A mutual backup switching system and method between combined unit superchargers

Abstract

The application discloses a combined unit booster inter-stand mutual standby switching system and method, relates to the technical field of combined cycle power stations, and aims to solve the problem of high cost required by the existing non-disturbance switching mode of the booster inter-stand, and the system comprises three sets of booster units, the booster units comprise two sets of normally-operated booster units and one set of standby booster units; one end of the three sets of booster units is connected with corresponding DBB valve groups, the DBB valve groups are connected with metering and filtering units of natural gas pressure regulating station inlets, the other end of the three sets of booster units is connected with standby switching valve groups, and the standby switching valve groups switch among the booster units according to the operation states of the booster units and switching instructions. The application can save the cost required by the booster switching, and greatly improves the switching reliability of the system.

Description

Technical Field

[0001] This invention relates to the field of combined cycle power plant technology, specifically to a system and method for mutual backup switching between booster compressors of combined units. Background Technology

[0002] Currently, there are two main methods for achieving seamless switching between booster compressors in combined cycle power units, both domestically and internationally.

[0003] (1) Pipeline capacity buffer scheme: There is usually a long distance between the turbocharger outlet and the gas turbine room, which generally passes through the plant pipe rack (or plant direct buried section), gas turbine fuel pre-mounted module, and gas turbine fuel module pipeline. Therefore, in the power plant feasibility study and preliminary design stage, under the premise of reasonable overall layout, the distance between the turbocharger and the gas turbine room can be appropriately increased, and the pipe diameter can be appropriately increased so that the pipeline volume between the turbocharger and the gas turbine fuel module meets the minimum buffer volume requirement.

[0004] (2) Compression Buffer Tank Scheme: To meet the minimum buffer volume requirement, a compression buffer tank device can also be installed. When the unit is running normally, the isolation valves before and after the compressor are open, the compressor works, and the natural gas from the natural gas header is compressed and pressurized to the set pressure. The isolation valves are then closed, and the compressor stops running. When the unit's booster compressor needs to be switched, the isolation valve after the compression buffer tank is opened, and the natural gas is depressurized to the set pressure through the pressure reducing valve, continuously supplying natural gas to the gas turbine until the unit's booster compressor completes the switching process.

[0005] However, the above methods (1) require reasonable arrangement in the preliminary design stage to increase the distance between the booster and the gas turbine room, and methods (2) require the installation of a compression buffer tank device, which is costly and not universally applicable. Summary of the Invention

[0006] This invention solves the problem of high cost required for existing seamless switching methods between booster compressors, and proposes a system and method for mutual backup switching between booster compressors in a combined unit, which saves the cost required for booster compressor switching and greatly improves the reliability of system switching.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a backup switching system between booster units in a combined unit, comprising three booster units, including two normally operating booster units and one standby booster unit; one end of each of the three booster units is connected to a corresponding DBB valve group, the DBB valve group being connected to a metering and filtering unit at the inlet of a natural gas pressure regulating station, and the other end of each of the three booster units is connected to a backup switching valve group, the backup switching valve group performing switching between booster units according to the operating status and switching command of the booster units.

[0008] This technical solution mainly includes three DBB valve groups, three booster units corresponding to the natural gas consumption of one gas turbine at 100% load, and a standby switching valve group. The standby switching valve group includes six pneumatic switching valve groups. The natural gas from the metering and filtering unit at the inlet of the natural gas pressure regulating station is divided into three paths, which enter the three booster units through the DBB valve groups respectively. The booster units boost the natural gas from 4~12 barg to 50.8~53.8 barg before it enters the standby switching valve group between the booster units for seamless switching.

[0009] The present invention is further configured such that the booster unit includes: The first booster unit has a first DBB valve group connected at one end and a first booster outlet branch connected at the other end to a standby switching valve group. The second booster unit has a second DBB valve group connected at one end and a second booster outlet branch connected to a standby switching valve group at the other end. The third booster unit is connected to the third DBB valve group at one end and to the third booster outlet branch of the standby switching valve group at the other end.

[0010] In this technical solution, the first booster unit is connected to the first DBB valve group, the second booster unit is connected to the second DBB valve group, and the third booster unit is connected to the third DBB valve group.

