CN108443859B - Water supply flow control method adaptive to rapid load fluctuation - Google Patents
Water supply flow control method adaptive to rapid load fluctuation Download PDFInfo
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- CN108443859B CN108443859B CN201810301487.5A CN201810301487A CN108443859B CN 108443859 B CN108443859 B CN 108443859B CN 201810301487 A CN201810301487 A CN 201810301487A CN 108443859 B CN108443859 B CN 108443859B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D5/00—Controlling water feed or water level; Automatic water feeding or water-level regulators
- F22D5/26—Automatic feed-control systems
- F22D5/34—Applications of valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D5/00—Controlling water feed or water level; Automatic water feeding or water-level regulators
- F22D5/26—Automatic feed-control systems
- F22D5/28—Automatic feed-control systems responsive to amount of steam withdrawn; responsive to steam pressure
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Abstract
The invention relates to the technical field of supercritical unit water supply control, in particular to a water supply flow control method adaptive to rapid load fluctuation, which takes main steam flow as a main water supply control input signal, superposes a target load difference value after the unit is subjected to the same speed limit, a target main steam pressure value and actual main steam pressure deviation, and a target temperature and actual separator outlet temperature deviation on a water supply flow set value, relatively and independently separates coal quantity change and water supply quantity change, and adds intermediate point temperature deviation to correct the water supply quantity. Aiming at the problems of pressure fluctuation, large overshoot and the like of main steam pressure of a supercritical circulating fluidized bed boiler, the flow control method ensures that the water supply system establishes enough water supply flow and pressure during operation, protects the cooling water quantity of all heating surfaces and the stability of the hydrodynamic force circulation in a water wall, ensures that a unit works in a working condition area with a pressure set value, and achieves the purpose of improving the economic benefit of the unit.
Description
Technical Field
The invention relates to the technical field of water supply control of supercritical units, in particular to a water supply flow control method adaptive to rapid load fluctuation.
Background
The power grid monitors the fluctuation of the frequency of the power system in real time and adjusts the output of the generator in time through the ACE to ensure the real-time balance of power supply and demand. With the rapid development of economy and the rapid increase of power consumption requirements in China, the installed capacity of thermal power is also rapidly increased, and a newly added unit is required to rapidly respond to the change of ACE load, so that the frequency stability of a power grid is ensured. The supercritical unit in the newly added unit is a main unit, the supercritical unit generally adjusts water supply control according to a coal-water ratio, and the specific control strategy is to take a coal quantity instruction or coal quantity feedback as a basic quantity to act on a coal-water function to convert the coal-water function into water supply basic quantity, but with the rapid development of the power industry, a generator unit is required to rapidly respond to load change after the ACE, but the fluctuation range of the load instruction is large, when the fluctuation frequency is high, in order to ensure that the unit rapidly responds to the load change, a steam turbine instruction can rapidly respond, a steam turbine high-pressure throttle rapidly fluctuates, when the water supply flow is directly controlled according to the traditional coal-water ratio, the main steam turbine side is easy to cause large pressure fluctuation, long overproof time, serious problems of undervoltage or serious pressure problems due to the relative lag of coal.
Disclosure of Invention
Aiming at the problems of main steam pressure fluctuation, large overshoot and the like of a supercritical circulating fluidized bed boiler, the invention provides a water supply flow control method adaptive to rapid load fluctuation, and a water supply system establishes enough water supply flow and pressure during operation so as to protect the cooling water quantity of all heating surfaces and the stability of hydrodynamic circulation in a water wall, ensure that a unit works in a working condition area with a pressure set value, and achieve the purpose of improving the economic benefit of the unit.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a water supply flow control method adapting to rapid load fluctuation takes main steam flow as a water supply control main input signal, and superposes a target load difference value after a unit target load is the same as a speed limit, a target main steam pressure value and actual main steam pressure deviation, and a target temperature and actual separator outlet temperature deviation to act on a water supply flow set value.
The main steam flow is controlled by a high-pressure regulating valve and is calculated by adopting parameters such as pressure, temperature and the like after the regulating stage.
The main steam flow is corrected by the desuperheating water flow.
And a two-step delay link is arranged behind the main steam flow.
And correcting the difference value of the target load of the unit and the target load after speed limiting through load deviation.
And correcting the difference value between the target main steam pressure and the pressure set value through pressure deviation.
The deviation of the target temperature and the actual temperature of the outlet of the separator is a midpoint temperature deviation.
