U.S. patent application number 16/093564 was filed with the patent office on 2019-03-07 for generalized frequency conversion system for steam turbine generator unit.
The applicant listed for this patent is Weizhong FENG. Invention is credited to Weizhong FENG.
Application Number | 20190071992 16/093564 |
Document ID | / |
Family ID | 60042247 |
Filed Date | 2019-03-07 |
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United States Patent
Application |
20190071992 |
Kind Code |
A1 |
FENG; Weizhong |
March 7, 2019 |
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.
Inventors: |
FENG; Weizhong; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FENG; Weizhong |
Shanghai |
|
CN |
|
|
Family ID: |
60042247 |
Appl. No.: |
16/093564 |
Filed: |
September 13, 2016 |
PCT Filed: |
September 13, 2016 |
PCT NO: |
PCT/CN2016/098827 |
371 Date: |
October 12, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 15/10 20130101;
H02P 9/04 20130101; H02P 27/047 20130101; F01K 7/165 20130101; F01K
13/02 20130101 |
International
Class: |
F01D 15/10 20060101
F01D015/10; H02P 9/04 20060101 H02P009/04; F01K 7/16 20060101
F01K007/16; H02P 27/04 20060101 H02P027/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2016 |
CN |
201610228304.2 |
Apr 13, 2016 |
CN |
201620307455.2 |
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
FIELD OF THE INVENTION
[0001] The present invention relates to the field of steam turbine
generator units, and in particular to a generalized frequency
conversion system for a steam turbine generator unit.
DESCRIPTION OF THE PRIOR ART
[0002] During production of power plants, water is heated into
steam in the boiler; and then steam is used to drive the steam
turbine to rotate, thereby driving the generator to rotate and
finally converting the chemical energy of the fuel into
electricity. In the process of power generation, a large number of
rotating auxiliary machines such as pumps and fans provided in the
power plants need to consume a large amount of electricity. At
present, the general practice is to use a plant transformer to draw
part of the generated electricity for the use of plant auxiliary
machines.
[0003] In engineering design of power plants, the capacity of
auxiliary machines is usually selected according to a maximum
demand plus a certain allowance, so the auxiliary machines in
actual operation have a relatively large margin. However, when the
auxiliary machines running at a fixed speed do not operate at full
load, especially at low load, their working efficiency will drop
sharply, which causes a serious waste of electricity. If the
frequency conversion technology is adopted, the working point of
the auxiliary machines can be enabled to be as close to the high
efficiency area as possible, and the throttling loss of the fan
baffle and valve can be reduced to the maximum extent, the energy
consumption of the equipment in operation can be greatly reduced,
and the service life of the equipment can be prolonged. Taking
centrifugal fans as an example, according to the principle of fluid
mechanics, shaft power is directly proportional to the third power
of rotating speed. When the required air volume is reduced and the
fan speed decreases, the power falls by the third power of the
speed. Therefore, the energy saving effect of variable-speed
operation is very considerable.
[0004] Frequency conversion speed adjustment technology is an
important means to save energy and reduce emission, improve process
flow to improve product quality and improve the environment, and
promote technological progress. Frequency conversion speed
adjustment is recognized as the most promising speed adjustment
mode at home and abroad because of its excellent speed adjustment
and starting and braking performance, high efficiency, high power
factor and power saving effect. At present, the frequency converter
is mainly mounted in power plants to change the frequency of the
pump or fan motor, thereby changing the rotating speed of the pump
or fan, improving its operation efficiency, to achieve the purposes
of energy saving and emission reduction.
[0005] Now the frequency conversion methods mainly include silicon
controlled rectifier frequency conversion, hydraulic coupling
frequency conversion and magnetic coupling frequency conversion.
Among the three frequency conversion methods, the hydraulic
coupling frequency conversion has the advantages of high power, low
reliability and low cost, its efficiency is directly proportional
to the first power of the rotating speed, and its adjustment
precision is low. Magnetic coupling frequency conversion has high
reliability and the highest cost, its efficiency is directly
proportional to the square of the rotating speed, the efficiency is
low when the rotating speed is low, and if a magnetic coupling
device is additionally mounted, the mounting position of the motor
or equipment needs to be changed and the original civil
construction foundation needs to be removed. Silicon controlled
rectifier frequency conversion has the advantage of the highest
efficiency, its efficiency is not affected by load changes, the
response is the fastest, and the adjustment accuracy is the
highest. In these three frequency conversion methods, the cost of
silicon controlled rectifier frequency conversion is in the middle.
