Method for drawing working condition diagram and feasible region of double-back-extraction heat supply unit

Abstract

The invention aims to provide a method for drawing a working condition diagram and a feasible region of a double-extraction back heat supply unit. The method comprises the following steps: S1, obtaining a digital twin model of a combined heat and power generation system of a target double-extraction back heat supply unit; s2, determining operation boundary conditions during drawing of a working condition diagram and feasible region drawing of the double-back-extraction heat supply unit combined heat and power generation system; s3, generating data of operation boundary conditions required for drawing a working condition diagram and a feasible region through a digital twinborn model of the double-back-extraction heat supply unit combined heat and power generation system; and S4, drawing a visual working condition diagram and a feasible region by using the data obtained in the step S3 through a computer graphics method. According to the working condition diagram and the feasible region drawn through the method, the accuracy of the working condition diagram and the feasible region can be improved, and the limitation of measurement means when the working condition diagram and the feasible region are drawn in an experimental mode can be avoided.

Description

Technical Field

[0001] The present invention relates to the field of energy technologies, and particularly to a method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit. Background Art

[0002] The digital twin model is a technology that combines a physical entity with a virtual model, and it can monitor and analyze the state of a system in real time. Through this technology, the feasible region and operating condition diagram of the system can be understood more effectively, thereby achieving more accurate and reliable system control and optimization. With the rapid development of industry, digital twin technology has become an important industrial application. It can map the state, performance, and data of physical equipment to the virtual world, enabling real-time monitoring and analysis of the equipment and system. Specifically, digital twin technology realizes data synchronization between the two by constructing a virtual model corresponding to the actual physical entity. This virtual model can be an exact replica of a product, system, or process, used to simulate, analyze, and control its physical counterpart. The feasible region refers to the range of parameters within which the system can operate stably under specific conditions; the operating condition diagram shows various different operating states and conditions that the system may encounter within this range.

[0003] Over time, the digital twin model can gradually learn and optimize itself, predict the system behavior under different operating conditions, and generate the corresponding feasible region and operating condition diagram. This enables engineers to better understand the system's response in different scenarios and make corresponding decisions. Among them, the feasible region refers to the range or area within which the system can operate safely and stably under certain constraint conditions. In the context of cogeneration, this may involve factors such as the heat and electricity produced, the operating conditions of the equipment, and environmental emissions. The operating condition diagram describes the performance of cogeneration under different operating conditions (such as different loads, fuel types, environmental conditions, etc.); it can be a graph marked with key parameters such as the output, efficiency, and emissions of cogeneration under different conditions. For the actual design, operation, or optimization of cogeneration, as well as fault diagnosis and maintenance, both of these concepts are important; further, there is an interaction between the performance and design of the unit, that is, the performance parameters in the feasible region diagram are directly affected by the system design conditions shown in the operating condition diagram; further, for the operation strategy and optimization of the unit, the operating condition diagram helps operating staff and engineers understand the specific operation details of the thermal power plant, thereby formulating appropriate operation strategies and ensuring that the thermal power plant can operate under the optimal conditions defined by the feasible region; at the same time, for the fault diagnosis and maintenance of the unit, the operating condition diagram is crucial for identifying and diagnosing system faults. It shows the layout and interconnection of the equipment, helping to trace the source of the problem, while the feasible region can indicate which operating conditions may lead to performance degradation or safety problems. Using the feasible region and the operating condition diagram together helps to locate and solve problems more quickly.

[0004] Generating the feasible region and operating condition diagram is of great significance for optimizing system performance, improving operation strategies, and predicting faults and abnormal conditions. Through the digital twin model, the operating boundary conditions and operation limitations of the system can be better understood, providing support for decision-making in actual operation. However, there is currently no application of digital twin technology in the drawing of the feasible region and operating condition diagram. Summary of the Invention

[0005] The object of the present invention is to provide a method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit, which can not only improve the accuracy of the operating condition diagram and feasible region but also avoid the limitations of measurement means when drawing the operating condition diagram and feasible region by experimental methods.

[0006] In one aspect of the present invention, the present invention proposes a method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit. According to an embodiment of the present invention, the method includes the following steps:

[0007] S1. Obtain the digital twin model of the cogeneration system of the target double-extraction back-pressure heating unit; wherein the digital twin model of the cogeneration system of the target double-extraction back-pressure heating unit is an existing and complete digital twin model, and this model can directly simulate to obtain any data required.

[0008] S2. Determine the operating boundary conditions when drawing the operating condition diagram and feasible region of the cogeneration system of the double-extraction back-pressure heating unit;

[0009] S3. Generate the data of the operating boundary conditions required for drawing the operating condition diagram and feasible region through the digital twin model of the cogeneration system of the double-extraction back-pressure heating unit;

[0010] S4. Draw the visualized operating condition diagram and feasible region by using the data obtained in step S3 through the method of computer graphics.

[0011] In addition, according to a method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to the above embodiment of the present invention, it may also have the following additional technical features:

[0012] In some embodiments of the present invention, in step S1, the digital twin model is used to reflect the attributes of the target double-extraction back-pressure heating unit, simulate the behavior of the target double-extraction back-pressure heating unit, and predict the trends of the target double-extraction back-pressure heating unit. Further, the attributes of the target double-extraction back-pressure heating unit include, but are not limited to, mechanical attributes, thermodynamic attributes, electrical attributes, physical dimensions, etc., such as rotor mass, housing structure, designed steam temperature and pressure, thermal efficiency, electrical efficiency, length, diameter, height, etc.; the behaviors of the target double-extraction back-pressure heating unit include, but are not limited to, operating states, operating behaviors, vibration and noise, efficiency and performance, etc., such as rotational speed changes, load fluctuations, start-up and shutdown processes, load adjustment and scheduling, vibration frequency and amplitude, real-time efficiency changes, etc.; the trends of the target double-extraction back-pressure heating unit include, but are not limited to, performance degradation, fault prediction, energy consumption analysis, environmental impact, etc., such as component wear and aging trends, efficiency decline trends, fault warnings for key components, energy-saving potential, environmental policy impact analysis, etc.

[0013] In some embodiments of the present invention, in step S2, the operating condition diagram of the cogeneration system of the double-extraction back-pressure heating unit represents the steam consumption characteristic curve between the power of the double-extraction back-pressure steam turbine generator set and the flow rate, and the feasible region of the cogeneration system of the double-extraction back-pressure heating unit refers to the way that can express the safe adjustment range where the thermoelectric load of the double-extraction back-pressure heating unit can operate.

