A deep peak-shaving steam turbine generator set and its control method

Abstract

This invention discloses a deep peak-shaving steam turbine generator set and its control method, relating to the field of steam turbine power generation technology. The invention includes an intermediate and high-pressure module, a through-connecting shaft, a hollow low-pressure rotor, a clutch, a speed-changing transmission device, and a control system. The generator rotor is located at the end of the unit's shaft system and maintains a conventional arrangement; the low-pressure rotor is a hollow structure, coaxially sleeved on the outside of the through-connecting shaft and supported by independent bearings; the clutch controls the transmission connection between the low-pressure rotor and the intermediate and high-pressure module; the speed-changing transmission device can drive the low-pressure rotor to operate independently at varying speeds when the clutch is disengaged, and the speed does not exceed the speed of the intermediate and high-pressure rotor under any operating condition. The invention also includes a low-pressure cylinder cooling steam bypass system, which introduces controllable cooling steam into the low-pressure cylinder during cylinder cut-off. This invention achieves independent controllable low-pressure rotor speed, significantly reducing thermal standby energy consumption, while possessing inherent safety characteristics and comprehensive cooling protection, making it suitable for deep peak-shaving retrofitting of thermal power units.

Description

Technical Field

[0001] This invention relates to a deep peak-shaving steam turbine generator set and its control method, belonging to the field of steam turbine power generation technology. Background Technology

[0002] As the proportion of renewable energy generation continues to increase, coal-fired power units need to frequently perform deep peak shaving, and even need to be on standby at extremely low loads. Traditional steam turbine generator sets typically adopt a coaxial constant-speed design with high-pressure, medium-pressure rotors, low-pressure rotors, and generator rotors rigidly connected in series. This design suffers from problems such as low efficiency, high energy consumption for hot standby, and poor peak shaving flexibility when operating at low loads.

[0003] To address the aforementioned issues, NCB (condensing-extraction back-type) steam turbine units have emerged in the prior art. For example, an NCB-type heating steam turbine disclosed in document CN108167032B has a shaft system arrangement where the generator, intermediate and high-pressure cylinders, SSS clutch, and low-pressure cylinder are connected in sequence, with the generator located on the turbine head side. This unit uses the SSS clutch to achieve the disengagement and engagement of the low-pressure module. When the clutch is disengaged, steam does not enter the low-pressure cylinder, and the low-pressure rotor is in a disengaged, low-speed state (approximately 200 r / min).

[0004] However, existing NCB technology has the following shortcomings:

[0005] 1. The generator is located on the side of the turbine head, which changes the conventional layout of traditional thermal power units, increases the complexity of plant design and equipment layout, and is not conducive to the retrofitting and application of existing power plants.

[0006] 2. Low-pressure rotor speed is uncontrollable: When the clutch is disengaged, the low-pressure rotor only relies on the damping effect of the lubricating oil inside the clutch to maintain low-speed rotation, and the speed cannot be independently adjusted and controlled.

[0007] 3. Incomplete hot standby: Although the low-pressure rotor is at a low speed, it is still mechanically connected to the shaft system, and cannot achieve true zero-energy hot standby.

[0008] 4. Potential overspeed safety hazard: When the clutch disengages, if the steam valve is not closed tightly, a small amount of leaked steam may cause the low-pressure rotor to accelerate, and the existing technology lacks effective means to limit the speed of the low-pressure rotor.

[0009] Furthermore, in existing low-pressure cylinder cut-off technology, after the regulating valve on the low-pressure cylinder connecting pipe is closed, a cooling steam bypass system is usually required to prevent the low-pressure rotor from overheating and being damaged due to the blower effect. However, existing cooling steam systems mostly adopt desuperheating and depressurization schemes, which have problems such as low regulation accuracy and slow response speed. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a deep peak-shaving steam turbine generator set and its control method, which realizes independent controllability of low-pressure rotor speed, significantly reduces thermal standby energy consumption, and has inherent safety characteristics and perfect cooling protection, and is suitable for deep peak-shaving retrofit of thermal power units.

[0011] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0012] In a first aspect, the present invention provides a deep peak-shaving steam turbine generator set, comprising:

[0013] The high- and medium-pressure module includes a high- and medium-pressure rotor and a generator rotor rigidly connected coaxially to the high- and medium-pressure rotor, wherein the generator rotor is located at the end of the unit's shaft system;

[0014] A through-connecting shaft is coaxially and fixedly connected between the high-pressure rotor and the generator rotor to form an inner shaft system;

[0015] The low-voltage module includes a low-voltage rotor, which is a hollow rotor structure and is coaxially sleeved on the outside of the through-connecting shaft, with a radial gap between it and the through-connecting shaft.

