CN113914944A - RB control method for direct air cooling system of full-load subcritical unit - Google Patents
RB control method for direct air cooling system of full-load subcritical unit Download PDFInfo
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- CN113914944A CN113914944A CN202111204292.7A CN202111204292A CN113914944A CN 113914944 A CN113914944 A CN 113914944A CN 202111204292 A CN202111204292 A CN 202111204292A CN 113914944 A CN113914944 A CN 113914944A
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- 238000001816 cooling Methods 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 23
- 230000000630 rising effect Effects 0.000 claims abstract description 25
- 238000012544 monitoring process Methods 0.000 claims abstract description 4
- 230000009471 action Effects 0.000 abstract description 14
- 230000002159 abnormal effect Effects 0.000 abstract description 7
- 230000008859 change Effects 0.000 abstract description 5
- 230000008569 process Effects 0.000 abstract description 4
- 230000009467 reduction Effects 0.000 abstract description 4
- 238000010977 unit operation Methods 0.000 description 7
- 238000013461 design Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
- F01D21/14—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for responsive to other specific conditions
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Abstract
The invention discloses a RB control method for a direct air cooling system of a full-load subcritical unit, which comprises the steps of monitoring the steam exhaust pressure value and the steam exhaust pressure rising rate value of the unit, judging whether abnormal working conditions such as air cooling fan faults occur in the operation process according to the steam exhaust pressure and the steam exhaust pressure rising rate change condition, triggering the RB system in time when the abnormal working conditions are detected, carrying out a series of protection actions, realizing the rapid load reduction of the unit, switching to the constant-pressure operation, carrying out the over-frequency operation of the air cooling fan, and maintaining the safe and stable operation of the unit.
Description
Technical Field
The invention belongs to the technical field of control engineering, and particularly relates to a RB control method for a direct air cooling system of a full-load subcritical unit.
Background
RB (RUN BACK) in the thermal generator set refers to that when the output of the set is limited due to fault tripping of main auxiliary machines of the set, in order to adapt to the output of equipment and maintain safe and stable operation of the set, a control system forcibly reduces the load of the set to a load target value which can be borne by the auxiliary machines which are still in operation, and the function is also called auxiliary machine fault load reduction. Whether the RB control function is put into operation or not and whether the RB control function is put into operation or not directly influence the safe and economic operation of the unit. Therefore, the application effect of the RB control function is an important index for evaluating the control performance of the unit.
The direct air cooling unit has higher and higher occupation ratio in a newly-built thermal power generating unit due to obvious water saving advantage, but the direct air cooling unit has high steam turbine exhaust pressure in high-temperature periods in summer, and the unit trip accident is easy to happen due to equipment failure or environmental condition change.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an RB control method for a direct air cooling system of a full-load subcritical unit, so as to solve the problems that equipment faults or environmental conditions are changed when in complex and rapid change and unit trip accidents are easy to happen in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a RB control method for a direct air cooling system of a full-load subcritical unit comprises the following steps:
step 1, setting a critical value of the exhaust steam pressure and a critical value of the rising rate of the exhaust steam pressure of a steam turbine when RB acts;
step 2, monitoring the exhaust steam pressure value and the exhaust steam pressure rising rate value of the unit;
and 3, when the exhaust steam pressure value reaches the exhaust steam pressure critical value and the exhaust steam pressure rising rate value reaches the exhaust steam pressure rising rate critical value, RB acts, the operation load of the unit is reduced, the unit is switched to the constant-pressure operation, and the air cooling fan operates in an overfrequency mode.
The invention is further improved in that:
preferably, in step 1, the critical value of the exhaust steam pressure in the steam turbine is 50 kPa.
Preferably, in the step 1, the critical value of the rising rate of the exhaust steam pressure is 1 kPa/min.
Preferably, in step 2, the exhaust steam pressure value and the exhaust steam pressure rising rate value of the unit are monitored through the distributed control system.