And the target temperature is obtained by correcting the saturation temperature corresponding to the outlet pressure of the steam-water separator and the superheat degree of the target load.
And the deviation of the target temperature and the actual temperature at the outlet of the separator synchronously acts on a main control coal quantity instruction of the boiler when acting on the feed water flow.
Compared with the prior art, the invention has the beneficial effects that:
firstly, the method comprises the following steps: when the unit load fluctuates rapidly, particularly in an ACE mode, the steam turbine master control responds rapidly, the high-pressure regulating valve of the steam turbine acts rapidly, the steam flow changes rapidly, the obtained steam flow and the desuperheating water amount are balanced to the water supply flow, compared with the traditional method that the coal amount is used as a water supply main control factor, the required water supply flow can be calculated more accurately, the real-time response effect is good, the load tracking effect is better, the main steam pressure is adjusted rapidly to the target pressure due to the timely response of the water supply flow, the overpressure or underpressure problem is reduced, and the economic and efficient operation of the unit is guaranteed.
Secondly, the method comprises the following steps: the control strategy of the invention is adopted, the coal quantity change and the water supply quantity change are relatively independent, the water supply quantity is corrected by adding the intermediate point temperature deviation, the enthalpy value correction of a separator outlet is not adopted, the main steam temperature lag time is long and cannot be used as a water supply flow control factor, the intermediate point temperature can be selected earlier, more quickly and not influenced by other factors, the main steam temperature change trend is reflected, the lag time of the main steam temperature regulation is reduced, the working medium temperature of a water wall is controlled in time, the heat transfer deterioration of the water wall is prevented, and for operating personnel, the intermediate point temperature correction is more intuitive than the intermediate point enthalpy value correction, The method is convenient, the enthalpy value of the superheated steam represents the acting capacity of the superheated steam, the enthalpy value of the steam at the intermediate point of the outlet of the separator is controlled, namely the initial acting capacity of the steam at the inlet of the superheater is controlled, load control is facilitated, reverse adjustment of temperature and pressure is easy to occur, therefore, load adjustment is realized rapidly mainly by adjusting a valve of the steam turbine, the required main steam pressure and main steam temperature are stabilized by means of water supply flow and coal quantity, water supply is corrected by means of intermediate point temperature deviation, the fluctuation of the main steam temperature can be guaranteed, the purpose of stabilizing the main steam temperature is achieved, and safe and stable operation of a unit is guaranteed.
Thirdly, the method comprises the following steps: compared with the method that water supply is adjusted by coal quantity signals, the method has the advantages that main steam pressure and temperature are coordinately controlled, the effect is better, pressure is timely adjusted when pressure fluctuation is large, temperature is synchronously adjusted when temperature deviates, coupling is stronger, energy requirements are guaranteed, and meanwhile, the main steam pressure economic operation point is guaranteed not to deviate, so that steam consumption of a steam turbine is guaranteed to be low, and economic benefits of a unit are improved.
Drawings
FIG. 1 is a logic diagram of a feedwater flow control method adapted to rapid load fluctuation according to the present invention;
FIG. 2 is a graph of the functional relationship between the main steam flow corrected by desuperheating water and the basic amount of the feedwater flow set value;
FIG. 3 is a graph of a load offset correction function;
FIG. 4 is a graph of pressure deviation correction function;
FIG. 5 is a graph of superheat correction function relationship;
FIG. 6 is a relationship diagram of a boiler master control superheat correction function;
FIG. 7 is a trend chart of the application effect of the method for controlling the flow of feedwater to adapt to the rapid fluctuation of the load.
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.
As shown in figure 1, a feedwater flow control method adapting to rapid load fluctuation takes main steam flow as a feedwater control main input signal, and a feedwater flow set value is acted by a target load difference value after the target load of a unit is identical to a limited speed, a deviation between a target main steam pressure value and an actual main steam pressure, and a deviation between a target temperature and an actual temperature of an outlet of a separator. The coal quantity change and the water supply quantity change are relatively independent, when the load changes rapidly, the steam turbine instruction responds rapidly by changing the high-pressure regulating valve, the synchronous change of the steam flow is reflected, the pressure is increased after the regulating stage, the main steam flow is increased, the dynamic function relationship exists between the water supply flow, the desuperheating water flow and the main steam flow, and the coal quantity change and the water supply quantity change are relatively independent. The main steam flow, the unit target load and the target load difference after speed limiting, the deviation between the target main steam pressure value and the actual main steam pressure, and the deviation between the target temperature and the actual temperature of the outlet of the separator are used for jointly forming a water supply flow set value, controlling the required target water supply amount, and enabling the deviation between the target temperature and the actual temperature of the outlet of the separator to synchronously act on the water supply flow and the boiler main control, so that the main steam pressure and temperature change caused by quick response of load fluctuation is achieved.
