An automatic load reduction method for boiler trip

Abstract

The present invention specifically relates to a high- and low-pressure bypass control system for a reheat unit in the power generation industry. This high- and low-pressure bypass control system includes: a high- and low-pressure bypass system load control module, an axial displacement latching calculation module, a unit detection module, a high-pressure bypass valve, and a low-pressure bypass valve; lock the current axial displacement value according to the operating state of the steam turbine, and control the corresponding bypass valve to perform load increasing or decreasing actions; the axial displacement latching calculation module is adapted to calculate the axial displacement change amount, and the unit detection module is adapted to detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress, that is, alternately control the high-pressure bypass valve and the low-pressure bypass valve to perform corresponding actions; the present invention has the function of automatically controlling the high- and low-pressure bypass during the steam turbine load increase and decrease periods during boiler parallel and steam disconnection, and overcomes the problem of the traditional high- and low-pressure bypass system having a thrust bearing burning accident during normal load reduction and shutdown.

Description

[0001] This application is a divisional application. The application number of the original application is 202110020910.6, the application date is January 8, 2021, and it is a divisional application of the invention titled "A High and Low Pressure Bypass Control System for Intermediate Reheat Units in the Power Generation Industry". Technical Field

[0002] The present invention belongs to the technical field of reheat units, and specifically relates to a high and low pressure bypass control system for intermediate reheat units in the power generation industry. Background Art

[0003] With the continuous increase of the urbanization rate in China and people's attention to the living environment, the market competition in the waste incineration power generation industry is fierce, the waste treatment fee is getting lower and lower, and at the same time, the environmental protection emission standards are getting stricter, resulting in higher and higher operating costs and narrower and narrower profit margins. At present, the overall thermal efficiency of domestic conventional waste power generation projects is about 21%. The Jiangyin Phase III project adopts the reheat technology of two boilers and one turbine with header system in the industry. After third-party functional testing, the overall thermal efficiency of the plant reaches 28.69%, and the power generation per ton of waste incinerated is 595 kW·h / t. However, there are many technical problems in the bypass system control of the header system reheat unit, which hinder the popularization and use of this technology. Specifically as follows: The layout of the high and low pressure bypass systems is complex, and the operation is complicated; during the boiler parallel and steam disconnection periods, it is difficult to operate the steam turbine to increase or decrease the load, and the accident rate is high. The traditional bypass system control of the header system reheat unit has a thrust bearing burning accident during normal load reduction and shutdown; after investigation, the two boilers and one turbine header system reheat unit operating in the foreign Vietnam coal power project also has difficulty in operating the steam turbine to increase or decrease the load during the boiler parallel and steam disconnection periods, and has had a thrust bearing burning accident.

[0004] Therefore, it is urgent to develop a new high and low pressure bypass control system for intermediate reheat units in the power generation industry to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a high and low pressure bypass control system for intermediate reheat units in the power generation industry.

[0006] To solve the above technical problems, the present invention provides a high and low pressure bypass control system for a reheat unit in the power generation industry, including: a high and low pressure bypass system load control module, an axial displacement latching calculation module electrically connected to the high and low pressure bypass system load control module, a unit detection module, a high pressure bypass valve, and a low pressure bypass valve; wherein the high and low pressure bypass system load control module is adapted to lock the current axial displacement value according to the operating state of the steam turbine, the axial displacement latching calculation module is adapted to calculate the axial displacement change amount through the locked current axial displacement value, the unit detection module is adapted to detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress; and after the boiler starts and is put into parallel operation, the high and low pressure bypass system load control module gradually closes the high pressure bypass valve and the low pressure bypass valve by alternately controlling them repeatedly until the high pressure bypass valve is closed to zero and the low pressure bypass valve is closed to zero, that is, controlling the steam turbine to increase the load; and after the boiler to be taken out of service is given, the high and low pressure bypass system load control module gradually opens the high pressure bypass valve and the low pressure bypass valve by alternately controlling them repeatedly until the high pressure bypass valve is fully opened and the low pressure bypass valve is fully opened, that is, controlling the steam turbine to reduce the load.

