CN110966170A - Real-time control method for cold end back pressure of indirect air cooling generator set - Google Patents
Real-time control method for cold end back pressure of indirect air cooling generator set Download PDFInfo
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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
- F04B49/06—Control using electricity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K19/00—Regenerating or otherwise treating steam exhausted from steam engine plant
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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
- F04B23/00—Pumping installations or systems
- F04B23/04—Combinations of two or more pumps
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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
- F04B49/007—Installations or systems with two or more pumps or pump cylinders, wherein the flow-path through the stages can be changed, e.g. from series to parallel
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Abstract
The invention relates to a real-time control method for cold end backpressure of an indirect air-cooled generator set, which utilizes a DCS control system to obtain optimal economic backpressure corresponding to different loads under different environmental temperatures according to heat load changes of condensers under different working conditions, influences of backpressure on power and power consumption of circulating water flow of different hosts, and realizes automatic control in the set DCS, wherein the control process comprises the steps of determining power consumption of different circulating water quantities by ⑴, determining circulating water flow of the hosts by ⑵, determining heat load of the condensers by ⑶, determining circulating water temperature rise of the condensers by ⑷, determining backpressure of the condensers by ⑸, determining influences of the backpressure on the set load by ⑹, determining optimal economic backpressure and corresponding circulating water quantity by ⑺, and adjusting the frequency of the circulating pump by ⑻.
Description
Technical Field
The invention belongs to the technical field of industrial production automatic control, and relates to a real-time control method for cold end backpressure of an indirect air cooling generator set.
Background
In thermal power generation or chemical enterprises, steam after work is done in a steam turbine needs to be discharged into a condenser to be condensed into water, and then the water is returned to a boiler for recycling. The heat of the condenser is taken away by the circulating water, so that the circulating water and cold air generate heat exchange in the cooling tower, and finally the heat is released to the atmosphere. The indirect air cooling system is very commonly applied to newly built units in northern China and mainly comprises an air cooling radiator, an indirect cooling tower, a shutter and a driver.
The pressure at the steam outlet of the low-pressure cylinder of the steam turbine is called the back pressure of the steam turbine. The change of the back pressure of the unit has important influence on the circulating heat efficiency of the steam turbine unit, the back pressure is reduced by 1%, the coal consumption is increased by 0.1-0.15%, so that the back pressure of the unit is well controlled, the unit is ensured to run under the optimal back pressure, and the method has important significance on the economy of the unit. The operation backpressure of the condensing turbine in the power plant is influenced by parameters in various aspects, such as heat load of a condenser, operation condition of the condenser, circulating water flow, heat exchange effect of an indirect cooling system, ambient temperature, wind speed and the like. The determination of the optimal economic backpressure can be calculated and deduced through a theoretical formula, but the process is complex, and the operation of the optimal economic backpressure cannot be maintained in real time in practice. The backpressure regulation of the indirect air-cooled steam turbine unit is generally realized by changing the opening degree of a shutter, changing the high and low rotating speeds of a power frequency circulating pump and increasing or decreasing the number of running circulating pumps to control the circulating water flow, so that the purpose of controlling the backpressure of the unit is achieved, and the indirect air-cooled steam turbine unit is in a manual, rough and qualitative regulation mode.
Disclosure of Invention
The invention aims to provide a real-time control method for cold end backpressure of an indirect air-cooling generating set, which utilizes a DCS (distributed control system) control system to automatically regulate and control in real time according to heat loads of condensers under different working conditions, temperature change of circulating water of a main machine and influence of backpressure on power of the generating set, so that the generating set runs under optimized economic backpressure, and the economic benefit of production of the generating set of a thermal power plant is improved.
