Steam source switching device and method suitable for water feeding pump steam turbine of thermal power generating unit

Abstract

The invention provides a steam source switching device and method suitable for a thermal power generating unit feed pump turbine, and relates to the technical field of thermal power generation. The steam source switching device comprises a conventional steam supply unit used for conveying first steam to the water feed pump turbine and the coupling unit; the auxiliary steam supply unit is connected with the air inlet of the coupling unit and is used for conveying auxiliary steam to the coupling unit; the pressure of the auxiliary steam is higher than that of the first steam, and the temperature of the auxiliary steam is higher than that of the first steam; the coupling unit is connected with an air inlet of the water feeding pump turbine and used for coupling the first steam and the auxiliary steam to form second steam and conveying the second steam to the water feeding pump turbine. According to the steam source switching device and method, the problem that in the prior art, when a standby air source is switched, the running fluctuation of a water feeding pump steam turbine is large is solved, low-quality first steam is utilized, the use amount of high-quality auxiliary steam is reduced, the purposes of saving energy and reducing consumption are achieved, and the economical efficiency of a thermal power generating unit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and in particular to a steam source switching device applicable to a feedwater pump steam turbine of a thermal power unit and a steam source switching method applicable to a feedwater pump steam turbine of a thermal power unit. Background Art

[0002] Feedwater pump steam turbines have mature technology and safe and reliable operation. New investment units tend to use feedwater pump steam turbines as power equipment to drive feedwater pumps. It is an important means to promote the consumption of clean energy for thermal power units to carry out deep peak-shaving operation and give up power space to zero-carbon emission new energy. Achieving deep peak-shaving and improving the flexibility of unit operation have become important means to improve the market competitiveness of thermal power companies.

[0003] In actual operation, especially in coal-fired thermal power plants, in order to adapt to the current power market, the units often slide pressure to low load conditions, resulting in the pressure and temperature of the conventional steam source of the feedwater pump turbine seriously deviating from the design value, causing the feedwater pump output to be unable to meet the safe operation requirements of the unit. In order to ensure the safe and reliable operation of the feedwater pump turbine, the conventional practice is to switch to a standby high-pressure steam source. However, during the switching process, due to a certain degree of difference between the standby steam source and the original feedwater pump turbine steam parameters, the operating conditions of the feedwater pump turbine fluctuate greatly, increasing the probability of unstable operation of the coal-fired power plant's feedwater system, thereby affecting the safe operation of the entire thermal power unit. At the same time, the high-quality steam source needs to be reduced if necessary to meet the steam inlet parameters required for the feedwater pump turbine, resulting in a significant decrease in the unit's economic efficiency.

[0004] Therefore, there is an urgent need for a device that can solve at least one of the above problems. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide a steam source switching device and method suitable for a feedwater pump turbine of a thermal power unit, so as to solve the problem of large operating fluctuations of the feedwater pump turbine when switching the backup gas source in the prior art.

[0006] In order to achieve the above-mentioned object, the present invention provides a steam source switching device suitable for a feedwater pump turbine of a thermal power unit, the steam source switching device comprising: a conventional steam supply unit connected to an air inlet of the feedwater pump steam turbine and an air inlet of the coupling unit, and used for delivering first steam to the feedwater pump steam turbine and the coupling unit; An auxiliary steam supply unit is connected to the air inlet of the coupling unit and is used to deliver auxiliary steam to the coupling unit; wherein the pressure of the auxiliary steam is greater than the pressure of the first steam, and the temperature of the auxiliary steam is higher than the temperature of the first steam; The coupling unit is connected to the air inlet of the feedwater pump steam turbine, and is used for coupling the first steam and the auxiliary steam to form the second steam, and conveying the second steam to the feedwater pump steam turbine.

[0007] Specifically, the conventional steam supply unit comprises: a conventional steam source, a first steam supply pipeline, a first regulating valve, a first check valve and a first isolation valve; The conventional steam source is used to provide first steam; The conventional steam source is connected to the air inlet of the feedwater pump steam turbine through a first steam supply pipeline, and the first steam is delivered to the feedwater pump steam turbine through the first steam supply pipeline; The first regulating valve, the first check valve and the first isolation valve are sequentially arranged on the first steam supply pipeline along the conveying direction of the first steam.