[0016] The low-pressure rotor support bearing includes adjusting end bearings and electric end bearings located at both ends of the low-pressure rotor, which are used to bear the weight of the low-pressure rotor and the steam force.

[0017] A clutch is disposed between the through connecting shaft and the high- and medium-pressure module, and is used to control the transmission connection or disconnection between the low-pressure rotor and the high- and medium-pressure module;

[0018] A speed-changing transmission device, connected to the low-pressure rotor, is used to enable the low-pressure rotor to rotate independently at different speeds when the clutch is disengaged;

[0019] The medium and low pressure cylinder connecting pipe system includes a medium and low pressure cylinder connecting pipe and a low pressure steam inlet regulating butterfly valve installed on the medium and low pressure cylinder connecting pipe. The inlet end of the medium and low pressure cylinder connecting pipe is connected to the medium pressure exhaust port of the high and medium pressure cylinder, and the outlet end is connected to the low pressure cylinder steam inlet.

[0020] The low-pressure cylinder cooling steam bypass system includes a cooling steam bypass pipe and a bypass regulating valve installed on the cooling steam bypass pipe. The cooling steam bypass pipe is connected in parallel to both ends of the low-pressure steam inlet regulating butterfly valve.

[0021] The control system, which is signal-connected to the clutch, transmission device, low-pressure steam inlet regulating butterfly valve and bypass regulating valve, is configured to execute different operating modes.

[0022] Furthermore, the transmission is configured such that when the clutch is disengaged and the low-pressure rotor operates independently, the speed of the low-pressure rotor does not exceed the speed of the high- and medium-pressure rotor under any operating condition.

[0023] Furthermore, the transmission device includes a gearbox and an auxiliary drive motor, wherein:

[0024] The gearbox has a first port, a second port and a third port, the first port being drivenly connected to the low-pressure rotor and the second port being drivenly connected to the clutch.

[0025] The auxiliary drive motor is connected to the third port of the gearbox, and the auxiliary drive motor is used to drive the low-pressure rotor to rotate independently at different speeds through the gearbox when the clutch is disengaged.

[0026] Furthermore, the clutch is a synchronous self-shifting clutch or an SSS clutch.

[0027] Furthermore, the low-pressure cylinder cooling steam bypass system also includes a throttling component installed on the bypass pipe, wherein the throttling component is a throttling orifice plate or a tapered nozzle.

[0028] Furthermore, the low-pressure cylinder cooling steam bypass system also includes a water spray desuperheating device installed on the bypass pipeline.

[0029] Furthermore, it also includes a low-pressure cylinder steam inlet bypass system, which includes a low-pressure cylinder steam inlet bypass pipe and a bypass control valve. One end of the low-pressure cylinder steam inlet bypass pipe is connected to the medium and low-pressure cylinder connecting pipe and is located before the low-pressure steam inlet adjusting butterfly valve, and the other end is connected to the condenser. The bypass control valve is installed on the low-pressure cylinder steam inlet bypass pipe.

[0030] Furthermore, it also includes a heating steam extraction system, which includes a middle exhaust steam extraction pipe connected to the medium and low pressure cylinder connecting pipe and located before the low pressure steam inlet regulating butterfly valve, and an extraction steam control valve installed on the extraction steam pipe.

[0031] In a second aspect, the present invention provides a control method for implementing the deep peak-shaving steam turbine generator set described in any of the preceding claims, comprising:

[0032] Normal power generation mode: When the clutch is closed, the low-pressure rotor rotates at the same speed as the intermediate and high-pressure modules, the low-pressure steam inlet regulating butterfly valve is opened, and steam is simultaneously introduced into the intermediate and high-pressure cylinders and the low-pressure cylinder to generate electricity.

[0033] Deep peak shaving mode: When the target power generation load is lower than the preset threshold, the low-pressure steam inlet regulating butterfly valve is closed to cut off the main steam inlet of the low-pressure cylinder; the clutch is disengaged to disconnect the low-pressure rotor from the intermediate and high-pressure modules; the transmission device drives the low-pressure rotor to run at a speed lower than the set speed threshold; at the same time, cooling steam is introduced into the low-pressure cylinder through the low-pressure cylinder cooling steam bypass system to remove the heat from the blower; only the intermediate and high-pressure modules drive the generator rotor to generate electricity.

