阅读说明：本技术 660mw超临界机组旁路控制系统及其控制方法 (660MW supercritical unit bypass control system and control method thereof ) 是由 赖艳云 王孟 李斐 钱海龙 王金梁 王涛 于 2020-06-24 设计创作，主要内容包括：本发明公开了660MW超临界机组甩负荷后旁路控制方法,术语火力发电厂自动控制领域,甩负荷后蒸汽通流通道可以无扰切换,蒸汽压力可控。包括1号管道、2号管道、3号管道和4号管道,所述的3号管道的尾端、2号管道的尾端和4号管道的头端三者通过减温减压器相连通,所述的1号管道的尾端与2号管道的头端相连通,所述的1号管道与2号管道间设有支管,所述的支管中设有蒸汽轮机。高旁旁路控制系统自动适应任意负荷下的甩负荷或者FCB工况,避免负荷巨幅波动造成的机组参数急剧变化,满足甩负荷及FCB工况要求,并且安全性高,可靠性好,结构简单。(The invention discloses a 660MW supercritical unit load shedding after-bypass control method, which belongs to the field of automatic control of thermal power plants. Including No. 1 pipeline, No. 2 pipeline, No. 3 pipeline and No. 4 pipeline, the tail end of No. 3 pipeline, the tail end of No. 2 pipeline and the head end three of No. 4 pipeline be linked together through the pressure reducer that subtracts the temperature, the tail end of No. 1 pipeline be linked together with the head end of No. 2 pipeline, No. 1 pipeline and No. 2 pipelines between be equipped with the branch pipe, the branch pipe in be equipped with steam turbine. The high-side bypass control system automatically adapts to load shedding or FCB working conditions under any load, avoids rapid change of unit parameters caused by large fluctuation of the load, meets the requirements of the load shedding and FCB working conditions, and has the advantages of high safety, good reliability and simple structure.)

1.660MW supercritical unit bypass control system which characterized in that: the pipeline cooling system comprises a No. 1 pipeline, a No. 2 pipeline, a No. 3 pipeline and a No. 4 pipeline, wherein the tail end of the No. 3 pipeline, the tail end of the No. 2 pipeline and the head end of the No. 4 pipeline are communicated through a temperature and pressure reducer, the tail end of the No. 1 pipeline is communicated with the head end of the No. 2 pipeline, a branch pipe is arranged between the No. 1 pipeline and the No. 2 pipeline, and a steam turbine is arranged in the branch pipe;

the space between the No. 3 pipeline and the temperature and pressure reducing device, the space between the No. 2 pipeline and the temperature and pressure reducing device, and the space between the steam turbine and the branch pipe are respectively controlled by valves;

the No. 1 pipeline, the No. 2 pipeline, the No. 3 pipeline, the No. 4 pipeline, the temperature and pressure reducer, the steam turbine and the valve are respectively controlled by the controller.

2. The 660MW supercritical unit bypass control system according to claim 1, characterized by: the branch pipe in be equipped with No. 1 valve, No. 1 valve and steam turbine between be equipped with No. 1.1 valve, No. 3 pipelines in be equipped with No. 3 valves, No. 3 valves and pressure and temperature reduction ware between be equipped with No. 3.1 valves, No. 2 pipelines in be equipped with No. 2 valves.

3. The 660MW supercritical unit bypass control system according to claim 2, characterized by: the No. 1 valve is a main valve, the No. 1 valve is a main steam regulating valve, the No. 3 valve is a high-pressure temperature-reducing water isolation valve, the No. 3.1 valve is a high-pressure temperature-reducing water regulating valve, and the No. 2 valve is a high-pressure bypass valve.