[0014] In some embodiments of the present invention, in step S2, the operating boundary conditions for drawing the operating condition diagram and the feasible region of the cogeneration system of the double-extraction back-pressure heating unit are as follows:

[0015] Boundary 1: Determine the minimum output condition surface: Find the points with the minimum power of the double-extraction back-pressure heating unit under different operating conditions, and connect the found points in sequence to form the minimum output condition surface. Among them, the points with the minimum power of the double-extraction back-pressure heating unit under different operating conditions include the minimum power points corresponding to different main steam flow rates and different extraction steam flow rates;

[0016] Boundary 2: Determine the maximum output condition surface: Find the points with the maximum power of the double-extraction back-pressure heating unit under different operating conditions, and then connect the found points in sequence to form the maximum output condition surface. Among them, the points with the maximum power of the double-extraction back-pressure heating unit under different operating conditions include the maximum power points corresponding to different main steam flow rates and different extraction steam flow rates;

[0017] Boundary 3: Determine the minimum low-pressure extraction condition surface: Find the points of the double-extraction back-pressure heating unit with the minimum low-pressure extraction steam flow rate, and then connect the found points in sequence to form the minimum low-pressure extraction condition surface. Among them, the points of the double-extraction back-pressure heating unit with the minimum low-pressure extraction steam flow rate are the power points corresponding to different main steam flow rates and different medium-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is the smallest;

[0018] Boundary 4. Determine the maximum low-pressure extraction steam condition surface: Locate the points of the dual-extraction back-pressure heating unit at the maximum low-pressure extraction steam volume, and then connect the located points in sequence to form the maximum low-pressure extraction steam condition surface. Among them, the points of the dual-extraction back-pressure heating unit at the maximum low-pressure extraction steam volume are the power points corresponding to different main steam flows and different intermediate-pressure extraction steam volumes when the low-pressure extraction steam volume is the largest;

[0019] Boundary 5. Determine the minimum intermediate-pressure extraction steam condition surface: Locate the points of the dual-extraction back-pressure heating unit at the minimum intermediate- and low-pressure extraction steam volumes, and then connect the located points in sequence to form the minimum intermediate-pressure extraction steam condition surface. Among them, the points of the dual-extraction back-pressure heating unit at the minimum intermediate-pressure extraction steam volume are the power points corresponding to different main steam flows and different low-pressure extraction steam volumes when the intermediate-pressure extraction steam volume is the smallest;

[0020] Boundary 6. Determine the maximum intermediate-pressure extraction steam condition surface: Locate the points of the dual-extraction back-pressure heating unit at the maximum intermediate- and low-pressure extraction steam volumes, and then connect the located points in sequence to form the maximum intermediate-pressure extraction steam condition surface. Among them, the points of the dual-extraction back-pressure heating unit at the maximum intermediate-pressure extraction steam volume are the power points corresponding to different main steam flows and different low-pressure extraction steam volumes when the intermediate-pressure extraction steam volume is the largest;

[0021] Boundary 7. Determine the maximum main steam flow condition surface: Locate the points of the dual-extraction back-pressure heating unit at the maximum main steam flow, and then connect the located points in sequence to form the maximum main steam flow condition surface. Among them, the points of the dual-extraction back-pressure heating unit at the maximum main steam flow are the power points corresponding to different intermediate-pressure extraction steam volumes and different low-pressure extraction steam volumes when the main steam flow is the largest; The maximum main steam flow is the maximum steam inlet volume limit specified for the dual-extraction back-pressure heating unit during the design stage.

[0022] In some embodiments of the present invention, step S3 specifically includes the following steps:

[0023] S301. Determine the corresponding minimum power of the unit when the main steam flow, the first-stage extraction steam volume, and the second-stage extraction steam volume are different, that is, determine the minimum output condition surface;

[0024] S302. Determine the corresponding maximum power of the unit when the main steam flow, the first-stage extraction steam volume, and the second-stage extraction steam volume are different, that is, determine the maximum output condition surface;

[0025] S303. Determine the corresponding power of the unit when the low-pressure extraction steam volume is the smallest, the main steam flow is different, and the intermediate-pressure extraction steam volume is different, that is, determine the minimum low-pressure extraction steam condition surface;

[0026] S304. Determine the corresponding power of the unit when the low-pressure extraction steam volume is the largest, the main steam flow is different, and the intermediate-pressure extraction steam volume is different, that is, determine the maximum low-pressure extraction steam condition surface;

[0027] S305. Determine the corresponding power of the unit when the intermediate-pressure extraction steam flow is the smallest, at different main steam flows and different low-pressure extraction steam flows, that is, the minimum intermediate-pressure extraction steam operating condition surface;

[0028] S306. Determine the corresponding power of the unit when the intermediate-pressure extraction steam flow is the largest, at different main steam flows and different low-pressure extraction steam flows, that is, the maximum intermediate-pressure extraction steam operating condition surface;

[0029] S307. Determine the corresponding power of the unit when the main steam flow is the largest, at different intermediate-pressure extraction steam flows and different low-pressure extraction steam flows, that is, the maximum main steam flow operating condition surface.

[0030] In some embodiments of the present invention, in the step S301, the minimum power generation method is as follows: determine the calculation step size, and start the calculation through the digital twin model from the backpressure operating condition where the extraction steam flow is 0 or the minimum and the power is the minimum. Enumerative iterative calculation is performed on the main steam flow, intermediate-pressure extraction steam flow, and low-pressure extraction steam flow in the double-extraction back-pressure heating unit system according to the pre-designed calculation step size, and the data of the minimum power during the operation of the steam turbine corresponding to different main steam flows and different extraction steam flow conditions are obtained;

[0031] In the step S302, the maximum power generation method is as follows: determine the calculation step size, and start the calculation through the digital twin model from the backpressure operating condition where the extraction steam flow is 0 or the minimum and the power is the minimum. Enumerative iterative calculation is performed on the main steam flow, intermediate-pressure extraction steam flow, and low-pressure extraction steam flow in the unit system according to the pre-designed calculation step size (increment), and the data of the maximum power during the operation of the steam turbine corresponding to different main steam flows and different extraction steam flow conditions are obtained through iterative calculation;

[0032] In the step S303, the method for generating the data of the minimum low-pressure extraction steam operating condition is as follows: fix the low-pressure extraction steam flow at 0 or the minimum, then determine the calculation step size, and start the calculation through the digital twin model from the backpressure operating condition where the intermediate-pressure extraction steam flow is the minimum extraction steam flow and the power is the minimum. Enumerative variable-condition iterative calculation is performed on the main steam flow and intermediate-pressure extraction steam flow in the unit system according to the pre-designed calculation step size, and the calculation data of the power generation of the unit system at different main steam flows and different intermediate-pressure extraction steam flows when the low-pressure extraction steam flow is the minimum value are obtained;

[0033] In the step S304, the method for generating the data of the maximum low-pressure extraction steam operating condition is as follows: fix the low-pressure extraction steam flow at the maximum, then determine the calculation step size, and start the calculation through the digital twin model from the single-extraction backpressure operating condition where the intermediate-pressure extraction steam flow is the minimum extraction steam flow and the power is the minimum. Enumerative variable-condition iterative calculation is performed on the main steam flow and intermediate-pressure extraction steam flow in the unit system according to the pre-designed calculation step size (i.e., increment), and the calculation data of the power generation of the unit system at different main steam flows and different intermediate-pressure extraction steam flows when the low-pressure extraction steam flow is the maximum are obtained;

[0034] In step S305, the method for generating the minimum medium-pressure extraction steam condition data is as follows: fix the medium-pressure extraction steam volume at the minimum, then determine the calculation step size. Starting from the backpressure condition with the minimum low-pressure extraction steam volume and the minimum power, calculate through the digital twin model. Use the enumeration method to perform off-design iteration calculations on the main steam flow rate and low-pressure extraction steam volume in the unit system according to the pre-set calculation step size. When the medium-pressure extraction steam volume is at the minimum value, obtain the calculation data of the power generation of the unit system under different main steam flow rates and different low-pressure extraction steam volumes;

[0035] In step S306, the method for generating the maximum medium-pressure extraction steam condition data is as follows: fix the medium-pressure extraction steam volume at the maximum, then determine the calculation step size. Starting from the single-extraction backpressure condition with the minimum low-pressure extraction steam volume and the minimum power, calculate through the digital twin model. Use the enumeration method to perform off-design iteration calculations on the main steam flow rate and low-pressure extraction steam volume in the unit system according to the pre-set calculation step size. When the medium-pressure extraction steam volume is at the maximum value, obtain the calculation data of the power generation of the unit system under different main steam flow rates and different low-pressure extraction steam volumes.

