 550MW, and 600MW. The historical data showed different main steam pressures at each unit load. For example, at a unit load of 450MW, the main steam pressure fluctuated between 14MPa and 17MPa. Data clustering was performed at 0.5MPa intervals based on the steady-state operating condition judgment criteria. The average values of the basic data at different main steam pressures are shown in Table 3.

[0040] Table 3 List of historical data of unit load 450MW

[0041] Working condition name unit Design value Working condition_1 Working condition_2 Working condition_3 Working condition_4 Working condition_5 Working condition_6 Working condition_7 Test power MW 450 450.12 449.13 451.04 450.76 450.67 450.39 450.15 Main steam pressure MPa 16.7 14.01 14.52 15.02 15.48 16.03 16.51 17.03 <![CDATA[Circulating water inlet temperature t1]]> ℃ 20 25.36 16.16 10.36 18.27 25.36 8.56 21.36 <![CDATA[Outlet temperature t2 of circulating water]]> ℃ 35 41.42 35.38 33.12 40.91 41.11 31.51 41.31 Circulating cooling water flow D t / h 56000 52300 43301 36302 36303 52304 36305 42306

[0042] When determining the optimal main steam pressure operating point, the difference in turbine heat dissipation under different main steam pressures can be ignored, and the heat loss Q at the cold end of the turbine, that is, the heat carried away by the condenser circulating cooling water, can be used as the evaluation indicator. The calculation method is as follows:

[0043] Q=D·C·(t2-t1) (1)

[0044] Where: Q is the turbine heat loss, kJ / / h; D is the circulating water flow rate, kg / h; C is the mass heat capacity of the circulating water, kJ / (kg·℃); t2 is the condenser circulating water outlet temperature, ℃; t1 is the condenser circulating water inlet temperature, ℃.

[0045] Under the same load and different main steam pressures, the main steam pressure corresponding to the minimum value of Q is taken as the optimal operating main steam pressure.

[0046] From the data in Table 3 and calculation by formula (1), it can be seen that the main steam pressure turbine heat loss Q corresponding to operating condition 4 is the smallest, and the corresponding main steam pressure is 15.48 MPa. The optimal operating main steam pressure of 15.48 MPa corresponding to the 480 MW load is stored in the thermal economy evaluation module as a reference value.

[0047] By analogy, we can obtain the optimal operating main steam pressures for the other eight turbine operating conditions: 200MW, 250MW, 300MW, 350MW, 400MW, 500t / h, 550MW, and 600MW. Connecting the optimal operating main steam pressure points under different loads creates the turbine's optimized operating curve.

[0048] The optimized operation decision module issues main steam pressure control instructions based on the real-time operating load of the unit and the turbine optimized operation curve in the thermal economy evaluation module.

[0049] Further explanation: when the grid instruction requires the unit operating load to be 450MW, the optimization operation decision module finds the corresponding optimal operating main steam pressure according to the optimization operation curve determined by the thermal economy evaluation module, and sends a main steam pressure control instruction to the DCS system.

[0050] A self-update module fine-tunes the optimal operating main steam pressure at each load point in the thermal economy evaluation module. When a different main steam pressure makes the corresponding heat loss smaller, the main steam pressure corresponding to the load point in the thermal economy evaluation module is updated to the fine-tuned main steam pressure value; when a different main steam pressure does not make the corresponding heat loss smaller, the main steam pressure remains unchanged.

[0051] It should be noted that when a steam turbine has been in operation for a long time, the optimal operating main steam pressure may change due to aging or major or minor repairs. Therefore, after a long period of operation, the optimal operating main steam pressure corresponding to each load point should be fine-tuned. For example, the optimal operating main steam pressure corresponding to the 480MW load in Table 1 is 15.48MPa. After a long period of operation, such as 2 years, the main steam pressure can be fine-tuned to 15.28MPa, 15.38MPa, 15.58MPa, and 15.68MPa. After the parameters stabilize, the steam turbine heat loss is calculated. If the heat loss corresponding to 15.38MPa is less than the heat loss corresponding to the 15.48MPa operating condition in Table 1, the optimal operating main steam pressure corresponding to this load in the thermal economy evaluation module is updated to 15.38MPa. If there is no other main steam pressure corresponding to a heat loss less than the heat loss corresponding to the 15.48MPa operating condition in Table 1, it remains unchanged.