4. The control method of the 660MW supercritical unit bypass control system according to claim 3, characterized by the following steps:

the control method comprises step opening control of the No. 2 valve when load shedding or FCB occurs, wherein the opening of the No. 2 valve is as follows:

through a steam flow calculation book, a bypass steam enthalpy value and steam balance during load shedding, undisturbed switching of a steam channel during load shedding is realized, public duty balance of the unit is maintained, and the integral stability of the unit is kept;

the steam flow balance relationship is as described in equation (1):

Q₁＝Q₂(1)

wherein Q₁The steam flow (t/h) and Q passing through the No. 1 pipeline before load shedding₂The steam flow (t/h) passing through the No. 2 pipeline after load shedding; q₁Relationship to load and regulated stage pressure: q₁Can be regulated by stage pressure p₁Obtained by calculation, f (p)₁) The main steam flow rate without temperature correction is shown in formula (2);

and steam flow Q after the high pressure bypass valve₂(T/h) and the opening degree kn (%) of opening of the No. 2 valve and the steam temperature T before the No. 2 valve₂(K) Due to adjacent ducts, T₂With main steam temperature T₁Equal value, front steam pressure p of No. 2 valve₂(MPa), vapor enthalpy E (J/kg) through valve No. 2 through T₂(K)、p₂The pressure is inquired and obtained, and the delta P is the front-back differential pressure of the No. 2 valve;

the relationship shown in equation (2) is written according to valve flow calculation No. 2:

Q₂＝kn*ΔP*p₂*[507*(0.03*E(T₂,p₂)-18.7)](3)

when the unit normally operates, the No. 2 valve is closed, steam enters from the No. 1 and No. 1.1 valves, and the operation of the steam turbine is maintained; when the unit is unloaded, the valves 1 and 1.1 are quickly closed instantly, and the valve 2 is quickly opened;

in order to ensure the safe operation of the unit during the load shedding period, avoid the severe fluctuation of the unit and maintain the balance of working media, the opening degree of instantaneous step opening of the No. 2 valve during the load shedding period can be accurately calculated by the above notations (1), (2) and (3), as shown in a formula (4):

p₁(MPa) is the steam pressure behind the valve V1.1, the pressure of the regulating stage, p₂(MPa) is the pressure of steam before the valve V2₁(K) Is the pre-valve steam temperature, f (p), of V2₁) For the main steam flow corresponding to the pressure of the regulating stage, without temperature correction, the steam enthalpy E (J/kg) is passed through T₁(K)、p₂(MPa) the pressure difference is obtained by inquiring, wherein the delta P is the front-back differential pressure of the valve V2;

for more precise calculation of the opening of the No. 2 valve, f (p) is paired₁) And (3) making a piecewise broken line function:

when p is₁When f is less than or equal to 5.8, f (p)₁)＝600；

When 5.8<p₁When f is less than or equal to 7.5, f (p)₁)＝600+(p₁-5.8)*88.23,

When 7.5<p₁When f is less than or equal to 9.43, f (p)₁)＝750+(p₁-7.5)*129.53,

When 9.43<p₁When f is less than or equal to 11.18, f (p)₁)＝1000+(p₁-9.43)*114.28,

When 11.18<p₁When f is less than or equal to 12.52, f (p)₁)＝1200+(p₁-11.18)*111.94,

When 12.52<p₁When f is less than or equal to 13.56, f (p)₁)＝1350+(p₁-12.52)*144.23,

When 13.56<p₁When f is less than or equal to 16.8, f (p)₁)＝1500+(p₁-13.56)*133.93,

When 16.8 is used<p₁When f is less than or equal to 17.64, f (p)₁)＝1800+(p₁-16.8)*119.05,

When 17.64<p₁When f is less than or equal to 18.73, f (p)₁)＝1900+(p₁-17.64)*90.1,