[0036] In step S307, the method for generating the maximum main steam flow rate condition data is as follows: determine the maximum main steam flow rate, then determine the calculation step size. Starting from the backpressure condition with the medium-pressure extraction steam volume and the low-pressure extraction steam volume being 0 (the minimum extraction steam volume) and the minimum power, calculate through the digital twin model. Use the enumeration method to perform off-design iteration calculations on the medium-pressure extraction steam volume and the low-pressure extraction steam volume in the unit system according to the pre-set calculation step size. When the main steam flow rate is at the maximum value, obtain the calculation data of the power generation of the unit system under different medium-pressure extraction steam volumes and different low-pressure extraction steam volumes.

[0037] In some embodiments of the present invention, the calculation step size is the increment of the main steam flow rate or the increment of the medium-pressure extraction steam volume or the increment of the medium-pressure extraction steam volume.

[0038] In some embodiments of the present invention, in step S4, when drawing a visual working condition diagram and a feasible region through computer graphics methods, it is necessary to denoise the data obtained in step S3, and then use computer graphics methods to connect or fit the processed data into curves or three-dimensional surfaces. Subsequently, combine the fitted curves and three-dimensional surfaces into a three-dimensional solid figure, which can become the visual working condition diagram and the feasible region.

[0039] In some embodiments of the present invention, step S4 specifically includes the following steps:

[0040] S401. Determine the visualization target: clarify the target to be achieved through data visualization and the information to be conveyed, and determine the data set and data type to be used;

[0041] S402. Data preprocessing: Clean and process the data to ensure it is suitable for visualization; perform necessary transformations on the data, where the necessary transformations include calculating statistics and normalization;

[0042] S403. Select suitable visualization tools and software;

[0043] S404. Data mapping and modeling: Map the data into a multi-dimensional space and determine how to transform data points into the shape, size, and position of multi-dimensional graphics in a two-dimensional plane;

[0044] S405. Add textures and color coding;

[0045] S406. Set lighting and camera perspective;

[0046] S407. Rendering and optimization;

[0047] S408. Interaction design;

[0048] S409. Final review and adjustment.

[0049] In some embodiments of the present invention, in step S401, the goal to be achieved through data visualization refers to the feasible region and operating condition diagram of the target unit; the information to be conveyed refers to the safe operating range or area of the target unit, as well as its performance under different operating conditions; the dataset and data types to be used refer to the dataset and data types required for drawing the feasible region and operating condition diagram of the target unit; among them, the dataset includes the full operating condition performance data of the unit, steam state parameters, and performance data of equipment in the auxiliary system, and the data types refer to the data types that can be operated by the software or tools selected when drawing the feasible region and operating condition diagram;

[0050] In step S405, adding textures means adding textures to the multi-dimensional model to enhance the visual effect and information expression; color coding refers to using color coding to represent different attributes or values of the data; the mass flow rate of medium-pressure extraction steam and its mass flow rate under different operating conditions during the actual operation of the double-extraction back-pressure heating unit are expressed through color coding;

[0051] In step S407, rendering and optimization refer to rendering the final multi-dimensional graphics, calculating lighting, shadows, and colors, generating the final image, and finally optimizing the graphics;

[0052] In step S408, interaction design refers to adding interaction functions to the multi-dimensional graphics, and the interaction functions include, for example, zooming, rotating the view, and clicking to view details.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] 1) The method of the present invention can, based on a computer program, automatically obtain the data required for drawing the operating condition diagram and feasible region of the cogeneration system of a double-extraction back-pressure heating unit from the realized digital twin model according to the realized digital twin model, and realize the drawing of the operating condition diagram and feasible region through computer graphics technology.

[0055] 2) The operating condition diagram and feasible region drawn by the method of the present invention can not only improve the accuracy of the operating condition diagram and feasible region, but also avoid the limitations of measurement means when drawing the operating condition diagram and feasible region based on experimental methods.

[0056] 3) At the same time, since the double-extraction back-pressure heating unit produces at least two different grades of heat energy in addition to generating electric energy. Therefore, in order to accurately express the steam consumption characteristics of the unit itself during the actual operation of the double-extraction back-pressure unit, and at the same time, since the unit produces two different grades of heating steam, it is necessary to express four-dimensional information in a planar graph, including expressing power, main steam, and low-pressure extraction steam through three-dimensional coordinate axes, and at the same time using color or contour lines as the fourth-dimensional coordinate axis to express medium-pressure extraction steam; when expressing the feasible region and operating condition diagram of the double-extraction back-pressure unit through a four-dimensional graph, the performance change law and safety boundary of the double-extraction back-pressure unit during the adjustment between different grades of heat energy and electric energy can be reflected more accurately and clearly. Therefore, the method of the present invention can also reflect different grades of heat energy on the operating condition diagram or feasible region, providing a more accurate and detailed reference for the operation guidance of the power plant unit. Description of the Drawings

[0057] Figure 1 It is the flowchart of the method for drawing the operating condition diagram and feasible region of the double-extraction back-pressure heating unit in the embodiment of the present invention;

[0058] Figure 2 It is the flowchart of the step for determining the operating boundary when drawing the operating condition diagram and feasible region of the double-extraction back-pressure unit in the embodiment of the present invention;

[0059] Figure 3 It is the flowchart of the step for generating the data required for the operating boundary when drawing the operating condition diagram and feasible region of the double-extraction back-pressure unit in the embodiment of the present invention;

[0060] Figure 4 It is the flowchart of the step for using computer graphics technology when drawing the operating condition diagram and feasible region of the double-extraction back-pressure unit in the embodiment of the present invention;

[0061] Figure 5 It is the front view of the operating condition diagram and feasible region of the double-extraction back-pressure unit drawn in the embodiment of the present invention;

[0062] Figure 6 It is the back view of the operating condition diagram and feasible region of the double-extraction back-pressure unit drawn in the embodiment of the present invention. Specific embodiments

[0063] Next, in conjunction with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0064] See Figure 1 , a method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit, comprising the following steps:

[0065] 1. Obtain the digital twin model of the target combined heat and power unit.

[0066] The digital twin model includes but is not limited to the ability to accurately reflect the attributes of the target unit, clearly simulate the behavior of the target unit, and accurately predict the trends of the target unit. Further, the attributes of the target unit include but are not limited to mechanical attributes, thermodynamic attributes, electrical attributes, physical dimensions, etc., that is, rotor mass, housing structure, designed steam temperature and pressure, thermal efficiency, electrical efficiency, length, diameter, height, etc.; the behaviors of the target unit include but are not limited to operating states, operating behaviors, vibration and noise, efficiency and performance, etc., that is, speed changes, load fluctuations, start-up and shutdown processes, load adjustment and scheduling, vibration frequency and amplitude, real-time efficiency changes, etc.; the trends of the target unit include but are not limited to performance degradation, fault prediction, energy consumption analysis, environmental impact, etc., that is, component wear and aging trends, efficiency decline trends, fault warnings of key components, energy-saving potential, environmental policy impact analysis, etc.

[0067] 2. Determine the operating boundaries when drawing the operating condition diagram and feasible region of the combined heat and power system of the double-extraction back-pressure heating unit.

