GENERALIZED FREQUENCY CONVERSION SYSTEM FOR STEAM TURBINE GENERATOR UNIT

Abstract

The present invention provides a generalized frequency conversion system for a steam turbine generator unit. The system comprises at least a steam turbine (T) with an adjustable rotating speed, a water feeding pump (BFP), a generator (G), a speed increasing gearbox (GB), a variable frequency bus (a, c) and an auxiliary machine connected thereto. With a change in load of the unit, parameters of steam entering the steam turbine (T) and an extracted steam amount are correspondingly adjusted (changed), so that the rotating speed of the steam turbine (T) changes correspondingly; and thus the rotating speed of the water feeding pump (BFP) is changed through the speed increasing gearbox (GB) on the one hand, and the frequency of an alternating current outputted by the generator (G) is changed on the other hand. Other types of frequency converters do not need to be additionally provided. The system is simple, reliable, low in cost, and high in efficiency.

Claims

1. A generalized frequency conversion system for a steam turbine generator unit, comprising a steam turbine with an adjustable rotating speed, a water feeding pump, a generator, a speed increasing gearbox, a variable frequency bus and an auxiliary machine, characterized in that the steam turbine is connected with the water feeding pump through the speed increasing gearbox to drive the water feeding pump; the steam turbine is connected with the generator to drive the generator to generate power; and the generator is connected with a motor of the auxiliary machine through the variable frequency bus.

2. The generalized frequency conversion system according to claim 1, characterized in that the generalized frequency conversion system further comprises an industrial frequency bus and an industrial frequency power supply; and the motor of the auxiliary machine is connected with the industrial frequency power supply through the industrial frequency bus.

3. The generalized frequency conversion system according to claim 1, characterized in that the generalized frequency conversion system further comprises a clutch system provided between the steam turbine and the generator.

4. The generalized frequency conversion system according to claim 3, characterized in that the clutch system can be a separate safety coupling, or a separate clutch or a combination of a safety coupling and a clutch.

5. The generalized frequency conversion system according to claim 1, characterized in that the generalized frequency conversion system further comprises a voltage transformer; and the voltage transformer is provided at the rear of an output end of the generator and is connected with the motor of the auxiliary machine through the variable frequency bus.

6. The generalized frequency conversion system according to claim 1, characterized in that the generalized frequency conversion system further comprises a switch and an industrial frequency bus; the motor of the auxiliary machine is connected with the variable frequency bus through the switch; and the motor of the auxiliary machine is connected with the industrial frequency bus through the switch.

7. The generalized frequency conversion system according to claim 1, characterized in that the number of the auxiliary machines is at least one.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5 are schematic diagrams of systems according to specific embodiments of the present invention.

DESCRIPTION OF REFERENCE SIGNS IN THE DRAWINGS

[0030] T: steam turbine; G: generator; BFP: water feeding pump; GB: gearbox; C: clutch system; Tr: double-winding voltage transformer; Tr: three-winding voltage transformer;

[0031] a: variable frequency bus; b: industrial frequency bus;

[0032] c: variable frequency bus; d: industrial frequency bus;

[0033] 1a, 2a, 3a, . . . , na: switch between auxiliary machine and variable frequency bus;

[0034] 1b, 2b, 3b, . . . , nb: switch between auxiliary machine and industrial frequency bus;

[0035] 1c, 2c, 3c, . . . , nc: switch between auxiliary machine and variable frequency bus;

[0036] 1d, 2d, 3d, . . . , nd: switch between auxiliary machine and industrial frequency bus;

[0037] M1, M2, M3, . . . , Mn: motor of auxiliary machine;

[0038] M1, M2, M3, . . . , Mn: motor of auxiliary machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

[0039] As illustrated in FIG. 1, it illustrates a specific embodiment of a generalized frequency conversion system for a steam turbine generator unit, comprising a steam turbine T, a water feeding pump BFP, a generator G, a speed increasing gearbox GB, a variable frequency bus a and an industrial frequency bus b. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus a through switches 1a, 2a, 3a, . . . , na, and are connected with the industrial frequency bus b through switches 1b, 2b, 3b, . . . , nb. With a change in load of the unit, parameters of steam entering the steam turbine and an extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on the one hand, the rotating speed of the water feeding pump is changed indirectly through the gearbox; and on the other hand, the frequency of alternating current outputted by the generator is changed directly. The generator provides a variable frequency power supply for all auxiliary machines connected to the variable frequency bus a. The industrial frequency bus b and the variable frequency bus a may be switched to each other for a standby use. When the variable frequency steam turbine or generator fails or is under other special working conditions, all auxiliary machines on the variable frequency bus a can switch to the industrial frequency bus b quickly, thus ensuring the safe operation of the main steam turbine generator unit.