[0034] Grid-connected recovery mode: When it is necessary to increase the power generation load, the control system gradually increases the speed of the low-pressure rotor through the speed transmission device, but keeps its speed below or equal to the rated speed of the intermediate and high-pressure rotors; when the speed of the low-pressure rotor increases to the point that the difference between its speed and that of the intermediate and high-pressure rotors is less than the preset synchronization range, the control clutch is closed; the low-pressure steam inlet regulating butterfly valve is gradually opened to allow steam to re-enter the low-pressure cylinder to do work, and the unit returns to normal power generation mode.

[0035] Furthermore, in the deep peak shaving mode, the low-pressure rotor speed is controlled below 500 rpm, and the cooling steam flow rate is controlled at 2% to 5% of the rated intake flow rate of the low-pressure cylinder.

[0036] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0037] 1. Maintain conventional generator tail layout: The generator is still located at the end of the shaft system, which is consistent with the layout of most existing thermal power units. This facilitates the transformation and upgrading of existing power plants without changing the plant layout and equipment foundation.

[0038] 2. Through-shaft + hollow rotor structure: By designing the low-pressure rotor as a hollow structure, coaxially sleeved on the outside of the narrow-diameter through-shaft, and independently supported at both ends, a dual-rotor arrangement is realized in a limited space, with a compact structure and reasonable and reliable mechanical support.

[0039] 3. Independent controllable low-pressure rotor speed: The low-pressure rotor speed can be actively and precisely controlled through the variable speed transmission device, and the speed can be optimized according to the operating conditions to further reduce the energy consumption of thermal standby.

[0040] 4. Extremely efficient hot standby: By reducing the low-pressure rotor to an ultra-low speed of less than 500 rpm, the blower loss of the low-pressure cylinder under low load is completely eliminated, and the power consumption of the plant is greatly reduced.

[0041] 5. Intrinsically safe design: By imposing hard constraints on the low-pressure rotor speed through the control system, it is ensured that the low-pressure rotor speed will never exceed the high- and medium-pressure rotor speed under any circumstances, fundamentally eliminating the risk of catastrophic accidents such as runaway after the low-pressure rotor is disengaged.

[0042] 6. Comprehensive cooling guarantee: By setting up a low-pressure cylinder cooling steam bypass system, even when the low-pressure steam inlet regulating butterfly valve is fully closed, it can still provide precise and controllable cooling steam to the low-pressure cylinder, effectively removing the heat from the blower and preventing the low-pressure rotor from overheating and being damaged.

[0043] 7. Year-round deep peak shaving capability: By setting up a low-pressure cylinder steam inlet bypass, the low-pressure cylinder can be completely cut off even in the non-heating season, enabling the unit to have year-round deep peak shaving capability without seasonal restrictions.

[0044] 8. Precise flow control: By setting a throttling component and multi-stage regulating pipeline in the cooling steam bypass, precise regulation under small flow conditions is achieved, avoiding the problem of poor regulation characteristics of traditional butterfly valves at small openings. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a deep peak-shaving steam turbine generator set provided in an embodiment of the present invention.

[0046] In the diagram: 1. High and medium pressure cylinder; 2. High and medium pressure rotor; 3. Generator; 4. Generator rotor; 5. Through-connecting shaft; 6. Low pressure cylinder; 7. Low pressure rotor; 8. Adjusting end bearing; 9. Electrical end bearing; 10. Clutch; 11. Speed ​​transmission device; 12. Connecting pipe between medium and low pressure cylinders; 13. Low pressure steam inlet adjusting butterfly valve; 14. Cooling steam bypass pipe; 15. Bypass regulating valve; 16. Throttling component; 17. Water spray desuperheating device; 18. Low pressure cylinder steam inlet bypass pipe; 19. Bypass control valve; 20. Intermediate exhaust steam extraction pipe; 21. Steam extraction control valve; 22. First station of the heating network; 23. Condenser; 24. Control system. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0048] Example 1, such as Figure 1 As shown, this embodiment provides a deep peak-shaving steam turbine generator set with a hollow variable-speed low-pressure rotor for a 350MW thermal power unit. The generator set includes:

[0049] The high-pressure cylinder 1 and high-pressure rotor 2, generator 3 and generator rotor 4, with generator rotor 4 located at the end of the shaft system (tail side). The high-pressure rotor 2 and generator rotor 4 are rigidly connected coaxially via a thin-diameter through-shaft 5, forming an inner shaft system. This inner shaft system is supported by the original #2 bearing (not shown in the figure) of the high-pressure rotor and the original #3 bearing (not shown in the figure) of the generator rotor, and operates at a constant speed of 3000 rpm in parallel with the grid.