[0068] The operating condition diagram of the combined heat and power system of the double-extraction back-pressure heating unit refers to the steam consumption characteristic curve representing the power and flow rate of the double-extraction steam turbine generator set; the feasible region of the combined heat and power system of the double-extraction back-pressure heating unit refers to the way that can express the safe adjustment range of the thermoelectric load of the double-extraction back-pressure heating unit that can operate.

[0069] See Figure 2 , the steps for determining the operating boundaries when the double-extraction back-pressure unit draws the operating condition diagram and feasible region according to the realized digital twin model are as follows;

[0070] (1) Determine the operating boundary surface when the double-extraction back-pressure unit draws the operating condition diagram and feasible region according to the realized digital twin model.

[0071] The operating boundaries of the double-extraction backpressure unit's operating condition diagram and feasible region are the output boundary surfaces of the unit system restricted by the performance of internal equipment in the unit system; this output boundary surface should at least include the minimum output condition surface, the maximum output condition surface, the minimum low-pressure extraction condition surface, the maximum low-pressure extraction condition surface, the minimum intermediate-pressure extraction condition surface, the maximum intermediate-pressure extraction condition surface, and the maximum main steam flow condition surface.

[0072] (2) Determine the screening conditions for the operating boundary surface.

[0073] The screening conditions for the operating boundary of the double-extraction backpressure unit's operating condition diagram and feasible region are the conditions used to screen each operating boundary surface; the screening conditions are determined based on the upper and lower operating limits of each device in the cogeneration system of the double-extraction backpressure unit. For example, when determining the minimum output condition surface, it is necessary to determine the data screening conditions for the minimum condition surface at the same time, that is, the minimum power generation condition of the steam turbine, P = Pmin; similarly, the data screening conditions required for other operating boundary surfaces of the double-extraction backpressure unit's operating condition diagram and feasible region can be determined.

[0074] Specifically, the operating boundary conditions required for drawing the operating condition diagram and feasible region of the double-extraction backpressure steam turbine unit are as follows:

[0075] Boundary 1: Determine the minimum output condition surface. Find the point with the minimum power of the unit under different operating conditions, that is, P = Pmin; the point with the minimum power of the unit under different operating conditions is the corresponding minimum power point when different main steam flows and different extraction steam flows; then connect the found points in sequence to form the minimum output condition surface.

[0076] Boundary 2: Determine the maximum output condition surface. Find the point with the maximum power of the unit under different operating conditions, that is, P = Pmax; the point with the maximum power of the unit under different operating conditions is the corresponding maximum power point when different main steam flows and different extraction steam flows; then connect the found points in sequence to form the maximum output condition surface.

[0077] Boundary 3: Determine the minimum low-pressure extraction condition surface. Find the point with the minimum low-pressure extraction steam volume of the unit, that is, Dd = Ddmin; the point with the minimum low-pressure extraction steam volume of the unit is the corresponding power point when the low-pressure extraction steam volume Dd = 0 or Dd = Ddmin, different main steam flows, and different intermediate-pressure extraction steam volumes; then connect the found points in sequence to form the minimum low-pressure extraction condition surface.

[0078] Boundary 4: Determine the maximum low-pressure extraction condition surface. Find the point with the maximum low-pressure extraction steam volume of the unit, that is, Dd = Ddmax; the point with the maximum low-pressure extraction steam volume of the unit is the corresponding power point when the low-pressure extraction steam volume Dd = Ddmax, different main steam flows, and different intermediate-pressure extraction steam volumes; then connect the found points in sequence to form the maximum low-pressure extraction condition surface.

[0079] Boundary 5: Determine the minimum intermediate-pressure extraction steam condition surface. Locate the point of the unit at the minimum intermediate and low-pressure extraction steam flow rate, i.e., Dg = Dgmin; the point of the unit at the minimum intermediate-pressure extraction steam flow rate is the power point corresponding to different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate Dg = 0 or Dg = Dgmin; then connect the located points in sequence to form the minimum intermediate-pressure extraction steam condition surface.

[0080] Boundary 6: Determine the maximum intermediate-pressure extraction steam condition surface. Locate the point of the unit at the maximum intermediate and low-pressure extraction steam flow rate, i.e., Dg = Dgmax; the point of the unit at the maximum intermediate-pressure extraction steam flow rate is the power point corresponding to different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate Dg = Dgmax; then connect the located points in sequence to form the maximum intermediate-pressure extraction steam condition surface.

[0081] Boundary 7: Determine the maximum main steam flow rate condition surface. Locate the point of the unit at the maximum main steam flow rate, i.e., G = Gmax; the point of the unit at the maximum main steam flow rate is the power point corresponding to different intermediate-pressure extraction steam flow rates and different low-pressure extraction steam flow rates when the main steam flow rate G = Gmax; then connect the located points in sequence to form the maximum main steam flow rate condition surface. Further, the maximum main steam flow rate is the maximum steam inlet amount limit specified during the design stage of the unit.

[0082] 3. Generate the data of the operating boundaries required for drawing the condition diagram and the feasible region through the digital twin model of the target cogeneration unit.

[0083] The boundary data required for drawing the condition diagram and the feasible region of the cogeneration system of the double-extraction back-pressure heating unit should at least include but not be limited to the data included in step 2.

[0084] See Figure 3 , in this embodiment, the steps for generating the data of the operating boundaries required for drawing the condition diagram and the feasible region of the double-extraction back-pressure unit are as follows:

[0085] (1) Determine the screening conditions for the operating boundary surface. The screening conditions for the operating boundary surface when drawing the condition diagram and the feasible region of the double-extraction back-pressure unit are the conditions used to screen each operating boundary surface; the determined screening conditions for the operating boundary are the screening conditions corresponding to the selected operating boundary surfaces in step 2 above; the screening conditions are determined based on the upper and lower operating limits of each device in the cogeneration system of the double-extraction back-pressure unit.

[0086] (2) Select the base condition for iterative calculation. When drawing the condition diagram and the feasible region of the double-extraction back-pressure heating unit, the base condition for the iterative calculation can be the minimum pure back-pressure condition, or extreme conditions such as the maximum output extraction steam condition, etc., so as to facilitate the full-condition characteristic simulation calculation after the step size is selected.

[0087] (3) Select the calculation variables and their calculation steps. This step is based on the selected iterative base operating condition and the operating boundary surface for calculation, and selects the calculation variables and their calculation steps. The selected calculation variables can be the intermediate-pressure extraction steam flow rate, the main steam flow rate, or the low-pressure extraction steam flow rate, or other variables; when selecting the calculation variables, it can be any combination of the above variables or one of them, and the specific selection needs to be made according to the actual calculation requirements; for example, when drawing the minimum output condition surface, the selected calculation variables are the main steam flow rate, the intermediate-pressure extraction steam flow rate, and the low-pressure extraction steam flow rate, while when drawing the maximum main steam flow rate output condition surface, the selected calculation variables are the intermediate-pressure extraction steam flow rate and the low-pressure extraction steam flow rate; further, the calculation step is the increment corresponding to the selected calculation variable. When the calculation step is small enough, the operating boundary surface drawn from the calculation results is more accurate.

[0088] (6) Perform enumeration iterative calculation. The enumeration iterative calculation is carried out according to the calculation variables and the corresponding calculation steps selected in the previous step through the digital twin model of the thermodynamic system of the double-extraction back-pressure heating unit, and then the thermal characteristic data results obtained from each iterative calculation are saved to the computer or database.