[0008] Specifically, the auxiliary steam supply unit includes: a backup steam source, a second steam supply pipeline, a second regulating valve and a second isolation valve; The standby steam source is used to provide auxiliary steam; The standby steam source is connected to the air inlet of the coupling unit through the second steam supply pipeline, and is used to deliver auxiliary steam to the coupling unit through the second steam supply pipeline; The second regulating valve and the second isolating valve are sequentially arranged on the second steam supply pipeline along the conveying direction of the auxiliary steam.

[0009] Specifically, the coupling unit includes: a coupling branch, a steam ejector, a third isolation valve and a coupled steam supply pipeline; the steam inlet of the steam ejector is connected to the second steam supply pipeline as the air inlet of the coupling unit; The coupling branch is connected between the first steam supply pipeline and the steam inlet of the steam ejector, and the first steam flowing from the conventional steam source through the first steam supply pipeline to the feedwater pump turbine can be diverted and enter the steam ejector from the coupling branch; After the auxiliary steam flowing through the second steam supply pipeline enters the steam ejector, it is coupled with the first steam entering the steam ejector through the coupling branch to form the second steam; The third isolation valve is arranged on the coupling branch and is used to control the flow state of the first steam in the coupling branch; The coupled steam delivery pipeline is connected between the steam outlet of the steam ejector and the air inlet of the feedwater pump turbine.

[0010] Specifically, the steam source switching device further includes: a fourth isolation valve, which is arranged on the coupled steam supply pipeline and is used to control the flow state of the second steam in the coupled steam supply pipeline.

[0011] Specifically, the steam source switching device also includes: a pressure detector, which is arranged at the air inlet of the feedwater pump steam turbine and is used to detect the steam pressure at the air inlet of the feedwater pump steam turbine.

[0012] Specifically, the steam source switching device also includes: a switching controller, which is connected to the pressure detector and the control end signal of the second regulating valve, and the switching controller is used to control the valve core opening of the second regulating valve according to the air inlet pressure of the feedwater pump turbine.

[0013] Another aspect of the present invention further provides a steam source switching method applicable to a feedwater pump turbine of a thermal power unit, which is implemented based on any of the above-mentioned steam source switching devices, and the steam source switching method comprises: Get the current load of the thermal power unit; Determining that the current load of the thermal power unit is at a first load, supplying first steam to the feedwater pump turbine; Determine that the current load of the thermal power unit is at the second load, and supply the second steam formed by coupling the first steam and the auxiliary steam to the feedwater pump turbine; wherein the pressure of the auxiliary steam is greater than the pressure of the first steam, and the temperature of the auxiliary steam is higher than the temperature of the first steam.

[0014] Specifically, the first load is greater than or equal to 40% of the rated load of the thermal power unit, and the second load is less than 40% of the rated load of the thermal power unit.

[0015] Specifically, it also includes: Detect the steam pressure at the air inlet of the feedwater pump turbine; The amount of auxiliary steam is adjusted according to the steam pressure at the air inlet of the feed pump turbine.

[0016] The steam source switching device and method for a feedwater pump steam turbine of a thermal power unit provided by the present invention delivers first steam to the feedwater pump steam turbine and the coupling unit through a conventional steam supply unit, delivers auxiliary steam to the coupling unit through an auxiliary steam supply unit, and the first steam and the auxiliary steam are coupled to become the second steam in the coupling unit and then delivered to the feedwater pump steam turbine. The auxiliary steam and the first steam are coupled by the coupling unit to form the second steam, so that the pressure and temperature of the second steam are closer to the first steam, and the operation fluctuation caused when the second steam is delivered to the feedwater pump steam turbine after the steam source is switched is avoided. Moreover, the coupling of the first steam and the auxiliary steam not only utilizes the low-quality first steam, but also reduces the amount of high-quality auxiliary steam, thus achieving the purpose of energy saving and consumption reduction, and improving the economy of the thermal power unit. The steam source switching device and method for a feedwater pump steam turbine of a thermal power unit provided by the present invention solves the problem of large operation fluctuation of the feedwater pump steam turbine caused by switching the backup gas source in the prior art.

[0017] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings: Figure 1 The present invention is a schematic diagram of the layout of a steam source switching device suitable for a feedwater pump turbine of a thermal power unit provided by an embodiment of the present invention.

