Multi-mode intelligent control system for steam turbine shaft seal electric heater

Abstract

The invention provides a multi-mode intelligent control system for a steam turbine shaft seal electric heater. The multi-mode intelligent control system comprises a high-pressure cylinder, an intermediate-pressure cylinder, the shaft seal electric heater, a multi-redundancy sensing system and an intelligent control unit. The high-pressure cylinder and the medium-pressure cylinder are respectively provided with a high-pressure cylinder shaft seal and a medium-pressure cylinder shaft seal; the shaft seal electric heater is respectively connected with a high-pressure cylinder shaft seal steam inlet main pipe and a medium-pressure cylinder shaft seal steam inlet main pipe through a shaft seal electric heater inlet pipeline and a shaft seal electric heater outlet pipeline; the high-pressure cylinder shaft seal steam inlet header pipe and the intermediate-pressure cylinder shaft seal steam inlet header pipe are respectively connected with a high-pressure cylinder shaft seal and an intermediate-pressure cylinder shaft seal; the shaft seal electric heater is provided with a multi-redundancy sensing system; the intelligent control unit controls the system to operate. The system solves the problems that a traditional shaft seal system is low in temperature control precision, poor in working condition adaptability, insufficient in automation level and the like, has the advantages of being high in control precision, safe, reliable and good in integration degree, and is suitable for intelligent control and transformation of a steam turbine shaft seal system of a modern power plant.

Description

Technical Field

[0001] This invention belongs to the field of thermal power plant thermal system control technology, specifically relating to a multimodal intelligent control system for a steam turbine shaft seal electric heater. Background Technology

[0002] The turbine shaft sealing system is a crucial component of thermal power generating units. Its primary function is to prevent high-pressure steam leakage and the entry of external air into the cylinders, which could affect unit efficiency and safety. Traditional shaft sealing systems mostly employ steam sealing; however, during unit start-up, shutdown, or low-load operation, large fluctuations in steam parameters can easily lead to water carryover or temperature mismatch in the shaft sealing steam, resulting in problems such as equipment corrosion and increased vibration. Current technologies lack precise control over the shaft sealing steam temperature and adaptability to various operating conditions, especially under special conditions such as hot and extremely hot states, making it difficult to guarantee system stability and safety. Therefore, it is necessary to propose a control system capable of achieving precise control of the shaft sealing steam temperature and improving system adaptability. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of inaccurate steam temperature control and poor adaptability to operating conditions in existing steam turbine shaft seal systems, and to propose a multimodal intelligent control system for steam turbine shaft seal electric heaters.

[0004] A multimodal intelligent control system for a turbine shaft seal electric heater includes a high-pressure cylinder, an intermediate-pressure cylinder shaft seal electric heater, a multi-redundant sensing system, and an intelligent control unit. The high-pressure cylinder and intermediate-pressure cylinder are respectively equipped with high-pressure cylinder shaft seals and intermediate-pressure cylinder shaft seals. The shaft seal electric heater is connected to the high-pressure cylinder shaft seal steam inlet manifold and the intermediate-pressure cylinder shaft seal steam inlet manifold via an inlet pipe and an outlet pipe, respectively. The high-pressure cylinder shaft seal steam inlet manifold and the intermediate-pressure cylinder shaft seal steam inlet manifold are respectively connected to the high-pressure cylinder shaft seal and the intermediate-pressure cylinder shaft seal. The shaft seal electric heater is equipped with a multi-redundant sensing system. The intelligent control unit controls the operation of the control system.

[0005] Furthermore, the multi-redundant sensing system includes three inlet temperature sensors, three outlet temperature sensors, and two pressure sensors, with the two pressure sensors respectively installed at the inlet and outlet ends of the shaft seal electric heater.

[0006] Furthermore, the shaft seal electric heater inlet pipe is sequentially equipped with a shaft seal electric heater inlet shut-off valve, shaft seal electric heater inlet temperature sensor A, shaft seal electric heater inlet temperature sensor B, and shaft seal electric heater inlet temperature sensor C along the steam flow direction; the shaft seal electric heater outlet pipe is equipped with a shaft seal electric heater outlet temperature sensor A, shaft seal electric heater outlet temperature sensor B, shaft seal electric heater outlet temperature sensor C, and shaft seal electric heater outlet shut-off valve.

[0007] Furthermore, a bypass pipe for the high-pressure cylinder shaft seal is connected between the main steam inlet pipe of the high-pressure cylinder shaft seal and the inlet and outlet pipes of the shaft seal electric heater. The bypass pipe for the high-pressure cylinder shaft seal is equipped with a bypass check valve and a bypass shut-off valve.