[0011] The present invention is further configured such that: the first booster outlet branch is a branch including a first pneumatic switching valve, the second booster outlet branch is a branch including a fourth or fifth pneumatic switching valve, and the third booster outlet branch is a branch including a sixth pneumatic switching valve.

[0012] In this technical solution, the inlet of the first pneumatic switching valve is connected to the first booster unit, and the outlet of the first pneumatic switching valve is connected to the first gas turbine pre-module. The inlets of the fourth and fifth pneumatic switching valves are both connected to the second booster unit, the outlet of the fourth pneumatic switching valve is connected to the first gas turbine pre-module, the outlet of the fifth pneumatic switching valve is connected to the second gas turbine pre-module, the inlet of the sixth pneumatic switching valve is connected to the third booster unit, and the outlet of the sixth pneumatic switching valve is connected to the second gas turbine pre-module.

[0013] The present invention is further configured such that: the inlet of the first pneumatic switching valve is connected to the inlet of the second pneumatic switching valve, and the outlet of the second pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

[0014] In this technical solution, when switching from the third booster unit to the first booster unit, the second pneumatic switching valve needs to be opened.

[0015] The present invention is further configured such that: the outlet of the first pneumatic switching valve is connected to the outlet of the third pneumatic switching valve, and the inlet of the third pneumatic switching valve is connected to the inlet of the sixth pneumatic switching valve.

[0016] In this technical solution, when switching from the first booster unit to the third booster unit, the third pneumatic switching valve needs to be opened.

[0017] The present invention is further configured such that: the fourth pneumatic switching valve and the fifth pneumatic switching valve are connected in parallel, the outlet of the fourth pneumatic switching valve is connected to the outlet of the first pneumatic switching valve, and the outlet of the fifth pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

[0018] In this technical solution, when switching from the first or third booster unit to the second booster unit, the fourth and fifth pneumatic switching valves are opened respectively.

[0019] A method for mutual backup switching between booster compressors in a combined generating unit, applicable to the aforementioned mutual backup switching system between booster compressors in a combined generating unit, includes: S1, when the first and second booster units are operating normally, the first and second booster units are switched to the third booster unit respectively through the standby switching valve group; S2, when the first and third booster units are operating normally, the first and third booster units are switched to the second booster unit respectively through the standby switching valve group; S3, when the second and third booster units are operating normally, the second and third booster units are switched to the first booster unit through the standby switching valve group.

[0020] In this technical solution, backup switching is carried out in a targeted manner according to the different operating states of the booster units; S1, S2 and S3 respectively represent the specific methods of switching booster units under different scenarios. By switching S1, S2 and S3, engineering investment is saved, system reliability is improved, and the problem of seamless switching of booster units is solved to a certain extent.

[0021] The present invention is further configured such that S1 includes: Switching from the first booster unit to the third booster unit: Open the third pneumatic switching valve to connect the third booster unit to the outlet branch of the first booster unit; Switching from the second booster unit to the third booster unit: Open the sixth pneumatic switching valve to connect the third booster unit to the outlet branch of the second booster unit.

[0022] In this technical solution, the condition of S1 is adjusted by opening the third pneumatic switching valve or the sixth pneumatic switching valve.

[0023] The present invention is further configured such that S2 includes: Switching from the first booster unit to the second booster unit: Open the fourth pneumatic switching valve to connect the second booster unit to the outlet branch of the first booster unit; Switching from the third booster unit to the second booster unit: Open the fifth pneumatic switching valve to connect the second booster unit to the outlet branch of the third booster unit.

[0024] In this technical solution, the condition of S2 is adjusted by opening the fourth pneumatic switching valve or the fifth pneumatic switching valve.

[0025] The present invention is further configured such that S3 includes: Switching from the second booster unit to the first booster unit: Open the first pneumatic switching valve to connect the first booster unit to the outlet branch of the second booster unit; Switching from the third booster unit to the first booster unit: Open the second pneumatic switching valve to connect the first booster unit to the outlet branch of the third booster unit.

[0026] In this technical solution, the situation of S3 is adjusted by opening the first pneumatic switching valve or the second pneumatic switching valve.