[0019] Description of Reference Numerals 1- conventional steam supply unit; 2- feed pump turbine; 3- auxiliary steam supply unit; 4- coupling unit; 5- fourth isolating valve; 11- first steam supply pipeline; 12- first regulating valve; 13- first check valve; 14- first isolating valve; 31- second steam supply pipeline; 32- second regulating valve; 33- second isolating valve; 41- coupling branch; 42- steam ejector; 43- third isolating valve; 44- coupling steam supply pipeline. DETAILED DESCRIPTION

[0020] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0021] Figure 1 Applicable to the steam source switching device of the feed water pump turbine of the thermal power unit. Figure 1 As shown, the present invention provides a steam source switching device suitable for a feedwater pump turbine of a thermal power unit, the steam source switching device comprising: A conventional steam supply unit 1 is connected to the air inlet of the feedwater pump steam turbine 2 and the air inlet of the coupling unit 4, and is used to deliver first steam to the feedwater pump steam turbine 2 and the coupling unit 4; The auxiliary steam supply unit 3 is connected to the air inlet of the coupling unit 4 and is used to deliver auxiliary steam to the coupling unit 4; wherein the pressure of the auxiliary steam is greater than the pressure of the first steam, and the temperature of the auxiliary steam is higher than the temperature of the first steam; The coupling unit 4 is connected to the air inlet of the feedwater pump steam turbine 2 , and is used for coupling the first steam and the auxiliary steam to form the second steam, and delivering the second steam to the feedwater pump steam turbine 2 .

[0022] The steam source switching device for a feedwater pump turbine of a thermal power unit provided by the present invention delivers first steam to a feedwater pump turbine 2 and a coupling unit 4 through a conventional steam supply unit 1, and delivers auxiliary steam to the coupling unit 4 through an auxiliary steam supply unit 3. The pressure and temperature of the auxiliary steam are higher than the first steam, and the auxiliary steam belongs to high-quality steam. In order to avoid operation fluctuations caused by switching the steam source of the feedwater pump turbine 2, the low-quality first steam and the high-quality auxiliary steam are coupled to form second steam through the coupling unit 4, and then the second steam is delivered to the feedwater pump turbine 2. The temperature and pressure of the coupled second steam are closer to the first steam. Therefore, after switching the steam source, the operation fluctuation caused by sending the second steam into the feedwater pump turbine 2 is minimized. At the same time, the first steam and the auxiliary steam are coupled, which not only utilizes the low-quality first steam, but also reduces the amount of high-quality auxiliary steam, thereby achieving the purpose of energy saving and consumption reduction, improving the economy of the thermal power unit, and solving the problem of large operation fluctuations of the feedwater pump turbine when switching the backup gas source in the prior art.

[0023] In one embodiment, Figure 1 As shown, the conventional steam supply unit 1 comprises: a conventional steam source, a first steam supply pipeline 11, a first regulating valve 12, a first check valve 13 and a first isolation valve 14; The conventional steam source is used to provide first steam; The conventional steam source is connected to the air inlet of the feedwater pump steam turbine 2 through the first steam supply pipeline 11, and the first steam is transported to the feedwater pump steam turbine 2 through the first steam supply pipeline 11; The first regulating valve 12 , the first check valve 13 and the first isolation valve 14 are sequentially arranged on the first steam supply pipeline 11 along the conveying direction of the first steam.

[0024] When the thermal power unit is operated under non-deep peak load regulation conditions, the operating load of the thermal power unit is greater than or equal to 40% of the rated load. At this time, the first steam is supplied to the feedwater pump turbine 2 by the conventional steam supply unit 1. At this time, the first regulating valve 12, the first check valve 13 and the first isolation valve 14 are all opened, and the first steam provided by the conventional steam source can be transported to the feedwater pump turbine 2 through the first steam supply pipeline 11. The first regulating valve 12 can adjust the flow of the first steam flowing through the first steam supply pipeline 11. The first check valve 13 can control the flow direction of the first steam to avoid the backflow of the first steam. The first isolation valve 14 is controlled to be opened, and the first steam can flow to the feedwater pump turbine 2 through the first steam supply pipeline 11. The closing of the first isolation valve 14 can cut off the flow state of the first steam in the first steam supply pipeline 11.