[0040] In this solution, the variable frequency steam turbine can choose longer last-stage blades because of its low rotating speed relative to the high speed water feeding pump steam turbine, so as to obtain a more adequate exhaust area and thus obtain a lower exhaust pressure. Taking a 53 MW variable frequency steam turbine as an example, the exhaust pressure is relatively reduced by 2.4 KPa, and the variable frequency steam turbine can therefore do more work by 3360 KW.

Embodiment 2

[0041] As illustrated in FIG. 2, it illustrates another specific embodiment of a generalized frequency conversion system for a steam turbine generator unit, comprising a steam turbine T, a water feeding pump BFP, a generator G, a speed increasing gearbox GB, a clutch system C, a variable frequency bus a and an industrial frequency bus b. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus a through switches 1a, 2a, 3a, . . . , na and are connected with the industrial frequency bus b through switches 1b, 2b, 3b, . . . , nb. With a change in load of the unit, the parameters of steam entering the steam turbine and the extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on the one hand, the rotating speed of the water feeding pump is changed indirectly through the gearbox; and on the other hand, the frequency of alternating current outputted by the generator is changed directly. The generator provides a variable frequency power supply for all auxiliary machines connected to the variable frequency bus a. The industrial frequency bus b and the variable frequency bus a may be switched to each other for a standby use. When the variable frequency steam turbine or generator fails or is under other special working conditions, auxiliary machines on the variable frequency bus a can switch to the industrial frequency bus b quickly, thus ensuring the safe operation of the main steam turbine generator unit.

[0042] Compared with embodiment 1, in this embodiment, the clutch system C is additionally provided. If an abnormal working condition (such as when the variable frequency generator or its electrical equipment fails and thus it is required that the generator must be shut down) occurs, the variable frequency generator can be disconnected directly through the clutch system, and instead, the steam turbine operates and drives the water feeding pump only. The reliability of the entire generalized frequency conversion system and the main steam turbine generator unit is improved.

Embodiment 3

[0043] As illustrated in FIG. 3, it illustrates another specific embodiment of a generalized frequency conversion system for a steam turbine generator unit, comprising a steam turbine T, a water feeding pump BFP, a generator G, a speed increasing gearbox GB, a double-winding voltage transformer Tr, a variable frequency bus a and an industrial frequency bus b. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus a through switches 1a, 2a, 3a, . . . , na and are connected with the industrial frequency bus b through switches 1b, 2b, 3b, . . . , nb. With a change in load of the unit, the parameters of steam entering the steam turbine and the extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on the one hand, the rotating speed of the water feeding pump is changed indirectly through the gearbox; and on the other hand, the frequency of alternating current outputted by the generator is changed directly. The generator provides a variable frequency power supply for all auxiliary machines connected to the variable frequency bus a. The industrial frequency bus b and the variable frequency bus a may be switched to each other for a standby use. When the variable frequency steam turbine or generator fails or is under other special working conditions, auxiliary machines on the variable frequency bus a can switch to the industrial frequency bus b quickly, thus ensuring the safety.

[0044] Compared with embodiment 1, in this embodiment, the double-winding voltage transformer Tr is additionally provided, so the output voltage of the generator, after voltage transformation, can meet the requirements of motors of all auxiliary machines at the same voltage level.