[0027] The present invention can bring the following beneficial effects: The present invention relates to a backup switching system between booster compressors in a combined unit, which saves the cost required for booster compressor switching and greatly improves the reliability of system switching. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a backup switching system between booster compressors in a combined unit, as described in this application.

[0029] Figure Labels 1. First booster unit; 2. Second booster unit; 3. Third booster unit; 4. First DBB valve group; 5. Second DBB valve group; 6. Third DBB valve group 11. First pneumatic switching valve; 12. Second pneumatic switching valve; 13. Third pneumatic switching valve; 14. Fourth pneumatic switching valve; 15. Fifth pneumatic switching valve; 16. Sixth pneumatic switching valve. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] Currently, the 9H-class gas-steam combined cycle unit is the most efficient gas turbine unit in the world. A certain combined cycle power plant project is designed with a 9H-class "two-on-one" gas-steam combined cycle unit, including two Mitsubishi M701JAC gas turbine generator sets, two three-pressure, reheat, natural circulation boilers, and one three-pressure, reheat pure condensing steam turbine generator set, using natural gas as fuel. The gas turbine output is 550.30MW, the steam turbine output is 539.12MW, and the total output of the combined cycle power plant is approximately 1639.72MW, with a net efficiency of 64.13%.

[0032] A certain combined cycle power plant project has placed high demands on the performance and reliability of the booster units, requiring that the booster units be able to serve as backups for each other without reducing the load on the gas turbine.

[0033] Currently, the main methods for achieving seamless switching between booster compressors in combined cycle units are the pipe capacity buffer scheme and the compression buffer tank scheme, but both methods have drawbacks.

[0034] Example 1 To address the high cost of existing seamless switching methods between booster compressors, this embodiment proposes a mutual backup switching system between booster compressors in a combined unit, referencing... Figure 1 It mainly includes three sets of booster units, of which two sets are in normal operation and one set is in standby status.

[0035] One end of each of the three booster units is connected to a corresponding DBB valve group, meaning each booster unit is connected to a DBB valve group. One end of the DBB valve group is connected to the metering and filtering unit at the inlet of the natural gas pressure regulating station, and the other end of the three booster units is connected to a standby switching valve group. The standby switching valve group can switch between booster units according to the operating status and switching command of the booster units.

[0036] The above technical solution mainly includes three DBB valve groups, three booster units corresponding to the natural gas consumption of one gas turbine at 100% load, and a standby switching valve group. The standby switching valve group includes six pneumatic switching valve groups. The natural gas from the metering and filtering unit at the inlet of the natural gas pressure regulating station is divided into three paths, which enter the three booster units through the DBB valve groups respectively. The booster units boost the natural gas from 4~12 barg to 50.8~53.8 barg before it enters the standby switching valve group between the booster units for seamless switching.

[0037] refer to Figure 1 More specifically, the booster units mainly include the first booster unit 1, the second booster unit 2, and the third booster unit 3.

[0038] One end of the first booster unit is connected to the first DBB valve group 4, and the other end of the first booster unit is connected to the first booster outlet branch of the standby switching valve group.

[0039] One end of the second booster unit is connected to the second DBB valve group 5, and the other end of the second booster unit is connected to the second booster outlet branch of the standby switching valve group. One end of the third booster unit is connected to the third DBB valve group 6, and the other end of the third booster unit is connected to the third booster outlet branch of the standby switching valve group.

[0040] In this technical solution, the first booster unit is connected to the first DBB valve group, the second booster unit is connected to the second DBB valve group, and the third booster unit is connected to the third DBB valve group.

[0041] Furthermore, the first booster compressor outlet branch includes the first pneumatic switching valve 11, the second booster compressor outlet branch includes the fourth pneumatic switching valve 14 or the fifth pneumatic switching valve 15, and the third booster compressor outlet branch includes the sixth pneumatic switching valve 16.

[0042] In the above technical solution, the inlet of the first pneumatic switching valve is connected to the first booster unit, the outlet of the first pneumatic switching valve is connected to the first gas turbine pre-module, the inlets of the fourth and fifth pneumatic switching valves are both connected to the second booster unit, the outlet of the fourth pneumatic switching valve is connected to the first gas turbine pre-module, the outlet of the fifth pneumatic switching valve is connected to the second gas turbine pre-module, the inlet of the sixth pneumatic switching valve is connected to the third booster unit, and the outlet of the sixth pneumatic switching valve is connected to the second gas turbine pre-module.