[0007] Further, after the boiler starts and is put into parallel operation, the high and low pressure bypass system load control module is adapted to lock the current axial displacement value of the steam turbine and control the high pressure bypass valve to gradually close at a set rate; the high and low pressure bypass system load control module is adapted to detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress through the unit detection module. When the cylinder temperature increase rate and the differential expansion change amount reach the set values, the high and low pressure bypass system load control module is adapted to control the high pressure bypass valve to stop closing and maintain the opening for warming up; the high and low pressure bypass system load control module is adapted to calculate the difference between the increased axial displacement amount and the locked axial displacement value through the axial displacement latching calculation module. When the difference reaches the set value, the high and low pressure bypass system load control module is adapted to control the high pressure bypass valve to maintain the current opening and start to close the low pressure bypass valve; the high and low pressure bypass system load control module is adapted to detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress through the unit detection module. When the cylinder temperature increase rate and the differential expansion change amount reach the set values, the high and low pressure bypass system load control module is adapted to control the low pressure bypass valve to stop closing and maintain the opening for warming up; the high and low pressure bypass system load control module is adapted to calculate the difference between the decreased axial displacement amount and the locked axial displacement value through the axial displacement latching calculation module. When the difference returns to the locked value, the high and low pressure bypass system load control module is adapted to control the low pressure bypass valve to maintain the current opening and start to close the high pressure bypass valve, that is, the high and low pressure bypass system load control module is adapted to alternately control the high pressure bypass valve and the low pressure bypass valve to gradually close until the high pressure bypass valve is closed to zero and the low pressure bypass valve is closed to zero.

[0008] Further, after the boiler to be disconnected from the grid is shut down, the load control module of the high and low pressure bypass system is adapted to lock the current axial displacement value of the steam turbine and gradually open the low pressure bypass valve at a set rate; the load control module of the high and low pressure bypass system is adapted to detect the unit load reduction rate, cylinder temperature reduction rate, differential expansion change amount and unit stress through the unit detection module. When any one of the parameters reaches the corresponding set value, the load control module of the high and low pressure bypass system is adapted to control the low pressure bypass valve to stop opening and maintain at this opening for warm-up; the load control module of the high and low pressure bypass system is adapted to calculate the difference between the reduced amount of axial displacement and the locked axial displacement value through the axial displacement latching calculation module. When the difference reaches the set value, the load control module of the high and low pressure bypass system is adapted to control the low pressure bypass valve to maintain the current opening and start to open the high pressure bypass valve; the load control module of the high and low pressure bypass system is adapted to calculate the difference between the increased amount of axial displacement and the locked axial displacement value through the axial displacement latching calculation module. When the difference returns to the locked value, the load control module of the high and low pressure bypass system is adapted to control the high pressure bypass valve to maintain the current opening and start to open the low pressure bypass valve, that is, the load control module of the high and low pressure bypass system is adapted to repeatedly and alternately control the high pressure bypass valve and the low pressure bypass valve to gradually open until the high pressure bypass valve is fully open and the low pressure bypass valve is fully open.

[0009] Further, each steam turbine is equipped with two boilers. Each boiler directly reduces the temperature and pressure of the main steam generated by the superheater in the boiler and then directly incorporates it into the cold end header of the reheater through the corresponding high pressure bypass valve, so as to be sent to the reheater of the corresponding boiler. That is, the reheated steam generated by each reheater is transported to the intermediate and low pressure cylinders of the steam turbine.

[0010] Further, each boiler is provided with a corresponding low pressure bypass valve, that is, the low pressure bypass valve directly reduces the temperature and pressure of the reheated steam generated by the reheater of the corresponding boiler and then transports it into the condenser.

[0011] On the other hand, the present invention provides a method for automatically increasing the load during boiler parallel steaming, which includes: after the boiler starts and parallel steams, locking the current axial displacement value of the steam turbine and gradually closing the high-pressure bypass valve at a set rate; detecting in real time the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress. When the cylinder temperature increase rate and differential expansion change amount reach the set values, the high-pressure bypass valve stops closing and remains at this opening for warming up; calculating the difference between the increased amount of axial displacement and the locked axial displacement value. When the difference reaches the set value, controlling the high-pressure bypass valve to maintain the current opening and starting to close the low-pressure bypass valve; detecting in real time the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress. When the cylinder temperature increase rate and differential expansion change amount reach the set values, the low-pressure bypass valve stops closing and remains at this opening for warming up; calculating the difference between the decreased amount of axial displacement and the locked axial displacement value. When the difference returns to the locked value, controlling the low-pressure bypass valve to maintain the current opening and starting to close the high-pressure bypass valve; repeatedly and alternately controlling the high-pressure bypass valve and the low-pressure bypass valve to gradually close until the high-pressure bypass valve is closed to zero and the low-pressure bypass valve is closed to zero.