[0050] The low-pressure cylinder 6 and the low-pressure rotor 7 are hollow cylindrical structures, coaxially sleeved on the outside of the through-connecting shaft 5, with a radial clearance between them, so they do not contact each other. Independent adjusting end bearings 8 and electric end bearings 9 are respectively installed at both ends of the low-pressure cylinder 6. These two bearings are used to bear the weight of the low-pressure rotor 7 and the steam force, and to ensure the radial clearance between the rotor and stationary parts.

[0051] Clutch 10, an SSS clutch, is located between the through-connecting shaft 5 and the high- and medium-pressure rotor 2 (i.e., the high- and medium-pressure side), and is used to control the transmission connection or disconnection between the low-pressure rotor 7 and the high- and medium-pressure module. Transmission device 11, including a gearbox and an auxiliary drive motor, is connected between the low-pressure rotor 7 and clutch 10, wherein the gearbox is a single-stage planetary gearbox. When clutch 10 is engaged, the gearbox synchronizes the low-pressure rotor 7 to 3000 rpm at a 1:1 transmission ratio; when clutch 10 is disengaged, the auxiliary drive motor can drive the low-pressure rotor 7 to continuously variable speed within the range of 0-3000 rpm, and the control system 24 sets its maximum speed to not exceed 3000 rpm.

[0052] The intermediate and low-pressure cylinder connecting pipe system includes an intermediate and low-pressure cylinder connecting pipe 12 and a low-pressure steam inlet regulating butterfly valve 13 installed on it. The exhaust steam from the intermediate-pressure cylinder enters the low-pressure cylinder 6 through the intermediate and low-pressure cylinder connecting pipe 12. The low-pressure steam inlet regulating butterfly valve 13 is used to control the main steam inlet flow and has the ability to be fully closed to zero and tightly shut.

[0053] The low-pressure cylinder cooling steam bypass system is connected in parallel across the low-pressure inlet steam regulating butterfly valve 13, and includes a cooling steam bypass pipe 14, a bypass regulating valve 15, a throttling assembly 16, and a water spray desuperheating device 17. One end of the cooling steam bypass pipe 14 is connected to the intermediate-low pressure cylinder connecting pipe 12 and is located before the low-pressure inlet steam regulating butterfly valve 13; the other end is connected to the low-pressure cylinder inlet and is located after the low-pressure inlet steam regulating butterfly valve 13. The bypass regulating valve 15 is used to precisely control the cooling steam flow rate, and the throttling assembly 16 (using a tapered nozzle type) is used to improve the regulation accuracy at low flow rates and facilitate flow measurement. The water spray desuperheating device 17 is used to reduce the cooling steam temperature when necessary to prevent the low-pressure cylinder exhaust temperature from exceeding the standard. Based on experience data from 350MW-class units, the design flow rate of the cooling steam bypass system is approximately 17.4 t / h, equivalent to 2%~5% of the rated inlet steam flow rate.

[0054] The low-pressure cylinder steam inlet bypass system includes a low-pressure cylinder steam inlet bypass pipe 18 and a bypass control valve 19, which is used to directly introduce the medium-pressure cylinder exhaust steam into the condenser 23 during deep peak shaving in the non-heating season.

[0055] The heating extraction steam system includes an intermediate-pressure extraction steam pipe 20 and an extraction steam control valve 21, used to lead part of the intermediate-pressure cylinder exhaust steam to the first station 22 of the heating network during the heating season. The control system 24 is connected to the clutch 10, the speed transmission device 11, the low-pressure steam inlet regulating butterfly valve 13, the bypass regulating valve 15, the bypass control valve 19, the extraction steam control valve 21, and the temperature and pressure monitoring unit installed in the low-pressure cylinder, and is used to execute different operating modes.