[0089] Specifically, the data acquisition method for the operating boundary surface is as follows:

[0090] (1) Determine the corresponding minimum power of the unit at different main steam flow rates, different first-stage extraction steam flow rates, and different second-stage extraction steam flow rates, that is, determine the minimum output condition surface; the method for generating the minimum power required for drawing the operating condition diagram and the feasible region of the cogeneration system of the double-extraction back-pressure unit is to determine the calculation step (the calculation step can be the main steam flow rate increment Δm, or the intermediate-pressure extraction steam flow rate increment Δe1, or the intermediate-pressure extraction steam flow rate increment Δe2, etc.), and start the calculation from the back-pressure condition with the extraction steam flow rate of 0 (the minimum extraction steam flow rate) and the minimum power through the digital twin model. The main steam flow rate, the intermediate-pressure extraction steam flow rate, and the low-pressure extraction steam flow rate in the unit system are iteratively calculated by the enumeration method according to the pre-designed calculation step (increment) to obtain the data of the minimum power during the operation of the steam turbine under different main steam flow rates and different extraction steam flow rate conditions.

[0091] (2) Determine the corresponding maximum power of the unit under different main steam flow rates, different first-stage extraction steam flow rates, and different second-stage extraction steam flow rates, that is, determine the maximum output operating condition surface. The method for generating the maximum power required to draw the operating condition diagram and feasible region of the cogeneration system of the double-extraction back-pressure unit is to determine the calculation step (the calculation step can be the increment of the main steam flow rate Δm, or the increment of the intermediate-pressure extraction steam flow rate Δe1, or the increment of the intermediate-pressure extraction steam flow rate Δe2, etc.). Starting from the back-pressure operating condition with the minimum extraction steam flow rate (0) and the minimum power, calculate through the digital twin model, and perform iterative calculations on the main steam flow rate, intermediate-pressure extraction steam flow rate, and low-pressure extraction steam flow rate in the unit system by enumeration according to the pre-designed calculation step (increment), so as to obtain the data of the maximum power during the operation of the steam turbine under different main steam flow rates and different extraction steam flow rate conditions.

[0092] (3) Determine the corresponding power of the unit under different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate Dd = 0 or Dd = Ddmin, that is, determine the minimum low-pressure extraction operating condition surface. The method for generating the data of the minimum low-pressure extraction operating condition required to draw the operating condition diagram and feasible region of the cogeneration system of the double-extraction back-pressure unit is to fix the low-pressure extraction steam flow rate at 0 or Dd = Ddmin, and then determine the calculation step (the calculation step can be the increment of the main steam flow rate Δm, or the increment of the intermediate-pressure extraction steam flow rate Δe1, etc.). Starting from the back-pressure operating condition with the minimum extraction steam flow rate (0) and the minimum power in the intermediate-pressure extraction steam, calculate through the digital twin model, and perform iterative calculations on the main steam flow rate and intermediate-pressure extraction steam flow rate in the unit system by enumeration according to the pre-designed calculation step (i.e., increment) under variable operating conditions, so as to obtain the calculation data of the power generation of the unit system under different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is at the minimum value.

[0093] (4) Determine the corresponding power of the unit under different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate Dd = Ddmax, that is, determine the maximum low-pressure extraction operating condition surface. The method for generating the data of the maximum low-pressure extraction operating condition required to draw the operating condition diagram and feasible region of the cogeneration system of the double-extraction back-pressure unit is to fix the low-pressure extraction steam flow rate at Dd = Ddmax, and then determine the calculation step (the calculation step can be the increment of the main steam flow rate Δm, or the increment of the intermediate-pressure extraction steam flow rate Δe1, etc.). Starting from the single-extraction back-pressure operating condition with the minimum extraction steam flow rate (0) and the minimum power in the intermediate-pressure extraction steam, calculate through the digital twin model, and perform iterative calculations on the main steam flow rate and intermediate-pressure extraction steam flow rate in the unit system by enumeration according to the pre-designed calculation step (i.e., increment) under variable operating conditions, so as to obtain the calculation data of the power generation of the unit system under different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is Ddmax.

[0094] (5) Determine the corresponding power of the unit when the intermediate-pressure extraction steam flow rate Dg = Dgmin, different main steam flow rates, and different low-pressure extraction steam flow rates, that is, the minimum intermediate-pressure extraction steam operating condition surface. The method for generating the data of the minimum intermediate-pressure extraction steam operating condition required for drawing the operating condition diagram and the feasible region of the combined heat and power system of the double-extraction back-pressure unit is to fix the intermediate-pressure extraction steam flow rate at 0 or Dg = Dgmin, and then determine the calculation step (the calculation step can be the increment of the main steam flow rate Δm, or the increment of the low-pressure extraction steam flow rate Δe2, etc.). Starting from the back-pressure operating condition with the low-pressure extraction steam flow rate of 0 (the minimum extraction steam flow rate) and the minimum power, calculate through the digital twin model. For the main steam flow rate and the low-pressure extraction steam flow rate in the unit system, use the enumeration method to perform off-design iterative calculations according to the pre-designed calculation step (i.e., the increment), and obtain the calculation data of the power generation power of the unit system under different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate is the minimum value.

[0095] (6) Determine the corresponding power of the unit when the intermediate-pressure extraction steam flow rate Dg = Dgmax, different main steam flow rates, and different low-pressure extraction steam flow rates, that is, the maximum intermediate-pressure extraction steam operating condition surface. The method for generating the data of the maximum intermediate-pressure extraction steam operating condition required for drawing the operating condition diagram and the feasible region of the combined heat and power system of the double-extraction back-pressure unit is to fix the intermediate-pressure extraction steam flow rate at Dg = Dgmax, and then determine the calculation step (the calculation step can be the increment of the main steam flow rate Δm, or the increment of the low-pressure extraction steam flow rate Δe2, etc.). Starting from the single-extraction back-pressure operating condition with the low-pressure extraction steam flow rate of 0 (the minimum extraction steam flow rate) and the minimum power, calculate through the digital twin model. For the main steam flow rate and the low-pressure extraction steam flow rate in the unit system, use the enumeration method to perform off-design iterative calculations according to the pre-designed calculation step (i.e., the increment), and obtain the calculation data of the power generation power of the unit system under different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate is Dgmax.

[0096] (7) Determine the corresponding power of the unit when the main steam flow rate G = Gmax, different intermediate-pressure extraction steam flow rates, and different low-pressure extraction steam flow rates, that is, the maximum main steam flow rate operating condition surface. The method for generating the data of the maximum main steam flow rate operating condition required for drawing the operating condition diagram and the feasible region of the combined heat and power system of the double-extraction back-pressure unit is to determine the maximum value of the main steam flow rate as G = Gmax, and then determine the calculation step (the calculation step can be the increment of the intermediate-pressure extraction steam flow rate Δe1, or the increment of the low-pressure extraction steam flow rate Δe2, etc.). Starting from the back-pressure operating condition with the intermediate-pressure extraction steam flow rate and the low-pressure extraction steam flow rate of 0 (the minimum extraction steam flow rate) and the minimum power, calculate through the digital twin model. For the intermediate-pressure extraction steam flow rate and the low-pressure extraction steam flow rate in the unit system, use the enumeration method to perform off-design iterative calculations according to the pre-designed calculation step (i.e., the increment), and obtain the calculation data of the power generation power of the unit system under different intermediate-pressure extraction steam flow rates and low-pressure extraction steam flow rates when the main steam flow rate is Gmax.

[0097] 7. Draw a visual operating condition diagram and feasible region.

