CN115450892A - Control method of cold end system of steam turbine - Google Patents

Control method of cold end system of steam turbine Download PDF

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Publication number
CN115450892A
CN115450892A CN202211284866.0A CN202211284866A CN115450892A CN 115450892 A CN115450892 A CN 115450892A CN 202211284866 A CN202211284866 A CN 202211284866A CN 115450892 A CN115450892 A CN 115450892A
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cooling water
steam turbine
circulating cooling
cold end
end system
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CN202211284866.0A
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Chinese (zh)
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程江南
王颖
姚坤
刘东旭
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Harbin Wohua Intelligent Power Technology Co ltd
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Harbin Wohua Intelligent Power Technology Co ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/02—Stopping, starting, unloading or idling control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B23/00—Pumping installations or systems
    • F04B23/04—Combinations of two or more pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/20—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by changing the driving speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28B—STEAM OR VAPOUR CONDENSERS
    • F28B11/00—Controlling arrangements with features specially adapted for condensers

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Turbines (AREA)

Abstract

A control method of a cold end system of a steam turbine relates to the technical field of control of the cold end system of a steam turbine set. The invention aims to solve the problem that the cold end operation economy of a steam turbine is poor due to low back pressure caused by excessive cooling of circulating water as the length of the existing steam turbine set is increased along with low load operation. According to the control method of the cold end system of the steam turbine, one of two circulating cooling water pumps of the cold end system of the steam turbine is a variable-frequency circulating cooling water pump, the other circulating cooling water pump is a power-frequency circulating cooling water pump, when T10 + K is larger than 700, the two circulating cooling water pumps of the cold end system of the steam turbine are kept to operate simultaneously, and otherwise, the variable-frequency circulating cooling water pumps of the cold end system of the steam turbine are kept to operate and the power-frequency circulating cooling water pumps are stopped.