[0043] The inlet of the first pneumatic switching valve is connected to the inlet of the second pneumatic switching valve 12, and the outlet of the second pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

[0044] In the above technical solution, when switching from the third booster unit to the first booster unit, the second pneumatic switching valve needs to be opened.

[0045] The outlet of the first pneumatic switching valve is connected to the outlet of the third pneumatic switching valve 13, and the inlet of the third pneumatic switching valve is connected to the inlet of the sixth pneumatic switching valve.

[0046] In the above technical solution, when switching from the first booster unit to the third booster unit, the third pneumatic switching valve needs to be opened.

[0047] The fourth and fifth pneumatic switching valves are connected in parallel. The outlet of the fourth pneumatic switching valve is connected to the outlet of the first pneumatic switching valve, and the outlet of the fifth pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

[0048] In the above technical solution, when switching from the first booster unit or the third booster unit to the second booster unit, the fourth pneumatic switching valve and the fifth pneumatic switching valve are opened respectively.

[0049] Example 2 This embodiment proposes a system for mutual backup switching between booster compressors in a combined unit, referring to... Figure 1 It mainly includes three sets of booster units, of which two sets are in normal operation and one set is in standby status.

[0050] One end of each of the three booster units is connected to a corresponding DBB valve group, meaning each booster unit is connected to a DBB valve group. One end of the DBB valve group is connected to the metering and filtering unit at the inlet of the natural gas pressure regulating station, and the other end of the three booster units is connected to a standby switching valve group. The standby switching valve group can switch between booster units according to the operating status and switching command of the booster units.

[0051] The above technical solution mainly includes three DBB valve groups, three booster units corresponding to the natural gas consumption of one gas turbine at 100% load, and a standby switching valve group. The standby switching valve group includes six pneumatic switching valve groups. The natural gas from the metering and filtering unit at the inlet of the natural gas pressure regulating station is divided into three paths, which enter the three booster units through the DBB valve groups respectively. The booster units boost the natural gas from 4~12 barg to 50.8~53.8 barg before it enters the standby switching valve group between the booster units for seamless switching.

[0052] refer to Figure 1 More specifically, the booster units mainly include the first booster unit, the second booster unit, and the third booster unit.

[0053] One end of the first booster unit is connected to the first DBB valve group, and the other end of the first booster unit is connected to the first booster outlet branch of the standby switching valve group.

[0054] One end of the second booster unit is connected to the second DBB valve group, and the other end of the second booster unit is connected to the second booster outlet branch of the standby switching valve group. One end of the third booster unit is connected to the third DBB valve group, and the other end of the third booster unit is connected to the third booster outlet branch of the standby switching valve group.

[0055] In this technical solution, the first booster unit is connected to the first DBB valve group, the second booster unit is connected to the second DBB valve group, and the third booster unit is connected to the third DBB valve group.

[0056] Furthermore, the first booster compressor outlet branch is a branch containing the first pneumatic switching valve, the second booster compressor outlet branch is a branch containing the fourth or fifth pneumatic switching valve, and the third booster compressor outlet branch is a branch containing the sixth pneumatic switching valve.

[0057] In the above technical solution, the inlet of the first pneumatic switching valve is connected to the first booster unit, the outlet of the first pneumatic switching valve is connected to the first gas turbine pre-module, the inlets of the fourth and fifth pneumatic switching valves are both connected to the second booster unit, the outlet of the fourth pneumatic switching valve is connected to the first gas turbine pre-module, the outlet of the fifth pneumatic switching valve is connected to the second gas turbine pre-module, the inlet of the sixth pneumatic switching valve is connected to the third booster unit, and the outlet of the sixth pneumatic switching valve is connected to the second gas turbine pre-module.

[0058] The inlet of the first pneumatic switching valve is connected to the inlet of the second pneumatic switching valve, and the outlet of the second pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

[0059] The outlet of the first pneumatic switching valve is connected to the outlet of the third pneumatic switching valve, and the inlet of the third pneumatic switching valve is connected to the inlet of the sixth pneumatic switching valve.