The technical scheme of the invention is as follows: a real-time control method for cold end backpressure of an indirect air cooling generator set utilizes a DCS control system to obtain optimal economic backpressure corresponding to different loads under different environmental temperatures according to heat load changes of condensers under different working conditions, influence of backpressure on power and power consumption of circulating water flow of different main machines; the control process is as follows:
⑴ determining the power consumption of different circulating water volumes:
obtaining a comprehensive frequency and power consumption corresponding table of a typical operation mode by utilizing the comprehensive operation frequency and power consumption of the main machine circulating pump, and calculating the power consumption corresponding to the operation of the circulating pump at different comprehensive frequencies by fitting a mathematical formula to the comprehensive frequency and power consumption curve; the relation between the comprehensive frequency and the power consumption of the host circulating pump is as follows:
Pb＝a1f2–b1f+c1 (1)
in the formula: pb: circulating pump power consumption, kW; f: circulation pump frequency, Hz; a1, b1, c1 are constant terms;
⑵, determining the circulating water flow of the main engine, wherein the change of the frequency of the circulating pump of the main engine influences the circulating water flow, and the circulating water flow of the main engine is calculated according to a flow proportion formula (2), wherein the calculation formula is as follows:
Q1/Q2＝n1/n2 (2)
in the formula: q1 flow rate, m3S; q2 is rated working condition flow, m3S; n1 is the pump speed of working condition 1, m3S; n2 is rated pump speed, m3/s；
Correcting the calculated flow value through actual flow measurement of typical frequency to obtain the corresponding relation of actual frequency flow;
⑶, determining the heat load of the condenser, wherein the heat load of the condenser is influenced by the conditions of low-pressure cylinder flow, backpressure, thermodynamic system change and the like, calculating the corresponding heat load of the condenser under different working conditions of the unit, and fitting a formula after correcting the heat load of the condenser according to a related performance test:
qn＝a2x2+b2x+c2 (3)
in the formula: q. q.snIs the heat load of a condenser, kJ/s; x is the low-pressure cylinder steam inlet flow rate, kg/s); a2, b2, c2 are constant terms;
⑷, determining the temperature rise of the circulating water of the condenser, namely obtaining a temperature rise formula of the circulating water of the condenser after determining the heat load of the condenser and the quantity of the circulating water:
wherein △ t is condenser circulating water temperature rising at DEG C, G is circulating water flow rate kg/s, qn: condenser heat load, kJ/s; c, specific heat of water 4.187, kJ/(kg. DEG C);
⑸, determining the back pressure of the condenser, wherein the calculation formula of the steam side temperature of the condenser is as follows according to the inlet temperature of the circulating water of the condenser, the temperature rise (△ t) of the circulating water of the condenser and the end difference (td) of the condenser:
tc＝tw1+△t+td (5)
wherein tc is the steam side temperature of the condenser and is DEG C, tw1 is the inlet temperature of the circulating water of the condenser and is DEG C, △ t is the temperature rise of the circulating water and is DEG C, and td is the end difference of the condenser;
the saturated pressure corresponding to the steam side temperature of the condenser is the condenser back pressure Pn;
⑹ determining the influence of the back pressure on the load of the unit, namely, according to the characteristic curve of the back pressure load of the unit, the power of the unit shows a negative increasing trend when the back pressure of the unit increases, obtaining the influence rate of any back pressure in the change range of the back pressure of the unit on the load of the unit according to the characteristic curve, and deriving the influence rate formula of the back pressure on the load of the unit;
⑺, determining the optimal economic back pressure and the corresponding circulating water quantity, namely obtaining the increment of the electric power of the unit after the back pressure changes △ Pj through the back pressure changes corresponding to different circulating water flows and the load change rate corresponding to the back pressure, obtaining the increment of the power consumption of the main engine circulating pump corresponding to the back pressure changes △ Pb, and when △ Pm is △ Pj- △ Pb is the maximum value, the optimal economic back pressure value of the unit is obtained, and the corresponding circulating water flow is the optimal economic circulating water flow.