Embodiment 4

[0045] As illustrated in FIG. 4, it illustrates another specific embodiment of a generalized frequency conversion system for a steam turbine generator unit, comprising a steam turbine T, a water feeding pump BFP, a generator G, a speed increasing gearbox GB, a double-winding voltage transformer Tr, a variable frequency bus a, an industrial frequency bus b, a variable frequency bus c and an industrial frequency bus d. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus a through switches 1a, 2a, 3a, . . . , na and are connected with the industrial frequency bus b through switches 1b, 2b, 3b, . . . , nb. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus c through switches 1c, 2c, 3c, . . . , nc and are connected with the industrial frequency bus d through switches 1d, 2d, 3d, . . . , nd. With a change in load of the unit, the parameters of steam entering the steam turbine and the extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on the one hand, the rotating speed of the water feeding pump is changed indirectly through the gearbox; and on the other hand, the frequency of alternating current outputted by the generator is changed directly. The generator provides a variable frequency power supply for all auxiliary machines connected to the variable frequency bus a. The industrial frequency bus b and the variable frequency bus a may be switched to each other for a standby use. At the same time, through the double-winding voltage transformer Tr, a variable frequency power supply is provided for all auxiliary machines on the variable frequency bus c at different voltage levels. The industrial frequency bus d and the variable frequency bus c may be switched to each other for a standby use.

[0046] When the variable frequency steam turbine or generator fails or is under other special working conditions, auxiliary machines on the variable frequency bus a can switch to the industrial frequency bus b quickly; and at the same time, auxiliary machines on the variable frequency bus c can switch to the industrial frequency bus d quickly, thus ensuring the safe operation of the main steam turbine generator unit.

[0047] Compared with embodiment 1, in this embodiment, the output voltage of the generator can not only meet the voltage requirements of part of motors of auxiliary machines directly, but also meet the requirements of motors of auxiliary machines at other voltage levels after the voltage is transformed by the double-winding voltage transformer Tr.

Embodiment 5

[0048] As illustrated in FIG. 5, it illustrates another specific embodiment of a generalized frequency conversion system for a steam turbine generator unit, comprising a steam turbine T, a water feeding pump BFP, a generator G, a speed increasing gearbox GB, a three-winding voltage transformer Tr, a variable frequency bus a, an industrial frequency bus b, a variable frequency bus c and an industrial frequency bus d. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus a through switches 1a, 2a, 3a, . . . , na and are connected with the industrial frequency bus b through switches 1b, 2b, 3b, . . . , nb. Auxiliary machines M1, M2, M3, . . . , Mn are connected with the variable frequency bus c through switches 1c, 2c, 3c, . . . , nc and are connected with the industrial frequency bus d through switches 1d, 2d, 3d, . . . , nd. With a change in load of the unit, the parameters of steam entering the steam turbine and the extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on the one hand, the rotating speed of the water feeding pump is changed indirectly through the gearbox; and on the other hand, the frequency of alternating current outputted by the generator is changed directly. The generator provides a variable frequency power supply for all auxiliary machines connected to the variable frequency bus a. The industrial frequency bus b and the variable frequency bus a may be switched to each other for a standby use. At the same time, through the double-winding voltage transformer Tr, a variable frequency power supply is provided for all auxiliary machines on the variable frequency bus c at different voltage levels. The industrial frequency bus d and the variable frequency bus c may be switched to each other for a standby use.

[0049] When the variable frequency steam turbine or generator fails or is under other special working conditions, auxiliary machines on the variable frequency bus a can switch to the industrial frequency bus b quickly; and auxiliary machines on the variable frequency bus c can switch to the industrial frequency bus d quickly, thus ensuring the safe operation of the main steam turbine generator unit.

[0050] Compared with embodiment 1, in this embodiment, the output voltage of the generator is transformed by the three-winding transformer Tr; and then a variable frequency power supply is provided for motors of auxiliary machines at two different voltage levels through the variable frequency buses a and c respectively.

[0051] It should be noted that in the above-mentioned embodiments of the present invention, the double-winding voltage transformer Tr, three-winding voltage transformer Tr and clutch system C can be combined into a variety of embodiments, but all of them should fall within the protective scope of the present invention patent.

[0052] Specific embodiments of the present invention are described in detail above. It should be understood that one skilled in the art could make various modifications and variations according to the concept of the present invention without contributing any inventive labor. Therefore, all technical solutions which could be obtained by one skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protective scope determined by the claims.