[0098] The obtained data is used to draw a visualized operating condition diagram and a feasible region through computer graphics methods. When drawing a visualized operating condition diagram and a feasible region through computer graphics methods, it is necessary to perform data denoising on the data obtained in step 3, and then connect or fit the processed data into curves or three-dimensional surfaces using computer graphics methods. Subsequently, the fitted curves and three-dimensional surfaces are combined into a three-dimensional solid figure, which can become the visualized operating condition diagram and feasible region.

[0099] The specific steps are as follows:

[0100] See Figure 4 , in this embodiment, when the double-extraction back-pressure unit draws the operating condition diagram and the feasible region according to the realized digital twin model, the step flow of using computer graphics technology is as follows:

[0101] (1) Determine the visualization objective. Clearly define the objective to be achieved through data visualization and the information to be conveyed, and determine the data set and data type to be used. The objective to be achieved through data visualization refers to the feasible region and the operating condition diagram of the target double-extraction back-pressure unit; the information to be conveyed refers to the safe operating range or area of the target double-extraction back-pressure unit and its performance under different operating conditions; the data set and data type to be used refer to the data set and data type required to draw the feasible region and the operating condition diagram of the target unit; among them, the data set includes but is not limited to the full operating condition performance data of the unit, steam state parameters, performance data of equipment in the auxiliary system, etc., and the data type refers to the data type that can be operated by the selected software or tool when drawing the feasible region and the operating condition diagram.

[0102] (2) Data preprocessing. Cleaning and processing the data to ensure its suitability for visualization means cleaning and removing the data that does not meet the operating rules of the unit from the calculated data, and selecting the data that conforms to the operating rules of the unit for drawing the feasible region and the operating condition diagram; performing necessary conversions on the data, such as calculating statistics, normalization, or other mathematical processes; performing necessary conversions on the data means improving the interpretability, standardization, comparability, calculation efficiency of the selected data through certain data processing methods, and making it more suitable for the requirements of the visualization tool.

[0103] (3) Select appropriate visualization tools and software. Visualization tools and software refer to selecting appropriate visualization tools according to the data type and visualization requirements, such as MATLAB, the Matplotlib library of Python, Tableau, or more professional three-dimensional graphics software, etc.

[0104] (4) Data mapping and modeling. Data mapping and modeling refer to mapping data into a three-dimensional or more-dimensional space, determining how to convert data points into the shape, size, and position of three-dimensional or even four-dimensional graphics in a two-dimensional plane; the created three-dimensional or four-dimensional model needs to be selected according to the types of products that the unit can actually produce, and as much unit information as possible should be comprehensively expressed; in the present invention, during the actual operation of the double-extraction back-pressure unit, in addition to expressing the steam consumption characteristics of the unit itself, since the unit will produce two different grades of heating steam, four-dimensional information needs to be expressed in a planar graph, including expressing power, main steam, and low-pressure extraction steam through three-dimensional coordinate axes, and at the same time using color or contour lines as the coordinate axis of the fourth dimension to express medium-pressure extraction steam; when expressing the feasible region and operating condition diagram of the double-extraction back-pressure unit through a four-dimensional graph, the performance change law and safety boundary of the double-extraction back-pressure unit during the adjustment between different grades of thermal energy and electric energy can be more accurately and clearly reflected; after the created model is used to express four-dimensional information, the quantitative relationship of the corresponding dimension can also be represented by the change law between different dimensions and values.

[0105] (5) Adding texture and color coding. Adding texture means adding texture to the three-dimensional model to enhance the visual effect and information expression; color coding means using color coding to represent different attributes or values of data; in the present invention, the existence of medium-pressure extraction steam during the actual operation of the target unit and the mass flow rate of medium-pressure extraction steam under different operating conditions are expressed through color coding.

[0106] (6) Setting lighting and camera perspective. Setting lighting and camera perspective means setting lighting in the scene to enhance the depth and realism of the three-dimensional graphics, defining the camera perspective and view, so as to display the data from the best angle.

[0107] (7) Rendering and optimization. Rendering and optimization mean rendering the final three-dimensional graphics, calculating lighting, shadows, colors, etc., generating the final image, and finally optimizing the graphics to ensure its clarity and easy understanding.

[0108] (8) Interaction design. Interaction design means adding interaction functions to the three-dimensional graphics, such as zooming, rotating the view, clicking to view details, etc., making the drawn feasible region and operating condition diagram more operable, and this step can be selected or discarded according to actual application requirements.

[0109] (9) Final review and adjustment. Final review and adjustment mean evaluating the visualization effect, ensuring that it accurately conveys the required information, and making corresponding adjustments and optimizations to the graphics according to the feedback to make the final result accurate.

[0110] See Figure 5 and Figure 6, which is the front and back effect display diagrams of an embodiment of a double-extraction back-pressure unit for drawing an operating condition diagram and a feasible region based on an implemented digital twin model; this diagram not only shows the feasible region of the target double-extraction back-pressure unit, but also can display the steam consumption characteristics of the unit through the relationship between power and flow rate, so as to complete the operating condition diagram of the double-extraction back-pressure heating unit.

[0111] This Figure 1 has a total of 4 dimensions, respectively expressing the power, main steam flow rate, low-pressure extraction steam volume, and medium-pressure extraction steam volume of the double-extraction back-pressure heating unit. Among them, the medium-pressure extraction steam volume is represented by color (contour lines), and the remaining variables are represented by three-dimensional coordinate axes in a two-dimensional plane. Through this method, not only can the operating range or region required to be expressed by the feasible region of the unit and the steam consumption characteristics required to be expressed by the operating condition diagram be reflected, but also the grades and corresponding quantities of the two heating extraction steams can be expressed.

[0112] Plane ABGH is the minimum low-pressure extraction steam plane of the double-extraction back-pressure heating unit. At this time, the low-pressure extraction steam volume Dd = Ddmin of the unit. Through the main steam flow rate G0 and the medium-pressure extraction steam volume Dg, according to the above steps, starting from the minimum load condition, that is, the minimum power (the lowest extraction steam volume), iterative enumeration is carried out for calculation. Through data processing with the screening condition Dd = Ddmin, all operating condition data satisfying the minimum low-pressure extraction steam plane can be obtained, where point G is the minimum load point.

[0113] Plane EDCH is the maximum low-pressure extraction steam plane of the double-extraction back-pressure heating unit. At this time, the low-pressure extraction steam volume Dd = Ddmax of the unit. Through the main steam flow rate G0 and the medium-pressure extraction steam volume Dg, according to the above steps, starting from the minimum load condition, that is, the minimum power (the lowest extraction steam volume), iterative enumeration is carried out for calculation. Through data processing with the screening condition Dd = Ddmax, all operating condition data satisfying the maximum low-pressure extraction steam plane can be obtained, where point D is the maximum load point.

[0114] Plane ABCD is the maximum medium-pressure extraction steam plane of the double-extraction back-pressure heating unit. At this time, the medium-pressure extraction steam volume Dg = Dgmax of the unit. Through the main steam flow rate G0 and the low-pressure extraction steam volume Dd, according to the above steps, starting from the minimum load condition, that is, the minimum power (the lowest extraction steam volume), iterative enumeration is carried out for calculation. Through data processing with the screening condition Dg = Dgmax, all operating condition data satisfying the maximum medium-pressure extraction steam plane can be obtained.

[0115] The plane EFGH is the minimum intermediate-pressure extraction surface of the double-extraction back-pressure heating unit. At this time, the intermediate-pressure extraction steam flow rate Dg of the unit is Dgmin. Through the main steam flow rate G0 and the low-pressure extraction steam flow rate Dd, according to the above steps, starting from the minimum load condition, that is, the minimum power (the lowest extraction steam flow rate), iterative enumeration is carried out for calculation. Through data processing with the screening condition Dg = Dgmin, all operating condition data that meet the minimum intermediate-pressure extraction surface can be obtained.

