Overspeed prevention system and method for steam turbine

Abstract

The invention relates to a turbine overspeed prevention system which comprises a flywheel energy storage device, a stator of the flywheel energy storage device is connected with a generator through a first switch and further connected with a bidirectional converter of a storage battery through a second switch, and the bidirectional converter is connected with a power grid through a third switch. And the power grid is connected with an outgoing line of the generator through a fourth switch. Accurate control over the rotating speed of the steam turbine is achieved, the overspeed phenomenon is effectively prevented, and the safety of system operation is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of steam turbines, and in particular relates to a steam turbine overspeed prevention system and method. Background Art

[0002] Steam turbine overspeed accidents are vicious accidents in power plants, which are extremely harmful. Steam turbine overspeed will cause blades, bolts and other parts to fly out, causing serious damage to equipment and personal injury. Generator overspeed will cause damage to sealing tiles and a large amount of hydrogen leakage from the generator end cover, which will cause hydrogen explosion accidents, causing serious damage to equipment and large-scale fire accidents on site. Although a variety of inspection and maintenance and operation adjustment methods are adopted, steam turbine overspeed accidents often occur, causing great economic losses and personal injuries.

[0003] Under the spot market model, thermal power units are started and stopped frequently, resulting in frequent problems such as oxide scale shedding. The steam inlet valve of the turbine is also stuck due to oxide scale blockage and other reasons. When the unit is shut down or trips, the steam inlet to the turbine cannot be cut off at the same time after being disconnected from the power grid, and the turbine overspeeds under the impulse of steam. Summary of the invention

[0004] (I) Purpose of the invention

[0005] In order to overcome the above disadvantages, the object of the present invention is to provide a steam turbine overspeed prevention system and method to solve the above technical problems.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the technical solutions provided by this application are as follows:

[0008] Beneficial effects:

[0009] 1. Efficient energy conversion: The flywheel energy storage device uses a flywheel made of carbon fiber composite materials, combined with a vacuum cavity design, which greatly improves the energy conversion efficiency and system response speed. Enhanced system safety:

[0010] 2. Through intelligent control strategies and algorithms, precise control of turbine speed is achieved, effectively preventing overspeed and ensuring the safety of system operation.

[0011] 3. Optimization of energy utilization: The system can intelligently distribute and convert energy between flywheel energy storage devices, batteries and power grids according to real-time needs, thereby improving energy utilization efficiency.

[0012] 4. Flexibility and adaptability: Through the multi-switch design, the system can flexibly respond to different operating states and external conditions, such as grid disconnection or loose steam inlet valves, ensuring stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0014] Figure 2 It is a structural diagram of a flywheel energy storage device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a detailed description of the present invention in conjunction with the specific implementation methods and with reference to the attached drawings. Figure 1-2 , the present invention is further described in detail. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0016] The present invention provides a steam turbine overspeed prevention system, comprising a flywheel energy storage device 5, wherein the stator of the flywheel energy storage device 5 is connected to the generator 2 through a first switch 12, and the stator of the flywheel energy storage device 5 is also connected to the bidirectional converter 7 of the battery 6 through a second switch 13, and the bidirectional converter 7 is connected to the power grid 4 through a third switch 14, and the power grid 4 is connected to the generator 2 output line through a fourth switch 15. The setting of the flywheel energy storage device can quickly absorb excess energy when the power grid is disconnected from the generator to prevent the steam turbine from overspeeding. The flywheel energy storage device is connected to the bidirectional converter 7 of the battery 6 through the second switch 13 to realize the bidirectional flow of energy, thereby improving the flexibility and energy utilization efficiency of the system.

[0017] The flywheel energy storage device 5 includes a flywheel housing 52, a vacuum cavity 55 is formed in the flywheel housing 52, and magnetic bearings 51 are provided at the upper and lower ends of the vacuum cavity 55. A rotating shaft 56 is provided on the two magnetic bearings 51, and a flywheel 53 and a flywheel generator 54 are provided on the rotating shaft 56. The material of the flywheel 53 is a carbon fiber composite material. The flywheel 53 adopts a carbon fiber composite material, which has the characteristics of high strength and light weight, can store more kinetic energy, and reduce the weight of the entire system. The flywheel generator includes a rotor and a stator. A vacuum cavity 55 is formed in the flywheel housing 52 to reduce air resistance and increase the speed and energy conversion efficiency of the flywheel. The use of magnetic bearings 51 reduces mechanical friction, prolongs the life of the equipment, and improves the response speed of the system.

[0018] The generator 2 is connected to the steam turbine 1, the steam turbine 1 includes a steam inlet valve 9, the generator 2 is connected to the excitation device 3, and the excitation device 3 is connected to the excitation starting power supply 8 through the fifth switch 10. The excitation device can provide excitation to the generator so that the generator generates voltage.