Description

Control method of cold end system of steam turbine
Technical Field
The invention belongs to the field of control of a cold end system of a steam turbine set.
Background
The cold end system of the power plant is composed of a last-stage group of low-pressure cylinders of the steam turbine, a condenser, a cooling tower, a circulating water pump, a circulating water supply system, an air extraction system and the like. In the running process of a cold end system of a power plant, exhaust steam enters a shell side of a condenser after leaving a low-pressure cylinder, circulating water provided by a circulating water pump flows into a condenser tank to serve as a cooling working medium, and the exhaust steam is condensed into water. The condenser in the cold end system is constantly condensed the exhaust steam of steam turbine into water, and the circulating water is constantly taken away the heat that emits when condensing the exhaust steam again, and the cooling tower releases the heat of circulating water to the environment, is about to go out the heat release in the thermodynamic cycle. If the heat release is not timely, the exhaust pressure is increased, and the expansion work of the unit is reduced; the increase of the electric power consumed by various pumps in the heat release process also increases the service power, and the net output work of the unit is reduced. The goal of the cold side system economy is therefore to obtain maximum power with minimum power consumption.
A cooling tower and 2 power frequency circulating cooling water pumps are arranged in a cold end system of a turbine of an existing power plant unit and used for providing low-temperature cooling water which enters a condenser to cool exhaust steam of the turbine. Wherein, 2 power frequency circulative cooling water pump exports of #1 unit and 2 power frequency circulative cooling water pump exports of #2 units are connected with communicating pipe, realize the operation of female pipe. However, with the increase of the low-load operation time length, the circulating water is cooled excessively, so that the back pressure is low, and the cold end operation economy of the steam turbine is poor.
Disclosure of Invention
The invention provides a control method of a cold end system of a steam turbine, aiming at solving the problems that the prior steam turbine set increases along with the low-load operation time length, the back pressure is low due to excessive cooling of circulating water, and the cold end operation economy of the steam turbine is poor.
A control method for a cold end system of a steam turbine is characterized in that one of two circulating cooling water pumps of the cold end system of the steam turbine is a variable-frequency circulating cooling water pump, and the other circulating cooling water pump is a power frequency circulating cooling water pump, and the control method comprises the following steps:
judging whether the following formula is satisfied:
T*10+K＞700，
wherein T is the water supply temperature of the cooling water, K is the load of the unit,
if so, keeping two circulating cooling water pumps of the cold end system of the steam turbine to operate simultaneously, otherwise keeping the variable-frequency circulating cooling water pump of the cold end system of the steam turbine to operate and stopping the power frequency circulating cooling water pump.
Further, when the two circulating cooling water pumps run simultaneously, the minimum rotating speed of the variable-frequency circulating cooling water pump is 45Hz; when the variable-frequency circulating cooling water pump operates independently, the minimum rotating speed of the variable-frequency circulating cooling water pump is 34Hz.
Further, the supply water temperature of the cooling water is the water temperature at the inlet of the condenser, and the unit load is the actual load of the steam turbine unit where the cold end system is located.
Further, the control method further comprises the step of controlling a condenser of a cold end system of the steam turbine, and specifically comprises the following steps:
and calculating a condenser backpressure set value F (K) according to the unit load K, calculating a condenser backpressure correction coefficient F (T) according to the cooling water supply temperature T, limiting the speed of the product of the condenser backpressure set value and the condenser backpressure correction coefficient through a speed limiting module, and inputting the product into the condenser to control the backpressure.
Furthermore, the speed limiting rate of the speed limiting module is 0.003kPa/s, and the output amplitude limit is [3kPa,10kPa ].
Further, when the two circulating cooling water pumps are operated simultaneously:
the corresponding relation between the unit load K and the condenser backpressure set value F (K) is shown as the following table:
K F(K)
350 11.62
400 12.00
450 12.39
500 12.79
550 13.20
600 13.36
650 14.01
，
the corresponding relation between the cooling water supply temperature T and the condenser backpressure correction coefficient F (T) is shown in the following table:
T F(T)
10 0.20
15 0.26
20 0.35
25 0.46
30 0.60
35 0.78
40 1
；
when the variable-frequency circulating cooling water pump operates independently:
the corresponding relation between the unit load K and the condenser backpressure set value F (K) is shown as the following table:
K F(K)
300 3.003
350 3.09
400 3.176
450 3.26
500 3.342
550 3.423
600 3.502
650 3.687
，
the corresponding relation between the cooling water supply temperature T and the condenser backpressure correction coefficient F (T) is shown in the following table:
T F(T)
10 1
15 1.294
20 1.665
25 2.131
30 2.711
35 3.430
40 4.316
。
further, when the variable-frequency circulating cooling water pump runs and the power frequency circulating cooling water pump is stopped due to faults, the variable-frequency circulating cooling water pump is switched to a manual mode, and the working frequency is switched to 50Hz.
The control method of the cold end system of the steam turbine can automatically switch the double-pump/single-pump operation, operate according to the most economical backpressure, and interlock the variable frequency pump to operate after the power frequency pump fails, so that the safety and economy of a unit are guaranteed.
Drawings
FIG. 1 is a schematic diagram of the operation of cold end main pipes of steam turbines of #1 and #2 units;
FIG. 2 is a schematic diagram of a single and double pump operation division;
FIG. 3 is a flow chart of the most economical operating back pressure at the cold end of the steam turbine of the #1 unit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The existing power plant unit steam turbine cold end system is provided with a cooling tower and 2 power frequency circulating cooling water pumps. In the control method of the steam turbine cold end system according to the embodiment, as shown in fig. 1, a power frequency circulating cooling water pump 2 of a #1 unit is changed into a variable frequency circulating cooling water pump, and the variable frequency circulating cooling water pump can adjust the amount of cooling water by adjusting the rotating speed of the pump.
As shown in fig. 2, the dual-pump operation is the joint operation of the No. 1 power frequency circulating water pump and the No. 2 variable frequency circulating cooling water pump; the single-pump operation is the operation of No. 1 power frequency circulating water pump shutdown and No. 2 variable frequency circulating cooling water pump. Thus:
when T10K is more than 700, the double pumps operate, and the cold end economy is optimal;
when T10K is less than or equal to 700, the single pump operates, and the cold end economy is optimal.
The T is the supply water temperature of the cooling water, specifically the water temperature at the inlet of the condenser. And K is the unit load, in particular the actual load of the steam turbine unit where the cold end system is located.
When the No. 1 power frequency circulating water pump and the No. 2 frequency conversion circulating cooling water pump run together, the minimum rotating speed of the No. 2 frequency conversion circulating cooling water pump is 45Hz. Calculating the back pressure of the condenser according to fig. 3, specifically: and calculating a condenser backpressure set value F (K) according to the unit load K, calculating a condenser backpressure correction coefficient F (T) according to the cooling water supply temperature T, limiting the speed of the product of the condenser backpressure set value and the condenser backpressure correction coefficient through a speed limiting module, and inputting the product into the condenser to control the backpressure. The limiting rate of the speed limiting module is 0.003kPa/s, and the output limiting amplitude is [3kPa,10kPa ].
The corresponding relation between the unit load K and the condenser backpressure set value F (K) is shown as the following table:
K F(K)
350 11.62
400 12.00
450 12.39
500 12.79
550 13.20
600 13.36
650 14.01
，
the corresponding relation between the cooling water supply temperature T and the condenser backpressure correction coefficient F (T) is shown as the following table:
T F(T)
10 0.20
15 0.26
20 0.35
25 0.46
30 0.60
35 0.78
40 1
。
when the power frequency circulating water pump 1 is stopped and the variable frequency circulating cooling water pump 2 is operated, the minimum rotating speed of the variable frequency circulating cooling water pump 2 is 34Hz. Calculating the back pressure of the condenser according to fig. 3, specifically: and calculating a condenser backpressure set value F (K) according to the unit load K, calculating a condenser backpressure correction coefficient F (T) according to the cooling water supply temperature T, limiting the speed of the product of the condenser backpressure set value and the condenser backpressure correction coefficient through a speed limiting module, and inputting the product into the condenser to control the backpressure. The limiting rate of the speed limiting module is 0.003kPa/s, and the output limiting amplitude is [3kPa,10kPa ].
The corresponding relation between the unit load K and the condenser backpressure set value F (K) is shown as the following table:
K F(K)
300 3.003
350 3.09
400 3.176
450 3.26
500 3.342
550 3.423
600 3.502
650 3.687
，
the corresponding relation between the cooling water supply temperature T and the condenser backpressure correction coefficient F (T) is shown in the following table:
T F(T)
10 1
15 1.294
20 1.665
25 2.131
30 2.711
35 3.430
40 4.316
。
and finally, after receiving a fault signal of the power frequency circulating cooling water pump: and switching the variable-frequency circulating cooling water pump into a manual mode, and switching the working frequency to 50Hz. When the communicating pipe is through-flow, taking or using the three power frequency pump fault signals as the power frequency pump fault signals; and when the communicating pipe does not flow through, taking the fault signal of the power frequency pump 1 as the fault signal of the power frequency pump.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims (7)