[0025] When the thermal power unit is operating under deep peak load regulation, the operating load of the thermal power unit is less than 40% of the rated load. In order to avoid excessive fluctuations in the operation of the feedwater pump turbine 2 when switching the steam source, such as Figure 1As shown, the auxiliary steam supply unit 3 includes: a backup steam source, a second steam supply pipeline 31, a second regulating valve 32 and a second isolation valve 33; The standby steam source is used to provide auxiliary steam; The standby steam source is connected to the air inlet of the coupling unit 4 through the second steam supply pipeline 31, and the auxiliary steam is delivered to the coupling unit 4 through the second steam supply pipeline 31; The second regulating valve 32 and the second isolating valve 33 are sequentially arranged on the second steam supply pipeline 31 along the conveying direction of the auxiliary steam.

[0026] The coupling unit 4 comprises: a coupling branch 41, a steam ejector 42, a third isolation valve 43 and a coupling steam supply pipeline 44; the steam inlet of the steam ejector 42 serves as the air inlet of the coupling unit 4 and is connected to the second steam supply pipeline 31; The coupling branch 41 is connected between the first steam supply pipeline 11 and the steam inlet of the steam ejector 42, and the first steam flowing from the conventional steam source through the first steam supply pipeline 11 to the feedwater pump steam turbine 2 can be diverted and enter the steam ejector 42 from the coupling branch 41; After the auxiliary steam flowing through the second steam supply pipeline 31 enters the steam ejector 42, it is coupled with the first steam entering the steam ejector 42 through the coupling branch 41 to form the second steam; The third isolation valve 43 is disposed on the coupling branch 41 and is used to control the flow state of the first steam in the coupling branch 41; The coupling steam supply line 44 is connected between the steam outlet connection of the steam ejector 42 and the feedwater pump turbine 2 .

[0027] The steam source switching device further includes: a fourth isolation valve 5 , which is arranged on the coupled steam supply pipeline 44 and is used to control the flow state of the second steam in the coupled steam supply pipeline 44 .

[0028] The second regulating valve 32 and the second isolating valve 33 are both opened, and the backup gas source delivers auxiliary steam to the steam ejector 42 of the coupling unit 4 through the second steam supply pipeline 31. By controlling the valve core opening of the second regulating valve 32, the flow rate of the auxiliary steam flowing through the second steam supply pipeline 31 can be controlled. The second isolating valve 33 can control the flow state of the auxiliary steam in the second steam supply pipeline 31. When the second isolating valve 33 is opened, the auxiliary steam flows to the coupling unit 4 through the second steam supply pipeline 31. When the second isolating valve 33 is closed, the auxiliary steam stops flowing in the second steam supply pipeline 31.

[0029] When the auxiliary steam enters the steam ejector 42, the third isolation valve 43 arranged on the coupling branch 41 is opened. The first steam delivered by the conventional steam supply unit 1 is divided into the coupling branch 41 after flowing through a section of the first steam supply pipeline 11, and finally enters the steam ejector 42. The first steam entering the steam ejector 42 is coupled with the auxiliary steam to form the second steam, which is then sent out from the steam ejector 42 and sent into the feedwater pump turbine 2 through the coupling steam supply pipeline 44. The pressure and temperature of the second steam are close to those of the first steam. Therefore, the operation fluctuation caused by the second steam entering the feedwater pump turbine 2 is relatively small. The fourth isolation valve 5 arranged on the coupling steam supply pipeline 44 is opened, and the second steam enters the feedwater pump turbine 2 through the coupling steam supply pipeline 44. The fourth isolation valve 5 is closed, and the second steam cannot flow in the coupling steam supply pipeline 44.

[0030] In order to ensure that the steam fed into the feed water pump steam turbine 2 can minimize the operating fluctuations of the feed water pump steam turbine 2, the steam source switching device also includes: a pressure detector, which is arranged at the air inlet of the feed water pump steam turbine 2, and is used to detect the steam pressure entering the feed water pump steam turbine 2.

[0031] The steam source switching device also includes: a switching controller, which is connected to the pressure detector and the second regulating valve 32 by signal, and the switching controller is used to control the valve core opening of the second regulating valve 32 according to the air inlet pressure of the feedwater pump turbine 2.

[0032] By detecting the steam pressure at the air inlet of the feedwater pump turbine 2, that is, detecting the steam pressure fed into the feedwater pump turbine 2, the operating fluctuation of the feedwater pump turbine 2 can be determined. For example, taking the pressure of the first steam as a reference standard, the closer the pressure of the steam fed into the feedwater pump turbine 2 is to the pressure of the first steam, the smaller the operating fluctuation of the feedwater pump turbine 2 will be. The switching controller adjusts the valve core opening of the second regulating valve 32 according to the steam pressure at the inlet of the feedwater pump turbine 2, thereby controlling the amount of auxiliary steam fed into the steam ejector 42 through the second steam supply pipeline 31, adjusting the pressure and temperature of the second steam formed by coupling, and ensuring that the operating fluctuation of the feedwater pump turbine 2 is minimized when the steam source is switched to feed the second steam into the feedwater pump turbine 2.