Wherein △ Pm is the difference between the electric power increment of the unit and the power consumption increment of the main engine circulating pump, kW, △ Pj is the electric power increment of the unit after backpressure change, kW, and the power consumption increment of the main engine circulating pump corresponding to △ Pb backpressure change, kW.
According to the method, the circulating water flow corresponding to the optimal economic back pressure of the working point is determined in the circulating water temperature and load change range of the condenser of the unit.
The adjustment mode of the circulating pump frequency is as follows: determining the total frequency of the circulating water pumps and the frequency of each circulating water pump according to the optimal circulating water flow, and determining the three-dimensional corresponding relation of the circulating water inlet temperature of the condenser, the heat load of the condenser and the frequency of the circulating water pumps of the host; and fixing the temperature point of the circulating water inlet of the condenser according to the adjusting range, converting the temperature point into a two-dimensional relation of condenser heat load-main engine circulating water pump frequency, and automatically adjusting the circulating flow in real time in a DCS (distributed control system) to maintain the optimal economic backpressure operation.
Condenser end difference Td is the temperature difference of condenser steam side temperature and play water side temperature of water, embodies the cooling situation of condenser, receives condenser vacuum tightness and condenser heat transfer surface clean degree influence, and the calculation formula of condenser end difference is:
Td＝tc-tw2 (6)
in the formula: td is condenser end difference, DEG C; tc is the condenser steam side temperature, DEG C; tw2 is the temperature of the outlet side outlet water temperature.
The optimal economic backpressure of the unit is determined according to the inlet water temperature of the circulating water of the condenser and the heat load of the condenser, and the comprehensive frequency of the circulating water pump is adjusted to change the flow rate of the circulating water, so that the unit is kept in the optimal economic backpressure operation. And calculating the optimal comprehensive frequency of the running of the circulating pump in the DCS according to the three-dimensional curves of the inlet water temperature of the circulating water of the condenser, the heat load of the condenser and the comprehensive frequency of the circulating water pump of the main machine. And determining corresponding relation curves of different condenser heat loads and the comprehensive frequency of the main circulating water pump according to different condenser circulating water inlet temperatures. The configuration of the indirect air cooling generator set main machine circulating pump is that 2-10 variable frequency pumps run in parallel, or 2-10 power frequency pumps run in parallel with 2-10 variable frequency pumps.
In order to keep the unit running under the optimal economic backpressure, a three-dimensional curve graph is drawn according to the relation between the circulating water flow of the host and the frequency of the circulating water pump of the host by calculating the circulating water flow corresponding to the optimal economic backpressure of the condenser according to the circulating water inlet temperature of the condenser and the heat load of the condenser. The temperature range of the circulating water inlet of the condenser covers all temperature points in the actual operation of the unit. The variable condenser circulating water inlet temperature is fixed, and a three-dimensional curve of the condenser circulating water inlet temperature, the condenser heat load and the host circulating water pump frequency is converted into a two-dimensional curve of the condenser heat load and the host circulating water pump frequency, so that the dimensionality reduction treatment is realized. The relation between the heat load of the condenser and the comprehensive frequency of the circulating water pumps of the main machine under different circulating water temperatures of the main machine is changed. And distributing the comprehensive frequency of the circulating water pump of the host to each frequency conversion host circulating pump which runs in parallel, and issuing starting and stopping instructions to the power frequency circulating pump to automatically maintain the circulating water flow of the host at the flow corresponding to the optimal economic backpressure.
According to the real-time control method for the cold end backpressure of the indirect air-cooling generator set, accumulated test data are combined with theoretical derivation, and according to the heat load change of condensers under different working conditions, the influence of backpressure on power and the power consumption of the circulating water flow of the main machine, the circulating water flow of the main machine is automatically regulated and controlled in real time by using the DCS control system, so that the indirect air-cooling generator set can maintain the optimal cold end backpressure operation in real time, and the economic benefit of unit production is improved.