[0012] Further, it is suitable for working with the high- and low-pressure bypass control systems of intermediate reheat units for the power generation industry as described above.

[0013] In the third aspect, the present invention provides a method for automatically reducing the load during boiler shutdown, which includes: after giving the boiler to be shut down and taken out of service, locking the current axial displacement value of the steam turbine and gradually opening the corresponding low-pressure bypass valve at a set rate; detecting in real time the unit load decrease rate, cylinder temperature decrease rate, differential expansion change amount, and unit stress. When any one of the parameters reaches the corresponding set value, the low-pressure bypass valve stops opening and remains at this opening for warming up; calculating the difference between the decreased amount of axial displacement and the locked axial displacement value. When the difference reaches the set value, controlling the low-pressure bypass valve to maintain the current opening and starting to open the high-pressure bypass valve; calculating the difference between the increased amount of axial displacement and the locked axial displacement value. When the difference returns to the locked value, controlling the high-pressure bypass valve to maintain the current opening and starting to open the low-pressure bypass valve; repeatedly and alternately controlling the high-pressure bypass valve and the low-pressure bypass valve to gradually open until the high-pressure bypass valve is fully open and the low-pressure bypass valve is fully open.

[0014] Further, it is suitable for working with the high- and low-pressure bypass control systems of intermediate reheat units for the power generation industry as described above.

[0015] The beneficial effects of the present invention are that the present invention has the function of automatically controlling the high- and low-pressure bypasses during the load increase and decrease of the steam turbine during boiler parallel steaming and shutdown, can realize the reheating production of two boilers and one steam turbine in a header system, and overcome the problem of the traditional high- and low-pressure bypass systems causing thrust bearing burning accidents during normal load reduction and shutdown.

[0016] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention.

[0017] To make the above objects, features and advantages of the present invention more comprehensible, the following specific embodiments are given in conjunction with the accompanying drawings and described in detail as follows. Brief Description of the Drawings

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 is the principle block diagram of the high and low pressure bypass control system of the intermediate reheat unit for the power generation industry of the present invention;

[0020] Figure 2 is the control logic block diagram of the steam turbine for increasing load of the present invention;

[0021] Figure 3 is the control logic block diagram of the steam turbine for reducing load of the present invention;

[0022] Figure 4 is the structure diagram of the reheating unit with two boilers and one turbine of the present invention;

[0023] Figure 5 is the flow chart of the method for automatically increasing the load during boiler parallel steam admission of the present invention;

[0024] Figure 6 is the flow chart of the method for automatically reducing the load during boiler trip of the present invention.

[0025] In the figures:

[0026] High pressure bypass valve 1, low pressure bypass valve 2, main steam header 3, cold reheat header 4, reheated steam 5. Detailed Description of the Embodiments

[0027] To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0028] Embodiment 1

[0029] Figure 1 It is the principle block diagram of the high and low pressure bypass control system for the intermediate reheat unit in the power generation industry of the present invention.

[0030] In this embodiment, as Figure 1 shown, this embodiment provides a high and low pressure bypass control system for the waste power generation industry, which includes: a high and low pressure bypass system load control module, an axial displacement latching calculation module electrically connected to the high and low pressure bypass system load control module, a unit detection module, a high pressure bypass valve, and a low pressure bypass valve; wherein the high and low pressure bypass system load control module is adapted to lock the current axial displacement value according to the operating state of the steam turbine, and control the corresponding bypass valve to perform a load increase or load decrease action; the axial displacement latching calculation module is adapted to calculate the axial displacement change amount through the locked current axial displacement value, and the unit detection module is adapted to detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress, that is, the high and low pressure bypass system load control module is adapted to alternately control the high pressure bypass valve and the low pressure bypass valve to perform corresponding actions according to the axial displacement change amount, unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress, so as to realize the load increase or load decrease of the steam turbine.