[0008] Furthermore, a bypass pipeline for the intermediate pressure cylinder shaft seal steam inlet main pipe and the heater pipeline is connected between the shaft seal electric heater intermediate pressure cylinder bypass pipeline, and a bypass check valve and a bypass shut-off valve for the shaft seal electric heater intermediate pressure cylinder are installed on the shaft seal electric heater intermediate pressure cylinder bypass pipeline.

[0009] Furthermore, the intelligent control unit executes multimodal operating logic, which includes:

[0010] Cold start mode: The electric heater body is kept in a de-energized state, allowing it to be used as a steam passage;

[0011] Hot start mode: Control the electric heater body to start, set its outlet temperature target value to the first predetermined temperature, and use PID algorithm to adjust its heating power;

[0012] Extremely hot start-up mode: Control the electric heater body to start, and set its outlet temperature target value to a second predetermined temperature that is higher than the first predetermined temperature. Use PID algorithm to adjust its heating power.

[0013] Emergency stop mode: The electric heater body is started by interlock and its outlet temperature target value is set to the third predetermined temperature. The heating power is adjusted by PID algorithm.

[0014] Furthermore, the intelligent control unit is also configured to execute intelligent protection and interlocking logic, which includes:

[0015] Start-up condition judgment: The electric heater body is started when the following four conditions are met simultaneously: the feeder switch of the electric heater body is closed, the remote start signal is valid, and the inlet and outlet pressure difference detected by the multi-redundant sensor system is greater than the first predetermined threshold.

[0016] Trip protection condition judgment: If any of the following conditions are met: the internal temperature of the electric heater body detected by the multi-redundant sensing system reaches the fourth predetermined threshold, the inlet and outlet pressure difference is lower than the second predetermined threshold, or the inlet and outlet temperature difference exceeds the third predetermined threshold, the operation of the electric heater body shall be stopped immediately.

[0017] Furthermore, the bypass check valve, the bypass shut-off valve, the intermediate pressure cylinder bypass check valve, and the intermediate pressure cylinder bypass shut-off valve of the shaft seal electric heater all have a non-reverse function and automatically switch bypasses according to the positive or negative pressure difference.

[0018] Furthermore, the intelligent control unit is implemented using a DCS or a programmable logic controller; the multi-redundant sensing system and the intelligent control unit transmit data using a 4-20mA analog signal.

[0019] Furthermore, the intelligent control unit's embedded control algorithm supports configurable strategies for PID and fuzzy PID.

[0020] The beneficial effects of this invention are as follows: This invention achieves precise control of the shaft seal steam temperature through a shaft seal electric heater and its control system, while avoiding excessively low or high steam temperatures, thus improving system safety; it employs multiple redundant temperature and pressure detection systems to enhance system reliability and adaptability; it is equipped with a bypass system that can automatically increase bypass operation according to the pressure difference direction to meet the steam flow area and heating requirements under different operating conditions, ensuring continuous and stable unit operation; it is applicable to various operating conditions such as hot and extremely hot states, and has strong engineering practicality and promotional value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the present invention;

[0022] Figure 2 This is a flowchart of the present invention.

[0023] In the diagram: 1. High-pressure cylinder; 2. High-pressure cylinder shaft seal; 3. Intermediate-pressure cylinder shaft seal; 4. Intermediate-pressure cylinder; 5. Shaft seal electric heater inlet pipe; 6. Shaft seal electric heater inlet temperature sensor A; 7. Shaft seal electric heater inlet temperature sensor B; 8. Shaft seal electric heater inlet temperature sensor C; 9. Shaft seal electric heater inlet and outlet pressure sensors A; 10. Shaft seal electric heater outlet temperature sensor A; 11. Shaft seal electric heater outlet temperature sensor B; 12. Shaft seal electric heater outlet temperature sensor C; 13. Shaft seal electric heater outlet pipe; 14. Shaft seal 15. Pressure sensor B for inlet and outlet of electric heater; 16. Shaft seal electric heater; 17. Bypass pipeline for high-pressure cylinder of shaft seal electric heater; 18. Bypass check valve for high-pressure cylinder of shaft seal electric heater; 19. Bypass shut-off valve for high-pressure cylinder of shaft seal electric heater; 20. Steam inlet main pipe for high-pressure cylinder shaft seal; 21. Bypass pipeline for intermediate-pressure cylinder of shaft seal electric heater; 22. Bypass check valve for intermediate-pressure cylinder of shaft seal electric heater; 23. Bypass shut-off valve for intermediate-pressure cylinder shaft seal; 24. Inlet shut-off valve for shaft seal electric heater; 25. Outlet shut-off valve for shaft seal electric heater. Detailed Implementation

[0024] The present invention will now be further described with reference to the accompanying drawings.