Preferably, in step 3, for the 330MW subcritical direct air cooling unit, when RB is activated, the unit load is reduced to 1/3 of the original operation value.
Preferably, when the load of the turbine unit is reduced to 1/3 of the original operation value, the exhaust pressure of the turbine is reduced to 10kPa or more.
Preferably, in step 3, for the 600MW subcritical direct air cooling unit, when RB is activated, the unit load is reduced to 1/6 of the original operation value.
Preferably, when the load of the turbine unit is reduced to 1/6 of the original operation value, the exhaust pressure of the turbine is reduced to 9.3kPa or more.
Preferably, the over-frequency operation frequency of the air cooling machine is 55 Hz.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a RB control method for a direct air cooling system of a full-load subcritical unit, which comprises the steps of monitoring the steam exhaust pressure value and the steam exhaust pressure rising rate value of the unit, judging whether abnormal working conditions such as air cooling fan faults occur in the operation process according to the steam exhaust pressure and the steam exhaust pressure rising rate change condition, triggering the RB system in time when the abnormal working conditions are detected, carrying out a series of protection actions, realizing the rapid load reduction of the unit, switching to the constant-pressure operation, carrying out the over-frequency operation of the air cooling fan, and maintaining the safe and stable operation of the unit.
Furthermore, the critical value of the exhaust steam pressure is set to be 50kPa, and the alarm value and the trip value far away from the unit are set, so that the continuous alarm of the unit is prevented while the unit is not adjusted.
Furthermore, the running data of the unit is monitored through the distributed control system, and the data can be transmitted in real time.
Furthermore, different action values are set for the units with different loads, so that the set values can accord with the actual conditions of the units.
Drawings
FIG. 1 is a flow chart corresponding to RB of the air cooling system of the 330MW unit.
FIG. 2 is a flow chart of RB corresponding to the air cooling system of the 600MW unit.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
the invention discloses a RB control method for a direct air cooling system of a full-load subcritical unit, which judges whether abnormal working conditions such as air cooling fan faults occur in the operation process or not according to the change conditions of the exhaust steam pressure and the exhaust steam pressure rising rate in the operation process of the unit, and triggers the RB system in time and carries out a series of protection actions when the abnormal working conditions are detected, so that the rapid load reduction of the unit is realized, and the safe and stable operation of the unit is maintained.
The detection flow of the abnormal working condition of the air cooling system is as follows:
when the unit is normally put into operation, the DCS monitors the exhaust steam pressure and the exhaust steam pressure rising rate in real time to judge and trigger the air cooling system RB.
The conditions for judging and triggering the air cooling system RB are as follows:
in order to avoid frequent movement of the air cooling system RB and protect the unit to operate safely, the RB movement steam exhaust pressure fixed value cannot be too low or too high. And designing an exhaust pressure alarm value and a trip value according to the steam turbine, wherein the RB action exhaust pressure fixed value is 50 kPa. And when the steam turbine exhaust pressure reaches 50kPa and the exhaust pressure rising rate reaches more than 1kPa/min, performing air cooling RB.
The air cooling system RB specifically performs a series of protection actions as follows:
1) for a 300MW class unit, the unit operation load is rapidly reduced by 1/3 of the current operation value; for a 600MW class unit, the unit operation load is rapidly reduced by 1/6 of the current operation value; and the air cooling fan rapidly runs at an overclocking frequency (f is 55Hz) (if the air cooling fan runs at a low speed), so that the unit is prevented from back pressure and high jump.
2) When the air cooling RB acts, in order to reduce the heat load of the air cooling condenser and improve the operation vacuum, the unit operation mode is switched to the constant pressure operation, and the steam inlet quantity of the air cooling condenser is reduced. The constant-pressure operation means that the pressure of main steam (steam at the inlet of a high-pressure cylinder of a steam turbine) is kept unchanged,
example 1330 MW subcritical direct air cooling unit
Referring to fig. 1, according to the test result of the influence of the design performance of the air cooling system and the load of the unit on the exhaust steam pressure, the influence of the load on the vacuum is larger as the ambient temperature increases. At the ambient temperature of 30 ℃, the influence of the unit load on the exhaust pressure is about 0.13kPa/MW near the rated load according to the design performance and the experimental calculation result. When the unit operates near the rated load, the load is rapidly reduced 1/3, and the exhaust pressure is reduced by more than 10 kPa.