As shown in fig. 2, the main steam flow is controlled by a high pressure regulating valve, and is calculated by using parameters such as pressure, temperature and the like after the regulating stage, and the main steam flow is corrected by the desuperheating water flow. The functional relationship between the main steam flow and the basic quantity of the set value of the water supply flow after the water reducing temperature correction is shown in the table 1:
table 1: functional relation between main steam flow corrected by desuperheating water and basic quantity of set value of water supply flow
| Main steam flow X (t/h) | 0 | 524 | 630 | 754 | 780 | 870 | 1000 | 1057 | 1100 |
| Water supply set flow Y (t/h) | 0 | 528 | 645 | 770 | 800 | 910 | 1080 | 1160 | 1180 |
In this embodiment, a two-step delay link is provided after the main steam flow.
As shown in fig. 3, the difference between the target load of the unit and the target load after speed limiting is corrected by load deviation. The load deviation correction function is shown in table 2:
table 2: load deviation correction function
| Load deviation X (MW) | -100 | -60 | -10 | 10 | 60 | 100 |
| Corresponding water supply flow Y (t/h) | -32 | -19 | 0 | 0 | 19 | 32 |
As shown in fig. 4, the difference between the target main steam pressure and the pressure set value is corrected by a pressure deviation, and the pressure deviation correction function is shown in table 3:
table 3: pressure deviation correction function
| Deviation in pressure X (MPa) | -10 | -0.2 | 0.2 | 10 |
| PID flow calculation deviation input Y | -10 | 0 | 0 | 10 |
As shown in fig. 5, the target temperature is corrected by the saturation temperature corresponding to the steam-water separator outlet pressure plus the superheat degree of the target load, and the superheat degree correction function is shown in table 4:
table 4: superheat correction function
| Degree of superheat deviation X (. degree. C.) | 20 | 10 | 5 | -5 | -10 | -20 |
| Corresponding feed water flow correction Y (t/h) | 45 | 20 | 10 | -10 | -20 | -45 |
And the deviation between the target temperature and the actual temperature at the outlet of the separator acts on the feed water flow and synchronously acts on a main control coal quantity instruction of the boiler.
As shown in fig. 6, which is a graph of the boiler master control superheat correction function, the boiler master control superheat correction function is shown in table 5:
table 5: boiler master control superheat correction function
| Degree of superheat deviation X (. degree. C.) | 15 | 10 | 5 | -5 | -10 | -15 |
| Corresponding boiler main control coal quantity Y (t/h) | -10 | -7 | -4 | 4 | 7 | 10 |
Example (b):
A2X 350MW supercritical circulating fluidized bed unit of a certain power plant in Shanxi adopts main steam flow as a main input factor, ensures quick response of main steam pressure, newly adds intermediate point temperature deviation feed water correction and intermediate point temperature boiler master control deviation, depends on main steam flow feedback adjustment when pressure fluctuation occurs, depends on intermediate temperature deviation to jointly act on water supply quantity and coal quantity when main steam temperature deviates from a target value tendency, and more reliably ensures the unit safety.
As shown in FIG. 7, the parameter recording curve after the water supply control strategy is adopted, wherein a curve 1 is a target load instruction, a curve 2 is the actual power of a generator, a curve 3 is a main steam pressure set value, a curve 4 is the pressure of a main air inlet pipe of the steam generator, a curve 5 is a water supply flow set value, a curve 6 is a middle point superheat degree, a curve 7 is a steam temperature higher than an outlet, a curve 8 is the total coal supply quantity of a boiler, two times of large load lifting occur in the whole day, the water supply flow can be seen to respond in time, the tracking effect of the pressure set value and the pressure actual measured value is good, the pressure deviation can be controlled within 1.5MPa, the main steam temperature deviation can be controlled within 8 ℃ in one time of load lifting by adopting the control strategy, the average value of the lifting load rate is 6.2MW/min, and when the maximum middle point temperature of the pressure deviation has the tendency of deviating from, the temperature fluctuation of the main steam is small. Therefore, the control strategy of the invention can better respond to the feed water control of the supercritical unit, optimally control the pressure and the temperature of the main steam, and synchronously guarantee the safe operation and the economic benefit
Although only the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art, and all changes are encompassed in the scope of the present invention.