[0060] The fourth and fifth pneumatic switching valves are connected in parallel. The outlet of the fourth pneumatic switching valve is connected to the outlet of the first pneumatic switching valve, and the outlet of the fifth pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

[0061] Based on the aforementioned system for mutual backup switching between booster compressors in a combined generating unit, this embodiment also proposes a method for mutual backup switching between booster compressors in a combined generating unit, which mainly includes the following process.

[0062] S1, when the first and second booster units are operating normally, that is, when the third booster unit is in standby mode, the first and second booster units are switched to the third booster unit by adjusting the standby switching valve group.

[0063] S2, when the first and third booster units are operating normally, that is, when the second booster unit is in standby mode, the first and third booster units are switched to the second booster unit by adjusting the standby switching valve group.

[0064] S3, when the second and third booster units are operating normally, that is, when the first booster unit is in standby mode, the second and third booster units are switched to the first booster unit by adjusting the standby switching valve group.

[0065] In the above technical solution, backup switching is carried out in a targeted manner according to the different operating states of the booster units; S1, S2 and S3 respectively represent the specific methods of switching booster units under different scenarios. By switching S1, S2 and S3, engineering investment is saved, system reliability is improved, and the problem of seamless switching of booster units is solved to a certain extent.

[0066] More specifically, in S1, when the first booster unit is switched to the third booster unit, the third pneumatic switching valve is opened to connect the third booster unit to the outlet branch of the first booster unit, so that the third booster unit replaces the first booster unit for normal operation.

[0067] When switching from the second booster unit to the third booster unit, the sixth pneumatic switching valve is opened to connect the third booster unit to the outlet branch of the second booster unit, so that the third booster unit can replace the second booster unit for normal operation.

[0068] In the above technical solution, S1 is adjusted by opening the third pneumatic switching valve or the sixth pneumatic switching valve.

[0069] More specifically, in S2, when the first booster unit is switched to the second booster unit, the fourth pneumatic switching valve is opened to connect the second booster unit to the outlet branch of the first booster unit, so that the second booster unit can replace the first booster unit for normal operation.

[0070] When the third booster unit is switched to the second booster unit, the fifth pneumatic switching valve is opened to connect the second booster unit to the outlet branch of the third booster unit, so that the second booster unit can replace the third booster unit for normal operation.

[0071] In this technical solution, the condition of S2 is adjusted by opening the fourth pneumatic switching valve or the fifth pneumatic switching valve.

[0072] More specifically, in S3, when the second booster unit switches to the first booster unit, the first pneumatic switching valve is opened, and the first booster unit is connected to the outlet branch of the second booster unit. The first booster unit replaces the second booster unit for normal operation.

[0073] When the third booster unit switches to the first booster unit, the second pneumatic switching valve is opened to connect the first booster unit to the outlet branch of the third booster unit, and the first booster unit replaces the third booster unit for normal operation.

[0074] In this technical solution, the situation of S3 is adjusted by opening the first pneumatic switching valve or the second pneumatic switching valve.

[0075] Example 3 Based on Example 2, and referring to Figure 1Taking a combined cycle power plant in a certain country as an example, this paper further details the seamless switching process between booster compressors as backups for each other under non-faulty operating conditions.

[0076] For S1, more specifically, when the first and second booster units are operating normally, the third booster unit is in standby mode. Therefore, the first DBB valve group, the second DBB valve group, the first pneumatic switching valve, and the fifth pneumatic switching valve are open, while the third DBB valve group, the second pneumatic switching valve, the third pneumatic switching valve, the fourth pneumatic switching valve, and the sixth pneumatic switching valve are closed.

[0077] (1) When the first booster unit needs to be switched to the third booster unit, the standby third booster unit is started, and the third DBB valve group is opened at the same time. When the parameters meet the requirements, the pneumatic switching valve (third pneumatic switching valve) connected to the third booster unit is opened. At this time, the first booster unit is shut down, and the safety shut-off valves before and after the first booster unit (first DBB valve group and first pneumatic switching valve) are automatically shut down as the booster unit is shut down. The natural gas outlet of the third booster unit is merged into the original outlet branch of the first booster unit.