Drawings
FIG. 1 is a schematic flow chart of a real-time control method for cold end backpressure of an indirect air-cooling generator set according to the invention;
FIG. 2 is a graph showing the relationship between the frequency of the circulation pump and the power consumption of the pump;
FIG. 3 is a graph of the effect of back pressure on unit load;
FIG. 4 is a three-dimensional curve of condenser circulating water inlet temperature, condenser heat load and host circulating water pump frequency;
fig. 5 is a division diagram of dead zones of the inlet water temperature of the circulating water of the condenser.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples. The scope of protection of the invention is not limited to the embodiments, and any modification made by those skilled in the art within the scope defined by the claims also falls within the scope of protection of the invention.
When the heat load of a condenser and the ambient temperature are fixed, the variable influencing the back pressure of the unit is mainly the circulating water flow, when the power of the circulating pump is increased, the circulating water flow of the condenser is also increased, and the back pressure of the turbine is reduced, the power of the turbine unit is increased, the increment of the electric power of the unit is △ Pj after the back pressure is changed, the increment of the power consumption of the main circulating pump corresponding to the change of the circulating water flow is △ Pb, and when △ Pm is △ Pj- △ Pb is the maximum, the optimal economic back pressure value of the unit is obtained.
Wherein △ Pm is the difference between the electric power increment of the unit and the power consumption increment of the main engine circulating pump, kW, △ Pj is the electric power increment of the unit after backpressure change, kW, and the power consumption increment of the main engine circulating pump corresponding to △ Pb backpressure change, kW.
The invention discloses a real-time control method for cold end backpressure of an indirect air cooling generator set, which utilizes a DCS control system to obtain optimal economic backpressure corresponding to different loads under different environmental temperatures according to heat load changes of condensers under different working conditions, influences of backpressure on power and power consumption of circulating water flow of different main machines. As shown in fig. 1, the control process is as follows:
⑴ determining power consumption of different circulating water volume, obtaining a typical operating frequency and power consumption corresponding table by using power consumption values corresponding to different frequencies of the main engine circulating pump, drawing a frequency and power consumption curve and fitting a mathematical formula, and calculating power consumption corresponding to any frequency by the formula, wherein table 1 is the power consumption measured value of two main engine circulating water pumps (variable frequency pumps), and the frequency and power consumption corresponding curve is shown in figure 2:
TABLE 1 comparison table of frequency and power consumption of host circulating pump
| Frequency of circulating pumps operating in parallel | Energy consumption of parallel operation circulating pumps |
| Hz | |
| 20 | |
| 25 | |
| 30 | A3 |
| 35 | A4 |
| 40 | A5 |
| 45 | |
| 50 | A7 |
The relation between the circulating pump frequency and the power consumption is as follows:
Pb＝a1f2–b1f+c1 (1)
in the formula: pb: circulating pump power consumption, kW; f: circulation pump frequency, Hz;
a1, b1 and c1 are constant terms, and three parallel variable frequency pumps with power of 1250kW are taken as examples: a1 is 0.6; b1 ═ 46.7; c1 ═ 1255.5;
⑵, determining the circulating water flow of the main engine, wherein the change of the frequency of the circulating pump of the main engine influences the circulating water flow, and the circulating water flow of the main engine is calculated according to a flow proportion formula (2), wherein the calculation formula is as follows:
Q1/Q2＝n1/n2 (2)
in the formula: q1 flow rate, m3S; q2 is rated working condition flow, m3S; n1 is the pump speed of working condition 1, m3S; n2 is rated pump speed, m3/s；
And correcting the calculated flow value to obtain the actual frequency flow corresponding relation through actual flow measurement of the typical frequency.