[0025] Specific implementation method one: Combining Figure 1This embodiment describes a multi-modal intelligent control system for a turbine shaft seal electric heater, comprising a high-pressure cylinder 1, an intermediate-pressure cylinder 4, a shaft seal electric heater 15, a multi-redundant sensing system, and an intelligent control unit. The high-pressure cylinder 1 and intermediate-pressure cylinder 4 are respectively equipped with a high-pressure cylinder shaft seal 2 and an intermediate-pressure cylinder shaft seal 3. The shaft seal electric heater 15 is connected to the high-pressure cylinder shaft seal steam inlet manifold 19 and the intermediate-pressure cylinder shaft seal steam inlet manifold 23 via a shaft seal electric heater inlet pipe 5 and a shaft seal electric heater outlet pipe 13, respectively. The high-pressure cylinder shaft seal steam inlet manifold 19 and the intermediate-pressure cylinder shaft seal steam inlet manifold 23 are respectively connected to the high-pressure cylinder shaft seal 2 and the intermediate-pressure cylinder shaft seal 3. The shaft seal electric heater 15 is equipped with a multi-redundant sensing system. The intelligent control unit controls the operation of the control system.

[0026] The intelligent control unit has sensor fault diagnosis and automatic signal rejection functions.

[0027] Specific Implementation Method Two: Combining Figure 1 This embodiment describes a redundant sensing system comprising three inlet temperature sensors, three outlet temperature sensors, and two pressure sensors. The two pressure sensors are respectively installed at the inlet and outlet ends of the shaft seal electric heater 15.

[0028] The intelligent control unit receives signals from the inlet and outlet pressure sensors A9 and B14 of the shaft seal electric heater (using two-out-of-one logic) to assist in judging the working status of the heater and the steam flow. Other components and connection methods are the same as in Specific Implementation Method 1.

[0029] Specific implementation method three: Combining Figure 1 In this embodiment, the shaft seal electric heater inlet pipe 5 is sequentially equipped with a shaft seal electric heater inlet shut-off valve 24, a shaft seal electric heater inlet temperature sensor A6, a shaft seal electric heater inlet temperature sensor B7, and a shaft seal electric heater inlet temperature sensor C8 along the steam flow direction; and the shaft seal electric heater outlet pipe 13 is equipped with a shaft seal electric heater outlet temperature sensor A10, a shaft seal electric heater outlet temperature sensor B11, a shaft seal electric heater outlet temperature sensor C12, and a shaft seal electric heater outlet shut-off valve 25.

[0030] The shaft seal electric heater 15 is an electric heater with stepless power adjustment. Its control unit receives signals from three inlet temperature sensors and three outlet temperature sensors. The control logic adopts the middle or average of three values ​​to ensure the reliability of the measurement. Other components and connection methods are the same as in specific implementation method two.

[0031] Specific implementation method four: Combination Figure 1In this embodiment, the high-pressure cylinder shaft seal steam inlet main pipe 19 is connected to the shaft seal electric heater inlet pipe 5 and outlet pipe 13 via a shaft seal electric heater high-pressure cylinder bypass pipe 16. The shaft seal electric heater high-pressure cylinder bypass pipe 16 is equipped with a shaft seal electric heater high-pressure cylinder bypass check valve 17 and a shaft seal electric heater high-pressure cylinder bypass shut-off valve 18. Other components and connection methods are the same as in specific embodiment three.

[0032] Specific Implementation Method Five: Combining Figure 1 In this embodiment, a bypass pipe 20 for the intermediate pressure cylinder shaft seal steam inlet main pipe 23 and the heater pipe is connected between them. The bypass pipe 20 for the intermediate pressure cylinder of the shaft seal electric heater is equipped with a bypass check valve 21 and a bypass shut-off valve 22 for the intermediate pressure cylinder of the shaft seal electric heater.

[0033] The two bypasses can automatically increase their operation according to the direction of the pressure difference to meet the steam flow area and heating requirements under different operating conditions, ensuring the continuous and stable operation of the unit. Other components and connection methods are the same as in Specific Implementation Method 4.