Aiming at a 330MW subcritical direct air cooling unit, the control method comprises the following specific steps:
step 1, designing an exhaust pressure alarm value of 43kPa and a trip value of 65kPa for the steam turbine. In order to avoid frequent action of the air cooling system RB and protect the unit to operate safely, the RB action exhaust steam pressure critical value cannot be too low or too high. And designing an exhaust pressure alarm value and a trip value according to the steam turbine, setting the RB action exhaust critical pressure value to be 50kPa, and setting the exhaust pressure rising rate critical value to be 1 kPa/min.
Step 2, the DCS continuously monitors the exhaust steam pressure value and the exhaust steam pressure rising rate value of the unit;
and 3, when the exhaust steam pressure of the steam turbine reaches 50kPa and the rising rate of the exhaust steam pressure reaches more than 1kPa/min, performing air cooling RB.
The air cooling system RB specifically performs a series of protection actions as follows:
1) 1/3, rapidly reducing the current operation value of the unit operation load; and the air cooling fan rapidly runs at an overclocking frequency (f is 55Hz) (if the air cooling fan runs at a low speed), so that the unit is prevented from back pressure and high jump.
2) When the air cooling RB acts, in order to reduce the heat load of the air cooling condenser and improve the operation vacuum, the unit operation mode is switched to the constant pressure operation, and the steam inlet quantity of the air cooling condenser is reduced.
Example 2600 MW subcritical direct air-cooling unit
Referring to FIG. 2, the influence of the unit load on the exhaust pressure at an ambient temperature of 39 ℃ is approximately 0.93kPa/MW, calculated from the test results and reference design properties. The load is reduced by 100MW, and the exhaust pressure can be reduced by 9.3 kPa. When the unit operates near the rated load, the load is quickly reduced by 1/6, the exhaust pressure is reduced by over 9.3kPa, the unit is quickly away from the trip protection value, and the trip accident is avoided.
Referring to fig. 2, for a 600MW subcritical direct air cooling unit, the control method specifically includes the steps of:
step 1, designing an exhaust pressure alarm value of 60kPa and a trip value of 65kPa for the steam turbine. If the whole row of fans have faults, the operation back pressure is 51.28kPa according to the calculation of the data obtained by the test. In order to avoid frequent action of the air cooling system RB and protect the unit to operate safely, the RB action exhaust steam pressure critical value cannot be too low or too high. And designing an exhaust pressure alarm value and a trip value according to the steam turbine, wherein the RB action exhaust critical pressure fixed value is 50kPa, and the exhaust pressure rising rate critical value is set to be 1 kPa/min.
Step 2, the DCS continuously monitors the exhaust steam pressure value and the exhaust steam pressure rising rate value of the unit;
and 3, when the exhaust steam pressure of the steam turbine reaches 50kPa and the rising rate of the exhaust steam pressure reaches more than 1kPa/min, performing air cooling RB.
The air cooling system RB specifically performs a series of protection actions as follows:
1) 1/6, rapidly reducing the current operation value of the unit operation load; and the air cooling fan rapidly runs at an overclocking frequency (f is 55Hz) (if the air cooling fan runs at a low speed), so that the unit is prevented from back pressure and high jump.
2) When the air cooling RB acts, in order to reduce the heat load of the air cooling condenser and improve the operation vacuum, the unit operation mode is switched to the constant pressure operation, and the steam inlet quantity of the air cooling condenser is reduced.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (9)
1. A RB control method for a direct air cooling system of a full-load subcritical unit is characterized by comprising the following steps:
step 1, setting a critical value of the exhaust steam pressure and a critical value of the rising rate of the exhaust steam pressure of a steam turbine when RB acts;
step 2, monitoring the exhaust steam pressure value and the exhaust steam pressure rising rate value of the unit;
and 3, when the exhaust steam pressure value reaches the exhaust steam pressure critical value and the exhaust steam pressure rising rate value reaches the exhaust steam pressure rising rate critical value, RB acts, the operation load of the unit is reduced, the unit is switched to the constant-pressure operation, and the air cooling fan operates in an overfrequency mode.