[0052] like Figure 2As shown, the steam turbine optimization operation control method of the present invention includes the following steps:

[0053] S1, obtain the historical operation data of the steam turbine;

[0054] Specifically, at least the following information is obtained from the steam turbine DCS system: unit load, main steam pressure, condenser circulating cooling water flow, condenser circulating cooling water inlet temperature, and condenser circulating cooling water outlet temperature.

[0055] S2, acquiring the steady-state operation history data of the steam turbine according to the steady-state criterion, and determining that the steam turbine is in a steady-state operating condition in the historical operation data of S1.

[0056] Specifically, according to the steady-state operating condition judgment criteria, as shown in Table 1, the steady-state operating conditions are divided according to the unit load. For example, the stable operating condition fluctuation range of a unit load of 450MW is 449.875MW to 451.125MW, and the fluctuation ranges of other load points are similar.

[0057] S3, calculating the heat loss of the steam turbine in the steady-state operating state at the same load point and different main steam pressures, and taking the main steam pressure corresponding to the lowest heat loss under each load as the optimal operating main steam pressure corresponding to the load;

[0058] Specifically, based on the stable operating condition data described in S2, the heat loss of the turbine at different main steam pressures at each load point of the computer group is calculated according to formula (1), and the unit load and the corresponding optimal main steam operating pressure are stored to form a reference value database.

[0059] S4, with the unit load as the horizontal axis and the optimal operating main steam pressure corresponding to each load point in S3 as the vertical axis, draw the relationship curve between the unit load and the main steam pressure, which is the turbine optimization operation curve, and issue the corresponding optimal operating main steam pressure control instruction according to the real-time operating load of the turbine.

[0060] Specifically, based on the obtained optimal operating main steam pressures corresponding to the unit loads under nine operating conditions, namely 200MW, 250MW, 300MW, 350MW, 400MW, 450MW, 500MW, 550MW, and 600MW, an operation optimization curve is drawn with the unit load as the horizontal axis and the optimal operating main steam pressure as the vertical axis. According to the actual operating conditions of the turbine, the optimal operating main steam pressure control instruction is made according to the turbine optimization operation curve.

[0061] S5, fine-tune the optimal operating main steam pressure at each load point described in S3. When there is a different main steam pressure that makes the corresponding heat loss smaller than the heat loss in S3, update the optimal operating main steam pressure corresponding to the load point to the fine-tuned value. When there is no different main steam pressure that makes the corresponding heat loss smaller than the heat loss in S3, keep it unchanged.

[0062] Furthermore, the optimal operating main steam pressure at each load point is fine-tuned. For example, the optimal main steam pressure corresponding to the aforementioned 480MW load is 15.48MPa. After a long period of operation, such as two years, the main steam pressure can be fine-tuned to 15.28MPa, 15.38MPa, 15.58MPa, and 15.68MPa. After the parameters stabilize, the turbine heat loss is calculated. If the heat loss corresponding to 15.38MPa is less than the heat loss corresponding to the 15.48MPa operating condition in Table 1, the optimal operating main steam pressure corresponding to this load in the thermal economy evaluation module is updated to 15.38MPa. If no other main steam pressure corresponds to a heat loss less than the heat loss corresponding to the 15.48MPa operating condition in Table 1, the pressure remains unchanged. The same applies to other load points.