[0031] In this embodiment, the axial displacement latching calculation module calculates the axial displacement change amount through active power, axial displacement, shaft vibration, main steam, and reheat steam pressure.

[0032] In this embodiment, this embodiment has the automatic control function of the high and low pressure bypass during the steam turbine load increase and decrease during the boiler parallel and steam disconnection periods, can realize the reheat production of two boilers and one machine in a header system, and overcome the problem of bearing burning accidents occurring in the traditional high and low pressure bypass system during normal load reduction and shutdown.

[0033] In this embodiment, the high and low pressure bypass system load control module controls the steam turbine to increase load after the boiler starts and parallelizes the steam; and the high and low pressure bypass system load control module controls the steam turbine to decrease load after a given boiler to be disconnected and shut down is given.

[0034] Figure 2 It is the control logic block diagram of the steam turbine load increase of the present invention.

[0035] In this embodiment, after the boiler starts and the steam is admitted, the steam turbine is in the "pressure control" mode. After the load increase button issues a load increase command to the load control module of the high and low pressure bypass system, the load control module of the high and low pressure bypass system automatically locks the current axial displacement value and controls the high pressure bypass valve to gradually close at a set rate (set to 2 MW / min for hot state, 0.5 MW / min for warm state, and 0.25 MW / min for cold state in this embodiment). After the steam turbine detects an increase in the main steam pressure, the DEH system of the steam turbine opens the high pressure control valve of the steam turbine to increase the load of the steam turbine and maintain the main steam pressure constant. At this time, the load control module of the high and low pressure bypass system automatically executes the following control:

[0036] In this embodiment, as Figure 2As shown, after the boiler starts up and is put into parallel operation, the load control module of the high and low pressure bypass system is adapted to lock the current axial displacement value of the steam turbine, and control the high pressure bypass valve to gradually close at a set rate (set to 2 MW / min for hot state, 0.5 MW / min for warm state, and 0.25 MW / min for cold state in this embodiment); the load control module of the high and low pressure bypass system is adapted to detect the unit load increase rate, cylinder temperature increase rate (2 °C / min in this embodiment), differential expansion change amount (>3 mm, <2.7 mm in this embodiment), and unit stress (red line of the preset curve) through the unit detection module. When the cylinder temperature increase rate and differential expansion change amount reach the set values, the load control module of the high and low pressure bypass system is adapted to control the high pressure bypass valve to stop closing and maintain at this opening for warm-up; the load control module of the high and low pressure bypass system is adapted to calculate the difference between the increased amount of axial displacement and the locked axial displacement value through the axial displacement latching calculation module. When the difference reaches the set value (set value is ≥0.05 mm in this embodiment), the load control module of the high and low pressure bypass system is adapted to control the high pressure bypass valve to maintain the current opening, and start to close the low pressure bypass valve (set the closing rate of the low pressure bypass valve to 0.5% / min in this embodiment). After the low pressure bypass valve closes, the reheat steam pressure rises, and the steam turbine load automatically rises; the load control module of the high and low pressure bypass system is adapted to detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress through the unit detection module. When the cylinder temperature increase rate and differential expansion change amount reach the set values, the load control module of the high and low pressure bypass system is adapted to control the low pressure bypass valve to stop closing and maintain at this opening for warm-up; the load control module of the high and low pressure bypass system is adapted to calculate the difference between the decreased amount of axial displacement and the locked axial displacement value through the axial displacement latching calculation module. When the difference returns to the locked value (set value is ≥ -0.05 mm in this embodiment), the load control module of the high and low pressure bypass system is adapted to control the low pressure bypass valve to maintain the current opening, and start to close the high pressure bypass valve, that is, the load control module of the high and low pressure bypass system is adapted to repeatedly and alternately control the high pressure bypass valve and the low pressure bypass valve to gradually close until the high pressure bypass valve closes to zero and the low pressure bypass valve closes to zero, and automatically set the high and low bypass control parameters and then put the high and low bypass into automatic control, and the automatic load increase is completed.

[0037] Figure 3 It is the control logic block diagram of the steam turbine load reduction of the present invention.