[0034] Specific Implementation Method Six: Combination Figure 1 This embodiment describes an intelligent control unit that executes multimodal operating logic, which includes:

[0035] Cold start mode: The electric heater body is kept in a de-energized state, allowing it to be used as a steam passage;

[0036] Hot start mode: Control the electric heater body to start, set its outlet temperature target value to the first predetermined temperature, and use PID algorithm to adjust its heating power;

[0037] Extremely hot start-up mode: Control the electric heater body to start, and set its outlet temperature target value to a second predetermined temperature that is higher than the first predetermined temperature. Use PID algorithm to adjust its heating power.

[0038] Emergency shutdown mode: The electric heater body is started by interlock and its outlet temperature target value is set to the third predetermined temperature. The heating power is adjusted by PID algorithm. Other components and connection methods are the same as in specific implementation method one.

[0039] Specific implementation method seven: Combining Figure 1 In this embodiment, the intelligent control unit is further configured to execute intelligent protection and interlocking logic, which includes:

[0040] Start-up condition judgment: The electric heater body is started when the following four conditions are met simultaneously: the feeder switch of the electric heater body is closed, the remote start signal is valid, and the inlet and outlet pressure difference detected by the multi-redundant sensor system is greater than the first predetermined threshold.

[0041] Trip protection condition judgment: If any of the following conditions are met: the internal temperature of the electric heater body detected by the multi-redundant sensing system reaches the fourth predetermined threshold, the inlet and outlet pressure difference is lower than the second predetermined threshold, or the inlet and outlet temperature difference exceeds the third predetermined threshold, the operation of the electric heater body will be stopped immediately. Other components and connection methods are the same as in specific implementation method six.

[0042] Specific implementation method eight: Combination Figure 1 This embodiment describes the bypass check valve, bypass shut-off valve, intermediate pressure cylinder bypass check valve, and intermediate pressure cylinder bypass shut-off valve of the shaft seal electric heater. These valves have a backflow prevention function and automatically switch bypasses according to the positive or negative pressure difference. Other components and connection methods are the same as in specific embodiment five.

[0043] Specific Implementation Method Nine: Combining Figure 1 This embodiment describes an intelligent control unit implemented using a DCS or a programmable logic controller; data transmission between the multi-redundant sensing system and the intelligent control unit is achieved using a 4-20mA analog signal.

[0044] Specific Implementation Method Ten: Combining Figure 1 This embodiment describes an intelligent control unit whose embedded control algorithm supports configurable strategies for PID and fuzzy PID.

[0045] This invention monitors the inlet and outlet steam temperatures in real time and dynamically adjusts the power of the shaft seal electric heater 15 via a control unit, stabilizing the outlet steam temperature within a set range and effectively preventing the shaft seal steam temperature from being too low or too high. A check valve on the bypass pipeline prevents steam from flowing only through the electric heater circuit during hot, extremely hot, and emergency shutdown conditions, ensuring system safety. This invention is particularly suitable for various operating conditions such as hot and extremely hot start-up and emergency shutdown of the unit, significantly improving the safety, adaptability, and reliability of the turbine shaft seal system.

[0046] Working Principle: During unit operation, the shaft seal steam enters the shaft seal electric heater 15 through the inlet pipe 5. Inlet temperature sensors A6, B7, and C8 monitor the steam temperature in real time and transmit the signal to the control unit. The intelligent control unit adjusts the power of the shaft seal electric heater 15 based on the difference between the set temperature and the actual temperature, achieving precise control of the outlet steam temperature. Outlet temperature sensors A10, B11, and C12 monitor the heated steam temperature, forming a closed-loop control. Inlet and outlet pressure sensors A9 and B14 monitor the pressure difference across the heater to determine whether heating should commence. The purpose of the bypass is to ensure that, under normal operating conditions, a large amount of steam leaks from the turbine to the outside, requiring additional pipelines to allow the large flow of steam to flow out smoothly. Under hot, extremely hot, and emergency shutdown conditions, steam is supplied to the turbine from the outside, the flow rate is reduced, and the steam must be heated to a certain temperature by an electric heater before being supplied to the turbine to ensure safe operation.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multimodal intelligent control system for a steam turbine shaft seal electric heater, characterized in that, The system includes a high-pressure cylinder (1), an intermediate-pressure cylinder (4), a shaft seal electric heater (15), a multi-redundant sensing system, and an intelligent control unit. The high-pressure cylinder (1) and the intermediate-pressure cylinder (4) are respectively equipped with a high-pressure cylinder shaft seal (2) and an intermediate-pressure cylinder shaft seal (3). The shaft seal electric heater (15) is connected to the high-pressure cylinder shaft seal steam inlet manifold (19) and the intermediate-pressure cylinder shaft seal steam inlet manifold (23) through the shaft seal electric heater inlet pipe (5) and the shaft seal electric heater outlet pipe (13), respectively. The high-pressure cylinder shaft seal steam inlet manifold (19) and the intermediate-pressure cylinder shaft seal steam inlet manifold (23) are respectively connected to the high-pressure cylinder shaft seal (2) and the intermediate-pressure cylinder shaft seal (3). The shaft seal electric heater (15) is equipped with a multi-redundant sensing system. The intelligent control unit controls the operation of the system.