[0063] It is understood that the present invention is described through embodiments. Those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention, and that none of these changes deviate from the method for determining an optimization curve and self-updating in the present technical solution. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A method for optimizing the operation and control of a steam turbine in a thermal power plant, characterized in that: The following steps are involved: S1. Obtain historical operating data of the unit, including at least: unit load, main steam pressure, condenser circulating cooling water flow, condenser circulating cooling water inlet temperature, and condenser circulating cooling water outlet temperature; S2. Acquire the steady-state operation history data of the steam turbine according to the steady-state criterion, and determine whether the steam turbine is in a steady-state operating condition in the historical operation data of S1; S3. Calculate the heat loss of the steam turbine in the steady-state operating state at the same load point and different main steam pressures, and use the main steam pressure corresponding to the lowest heat loss of the steam turbine at each load point as the optimal operating main steam pressure corresponding to the load; S4. With the unit load as the horizontal axis and the optimal operating main steam pressure corresponding to each load point in S3 as the vertical axis, a curve of the relationship between the unit load and the main steam pressure is drawn, which is the optimized operation curve of the turbine. The corresponding optimal operating main steam pressure control instruction is issued according to the real-time operating load of the turbine.

2. The method for optimizing operation and controlling a steam turbine in a thermal power plant according to claim 1, wherein: The calculation method of the steam turbine heat loss is: Q=D·C·(t2-t1) Where: Q is the heat loss of the steam turbine, kJ / / h; D is the circulating water flow rate, kg / h; C is the mass specific heat capacity of the condenser circulating cooling water, kJ / (kg·℃); t2 is the outlet temperature of the condenser circulating cooling water, °C; t1 is the condenser circulating cooling water inlet temperature, ℃.

3. The method for optimizing operation and controlling a steam turbine in a thermal power plant according to claim 1, wherein: The steady-state operating condition judgment criterion is: when the fluctuations of five variables, including unit load, main steam flow, main steam pressure, main steam temperature, and reheat steam temperature, are all less than the allowable values within no less than 30 minutes, it indicates that the operating condition is a steady-state condition.

4. The method for optimizing operation and controlling a steam turbine in a thermal power plant according to claim 1, wherein: In S3, the optimal operating main steam pressure at each load point in S3 is fine-tuned. When there is a different main steam pressure that makes the corresponding heat loss smaller than the minimum heat loss in S3, the optimal operating main steam pressure corresponding to the load point in S3 is updated to the fine-tuned value. When there is no different main steam pressure that makes the corresponding heat loss smaller than the minimum heat loss in S3, it remains unchanged.

5. The method for optimizing operation and controlling a steam turbine in a thermal power plant according to claim 2, wherein: Under the same unit load and different main steam pressure, the smaller the heat loss of the steam turbine is, the better the thermal economy of the steam turbine operation is.

6. A thermal power plant steam turbine optimized operation control device for implementing the method according to claim 2, characterized in that: include: A historical data acquisition module is used to obtain historical operating data of the unit, including at least: unit load, main steam pressure, condenser circulating cooling water flow, condenser circulating cooling water inlet temperature, and condenser circulating cooling water outlet temperature; a steady-state operating condition judgment module, which determines, according to a steady-state operating condition judgment criterion, that the steam turbine in the historical data acquisition module is in a steady-state operating condition; A thermal economic evaluation module is used to evaluate the heat loss of the steam turbine in steady-state operation at the same unit load point and different main steam pressures. The main steam pressure corresponding to the lowest heat loss of the steam turbine at each load point and the load are stored in this module as reference values; an optimization operation decision module, which forms a turbine optimization operation curve by connecting each main steam pressure point based on the reference value stored in the thermal economy evaluation module, with the unit load as the horizontal axis and the main steam pressure as the vertical axis, and issues a main steam pressure control instruction according to the real-time operating load of the turbine; A self-update module fine-tunes the main steam pressure at each load point in the thermal economy evaluation module, and when the heat loss corresponding to a different main steam pressure is smaller than the minimum heat loss value of the thermal economy evaluation module, updates the main steam pressure corresponding to the load point in the thermal economy evaluation module to the fine-tuned main steam pressure value.

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