[0038] In this embodiment, after the boiler to be taken out of service is given, the load control module of the high and low pressure bypass system automatically locks the current axial displacement value, and gradually opens the low pressure bypass valve at a set rate. The reheat steam pressure decreases, the steam inlet volume of the intermediate and low pressure cylinders decreases, and the steam turbine load drops. At this time, the load control module of the high and low pressure bypass system automatically executes the following control:

[0039] In this embodiment, as Figure 3 shown, after the boiler to be de - energized is given, the load control module of the high - and - low - pressure bypass system is adapted to lock the current axial displacement value of the steam turbine and gradually open the low - pressure bypass valve at a set rate (in this embodiment, the set rate for opening the low - pressure bypass valve is 1% / min); the load control module of the high - and - low - pressure bypass system is adapted to detect the unit load reduction rate (2 MW / min in this embodiment), the cylinder temperature reduction rate (2 °C / min in this embodiment), the differential expansion change amount (>3 mm, <2.7 mm in this embodiment), and the unit stress (red line of the preset curve) through the unit detection module. When any one of the parameters reaches the corresponding set value, the load control module of the high - and - low - pressure bypass system is adapted to control the low - pressure bypass valve to stop opening and maintain at this opening for warm - up; the load control module of the high - and - low - pressure bypass system is adapted to calculate the difference between the reduced amount of axial displacement and the locked axial displacement value through the axial displacement latching calculation module. When the difference reaches the set value (the set value is ≥ - 0.05 mm in this embodiment), the load control module of the high - and - low - pressure bypass system is adapted to control the low - pressure bypass valve to maintain the current opening and start to open the high - pressure bypass valve (the set rate for opening the high - pressure bypass valve is 0.8% / min in this embodiment). After the high - pressure bypass valve is opened, the main steam pressure drops, and the DEH system of the steam turbine closes the high - pressure control valve of the steam turbine to reduce the load of the steam turbine and maintain the main steam pressure unchanged; the load control module of the high - and - low - pressure bypass system is adapted to calculate the difference between the increased amount of axial displacement and the locked axial displacement value through the axial displacement latching calculation module. When the difference (>0.05 mm in this embodiment) returns to the locked value, the load control module of the high - and - low - pressure bypass system is adapted to control the high - pressure bypass valve to maintain the current opening and start to open the low - pressure bypass valve, that is, the load control module of the high - and - low - pressure bypass system is adapted to alternately control the high - and - low - pressure bypass valves to gradually open repeatedly until the high - pressure bypass valve is fully open and the low - pressure bypass valve is fully open, and automatically close the main steam, cold reheat, and hot reheat isolation valves of this boiler, de - energize this boiler, and complete the automatic load reduction of the high - and - low - bypass boilers.

[0040] Figure 4 is the structural diagram of the reheat unit with two boilers and one steam turbine of the present invention.

[0041] In this embodiment, as Figure 4 shown, each steam turbine is equipped with two boilers. Each boiler directly reduces the temperature and pressure of the main steam generated by the superheater in the boiler through the corresponding high - pressure bypass valve 1 and then directly merges it into the cold reheat header 4 to be sent to the reheater of the corresponding boiler, that is, the reheated steam 5 generated by each reheater is sent to the intermediate - and - low - pressure cylinders of the steam turbine to continue to do work.

[0042] In this embodiment, each boiler is provided with a corresponding low-pressure bypass valve 2, that is, the low-pressure bypass valve 2 directly cools and reduces the pressure of the reheated steam 5 generated by the corresponding boiler reheater and then transports it to the condenser.

[0043] Embodiment 2

[0044] Figure 5 It is a flowchart of the method for automatically increasing the load during boiler parallel operation of the present invention.

[0045] Based on Embodiment 1, as Figure 5 shown, this embodiment provides a method for automatically increasing the load of an intermediate reheat unit after boiler parallel operation, which includes: after the boiler starts and is parallel operated, lock the current axial displacement value of the steam turbine and gradually close the corresponding high-pressure bypass valve at a set rate; continuously detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress. When the cylinder temperature increase rate and differential expansion change amount reach the set values, stop closing the high-pressure bypass valve and keep it at this opening for warm-up; calculate the difference between the increased amount of axial displacement and the locked axial displacement value. When the difference reaches the set value, control the high-pressure bypass valve to maintain the current opening and start to close the corresponding low-pressure bypass valve; continuously detect the unit load increase rate, cylinder temperature increase rate, differential expansion change amount, and unit stress. When the cylinder temperature increase rate and differential expansion change amount reach the set values, stop closing the low-pressure bypass valve and keep it at this opening for warm-up; calculate the difference between the decreased amount of axial displacement and the locked axial displacement value. When the difference returns to the locked value, control the low-pressure bypass valve to maintain the current opening and start to close the high-pressure bypass valve; repeatedly and alternately control the high-pressure bypass valve and the low-pressure bypass valve to gradually close until the high-pressure bypass valve is closed to zero and the low-pressure bypass valve is closed to zero.