5. The control method of the 660MW supercritical unit bypass control system as claimed in claim 4, wherein:

the control method also comprises a method for generating the control target pressure of the No. 2 valve, and the set value of the steam pressure control is as follows:

after the No. 2 valve is opened to the opening degree calculated by the formula (4) in a step mode, the automatic control mode is enteredAutomatically adjusting the main steam pressure; testing steam pressure at each stable point of boiler load, taking the average value of stable time after the test as the pressure target set value p corresponding to the pressure load₄；p₄The value is determined by the size of the boiler load, is a related function of the boiler load, and is used as a set value for controlling the pressure of the high-pressure bypass valve after passing through a first-order inertia link:

p₄＝f(L)*(1-e^-t/20) (5)

t in the display (5) is time;

in order to obtain a more accurate target pressure, the target pressure p is in a linear relationship to the load₄Performing accurate calculation in a segmented manner; the calculated value is used as a set value of a target pressure value for automatic control after the high-pressure bypass is opened after load shedding:

when L is less than or equal to 30; p is a radical of₄＝10.33*(1-e^-t/20)

When 30 is turned into<When L is less than or equal to 40, p₄＝(10.33+0.305*(L-30))*(1-e^-t/20)；

When 40<When L is less than or equal to 50, p₄＝(13.38+0.282*(L-40))*(1-e^-t/20)；

When 50 is turned on<When L is less than or equal to 60, p₄＝(16.2+0.273*(L-50))*(1-e^-t/20)；

When 60 is turned on<When L is less than or equal to 70, p₄＝(18.93+0.302*(L-60))*(1-e^-t/20)；

When 70<When L is less than or equal to 80, p₄＝(21.95+0.186*(L-70))*(1-e^-t/20)；

When 80<When L is less than or equal to 90, p₄＝(23.81+0.019*(L-80))*(1-e^-t/20)；

When 90 is reached<When L is less than or equal to 100, p₄＝24；

Steam pressure P of No. 4 pipeline at inlet of steam turbine of feed pump₄The numerical value of (MPa) and the boiler load L form a certain linear relation, in order to obtain an accurate numerical value of the steam pressure of the No. 4 pipeline, piecewise function calculation is formulated, and the calculation result is used as a set value of the steam pressure of the No. 4 pipeline corresponding to the boiler load; the set value is used as a pressure set parameter for PID control after the No. 2 valve (switching valve) is opened in a step mode;

when L is less than or equal to 30，P₄＝0.58；

When 30 is turned into<When L is less than or equal to 40, P₄＝0.58+(L-30)*0.006；

When 40<When L is less than or equal to 50, P₄＝0.62+(L-40)*0.006；

When 50 is turned on<When L is less than or equal to 60, P₄＝0.68+(L-50)*0.008；

When 60 is turned on<When L is less than or equal to 70, P₄＝0.76+(L-60)*0.011；

When 70<When L is less than or equal to 80, P₄＝0.87+(L-70)*0.013；

When 80<When L is less than or equal to 90, P₄＝1.00+(L-80)*0.012；

When 90 is reached<When L is less than or equal to 95, P₄＝1.12+(L-90)*0.022；

When 95<When L is less than or equal to 100, P₄＝1.23+(L-95)*0.022；

When L > 100, P₄＝1.23；

The deviation between the pressure set value and the actual steam pressure enters a No. 2 valve PID control module for operation, the opening of the high-pressure bypass regulating valve is directly controlled through an operation output instruction, and the steam pressure is controlled to correspond to the load shedding load or the boiler combustion load after the FCB action.

Technical Field

The invention relates to a bypass control system, in particular to a 660MW supercritical unit bypass control system and a control method thereof.

Background

Because the supercritical unit FCB or when load shedding, the unit is disconnected from an external network, and the turbine throttle is closed. In order to maintain the safety and stability of the unit and avoid the blockage of the main steam channel, a high-pressure bypass needs to be opened for flowing a large amount of superheated steam, so that the working medium balance of the whole unit is maintained. The opening degree of the high-pressure bypass after load shedding is very critical, and the large opening degree can lose most energy and bring economic loss to the recovery of the normal operation of the unit; if the opening degree is too small, the steam channel is blocked, and the safety performance of the unit is influenced. After the high-pressure bypass is opened, the pressure needs to be continuously adjusted, the steam pressure is prevented from fluctuating greatly, the set target value of the pressure and the adjusting process can influence the safety, economic and technical indexes of the unit and the recovery operation time of the unit, and therefore, the method and the control method of the high-pressure bypass are of great significance under the load shedding working condition.