2. The multi-modal intelligent control system for a turbine shaft seal electric heater according to claim 1, characterized in that, The multi-redundant sensing system includes three inlet temperature sensors, three outlet temperature sensors, and two pressure sensors. The two pressure sensors are respectively installed at the inlet and outlet ends of the shaft seal electric heater (15).

3. The multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 2, characterized in that, The shaft seal electric heater inlet pipe (5) is sequentially equipped with a shaft seal electric heater inlet shut-off valve (24), shaft seal electric heater inlet temperature sensor A (6), shaft seal electric heater inlet temperature sensor B (7) and shaft seal electric heater inlet temperature sensor C (8) along the steam flow direction; the shaft seal electric heater outlet pipe (13) is equipped with a shaft seal electric heater outlet temperature sensor A (10), shaft seal electric heater outlet temperature sensor B (11), shaft seal electric heater outlet temperature sensor C (12) and shaft seal electric heater outlet shut-off valve (25).

4. The multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 3, characterized in that, The high-pressure cylinder shaft seal steam inlet manifold (19) is connected to the shaft seal electric heater inlet pipe (5) and outlet pipe (13) by a shaft seal electric heater high-pressure cylinder bypass pipe (16). The shaft seal electric heater high-pressure cylinder bypass pipe (16) is equipped with a shaft seal electric heater high-pressure cylinder bypass check valve (17) and a shaft seal electric heater high-pressure cylinder bypass shut-off valve (18).

5. The multi-modal intelligent control system for a turbine shaft seal electric heater according to claim 4, characterized in that, The intermediate pressure cylinder shaft seal steam inlet main pipe (23) and the heater pipe are connected by a shaft seal electric heater intermediate pressure cylinder bypass pipe (20). The shaft seal electric heater intermediate pressure cylinder bypass pipe (20) is equipped with a shaft seal electric heater intermediate pressure cylinder bypass check valve (21) and a shaft seal electric heater intermediate pressure cylinder bypass shut-off valve (22).

6. The multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 1, characterized in that, The intelligent control unit executes multimodal operation logic, which includes: Cold start mode: The electric heater body is kept in a de-energized state, allowing it to be used as a steam passage; Hot start mode: Control the electric heater body to start, set its outlet temperature target value to the first predetermined temperature, and use PID algorithm to adjust its heating power; Extremely hot start-up mode: Control the electric heater body to start, and set its outlet temperature target value to a second predetermined temperature that is higher than the first predetermined temperature. Use PID algorithm to adjust its heating power. Emergency stop mode: The electric heater body is started by interlock and its outlet temperature target value is set to the third predetermined temperature. The heating power is adjusted by PID algorithm.

7. The multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 6, characterized in that, The intelligent control unit is also configured to execute intelligent protection and interlocking logic, which includes: Start-up condition judgment: The electric heater body is started when the following four conditions are met simultaneously: the feeder switch of the electric heater body is closed, the remote start signal is valid, and the inlet and outlet pressure difference detected by the multi-redundant sensor system is greater than the first predetermined threshold. Trip protection condition judgment: If any of the following conditions are met: the internal temperature of the electric heater body detected by the multi-redundant sensing system reaches the fourth predetermined threshold, the inlet and outlet pressure difference is lower than the second predetermined threshold, or the inlet and outlet temperature difference exceeds the third predetermined threshold, the operation of the electric heater body shall be stopped immediately.

8. The multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 5, characterized in that, The bypass check valve (17), bypass shut-off valve (18), bypass check valve (21), and bypass shut-off valve (22) of the high-pressure cylinder of the shaft seal electric heater have a non-reverse function and automatically switch the bypass according to the positive or negative pressure difference.

9. A multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 7, characterized in that, The intelligent control unit is implemented using a DCS or a programmable logic controller; the multi-redundant sensing system and the intelligent control unit transmit data using a 4-20mA analog signal.

10. A multi-modal intelligent control system for a steam turbine shaft seal electric heater according to claim 9, characterized in that, The intelligent control unit has an embedded control algorithm that supports configurable strategies for PID and fuzzy PID.

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