⑶, determining the heat load of the condenser, wherein the heat load of the condenser is influenced by the conditions of low-pressure cylinder flow, backpressure, thermodynamic system change and the like, calculating the corresponding heat load of the condenser under different working conditions of the unit, and fitting a formula after correcting the heat load of the condenser according to a related performance test:
qn＝a2x2+b2x+c2 (3)
in the formula: q. q.snIs the heat load of a condenser, kJ/s; x is the low-pressure cylinder steam inlet flow rate, kg/s);
a2, b2 and c2 are constant terms, and take a 350MW unit as an example: a2 ═ 4.8; b2 ═ 2956.1; c2 ═ 73643;
⑷, determining the temperature rise of the circulating water of the condenser, and obtaining a condenser circulating water temperature rise formula after the heat load and the circulating water quantity of the condenser are determined:
wherein △ t is condenser circulating water temperature rising at DEG C, G is circulating water flow rate kg/s, qn: condenser heat load, kJ/s; c, specific heat of water 4.187, kJ/(kg-DEG C).
⑸, determining the backpressure of the condenser, calculating the steam side temperature of the condenser and the corresponding backpressure of the condenser according to the running end difference of the condenser, wherein the calculation formula of the steam side temperature of the condenser is as follows:
tc＝tw1+△t+td (5)
wherein tc is the steam side temperature of the condenser and is DEG C, tw1 is the inlet temperature of the circulating water of the condenser and is DEG C, △ t is the temperature rise of the circulating water and is DEG C, and td is the end difference of the condenser;
the condenser circulating water inlet temperature tw1 is actually measured due to the influence of the ambient temperature and the cleanliness of the indirect cooling heat exchange surface. The condenser end difference Td is the difference between the steam side temperature of the condenser and the outlet water temperature of the circulating water, and is influenced by the vacuum tightness of the condenser and the cleanness of the heat exchange surface of the condenser. The calculation formula of the condenser end difference is as follows:
Td＝tc-tw2 (6)
in the formula: td is condenser end difference, DEG C; tc is the condenser steam side temperature, DEG C; tw2 is the temperature of the outlet side outlet water temperature.
And the saturation pressure corresponding to the steam side temperature of the condenser is the condenser back pressure Pn.
⑹ determining the effect of back pressure on unit load;
according to the load characteristics of the back pressure of the unit, the power of the unit shows a negative increasing trend when the back pressure of the unit increases, as shown in fig. 3. And obtaining the influence rate of any backpressure on the unit load in the backpressure variation range of the unit according to the characteristic curve, and deriving the influence rate formula of the backpressure on the unit load.
⑺ determining the optimal economic circulating water quantity;
and calculating the determined optimal circulating water quantity corresponding to each working condition one by one according to different condenser circulating water inlet temperatures and different condenser heat loads in the unit operation. As shown in table 2, the inlet temperature of the condenser circulating water is 25 ℃ to 50 ℃ at the lowest, the load is 50% rated load (175MW) to 100% rated load (350MW) at the lowest, and the frequency of each circulating water pump corresponds to the optimal economic back pressure.
Table 2 relationship table of condenser circulating water inlet temperature, load, and circulating pump frequency.
⑻ scheme for automatic adjustment of optimum backpressure, which is to determine optimum economic backpressure in DCS according to current load and circulating water temperature, and obtain optimum circulating water flow and corresponding comprehensive frequency according to optimum economic backpressure fig. 4 is a three-dimensional curve of water inlet temperature of condenser circulating water-unit load-comprehensive frequency of main machine circulating water pump, and the comprehensive frequency is used for frequency distribution of each circulating pump, and the frequency distribution of two frequency conversion pumps and one power frequency pump is shown in table 3.