[0056] Example 2: This example provides a control method for a deep peak-shaving steam turbine generator set based on the method described in Example 1, including the following modes:

[0057] (1) Normal power generation mode (taking the heating season as an example)

[0058] When clutch 10 is engaged, transmission device 11 synchronizes low-pressure rotor 7 to 3000 rpm. Low-pressure steam inlet regulating butterfly valve 13 is fully open, bypass regulating valve 15 is closed, bypass control valve 19 is closed, and extraction steam control valve 21 adjusts its opening according to heating demand. High-pressure cylinder 1 and low-pressure cylinder 6 simultaneously receive steam to generate electricity. The unit operates at full load of 350MW and simultaneously supplies heat to the first heating station 22 of the heating network.

[0059] (2) Deep peak shaving mode (non-heating season)

[0060] When the power grid requires the generating units to operate below 20% of their rated load (70MW), they enter deep peak-shaving mode:

[0061] The control system 24 gradually closes the low-pressure steam inlet regulating butterfly valve 13 to the fully closed position, cutting off the main steam inlet of the low-pressure cylinder 6;

[0062] At the same time, the bypass control valve 19 is opened, and the steam from the intermediate pressure cylinder is introduced into the condenser 23 through the low pressure cylinder steam inlet bypass pipe 18.

[0063] When the main steam intake of the low-pressure cylinder 6 drops to zero, the control system 24 issues a command, the SSS clutch 10 automatically disengages, and the low-pressure rotor 7 separates from the high- and medium-pressure generator shaft system.

[0064] The auxiliary drive motor of the speed change transmission device 11 starts, reducing the speed of the low-pressure rotor 7 to 300 rpm to maintain rotation;

[0065] At this time, only the high-pressure cylinder 1 drives the generator 3 to generate electricity, and the load can be reduced to below 50MW;

[0066] During this period, the control system 24 adjusts the opening of the bypass regulating valve 15 according to the low-pressure cylinder temperature monitoring data, and introduces an appropriate amount of cooling steam (about 15-20t / h) into the low-pressure cylinder 6 through the cooling steam bypass system to ensure that the blower heat generated by the low-pressure rotor 7 at the ultra-low speed of 300rpm is carried away in time to prevent the blades from overheating and being damaged.

[0067] (3) Deep peak shaving mode (heating season)

[0068] When the power grid requires generating units to supply heat simultaneously under deep peak shaving conditions, the system enters the deep peak shaving mode for the heating season:

[0069] The control system 24 gradually closes the low-pressure steam inlet regulating butterfly valve 13 to the fully closed position, cutting off the main steam inlet of the low-pressure cylinder 6;

[0070] Open the extraction steam control valve 21 to introduce all or most of the exhaust steam from the intermediate pressure cylinder into the first station 22 of the heating network for heating.

[0071] The control system 24 issues a command to disconnect the clutch 10, and the transmission device 11 reduces the low-pressure rotor 7 to 300 rpm.

[0072] A suitable amount of cooling steam is introduced into the low-pressure cylinder 6 through the cooling steam bypass system to remove the heat from the blower.

[0073] At this time, the high-pressure cylinder 1 generates electricity and supplies heat to the outside, thus achieving thermoelectric decoupling.

[0074] (4) Grid-connected recovery mode

[0075] When the power grid requires the generating units to restore to 50% load (175MW), it enters grid connection restoration mode:

[0076] The control system 24 first instructs the auxiliary drive motor of the speed transmission device 11 to accelerate, gradually increasing the speed of the low-pressure rotor 7;

[0077] During the lifting process, the speed of the low-pressure rotor 7 must be strictly controlled to never exceed 3000 rpm.

[0078] When the speed of the low-pressure rotor 7 increases to 2980 rpm, the control system 24 detects that the speed is close to and slightly lower than 3000 rpm and issues a command to close the SSS clutch 10.

[0079] After the SSS clutch 10 engages smoothly, the low-pressure rotor 7 is synchronized to 3000 rpm;

[0080] Subsequently, depending on the operating conditions, the bypass control valve 19 or the extraction steam control valve 21 was gradually closed, while the low-pressure steam inlet regulating butterfly valve 13 was gradually opened, and the low-pressure cylinder 6 resumed steam intake to perform work, and the unit load steadily increased to 175MW.

[0081] Example 3: Precise Control Strategy for Cooling Steam

[0082] In this embodiment, the cooling steam bypass system employs the following control strategy to ensure the safe operation of the low-pressure cylinder during cylinder cut-off:

[0083] 1. Minimum flow guarantee: After the low-pressure steam inlet regulating butterfly valve 13 is fully closed, the bypass regulating valve 15 automatically opens to the preset minimum opening degree to ensure that the cooling steam flow rate is not lower than the design minimum value (such as 15t / h).