[0078] (2) When the second booster unit needs to be switched to the third booster unit, the standby third booster unit is started, and the third DBB valve group is opened at the same time. When the parameters meet the requirements, the pneumatic switching valve (sixth pneumatic switching valve) connected to the third booster unit is opened. At this time, the second booster unit is shut down, and the safety shut-off valves before and after the second booster unit (second DBB valve group and fifth pneumatic switching valve) are automatically closed as the booster unit is shut down. The natural gas outlet of the third booster unit is merged into the original outlet branch of the second booster unit.

[0079] For S2, more specifically, when both the first and third booster units are operating normally, the second booster unit is in hot standby mode. Therefore, the first DBB valve group, the third DBB valve group, the first pneumatic switching valve, and the sixth pneumatic switching valve are open, while the second DBB valve group, the second pneumatic switching valve, the third pneumatic switching valve, the fourth pneumatic switching valve, and the fifth pneumatic switching valve are closed.

[0080] (1) When the first booster unit needs to be switched to the second booster unit, the standby second booster unit is started, and the second DBB valve group is opened at the same time. When the parameters meet the requirements, the pneumatic switching valve (fourth pneumatic switching valve) connected to the second booster unit is opened. At this time, the first booster unit is shut down, and the safety shut-off valves (first DBB valve group and first pneumatic switching valve) before and after the first booster unit are automatically shut down as the booster unit is shut down. The natural gas outlet of the second booster unit is merged into the original outlet branch of the first booster unit.

[0081] (2) When the third booster unit needs to switch to the second booster unit, the standby second booster unit starts up, and the second DBB valve group opens at the same time. When the parameters meet the requirements, the pneumatic switching valve (fourth pneumatic switching valve) connected to the second booster unit opens. At this time, the third booster unit is shut down, and the safety shut-off valves before and after the third booster unit (third DBB valve group and sixth pneumatic switching valve) automatically close as the booster unit is shut down. The natural gas outlet of the second booster unit is merged into the original outlet branch of the third booster unit.

[0082] For S3, more specifically, when the second and third booster units are operating normally, the first booster unit is in hot standby mode. Therefore, the second DBB valve group, the third DBB valve group, the fourth pneumatic switching valve, and the sixth pneumatic switching valve are open, while the first DBB valve group, the first pneumatic switching valve, the second pneumatic switching valve, the third pneumatic switching valve, and the fifth pneumatic switching valve are closed.

[0083] (1) When the second booster unit needs to switch to the operation of the first booster unit, the standby first booster unit is started, and the first DBB valve group is opened at the same time. When the parameters meet the requirements, the pneumatic switching valve (first pneumatic switching valve) connected to the first booster unit is opened; at this time, the second booster unit is shut down, and the safety shut-off valves (second DBB valve group and fourth pneumatic switching valve) before and after the second booster unit are automatically shut down as the booster unit is shut down. The natural gas outlet of the first booster unit is merged into the original outlet branch of the second booster unit.

[0084] (2) When the third booster unit needs to switch to the first booster unit, the standby first booster unit starts up, and the first DBB valve group opens at the same time. When the parameters meet the requirements, the pneumatic switching valve (second pneumatic switching valve) connected to the first booster unit opens. At this time, the third booster unit shuts down, and the safety shut-off valves before and after the third booster unit (third DBB valve group and sixth pneumatic switching valve) automatically close as the booster unit shuts down. The natural gas outlet of the first booster unit is merged into the original outlet branch of the third booster unit.

[0085] Based on the above, this application achieves seamless switching between booster compressors under non-faulty operating conditions by utilizing a backup switching valve group. Compared to existing technologies, this application eliminates the compression buffer tank system and the pipe capacity buffer system, saving engineering investment, improving system reliability, and solving the problem of seamless switching between booster compressor units to a certain extent.