[0116] The plane ADEF is the maximum power surface of the double-extraction back-pressure heating unit. At this time, the power generation power P of the unit is Pmax. Through the main steam flow rate G0, the intermediate-pressure extraction steam flow rate, and the low-pressure extraction steam flow rate Dd, according to the above steps, starting from the minimum load condition, that is, the minimum power (the lowest extraction steam flow rate), iterative enumeration is carried out for calculation. Through data processing with the screening condition P = Pmax, all operating condition data that meet the maximum power surface can be obtained.

[0117] The plane BCHG is the minimum power surface of the unit. At this time, the power generation power P of the unit is Pmin. Through the main steam flow rate G0, the intermediate-pressure extraction steam flow rate, and the low-pressure extraction steam flow rate Dd, according to the above steps, starting from the minimum load condition, that is, the minimum power (the lowest extraction steam flow rate), iterative enumeration is carried out for calculation. Through data processing with the screening condition P = Pmin, all operating condition data that meet the minimum power surface can be obtained.

[0118] For the data between the plane ABGH and the plane EDCH, the plane ABGH is used as the calculation reference plane, and iterative enumeration calculations are carried out one by one through the set calculation step size.

[0119] Further interpreting this graph, if the graph is cut by a plane perpendicular to the main steam flow rate axis, the power change region corresponding to different extraction steam flow rates of the double-extraction back-pressure heating unit under the same main steam flow rate can be obtained; if the graph is cut by a plane perpendicular to the low-pressure extraction steam flow rate axis, the power change region corresponding to different main steam flow rates and intermediate-pressure extraction steam flow rates of the double-extraction back-pressure heating unit under the same low-pressure extraction steam flow rate can be obtained; if the graph is cut by a plane perpendicular to the power axis, the change region corresponding to different main steam flow rates and extraction steam flow rates of the double-extraction back-pressure heating unit under the same power can be obtained; if the graph is cut by a plane parallel to the intermediate-pressure extraction steam flow rate contour line, the power change region corresponding to different main steam flow rates and low-pressure extraction steam flow rates of the double-extraction back-pressure heating unit under the same intermediate-pressure extraction steam flow rate can be obtained.

[0120] The above content is only an example and explanation of the present invention. Those skilled in the art of this technology make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the structure of the present invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit, characterized in that, It includes the following steps: S1. Obtain the digital twin model of the cogeneration system of the target double-extraction back-pressure heating unit; S2. Determine the operating boundary conditions when drawing the operating condition diagram and feasible region of the cogeneration system of the double-extraction back-pressure heating unit; S3. Generate the data of the operating boundary conditions required for drawing the operating condition diagram and feasible region through the digital twin model of the cogeneration system of the double-extraction back-pressure heating unit; S4. Draw the visualized operating condition diagram and feasible region by using the data obtained in step S3 through the method of computer graphics.

2. The method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, wherein: In step S1, the digital twin model is used to reflect the attributes of the target double-extraction back-pressure heating unit, simulate the behavior of the target double-extraction back-pressure heating unit, and predict the trend of the target double-extraction back-pressure heating unit.

3. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that: In step S2, the operating condition diagram of the cogeneration system of the double-extraction back-pressure heating unit represents the steam consumption characteristic curve between the power and flow rate of the double-extraction back-pressure steam turbine generator set, and the feasible region of the cogeneration system of the double-extraction back-pressure heating unit refers to the way that can express the safe adjustment range of the thermoelectric load of the double-extraction back-pressure heating unit.

4. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that, In step S2, the operating boundary conditions when drawing the operating condition diagram and feasible region of the cogeneration system of the double-extraction back-pressure heating unit are as follows: Boundary 1. Determine the minimum output condition surface: Find the points with the minimum power of the double-extraction back-pressure heating unit under different conditions, and connect the found points in sequence to form the minimum output condition surface. Among them, the points with the minimum power of the double-extraction back-pressure heating unit under different conditions include the minimum power points corresponding to different main steam flow rates and different extraction steam flow rates; Boundary 2. Determine the maximum output condition surface: Find the points with the maximum power of the double-extraction back-pressure heating unit under different conditions, and then connect the found points in sequence to form the maximum output condition surface. Among them, the points with the maximum power of the double-extraction back-pressure heating unit under different conditions include the maximum power points corresponding to different main steam flow rates and different extraction steam flow rates; Boundary 3. Determine the minimum low-pressure extraction condition surface: Find the points of the double-extraction back-pressure heating unit at the minimum low-pressure extraction steam flow rate, and then connect the found points in sequence to form the minimum low-pressure extraction condition surface. Among them, the points of the double-extraction back-pressure heating unit at the minimum low-pressure extraction steam flow rate are the power points corresponding to different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is the smallest; Boundary 4. Determine the maximum low-pressure extraction condition surface: Find the points of the double-extraction back-pressure heating unit at the maximum low-pressure extraction steam flow rate, and then connect the found points in sequence to form the maximum low-pressure extraction condition surface. Among them, the points of the double-extraction back-pressure heating unit at the maximum low-pressure extraction steam flow rate are the power points corresponding to different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is the largest; Boundary 5. Determine the minimum intermediate-pressure extraction condition surface: Find the points of the double-extraction back-pressure heating unit at the minimum intermediate-low-pressure extraction steam flow rate, and then connect the found points in sequence to form the minimum intermediate-pressure extraction condition surface. Among them, the points of the double-extraction back-pressure heating unit at the minimum intermediate-pressure extraction steam flow rate are the power points corresponding to different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate is the smallest; Boundary 6. Determine the maximum intermediate-pressure extraction steam condition surface: Locate the points of the double-extraction back-pressure heating unit at the maximum intermediate and low-pressure extraction steam volumes, and then connect the located points in sequence to form the maximum intermediate-pressure extraction steam condition surface. Among them, the points of the double-extraction back-pressure heating unit at the maximum intermediate-pressure extraction steam volume are the power points corresponding to different main steam flows and different low-pressure extraction steam volumes when the intermediate-pressure extraction steam volume is the largest; Boundary 7. Determine the maximum main steam flow condition surface: Locate the points of the double-extraction back-pressure heating unit at the maximum main steam flow, and then connect the located points in sequence to form the maximum main steam flow condition surface. Among them, the points of the double-extraction back-pressure heating unit at the maximum main steam flow are the power points corresponding to different intermediate-pressure extraction steam volumes and different low-pressure extraction steam volumes when the main steam flow is the largest; The maximum main steam flow is the maximum steam inlet volume limit specified for the double-extraction back-pressure heating unit during the design stage.

5. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that, The specific steps of step S3 are as follows: S301. Determine the minimum power corresponding to the unit at different main steam flows, different primary extraction steam volumes, and different secondary extraction steam volumes, that is, determine the minimum output condition surface; S302. Determine the maximum power corresponding to the unit at different main steam flows, different primary extraction steam volumes, and different secondary extraction steam volumes, that is, determine the maximum output condition surface; S303. Determine the power corresponding to the unit at the minimum low-pressure extraction steam volume, different main steam flows, and different intermediate-pressure extraction steam volumes, that is, determine the minimum low-pressure extraction steam condition surface; S304. Determine the power corresponding to the unit at the maximum low-pressure extraction steam volume, different main steam flows, and different intermediate-pressure extraction steam volumes, that is, determine the maximum low-pressure extraction steam condition surface; S305. Determine the power corresponding to the unit at the minimum intermediate-pressure extraction steam volume, different main steam flows, and different low-pressure extraction steam volumes, that is, the minimum intermediate-pressure extraction steam condition surface; S306. Determine the power corresponding to the unit at the maximum intermediate-pressure extraction steam volume, different main steam flows, and different low-pressure extraction steam volumes, that is, the maximum intermediate-pressure extraction steam condition surface; S307. Determine the power corresponding to the unit at the maximum main steam flow, different intermediate-pressure extraction steam volumes, and different low-pressure extraction steam volumes, that is, the maximum main steam flow condition surface.

6. A method for drawing the condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that: In step S301, the method for generating the minimum power is as follows. Determine the calculation step size. Start the calculation from the back-pressure condition with the extraction steam volume being 0 or the minimum and the power being the minimum through the digital twin model. Perform enumeration method iterative calculations on the main steam flow, intermediate-pressure extraction steam volume, and low-pressure extraction steam volume in the double-extraction back-pressure heating unit system according to the pre-designed calculation step size to obtain the data of the minimum power during the operation of the steam turbine corresponding to different main steam flows and different extraction steam volume conditions; In step S302, the maximum power generation method is as follows: Determine the calculation step size. Start the calculation from the backpressure condition where the extraction steam flow is 0 or the minimum and the power is the minimum through the digital twin model. Use the enumeration method to perform iterative calculations on the main steam flow rate, intermediate-pressure extraction steam flow rate, and low-pressure extraction steam flow rate in the unit system according to the pre-designed calculation step size (increment). Through the iterative calculations, obtain the data with the maximum power during the operation of the steam turbine under different main steam flow rates and different extraction steam flow rate conditions; In step S303, the method for generating the minimum low-pressure extraction steam condition data is as follows: Fix the low-pressure extraction steam flow rate at 0 or the minimum. Then determine the calculation step size. Start the calculation from the backpressure condition where the intermediate-pressure extraction steam flow rate is the minimum extraction steam flow rate and the power is the minimum through the digital twin model. Use the enumeration method to perform off-design iterative calculations on the main steam flow rate and intermediate-pressure extraction steam flow rate in the unit system according to the pre-designed calculation step size to obtain the calculation data of the power generation of the unit system under different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is the minimum; In step S304, the method for generating the maximum low-pressure extraction steam condition data is as follows: Fix the low-pressure extraction steam flow rate at the maximum. Then determine the calculation step size. Start the calculation from the single-extraction backpressure condition where the intermediate-pressure extraction steam flow rate is the minimum extraction steam flow rate and the power is the minimum through the digital twin model. Use the enumeration method to perform off-design iterative calculations on the main steam flow rate and intermediate-pressure extraction steam flow rate in the unit system according to the pre-designed calculation step size (i.e., increment) to obtain the calculation data of the power generation of the unit system under different main steam flow rates and different intermediate-pressure extraction steam flow rates when the low-pressure extraction steam flow rate is the maximum; In step S305, the method for generating the minimum intermediate-pressure extraction steam condition data is as follows: Fix the intermediate-pressure extraction steam flow rate at the minimum. Then determine the calculation step size. Start the calculation from the backpressure condition where the low-pressure extraction steam flow rate is the minimum extraction steam flow rate and the power is the minimum through the digital twin model. Use the enumeration method to perform off-design iterative calculations on the main steam flow rate and low-pressure extraction steam flow rate in the unit system according to the pre-designed calculation step size to obtain the calculation data of the power generation of the unit system under different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate is the minimum; In step S306, the method for generating the maximum intermediate-pressure extraction steam condition data is as follows: Fix the intermediate-pressure extraction steam flow rate at the maximum. Then determine the calculation step size. Start the calculation from the single-extraction backpressure condition where the low-pressure extraction steam flow rate is the minimum extraction steam flow rate and the power is the minimum through the digital twin model. Use the enumeration method to perform off-design iterative calculations on the main steam flow rate and low-pressure extraction steam flow rate in the unit system according to the pre-designed calculation step size to obtain the calculation data of the power generation of the unit system under different main steam flow rates and different low-pressure extraction steam flow rates when the intermediate-pressure extraction steam flow rate is the maximum; In the step S307, the method for generating the maximum main steam flow condition data is as follows: determine the maximum main steam flow, then determine the calculation step size. Starting from the back pressure condition with the minimum extraction steam volume (0 for both the intermediate pressure extraction steam volume and the low pressure extraction steam volume) and the minimum power in the digital twin model, perform calculations. Use the enumeration method to perform off-design iteration calculations on the intermediate pressure extraction steam volume and the low pressure extraction steam volume of the unit system according to the pre-designed calculation step size, and obtain the calculation data of the power generation of the unit system under different intermediate pressure extraction steam volumes and low pressure extraction steam volumes when the main steam flow is the maximum.

7. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 6, characterized in that: The calculation step size is the increment of the main steam flow or the increment of the intermediate pressure extraction steam volume or the increment of the low pressure extraction steam volume.

8. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that: In the step S4, when drawing a visual working condition diagram and feasible region through the method of computer graphics, it is necessary to denoise the data obtained in the step S3, and then use the method of computer graphics to connect or fit the processed data into curves or three-dimensional surfaces. Subsequently, combine the fitted curves and three-dimensional surfaces into a three-dimensional solid figure, which can become the visual working condition diagram and feasible region.

9. A method for drawing the operating condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that, The step S4 specifically includes the following steps: S401. Determine the visualization target: clarify the target to be achieved through data visualization and the information to be conveyed, and determine the data set and data type to be used; S402. Data preprocessing: clean and process the data to ensure that the data is suitable for visualization; perform necessary conversions on the data, and the necessary conversions include calculating statistical quantities and normalization; S403. Select appropriate visualization tools and software; S404. Data mapping and modeling: map the data into a multi-dimensional space and determine how to convert data points into the shape, size, and position of a multi-dimensional graph in a two-dimensional plane; S405. Add textures and color coding; S406. Set lighting and camera perspectives; S407. Rendering and optimization; S408. Interaction design; S409. Final review and adjustment.

10. A method for drawing the working condition diagram and feasible region of a double-extraction back-pressure heating unit according to claim 1, characterized in that: In the step S401, the target to be achieved through data visualization refers to the feasible region and working condition diagram of the target unit; the information to be conveyed refers to the range or area of safe operation of the target unit and its performance under different working conditions; the data set and data type to be used refer to the data set and data type required for drawing the feasible region and working condition diagram of the target unit; among them, the data set includes the full working condition performance data of the unit, steam state parameters, and performance data of equipment in the auxiliary system, and the data type refers to the data type that can be operated by the software or tool selected when drawing the feasible region and working condition diagram; In the step S405, adding textures means adding textures to the multi-dimensional model to enhance the visual effect and information expression; color coding refers to using color coding to represent different attributes or values of the data; express the intermediate pressure extraction steam and the mass flow of the intermediate pressure extraction steam under different working conditions during the actual operation of the double-extraction back-pressure heating unit through color coding; In the step S407, rendering and optimization means rendering the final multi-dimensional graph, calculating lighting, shadows, and colors, generating the final image, and finally optimizing the graph; In the step S408, the interaction design refers to adding interaction functions to the multi-dimensional graph, and the interaction functions include, for example, zooming, rotating the view, and clicking to view details.

Images