[0033] Another aspect of the present invention further provides a steam source switching method applicable to a feedwater pump steam turbine of a thermal power unit, which is implemented based on any of the above-mentioned steam source switching devices applicable to a feedwater pump steam turbine of a thermal power unit, and the steam source switching method comprises: Get the current load of the thermal power unit; Determining that the current load of the thermal power unit is at a first load, supplying first steam to the feedwater pump turbine; It is determined that the current load of the thermal power unit is at the second load, and the first steam and auxiliary steam are supplied. The second steam formed by the coupling of the first steam and the auxiliary steam is transported to the feedwater pump turbine; wherein the pressure of the auxiliary steam is greater than the pressure of the first steam, and the temperature of the auxiliary steam is higher than the temperature of the first steam.

[0034] Specifically, the first load is greater than or equal to 40% of the rated load of the thermal power unit, and the second load is less than 40% of the rated load of the thermal power unit.

[0035] Specifically, it also includes: Detect the steam pressure at the air inlet of the feedwater pump turbine; The amount of auxiliary steam is adjusted according to the steam pressure at the air inlet of the feed pump turbine.

[0036] In order to reduce the operating fluctuation of the feedwater pump steam turbine when switching the steam source supplied to the feedwater pump steam turbine, the current load of the current thermal power unit is first obtained, and the steam source supplied to the feedwater pump steam turbine is controlled according to the current load of the thermal power unit. If the current load of the thermal power unit is at a first load, and the first load is greater than or equal to 40% of the rated load of the thermal power unit, then the first steam is supplied to the feedwater pump steam turbine; if the current load of the thermal power unit is at a second load, and the second load is less than 40% of the rated load of the thermal power unit, then the second steam formed by coupling the auxiliary steam and the first steam is supplied to the feedwater pump steam turbine, which not only utilizes the low-quality first steam, but also reduces the use of high-quality auxiliary steam, thereby achieving the purpose of energy saving and consumption reduction and improving the economy of the thermal power unit.

[0037] The steam source switching device and method for a feedwater pump steam turbine of a thermal power unit provided by the present invention delivers first steam to the feedwater pump steam turbine and the coupling unit through a conventional steam supply unit, delivers auxiliary steam to the coupling unit through an auxiliary steam supply unit, and the first steam and the auxiliary steam are coupled to become the second steam in the coupling unit and then delivered to the feedwater pump steam turbine. The auxiliary steam and the first steam are coupled by the coupling unit to form the second steam, so that the pressure and temperature of the second steam are closer to the first steam, and the operation fluctuation caused when the second steam is delivered to the feedwater pump steam turbine after the steam source is switched is avoided. Moreover, the coupling of the first steam and the auxiliary steam not only utilizes the low-quality first steam, but also reduces the amount of high-quality auxiliary steam, thus achieving the purpose of energy saving and consumption reduction, and improving the economy of the thermal power unit. The steam source switching device and method for a feedwater pump steam turbine of a thermal power unit provided by the present invention solves the problem of large operation fluctuation of the feedwater pump steam turbine caused by switching the backup gas source in the prior art.

[0038] The optional implementation modes of the embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical scheme of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

[0039] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0040] In addition, various implementation modes of the embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed by the embodiments of the present invention.

Claims

1. A steam source switching device suitable for a feedwater pump turbine of a thermal power unit, characterized in that: The steam source switching device comprises: A conventional steam supply unit (1) is connected to an air inlet of a feedwater pump steam turbine (2) and an air inlet of a coupling unit (4), and is used to deliver first steam to the feedwater pump steam turbine (2) and the coupling unit (4); An auxiliary steam supply unit (3) is connected to the air inlet of the coupling unit (4) and is used to deliver auxiliary steam to the coupling unit (4); wherein the pressure of the auxiliary steam is greater than the pressure of the first steam, and the temperature of the auxiliary steam is higher than the temperature of the first steam; The coupling unit (4) is connected to the air inlet of the feedwater pump steam turbine (2), and is used for coupling the first steam and the auxiliary steam to form the second steam, and for transmitting the second steam to the feedwater pump steam turbine (2).