TABLE 3 comprehensive frequency distribution to each circulation pump (taking two frequency conversion pumps and one power frequency pump as an example)
⑼ setting a dead zone for the temperature of the circulating water of the condenser, setting the dead zone for the temperature of the circulating water of the condenser in a DCS of the unit and dividing the dead zone into different temperature points, as shown in FIG. 5, when the temperature is in a 26 +/-0.5 ℃ interval, the temperature point is 26 ℃, in order to prevent the frequent adjustment of the frequency caused by the fluctuation of the temperature at the boundary of the two intervals, the dead zone with the temperature of 0.1 ℃ is set, when the temperature fluctuates at about 26.5 ℃ of the boundary point, if the temperature keeps rising trend, the temperature will jump out of 26 ℃ and fall to 27 ℃ only if the temperature is higher than 26.55 ℃, if the temperature keeps trend, the temperature will jump out of 27 ℃ and divide the temperature into 26 ℃ if the temperature is lower than 26.45 ℃, the temperature is divided into 26 temperature points, 25 ℃ -50 ℃, one temperature point is divided every 1 ℃, the temperature point is larger than 49.45 ℃ and the temperature is smaller than 25.65 ℃ and divided into 25 ℃.
Claims (7)
1. A real-time control method for cold end backpressure of an indirect air cooling generator set utilizes a DCS control system to obtain optimal economic backpressure corresponding to different loads under different environmental temperatures according to heat load changes of condensers under different working conditions, influence of backpressure on power and power consumption of circulating water flow of different main machines; the control process is as follows:
⑴, determining the power consumption of different circulating water quantities, namely obtaining a comprehensive frequency and power consumption corresponding table of a typical running mode by utilizing the running comprehensive frequency and power consumption of the main machine circulating pump, and calculating the power consumption corresponding to the running of the circulating pump at different comprehensive frequencies by fitting a mathematical formula to the comprehensive frequency and power consumption curve, wherein the relational expression of the comprehensive frequency and the power consumption of the main machine circulating pump is as follows:
Pb＝a1f2–b1f+c1 (1)
in the formula: pb: circulating pump power consumption, kW; f: circulation pump frequency, Hz; a1, b1, c1 are constant terms;
⑵, determining the circulating water flow of the main engine, wherein the change of the frequency of the circulating pump of the main engine influences the circulating water flow, and the circulating water flow of the main engine is calculated according to a flow proportion formula (2), wherein the calculation formula is as follows:
Q1/Q2＝n1/n2 (2)
in the formula: q1 flow rate, m3S; q2 is rated working condition flow, m3S; n1 is the pump speed of working condition 1, m3S; n2 is rated pump speed, m3/s；
⑶, determining the heat load of the condenser, wherein the heat load of the condenser is influenced by the flow rate and the back pressure of the low-pressure cylinder and the change of a thermodynamic system, calculating the corresponding heat load of the condenser under different working conditions of the unit, and fitting a formula after correcting the heat load of the condenser according to a related performance test.
qn＝a2x2+b2x+c2 (3)
In the formula: q. q.snIs the heat load of a condenser, kJ/s; x is the steam inlet flow of the low-pressure cylinder, kg/s; a2, b2, c2 are constant terms;
⑷, determining the temperature rise of the circulating water of the condenser, namely obtaining a temperature rise formula of the circulating water of the condenser after determining the heat load of the condenser and the quantity of the circulating water:
wherein △ t is the temperature rise of the circulating water of the condenser at DEG C, and G is the circulating waterFlow rate, kg/s; q. q.sn: condenser heat load, kJ/s; c, specific heat of water 4.187, kJ/(kg. DEG C);
⑸, determining the back pressure of the condenser, namely calculating the steam side temperature of the condenser according to the inlet temperature of the circulating water of the condenser, the temperature rise of the circulating water of the condenser and the end difference of the condenser, wherein the calculation formula is as follows:
tc＝tw1+△t+td (5)
wherein tc is the steam side temperature of the condenser and is DEG C, tw1 is the inlet temperature of the circulating water of the condenser and is DEG C, △ t is the temperature rise of the circulating water and is DEG C, and td is the end difference of the condenser and is DEG C;
the saturated pressure corresponding to the steam side temperature of the condenser is the condenser back pressure Pn;
⑹ determining the influence of back pressure on the load of the unit, wherein the power of the unit is in negative increasing trend when the back pressure of the unit is increased gradually according to the characteristic curve of the back pressure load of the unit, and the back pressure of the unit is basically in linear transformation when the back pressure of the unit is larger than the designed back pressure;
⑺ determining the optimal economic back pressure and the corresponding circulating water amount;
obtaining an increment △ Pj of the electric power of the unit after the back pressure changes and an increment △ Pb of the power consumption of the main circulating pump corresponding to the back pressure changes through back pressure changes corresponding to different circulating water flows and load change rates corresponding to the back pressure, wherein when △ Pm is △ Pj- △ Pb is the maximum value, the optimal economic back pressure value of the unit is obtained, and the corresponding circulating water flow is the optimal economic circulating water flow;
wherein △ Pm is the difference between the electric power increment of the unit and the power consumption increment of the main engine circulating pump, kW, △ Pj is the electric power increment of the unit after backpressure change, kW, and the power consumption increment of the main engine circulating pump corresponding to △ Pb backpressure change, kW.