[0084] 2. Temperature feedback control: A temperature monitoring point is set at the exhaust port of the low-pressure cylinder. When the exhaust temperature exceeds the set value (e.g., 80℃), the control system gradually opens the bypass regulating valve 15 to increase the cooling steam flow until the temperature drops back to a safe range.

[0085] 3. Pressure ratio protection control: The ratio of the inlet steam pressure to the outlet steam pressure of the low-pressure cylinder is monitored. When the ratio exceeds the safe range, the cooling steam flow rate is automatically adjusted to prevent the last stage blades of the low-pressure cylinder from fluttering due to the small volume flow rate.

[0086] 4. Multi-path parallel regulation: For a wider range of flow regulation needs, the cooling steam bypass system can be set up with multiple parallel small bypasses. Each small bypass is equipped with a small valve, and the flow rate can be precisely controlled in a step-like manner by opening different valves in combination.

[0087] Example 4: Security Protection Mechanism

[0088] In this embodiment, to further ensure safety, the control system 24 is equipped with multiple protections:

[0089] 1. Hard speed constraint: In the drive control program of the transmission device 11, 3000rpm is set as an insurmountable hard upper limit, and no control command can make the low-pressure rotor 7 speed exceed this value.

[0090] 2. Overspeed protection: An independent speed sensor is installed on the low-pressure rotor 7. When the detected speed exceeds 3050 rpm (including measurement error), the emergency brake is directly triggered, and the low-pressure steam inlet regulating butterfly valve 13, bypass regulating valve 15 and bypass control valve 19 are closed in an interlocking manner.

[0091] 3. Clutch status interlock: When the clutch 10 is detected to have disengaged unexpectedly, the control system 24 automatically switches the transmission device 11 to the speed control mode, controls the low-pressure rotor 7 at the preset safe speed (such as 300 rpm), and issues an alarm at the same time.

[0092] 4. Cooling failure protection: When the cooling steam flow rate is detected to be lower than the set minimum value and the exhaust steam temperature continues to rise above the alarm value, the control system 24 will automatically issue an alarm and prompt the operator to take measures. If necessary, it will automatically exit the deep peak shaving mode and restore the low-pressure cylinder steam intake.

[0093] Example 5: Shaft system dynamics design considerations

[0094] To ensure stable operation of the unit under various operating conditions, the dynamic characteristics of the shaft system were optimized.

[0095] The diameter and length of the through connecting shaft 5 are determined based on the critical speed calculation, so that it is far from the bending critical speed at the rated speed of 3000 rpm and has good unbalanced response characteristics.

[0096] The end bearings (adjusting end bearing 8 and electric end bearing 9) of the low-pressure rotor 7 are tilting pad bearings, which have good oil film stability and vibration resistance. The oil film stiffness and damping parameters of the bearings have been optimized to ensure that the low-pressure rotor 7 can remain stable when operating in a wide speed range of 300-3000 rpm.

[0097] The radial clearance between the through connecting shaft 5 and the low-pressure rotor 7 is determined based on thermal expansion calculations, and an elastic tooth seal is provided to minimize steam leakage loss while ensuring that no dynamic or static friction occurs.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A deep peak-shaving steam turbine generator set, characterized in that, include: The high- and medium-pressure module includes a high- and medium-pressure rotor and a generator rotor rigidly connected coaxially to the high- and medium-pressure rotor, wherein the generator rotor is located at the end of the unit's shaft system; A through-connecting shaft is coaxially and fixedly connected between the high-pressure rotor and the generator rotor to form an inner shaft system; The low-voltage module includes a low-voltage rotor, which is a hollow rotor structure and is coaxially sleeved on the outside of the through-connecting shaft, with a radial gap between it and the through-connecting shaft. The low-pressure rotor support bearing includes adjusting end bearings and electric end bearings located at both ends of the low-pressure rotor, which are used to bear the weight of the low-pressure rotor and the steam force. A clutch is disposed between the through connecting shaft and the high- and medium-pressure module, and is used to control the transmission connection or disconnection between the low-pressure rotor and the high- and medium-pressure module; A speed-changing transmission device, connected to the low-pressure rotor, is used to enable the low-pressure rotor to rotate independently at different speeds when the clutch is disengaged; The medium and low pressure cylinder connecting pipe system includes a medium and low pressure cylinder connecting pipe and a low pressure steam inlet regulating butterfly valve installed on the medium and low pressure cylinder connecting pipe. The inlet end of the medium and low pressure cylinder connecting pipe is connected to the medium pressure exhaust port of the high and medium pressure cylinder, and the outlet end is connected to the low pressure cylinder steam inlet. The low-pressure cylinder cooling steam bypass system includes a cooling steam bypass pipe and a bypass regulating valve installed on the cooling steam bypass pipe. The cooling steam bypass pipe is connected in parallel to both ends of the low-pressure steam inlet regulating butterfly valve. The control system, which is signal-connected to the clutch, transmission device, low-pressure steam inlet regulating butterfly valve and bypass regulating valve, is configured to execute different operating modes.

2. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, The transmission is configured such that when the clutch is disengaged and the low-pressure rotor operates independently, the speed of the low-pressure rotor does not exceed the speed of the high- and medium-pressure rotor under any operating condition.

3. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, The speed transmission device includes a gearbox and an auxiliary drive motor, wherein: The gearbox has a first port, a second port and a third port, the first port being drivenly connected to the low-pressure rotor and the second port being drivenly connected to the clutch. The auxiliary drive motor is connected to the third port of the gearbox, and the auxiliary drive motor is used to drive the low-pressure rotor to rotate independently at different speeds through the gearbox when the clutch is disengaged.

4. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, The clutch is a synchronous self-shifting clutch or an SSS clutch.

5. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, The low-pressure cylinder cooling steam bypass system also includes a throttling component installed on the bypass pipe, which is a throttling orifice plate or a tapered nozzle.

6. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, The low-pressure cylinder cooling steam bypass system also includes a water spray desuperheating device installed on the bypass pipeline.

7. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, It also includes a low-pressure cylinder steam inlet bypass system, which includes a low-pressure cylinder steam inlet bypass pipeline and a bypass control valve. One end of the low-pressure cylinder steam inlet bypass pipeline is connected to the medium and low-pressure cylinder connecting pipe and is located before the low-pressure steam inlet adjusting butterfly valve, and the other end is connected to the condenser. The bypass control valve is installed on the low-pressure cylinder steam inlet bypass pipeline.

8. The deep peak-shaving steam turbine generator set according to claim 1, characterized in that, It also includes a heating steam extraction system, which includes a middle exhaust steam extraction pipe connected to the medium and low pressure cylinder connecting pipe and located before the low pressure steam inlet regulating butterfly valve, and an extraction steam control valve installed on the extraction steam pipe.

9. A control method for a deep peak-shaving steam turbine generator set according to any one of claims 1 to 8, characterized in that, include: Normal power generation mode: When the clutch is closed, the low-pressure rotor rotates at the same speed as the intermediate and high-pressure modules, the low-pressure steam inlet regulating butterfly valve is opened, and steam is simultaneously introduced into the intermediate and high-pressure cylinders and the low-pressure cylinder to generate electricity. Deep peak shaving mode: When the target power generation load is lower than the preset threshold, the low-pressure steam inlet regulating butterfly valve is closed to cut off the main steam inlet of the low-pressure cylinder; the clutch is disengaged to disconnect the low-pressure rotor from the intermediate and high-pressure modules; the transmission device drives the low-pressure rotor to run at a speed lower than the set speed threshold; at the same time, cooling steam is introduced into the low-pressure cylinder through the low-pressure cylinder cooling steam bypass system to remove the heat from the blower; only the intermediate and high-pressure modules drive the generator rotor to generate electricity. Grid-connected recovery mode: When it is necessary to increase the power generation load, the control system gradually increases the speed of the low-pressure rotor through the speed transmission device, but keeps its speed below or equal to the rated speed of the intermediate and high-pressure rotors; when the speed of the low-pressure rotor increases to the point that the difference between its speed and that of the intermediate and high-pressure rotors is less than the preset synchronization range, the control clutch is closed; the low-pressure steam inlet regulating butterfly valve is gradually opened to allow steam to re-enter the low-pressure cylinder to do work, and the unit returns to normal power generation mode.

10. The control method for a deep peak-shaving steam turbine generator set according to claim 9, characterized in that, In the deep peak shaving mode, the low-pressure rotor speed is controlled below 500 rpm, and the cooling steam flow rate is controlled at 2% to 5% of the rated inlet flow rate of the low-pressure cylinder.

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