2. The steam source switching device according to claim 1, characterized in that: The conventional steam supply unit (1) comprises: a conventional steam source, a first steam supply pipeline (11), a first regulating valve (12), a first check valve (13) and a first isolation valve (14); The conventional steam source is used to provide first steam; The conventional steam source is connected to the air inlet of the feedwater pump steam turbine (2) via a first steam supply pipeline (11), and the first steam is transported to the feedwater pump steam turbine (2) via the first steam supply pipeline (11); The first regulating valve (12), the first check valve (13) and the first isolation valve (14) are arranged in sequence on the first steam supply pipeline (11) along a conveying direction of the first steam.

3. The steam source switching device according to claim 2, characterized in that: The auxiliary steam supply unit (3) comprises: a standby steam source, a second steam supply pipeline (31), a second regulating valve (32) and a second isolation valve (33); The standby steam source is used to provide auxiliary steam; The standby steam source is connected to the air inlet of the coupling unit (4) via a second steam supply pipeline (31), and auxiliary steam is transported to the coupling unit (4) via the second steam supply pipeline (31); The second regulating valve (32) and the second isolating valve (33) are arranged in sequence on the second steam supply pipeline (31) along the conveying direction of the auxiliary steam.

4. The steam source switching device according to claim 3, characterized in that: The coupling unit (4) comprises: a coupling branch (41), a steam ejector (42), a third isolation valve (43) and a coupling steam supply pipeline (44); the steam inlet of the steam ejector (42) serves as the air inlet of the coupling unit (4) and is connected to the second steam supply pipeline (31); The coupling branch (41) is connected between the first steam supply pipeline (11) and the steam inlet of the steam ejector (42), and the first steam flowing from the conventional steam source through the first steam supply pipeline (11) to the feedwater pump steam turbine (2) can be diverted and enter the steam ejector (42) from the coupling branch (41); After the auxiliary steam flowing through the second steam supply pipeline (31) enters the steam ejector (42), it is coupled with the first steam entering the steam ejector (42) through the coupling branch (41) to form second steam; The third isolation valve (43) is arranged on the coupling branch (41) and is used to control the flow state of the first steam in the coupling branch (41); The coupled steam delivery pipeline (44) is connected between the steam outlet of the steam ejector (42) and the air inlet of the feedwater pump steam turbine (2).

5. The steam source switching device according to claim 4, characterized in that: The steam source switching device further comprises: a fourth isolation valve (5), which is arranged on the coupled steam supply pipeline (44) and is used to control the flow state of the second steam in the coupled steam supply pipeline (44).

6. The steam source switching device according to claim 3, characterized in that: The steam source switching device further comprises: a pressure detector, which is arranged at the air inlet of the feedwater pump steam turbine (2) and is used to detect the steam pressure at the air inlet of the feedwater pump steam turbine (2).

7. The steam source switching device according to claim 6, characterized in that: The steam source switching device further comprises: a switching controller connected to the pressure detector and the control end signal of the second regulating valve (32), the switching controller being used to control the valve core opening of the second regulating valve (32) according to the air inlet pressure of the feedwater pump turbine (2).

8. A steam source switching method for a feedwater pump turbine of a thermal power unit, implemented based on the steam source switching device according to any one of claims 1 to 7, characterized in that: The steam source switching method comprises: Get the current load of the thermal power unit; Determining that the current load of the thermal power unit is at a first load, supplying first steam to the feedwater pump turbine; Determine that the current load of the thermal power unit is at the second load, supply the first steam and auxiliary steam, the first steam and the auxiliary steam are coupled to form the second steam which is transported to the feedwater pump turbine; wherein the pressure of the auxiliary steam is greater than the pressure of the first steam, and the temperature of the auxiliary steam is higher than the temperature of the first steam.

9. The steam source switching method according to claim 8, characterized in that: The first load is greater than or equal to 40% of the rated load of the thermal power unit, and the second load is less than 40% of the rated load of the thermal power unit.

10. The steam source switching method according to claim 8, characterized in that: Also includes: Detect the steam pressure at the air inlet of the feedwater pump turbine; The auxiliary steam supply is adjusted according to the steam pressure at the air inlet of the feedwater pump turbine.

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