In terms of cost and efficiency, the silicon controlled rectifier
frequency conversion technology is widely used in power plants.
[0006] Because of the high reliability of the equipment required in
power plants, the used rotating equipment such as circulating water
pump and blower have the advantages of high power and high voltage
level, so the requirement on the frequency converter used in power
plants is also extremely high. At present, the silicon controlled
rectifier technology is mainly used in frequency conversion
equipment in power plants. The biggest disadvantage of the silicon
controlled rectifier technology is that the higher the voltage
level is, the lower the reliability of the equipment is, the area
occupied by the frequency conversion equipment is large, and its
frequency conversion harmonic waves have influences on both the
power grid and the motor. Therefore, in the power plants, the
promotion and application of the silicon controlled rectifier
frequency conversion technology is relatively slow. With the
development of technology, some products have been able to better
solve the above-mentioned problems at present, but the high price
of these products hinders their further promotion.
[0007] For this, patent "ZL 2012 10006442.8" provides a frequency
conversion main power supply system for a thermal power plant,
which uses a separately arranged small steam turbine with
adjustable operating speed to drive a generator. By changing the
operating speed of the small steam turbine, the frequency of
alternating current outputted from the generator is changed. This
invention realizes that alternating current with required frequency
can be obtained without using a frequency converter, thus achieving
the purpose of energy saving. However, the shortcoming is that a
small steam turbine and a generator need to be additionally
configured; besides, corresponding auxiliary equipment such as
condenser and oil system, and control systems, electrical systems
and the like need to be supportively provided.
[0008] Therefore, patent "ZL 201420245755.3" further provides a
novel frequency conversion system for a thermal power plant, that
is, a water feeding pump steam turbine is directly connected to a
water feeding pump, a generator is indirectly connected through a
gearbox, the steam turbine also drives the generator through the
water feeding pump while driving the water feeding pump steam
turbine, this also realizes the same effect of obtaining
alternating current of required frequency without using other types
of frequency converters, and all auxiliary supporting systems are
combined into one. However, the shortcoming is that with the
increasing capacity of the unit at present, the capacity of the
feed water pump itself is relatively large, if the generator is
further driven, the power will be relatively greater. Taking a 1000
MW unit as an example, the design power of the water feeding pump
is about 38 MW and the rotating speed is generally 4500-5300 rpm,
which together with the auxiliary power of the generator lead to at
least 53 MW for the power of the water feeding pump steam turbine.
Moreover, the manufacturing process ability of water feeding pump
steam turbines is limited by factors such as cylinder structures
and blade strength at present, especially by the high stress at the
root of long blades caused by high centrifugal force under
high-speed rotation, the length of the last-stage blades and the
exhaust area of the steam turbine are limited, the exhaust pressure
of the water feeding pump steam turbines under the rated working
condition will be very high, and thus, not only the economy
efficiency is poor, but also it is difficult to match the rotating
speed of the water feeding pump.
[0009] Therefore, the present invention is devoted to developing a
generalized frequency conversion system having the advantages of
low cost, high reliability, high efficiency and simple
operation.
SUMMARY OF THE INVENTION
[0010] In view of the above-mentioned shortcomings of the prior
art, the purpose of the present invention is to provide a
generalized frequency conversion system having the advantages of
low cost, high reliability, high efficiency and simple
operation.
[0011] The present invention provides a generalized frequency
conversion system for a steam turbine generator unit. The system at
least comprises 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. The system is
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.
[0012] Further, the generalized frequency conversion system is
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.
[0013] Further, the generalized frequency conversion system is
characterized in that the generalized frequency conversion system
further comprises a clutch system provided between the steam
turbine and the generator.
[0014] Further, the generalized frequency conversion system is
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.
[0015] Alternatively, the generalized frequency conversion system
is characterized in that the generalized frequency conversion
system further comprises a corresponding voltage transformer
provided at the rear of an output end of the generator.
[0016] Alternatively, the generalized frequency conversion system
is 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.
[0017] Alternatively, the generalized frequency conversion system
is characterized in that the number of the auxiliary machines is at
least one.