Claims (7)
1. A feedwater flow control method adapting to rapid fluctuation of load is characterized in that: taking the main steam flow as a main input signal of water supply control, and superposing a target load difference value of a unit and a target load difference value after speed limiting, a target main steam pressure value and actual main steam pressure deviation, and a target temperature and actual temperature deviation of an outlet of a separator to act on a set value of water supply flow;
and the deviation of the target temperature and the actual temperature at the outlet of the separator is acted on the feed water flow and synchronously acted on a main control coal quantity instruction of the boiler.
2. The feedwater flow control method of claim 1 for accommodating rapid load fluctuations, wherein: the main steam flow is controlled by a high pressure damper.
3. The feedwater flow control method of claim 1 for accommodating rapid load fluctuations, wherein: the main steam flow is corrected by the desuperheating water flow.
4. The feedwater flow control method of claim 1 for accommodating rapid load fluctuations, wherein: and a two-step delay link is arranged behind the main steam flow.
5. The feedwater flow control method of claim 1 for accommodating rapid load fluctuations, wherein: and correcting the difference value of the target load of the unit and the target load after speed limiting through load deviation.
6. The feedwater flow control method of claim 1 for accommodating rapid load fluctuations, wherein: and correcting the deviation between the target main steam pressure value and the actual main steam pressure through pressure deviation.
7. The feedwater flow control method of claim 1 for accommodating rapid load fluctuations, wherein: and the target temperature is obtained by correcting the saturation temperature corresponding to the outlet pressure of the steam-water separator and the superheat degree of the target load.
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| CN108825316A (en) * | 2018-08-29 | 2018-11-16 | 山西格盟安全生产咨询有限公司 | A kind of steam extraction heat supply unit quick response load system |
| CN109737378A (en) * | 2018-12-05 | 2019-05-10 | 中国大唐集团科学技术研究院有限公司火力发电技术研究院 | The whole-process control method of supercritical DC furnace water supply correction amount under varying load condition |
| CN110319430A (en) * | 2019-07-02 | 2019-10-11 | 四川省电力工业调整试验所 | The calculation method and device of supercritical circulating fluidized bed unit feedwater flow instruction under isolated network mode |
| CN111780089B (en) * | 2020-07-20 | 2021-11-23 | 中国核动力研究设计院 | Water supply control method and system for once-through steam generator |
| CN111752203B (en) * | 2020-07-31 | 2023-12-22 | 浙江浙能兰溪发电有限责任公司 | Variable-load air classification dynamic control system and method |
| CN111794936A (en) * | 2020-08-13 | 2020-10-20 | 刘亚辉 | Method for changing steam feed pump system into full frequency-conversion high-rotation-speed electric feed pump system and brand new logic control system thereof |
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| CN112682770B (en) * | 2020-12-25 | 2022-12-27 | 中广核研究院有限公司 | Pressure control method and system for once-through steam generator |
| CN113093544B (en) * | 2021-03-31 | 2022-06-17 | 西安热工研究院有限公司 | Flexible coordination control method for external steam supply unit |
| CN113803707B (en) * | 2021-09-30 | 2024-02-27 | 山西河坡发电有限责任公司 | Double enthalpy difference correction water supply control method of supercritical unit adapting to frequency modulation requirement |
| CN115773491B (en) * | 2023-02-13 | 2023-04-28 | 北京全应科技有限公司 | Unit main pipe pressure control method based on corrected pressure trend |
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| CN104864385B (en) * | 2014-02-24 | 2017-05-24 | 北京国电智深控制技术有限公司 | Method and device for calculating feed water flow instruction of supercritical unit |
| CN104932566B (en) * | 2015-06-05 | 2017-09-29 | 国网山东省电力公司电力科学研究院 | A kind of control system and method for improving the quick adjustment capability of elementary generator group boiler |
| CN105465823B (en) * | 2015-12-29 | 2017-12-12 | 广东电网有限责任公司电力科学研究院 | Prevent the control method and system of thermal power plant's direct current cooker Fuel- Water Rate imbalance |
| CN107420874B (en) * | 2017-08-16 | 2021-12-14 | 江苏大唐国际吕四港发电有限责任公司 | Ultra-supercritical thermal generator set coordination control system |
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