[0046] In this embodiment, it is suitable to work with the high- and low-pressure bypass control system for intermediate reheat units in the power generation industry provided in Embodiment 1.

[0047] In this embodiment, the high- and low-pressure bypass control system for intermediate reheat units in the power generation industry has been clearly described in Embodiment 1.

[0048] Embodiment 3

[0049] Figure 6 It is a flowchart of the method for automatically reducing the load during boiler trip of the present invention.

[0050] Based on the above embodiments, as Figure 6As shown in the figure, this embodiment provides a method for automatically reducing the load during boiler shutdown, which includes: after the boiler to be shut down is specified, the current axial displacement value of the steam turbine is locked, and the corresponding low-pressure bypass valve is gradually opened at a set rate; the unit load reduction rate, cylinder temperature reduction rate, differential expansion change amount, and unit stress are detected in real time. When any one of the parameters reaches the corresponding set value, the low-pressure bypass valve stops opening and remains at this opening for warm-up; calculate the difference between the reduced amount of axial displacement and the locked axial displacement value. When the difference reaches the set value, control the low-pressure bypass valve to maintain the current opening and start opening the corresponding high-pressure bypass valve; calculate the difference between the increased amount of axial displacement and the locked axial displacement value. When the difference returns to the locked value, control the high-pressure bypass valve to maintain the current opening and start opening the low-pressure bypass valve; repeatedly and alternately control the high-pressure bypass valve and the low-pressure bypass valve to gradually open until the high-pressure bypass valve and the low-pressure bypass valve are fully open.

[0051] In this embodiment, it is suitable to work with the high- and low-pressure bypass control systems for reheat units in the power generation industry provided in the above embodiment.

[0052] In this embodiment, the high- and low-pressure bypass control systems for reheat units in the power generation industry have been clearly described in the above embodiment.

[0053] In summary, the present invention has the function of automatically controlling the corresponding high- and low-pressure bypasses during the load increase and decrease of the steam turbine during boiler connection and disconnection, can realize the reheating production of two boilers and one turbine in a header system, and overcome the problem of bearing burning accidents in the traditional high- and low-pressure bypass systems during normal load reduction and shutdown.

[0054] All the components selected in this application (components without specific structures described) are common standard components or components known to those skilled in the art. Their structures and principles can be known to those skilled in the art through technical manuals or obtained through conventional experimental methods. Moreover, the software programs involved in this application are all prior arts, and this application does not involve any improvement to the software programs.

[0055] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0056] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0057] Based on the above inspiration from the ideal embodiments of the present invention, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An automatic load reduction method for boiler disconnection, characterized in that Including: Step S1: After the boiler to be disconnected from the grid is given, lock the current axial displacement value of the steam turbine, and gradually open the corresponding low-pressure bypass valve at a set rate. Step S2: Real-time detect the unit load reduction rate, cylinder temperature reduction rate, differential expansion change amount, and unit stress. When any one of the parameters reaches the corresponding set value, the low-pressure bypass valve stops opening and remains at this opening for warm-up. Step S3: Calculate the difference between the reduced amount of axial displacement and the locked axial displacement value. When the difference reaches the set value, control the low-pressure bypass valve to maintain the current opening, and start to open the high-pressure bypass valve. Step S4: Calculate the difference between the increased amount of axial displacement and the locked axial displacement value. When the difference returns to the locked value, control the high-pressure bypass valve to maintain the current opening, and start to open the low-pressure bypass valve. Step S5: Repeat Steps S2 to S4 to alternately control the high-pressure bypass valve and the low-pressure bypass valve to gradually open until the high-pressure bypass valve is fully open and the low-pressure bypass valve is fully open.

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