[0019] A method for preventing overspeed of a steam turbine comprises the following steps:

[0020] S1 When the fourth switch 15 between the power grid 4 and the generator 2 is disconnected, and the steam inlet valve 9 is not tightly closed, the speed of the steam turbine 1 increases rapidly from 3000r / min to 3200r / min, and the fifth switch 10 is opened so that the excitation device 3 excites the generator 2, and the generator 2 generates voltage, which helps to stabilize the power grid and reduce the impact caused by the disconnection;

[0021] S2 closes the first switch, and the flywheel 53 of the flywheel energy storage device 5 starts to rotate at an increased speed, converting kinetic energy into electrical energy for storage. The speed increase rate of the flywheel 53 is adjusted by the flywheel generator 54, and the speed of the steam turbine 1 is controlled to be below 3300r / min, so as to effectively control the speed of the steam turbine 1, prevent overspeed, and ensure system safety;

[0022] The speed of turbine 1 is controlled within a safe range. The algorithm is as follows:

[0023]

[0024] Where u(t) is the controller output, e(t) is the deviation, i.e. the difference between the target speed and the actual speed, and Kp, Ki, and Kd are the proportional, integral, and differential gains, respectively.

[0025] Using this algorithm, the speed increase rate of the flywheel generator can be accurately adjusted, the speed of the steam turbine can be accurately controlled, and the stability and reliability of the system can be improved.

[0026] After the S3 steam inlet valve 9 is processed to be tight or the air intake source is depressurized, the speed of the steam turbine 1 decreases, the first switch is opened, the second switch is closed, the switch between the battery 6 and the bidirectional converter 7 or the third switch is closed 14, and the flywheel energy storage device 5 supplies power to the battery or the power grid. By switching the switch reasonably, the energy stored in the flywheel energy storage device is released to the battery or the power grid, which can provide emergency power support for the power grid and charge the battery, thereby enhancing the energy security capability of the system;

[0027] After the energy of the S4 flywheel energy storage device is released, open the switch between the battery and the bidirectional converter or the third switch, and open the second switch. After the energy of the flywheel energy storage device is released, disconnect the relevant switches in time to avoid energy waste, and prepare for the next energy storage, thereby improving the overall operation efficiency of the system.

[0028] The steam turbine overspeed prevention system of the present invention realizes precise control of steam turbine speed and effective management of energy through a series of innovative designs and intelligent control strategies, and has the following significant beneficial effects:

[0029] 1. Efficient energy conversion: The flywheel energy storage device uses a flywheel made of carbon fiber composite materials, combined with a vacuum cavity design, which greatly improves the energy conversion efficiency and system response speed. Enhanced system safety: 2. Through intelligent control strategies and algorithms, precise control of the turbine speed is achieved, effectively preventing overspeed and ensuring the safety of system operation. 3. Energy utilization optimization: The system can intelligently distribute and convert energy between the flywheel energy storage device, battery and power grid according to real-time needs, improving energy utilization efficiency. 4. Flexibility and adaptability: Through multi-switch design, the system can flexibly respond to different operating conditions and external conditions, such as disconnection of the power grid or loose steam inlet valves, ensuring the stable operation of the system.

[0030] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A steam turbine overspeed prevention system, characterized in that: It includes a flywheel energy storage device, the stator of which is connected to the generator through a first switch, the stator of which is also connected to a bidirectional converter of a battery through a second switch, the bidirectional converter is connected to a power grid through a third switch, and the power grid is connected to an output line of the generator through a fourth switch.

2. A steam turbine overspeed prevention system according to claim 1, characterized in that: The flywheel energy storage device comprises a flywheel housing, a vacuum cavity is formed in the flywheel housing, magnetic bearings are arranged at the upper and lower ends of the vacuum cavity, a rotating shaft is arranged on the two magnetic bearings, a flywheel and a flywheel generator are arranged on the rotating shaft, and the flywheel generator comprises a rotor and a stator.

3. A steam turbine overspeed prevention system according to claim 2, characterized in that: The flywheel is made of carbon fiber composite material.

4. A steam turbine overspeed prevention system according to claim 1, characterized in that: The generator is connected to a steam turbine, the steam turbine includes a steam inlet valve, the generator is connected to an excitation device, and the excitation device is connected to an excitation starting power supply through a fifth switch.

5. A method for preventing overspeed of a steam turbine, characterized in that: The following steps are involved: S1 When the fourth switch between the power grid and the generator is disconnected and the steam inlet valve is not tightly closed, the turbine speed rises rapidly from 3000r / min to 3200r / min, and the fifth switch is turned on so that the excitation device excites the generator, and the generator generates voltage; S2 closes the first switch, and the flywheel of the flywheel energy storage device starts to increase its speed and rotates, converting kinetic energy into electrical energy for storage. The speed increase rate of the flywheel is adjusted through the flywheel generator to control the speed of the steam turbine below 3300r / min; After the S3 steam inlet valve is treated to be tight or the air inlet source is depressurized, the speed of the steam turbine decreases, the first switch is opened, the second switch is closed, the switch between the battery and the bidirectional converter or the third switch is closed, and the flywheel energy storage device supplies power to the battery or the grid; After the energy of the S4 flywheel energy storage device is released, the switch between the battery and the bidirectional converter or the third switch is opened, and the second switch is opened.

6. A method for preventing overspeed of a steam turbine according to claim 5, characterized in that: To control the speed of the steam turbine within a safe range, the algorithm is as follows: Where u(t) is the controller output, e(t) is the deviation, i.e. the difference between the target speed and the actual speed, and Kp, Ki, and Kd are the proportional, integral, and differential gains, respectively.

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