2. The real-time control method for cold end back pressure of the indirect air-cooling generator set according to claim 1, is characterized in that: the adjustment mode of the circulating pump frequency is as follows: determining the total frequency of the circulating water pumps and the frequency of each circulating water pump according to the optimal circulating water flow, and determining the three-dimensional corresponding relation of the circulating water inlet temperature of the condenser, the heat load of the condenser and the frequency of the circulating water pumps of the host; and fixing the temperature point of the circulating water inlet of the condenser according to the adjusting range, converting the temperature point into a two-dimensional relation of condenser heat load-main engine circulating water pump frequency, and automatically adjusting the circulating flow in real time in a DCS (distributed control system) to maintain the optimal economic backpressure operation.
3. The real-time control method for cold end back pressure of the indirect air-cooling generator set according to claim 1, is characterized in that: the condenser end difference Td is the temperature difference between the steam side temperature of the condenser and the water outlet side water outlet temperature, and the calculation formula of the condenser end difference is as follows:
Td＝tc-tw2 (6)
in the formula: td is condenser end difference, DEG C; tc is the condenser steam side temperature, DEG C; tw2 is the temperature of the outlet water side outlet water temperature.
4. The real-time control method for cold end back pressure of the indirect air-cooling generator set according to claim 1, is characterized in that: the optimal economic backpressure of the unit is determined according to the inlet water temperature of the circulating water of the condenser and the heat load of the condenser, and the comprehensive frequency of the circulating water pump is adjusted to change the flow rate of the circulating water, so that the unit is kept in the optimal economic backpressure operation.
5. The real-time control method for cold end back pressure of the indirect air-cooling generator set according to claim 1, is characterized in that: and calculating the optimal comprehensive frequency of the running of the circulating pump in the DCS according to the three-dimensional curves of the inlet water temperature of the circulating water of the condenser, the heat load of the condenser and the comprehensive frequency of the circulating water pump of the main machine.
6. The real-time control method for cold end back pressure of the indirect air-cooling generator set according to claim 1, is characterized in that: and determining corresponding relation curves of different condenser heat loads and the comprehensive frequency of the main circulating water pump according to different condenser circulating water inlet temperatures.
7. The real-time control method for cold end back pressure of the indirect air-cooling generator set according to claim 1, is characterized in that: the configuration of the indirect air cooling generator set main machine circulating pump is 2-10 variable frequency pumps which are in parallel operation, or 2-10 power frequency pumps and 2-10 variable frequency pumps which are in parallel operation.
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| CN113834681A (en) * | 2021-07-27 | 2021-12-24 | 湖南凯利特能源科技有限公司 | Dynamic energy-saving evaluation method and evaluation system for evaporative air cooler group |
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| CN115450892A (en) * | 2022-10-17 | 2022-12-09 | 哈尔滨沃华智能电力技术有限公司 | Control method of cold end system of steam turbine |
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