1. A control method for a cold end system of a steam turbine is characterized in that one of two circulating cooling water pumps of the cold end system of the steam turbine is a variable frequency circulating cooling water pump, the other circulating cooling water pump is a power frequency circulating cooling water pump,
the control method comprises the following steps:
judging whether the following formula is satisfied:
T*10+K＞700，
wherein T is the water supply temperature of the cooling water, K is the load of the unit,
if so, keeping the two circulating cooling water pumps of the cold end system of the steam turbine to run simultaneously, otherwise, keeping the variable-frequency circulating cooling water pump of the cold end system of the steam turbine to run and stopping the power frequency circulating cooling water pump.
2. The method of controlling a cold end system of a steam turbine according to claim 1,
when the two circulating cooling water pumps run simultaneously, the minimum rotating speed of the variable-frequency circulating cooling water pump is 45Hz;
when the variable-frequency circulating cooling water pump operates independently, the minimum rotating speed of the variable-frequency circulating cooling water pump is 34Hz.
3. The method of claim 1, wherein the cooling water supply temperature is a water temperature at an inlet of a condenser, and the unit load is an actual load of a steam turbine unit in which the cold end system is located.
4. The method for controlling the cold end system of the steam turbine according to claim 1, 2 or 3, wherein the method for controlling the cold end system condenser of the steam turbine further comprises the following steps:
calculating a set value F (K) of the backpressure of the condenser according to the load K of the unit,
calculating a condenser backpressure correction coefficient F (T) according to the cooling water supply temperature T,
and limiting the speed of the product of the condenser backpressure set value and the condenser backpressure correction coefficient by a speed limiting module, and then inputting the product to the condenser to control the backpressure.
5. The method of claim 4, wherein the speed limiting module has a speed limit of 0.003kPa/s and an output limit of [3kPa,10kPa ].
6. The method of controlling a cold end system of a steam turbine according to claim 4,
when two circulating cooling water pumps are operated simultaneously:
the corresponding relation between the unit load K and the condenser backpressure set value F (K) is shown as the following table:
Figure FDA0003893664110000011
Figure FDA0003893664110000021
the corresponding relation between the cooling water supply temperature T and the condenser backpressure correction coefficient F (T) is shown in the following table:
T F(T) 10 0.20 15 0.26 20 0.35 25 0.46 30 0.60 35 0.78 40 1
；
when the variable-frequency circulating cooling water pump operates independently:
the corresponding relation between the unit load K and the condenser backpressure set value F (K) is shown as the following table:
K F(K) 300 3.003 350 3.09 400 3.176 450 3.26 500 3.342 550 3.423 600 3.502 650 3.687
，
the corresponding relation between the cooling water supply temperature T and the condenser backpressure correction coefficient F (T) is shown in the following table:
Figure FDA0003893664110000022
Figure FDA0003893664110000031
7. the method of claim 1, wherein when the variable frequency hydronic pump is running and the power frequency hydronic pump is down, the variable frequency hydronic pump is switched to manual mode and the operating frequency is switched to 50Hz.
CN202211284866.0A 2022-10-17 2022-10-17 Control method of cold end system of steam turbine Pending CN115450892A (en)

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Application Number Priority Date Filing Date Title
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110966170A (en) * 2019-11-27 2020-04-07 河北涿州京源热电有限责任公司 Real-time control method for cold end back pressure of indirect air cooling generator set
CN112096602A (en) * 2020-09-29 2020-12-18 国电华北电力有限公司廊坊热电厂 Method for automatically controlling frequency conversion circulating water pump set of wet cooling steam turbine power generation set

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110966170A (en) * 2019-11-27 2020-04-07 河北涿州京源热电有限责任公司 Real-time control method for cold end back pressure of indirect air cooling generator set
CN112096602A (en) * 2020-09-29 2020-12-18 国电华北电力有限公司廊坊热电厂 Method for automatically controlling frequency conversion circulating water pump set of wet cooling steam turbine power generation set

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
冯晓波等: "600MW机组循环水泵变频改造及运行优化", 宁夏电力, no. 4, 28 August 2022 (2022-08-28), pages 70 - 74 *
潘茂华: "分析火力发电厂汽机辅机的优化运行", 科技创业家, no. 10, 16 October 2013 (2013-10-16), pages 104 *

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