2. The RB control method of the full-load subcritical unit direct air cooling system according to claim 1, wherein in the step 1, the critical value of the steam exhaust pressure in the steam turbine is 50 kPa.
3. The RB control method for the direct air cooling system of the full-load subcritical unit according to claim 1, wherein in the step 1, the critical value of the rising rate of the exhaust steam pressure is 1 kPa/min.
4. The RB control method for the direct air cooling system of the full-load subcritical unit according to claim 1, wherein in the step 2, the steam exhaust pressure value and the steam exhaust pressure rising rate value of the unit are monitored through a decentralized control system.
5. The RB control method for the full-load subcritical unit direct air cooling system according to claim 1, wherein in the step 3, for the 330MW subcritical direct air cooling unit, when RB is activated, the unit load is reduced to 1/3 of the original operation value.
6. The RB control method for the full-load subcritical unit direct air cooling system according to claim 5, wherein when the unit load is reduced to 1/3 of an original operation value, the exhaust pressure of the steam turbine is reduced to more than 10 kPa.
7. The RB control method for the full-load subcritical unit direct air cooling system according to claim 1, wherein in the step 3, for the 600MW subcritical direct air cooling unit, when RB is activated, the unit load is reduced to 1/6 of the original operation value.
8. The RB control method for the full-load subcritical unit direct air cooling system according to claim 7, wherein when the unit load is reduced to 1/6 of an original operation value, the exhaust pressure of the steam turbine is reduced to be more than 9.3 kPa.
9. The RB control method for the direct air cooling system of the full-load subcritical unit according to any one of claims 1 to 8, wherein the over-frequency operation frequency of the air cooling machine is 55 Hz.
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| CN202111204292.7A CN113914944A (en) | 2021-10-15 | 2021-10-15 | RB control method for direct air cooling system of full-load subcritical unit |
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| CN202111204292.7A CN113914944A (en) | 2021-10-15 | 2021-10-15 | RB control method for direct air cooling system of full-load subcritical unit |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014196727A (en) * | 2013-03-29 | 2014-10-16 | 株式会社東芝 | Steam turbine cooling system and steam turbine cooling method |
| CN106247815A (en) * | 2016-07-19 | 2016-12-21 | 中国电力工程顾问集团西北电力设计院有限公司 | A kind of control method of the in line big machine air cooling system of the little machine of supercritical thermal power unit |
| CN113255160A (en) * | 2021-06-22 | 2021-08-13 | 西安热工研究院有限公司 | Low-vacuum heat supply operation backpressure optimizing system and method for direct air cooling unit |
-
2021
- 2021-10-15 CN CN202111204292.7A patent/CN113914944A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014196727A (en) * | 2013-03-29 | 2014-10-16 | 株式会社東芝 | Steam turbine cooling system and steam turbine cooling method |
| CN106247815A (en) * | 2016-07-19 | 2016-12-21 | 中国电力工程顾问集团西北电力设计院有限公司 | A kind of control method of the in line big machine air cooling system of the little machine of supercritical thermal power unit |
| CN113255160A (en) * | 2021-06-22 | 2021-08-13 | 西安热工研究院有限公司 | Low-vacuum heat supply operation backpressure optimizing system and method for direct air cooling unit |
Non-Patent Citations (2)
| Title |
|---|
| 祁军等: "CFB机组空冷RB控制策略研究及应用", 《工程科技Ⅱ辑》 * |
| 陈胜利等: "直接空冷机组空冷系统RB研究及应用", 《工程科技Ⅱ辑》 * |
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