Claims

1. A system for mutual backup switching between booster compressors in a combined generating unit, characterized in that, It includes three booster units, two of which are in normal operation and one is in standby status. Each of the three booster units is connected to a corresponding DBB valve group at one end. The DBB valve group is connected to the metering and filtering unit at the inlet of the natural gas pressure regulating station. The other end of the three booster units is connected to the first booster outlet branch, the second booster outlet branch, and the third booster outlet branch of the standby switching valve group, respectively. The standby switching valve group switches between booster units according to the operating status and switching command of the booster units. The first booster compressor outlet branch is a branch containing the first pneumatic switching valve, the second booster compressor outlet branch is a branch containing the fourth or fifth pneumatic switching valve, and the third booster compressor outlet branch is a branch containing the sixth pneumatic switching valve. The inlet of the first pneumatic switching valve is connected to the inlet of the second pneumatic switching valve, and the outlet of the second pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve; the outlet of the first pneumatic switching valve is connected to the outlet of the third pneumatic switching valve, and the inlet of the third pneumatic switching valve is connected to the inlet of the sixth pneumatic switching valve; the fourth and fifth pneumatic switching valves are connected in parallel, the outlet of the fourth pneumatic switching valve is connected to the outlet of the first pneumatic switching valve, and the outlet of the fifth pneumatic switching valve is connected to the outlet of the sixth pneumatic switching valve.

2. The mutual backup switching system between booster compressors of a combined unit according to claim 1, characterized in that, The booster unit includes: The first booster unit has a first DBB valve group connected at one end and a first booster outlet branch connected at the other end to a standby switching valve group. The second booster unit has a second DBB valve group connected at one end and a second booster outlet branch connected to a standby switching valve group at the other end. The third booster unit is connected to the third DBB valve group at one end and to the third booster outlet branch of the standby switching valve group at the other end.

3. The mutual backup switching system between booster compressors of a combined unit according to claim 2, characterized in that, The inlet of the first pneumatic switching valve is connected to the first booster unit, and the outlet of the first pneumatic switching valve is connected to the first gas turbine pre-module. The inlets of the fourth and fifth pneumatic switching valves are both connected to the second booster unit. The outlet of the fourth pneumatic switching valve is connected to the first gas turbine pre-module, and the outlet of the fifth pneumatic switching valve is connected to the second gas turbine pre-module. The inlet of the sixth pneumatic switching valve is connected to the third booster unit, and the outlet of the sixth pneumatic switching valve is connected to the second gas turbine pre-module.

4. The mutual backup switching system between booster compressors of a combined unit according to claim 3, characterized in that, When switching from the first or third booster unit to the second booster unit, the fourth and fifth pneumatic switching valves are opened respectively.

5. A method for mutual backup switching between booster compressors in a combined generating unit, applicable to the mutual backup switching system between booster compressors in a combined generating unit according to any one of claims 1-4, characterized in that, include: S1, when the first and second booster units are operating normally, the first and second booster units are switched to the third booster unit respectively through the standby switching valve group; S2, when the first and third booster units are operating normally, the first and third booster units are switched to the second booster unit respectively through the standby switching valve group; S3, when the second and third booster units are operating normally, the second and third booster units are switched to the first booster unit through the standby switching valve group.

6. The method for mutual backup switching between booster compressors in a combined unit according to claim 5, characterized in that, S1 includes: Switching from the first booster unit to the third booster unit: Open the third pneumatic switching valve to connect the third booster unit to the outlet branch of the first booster unit; Switching from the second booster unit to the third booster unit: Open the sixth pneumatic switching valve to connect the third booster unit to the outlet branch of the second booster unit.

7. The method for mutual backup switching between booster compressors in a combined unit according to claim 5, characterized in that, S2 includes: Switching from the first booster unit to the second booster unit: Open the fourth pneumatic switching valve to connect the second booster unit to the outlet branch of the first booster unit; Switching from the third booster unit to the second booster unit: Open the fifth pneumatic switching valve to connect the second booster unit to the outlet branch of the third booster unit.

8. A method for mutual backup switching between booster compressors in a combined unit according to claim 5, 6, or 7, characterized in that, S3 includes: Switching from the second booster unit to the first booster unit: Open the first pneumatic switching valve to connect the first booster unit to the outlet branch of the second booster unit; Switching from the third booster unit to the first booster unit: Open the second pneumatic switching valve to connect the first booster unit to the outlet branch of the third booster unit.

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