[0018] The basic principle of the generalized frequency conversion
system provided by the present invention is as follows: the steam
turbine with an adjustable rotating speed (called as "variable
frequency steam turbine") is used to connect the speed increasing
gearbox to drive the water feeding pump and to further drive the
generator, so as to adjust (change) parameters and an amount of
steam entering the variable frequency steam turbine according to a
load variation of the unit, so that the rotating speed changes
correspondingly, thus the frequency of alternating current
outputted from the generator is changed, the power frequency of
motors of all auxiliary machines connected to the variable
frequency bus is changed through the variable frequency bus, and
finally, the rotating speed of rotating machines of the auxiliary
machines is changed.
[0019] The auxiliary machine connected to the variable frequency
bus can also be connected to the industrial frequency bus.
Industrial frequency and variable frequency are switched to each
other as a backup. When the steam turbine or generator fails or is
under other special working conditions, the auxiliary machine
connected with the variable frequency bus can switch to the
industrial frequency quickly, thus ensuring the safe operation of
the unit.
[0020] It is also possible to further provide a clutch system
between the variable frequency steam turbine and the generator. If
a variable frequency generator or its electrical equipment fails
and thus it is required that the generator must be shut down, the
variable frequency generator can be disconnected directly through
the clutch system to ensure the normal operation of the water
feeding pump, thus ensuring the operation safety of the main steam
turbine generator unit. The clutch system may be a separate safety
coupling, or a separate clutch, or a combination of a safety
coupling and a clutch.
[0021] In addition, a corresponding voltage transformer can be
provided at the rear of the output end of the generator so that the
output voltage of the generator, after voltage transformation, can
meet the requirements of motors of all auxiliary machines at
different voltage levels.
[0022] As the load of the unit changes, the frequency conversion
system provides all auxiliary machines connected thereto with a
frequency modulation power supply having an initially adjusted
frequency. The adjustment structures on the auxiliary machines,
such as valves, baffles, or movable blades of adjustable axial-flow
fans, can be further fine-tuned to ensure that production
requirements are met. For example, the power supply frequency at
which the opening of the adjusting mechanism of the auxiliary
machine is 95% of the largest adjustable opening is used as the
frequency of the frequency modulation power supply.
[0023] The variable frequency steam turbine of the present
invention takes the steam extracted from the main steam turbine as
a working steam source. In addition, an inlet valve can be further
provided at the front of the variable frequency steam turbine of
the present invention, so that the rotating speed of the variable
frequency steam turbine can be accurately controlled through the
valve while the load of the unit changes.
[0024] The generalized frequency conversion system provided by the
present invention has the following advantages:
[0025] 1. The generalized frequency conversion system of the
present invention can obtain alternating current of a required
frequency without using other types of frequency converters, thus
greatly reducing the power consumption of the auxiliary machine
connected to the variable frequency bus.
[0026] 2. According to the feature that the rotating speed of the
water feeding pump and variable frequency steam turbine
synchronously varies with the load of the unit, the variable
frequency steam turbine used in the present invention drives both
the water feeding pump and the generator. Therefore, compared with
the solution of patent "ZL 201210006442.8", the water feeding pump
steam turbine is combined with the separately arranged variable
frequency steam turbine, and the correspondingly arranged auxiliary
machine systems are combined into one, the system is greatly
simplified and the investment is reduced. In addition, the capacity
of the combined steam turbine is relatively increased, and the
internal efficiency is improved accordingly.
[0027] 3. Since the variable-frequency steam turbine of the present
invention is connected with the water feeding pump through the
speed increasing gearbox, compared with the solution of the patent
"ZL 201420245755.3", on the one hand, the rotating speed of the
water feeding pump can be designed higher, the diameter of the pump
becomes smaller, and thus the manufacturing cost of the water
feeding pump can be reduced; the pump shell becomes thinner, and
the start-up and load-changing adaptability is strong; on the other
hand, the rotating speed of the variable frequency steam turbine is
relatively low, the variable frequency steam turbine can be
compatible with the existing industrial frequency steam turbine to
a certain extent, and it overcomes the problem that it is difficult
to match the rotating speeds of the variable frequency steam
turbine and of the water feeding pump; at the same time, the
exhaust residual velocity loss of the variable frequency steam
turbine at low speed is also relatively low, so a higher internal
efficiency can be obtained relatively; and besides, since longer
last-stage blades can be used for the variable frequency steam
turbine at low speed, the exhaust area is larger, and thus the
exhaust pressure can be relatively lower, that is, the actual total
enthalpy drop during the operation of the steam turbine is
relatively large, and the economic benefit will be better.
[0028] In order to fully understand the purpose, features and
effects of the present invention, the concept, specific structure
and produced technical effects of the present invention will be
further described below with reference to the drawings.
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.
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