Disclosure of Invention

The invention mainly solves the defects in the prior art, and provides a 660MW supercritical unit bypass control system and a control method thereof, which can monitor the whole response process of a high-pressure bypass load shedding process of a supercritical unit, and correspondingly respond to the control and steam adjusting process of the high-pressure bypass in the process according to the real-time monitoring result of the real-time working conditions of the unit before and after load shedding, so that the pressure in the whole process of bypass adjustment is controllable, and the steam entering the bypass flow meets the requirement of the working medium balance of the unit, and has high safety and good reliability.

The technical problem of the invention is mainly solved by the following technical scheme:

the 660MW supercritical unit bypass control system comprises a No. 1 pipeline, a No. 2 pipeline, a No. 3 pipeline and a No. 4 pipeline, wherein the tail end of the No. 3 pipeline, the tail end of the No. 2 pipeline and the head end of the No. 4 pipeline are communicated through a temperature and pressure reducer, the tail end of the No. 1 pipeline is communicated with the head end of the No. 2 pipeline, a branch pipe is arranged between the No. 1 pipeline and the No. 2 pipeline, and a steam turbine is arranged in the branch pipe;

the space between the No. 3 pipeline and the temperature and pressure reducing device, the space between the No. 2 pipeline and the temperature and pressure reducing device, and the space between the steam turbine and the branch pipe are respectively controlled by valves;

the No. 1 pipeline, the No. 2 pipeline, the No. 3 pipeline, the No. 4 pipeline, the temperature and pressure reducer, the steam turbine and the valve are respectively controlled by the controller.

Preferably, the branch pipe is internally provided with a valve No. 1, a valve No. 1 is arranged between the valve No. 1 and the steam turbine, a valve No. 3 is arranged in the pipeline No. 3, a valve No. 3.1 is arranged between the valve No. 3 and the temperature and pressure reducer, and a valve No. 2 is arranged in the pipeline No. 2.

Preferably, the valve 1 is a main valve, the valve 1.1 is a main steam regulating valve, the valve 3 is a high-pressure temperature-reducing water isolation valve, the valve 3.1 is a high-pressure temperature-reducing water regulating valve, and the valve 2 is a high-pressure bypass valve.

The working principle is as follows: the superheated steam flows through the pipeline No. 1, and enters the high-pressure cylinder of the steam turbine through the valve No. 1 and the valve No. 1.1, so that the normal operation of the steam turbine is maintained. When meetting the load shedding operating mode, 1 No. 1, 1.1 valve quick closing, superheated steam flows through No. 2 pipelines, and No. 2 pipelines and No. 1 pipeline are 4.5 meters in steam turbine top, and 5 meters positions in aircraft nose left side are connected with 60 degrees contained angles, are provided with No. 2 valves on No. 2 pipelines, and the flow of steam flow through No. 2 pipelines, the pressure of steam are adjusted through No. 2 valves. The regulated steam flows through a No. 4 pipeline and enters a temperature and pressure reducing device. No. 3 pipeline and No. 4 pipeline are connected through the temperature and pressure reduction ware with 45 degrees angles in 3 meters departments behind No. 2 valves, be provided with No. 3 valves on No. 3 pipelines, No. 3.1 valves, high pressure feed water passes through the feed pump export through No. 3 pipelines, the valve of No. 3 flows through, after No. 3.1 valve regulation, get into the temperature and pressure reduction ware, carry out temperature regulation to superheated steam, steam after the temperature and pressure reduction passes through No. 4 pipeline flow direction reheaters. The control ends of the valves No. 1, No. 1.1, No. 2, No. 3 and No. 3.1 are respectively connected with the controller. The steam pressure after load shedding is adjusted through the opening degree of the No. 2 valve, the steam temperature is adjusted through the No. 3.1 valve, and the steam through-flow is controlled to be matched with the actual working condition.

The relationship between load and regulation stage pressure, pressure after valve No. 1.1, and main steam flow is shown in table 1 below:

the control method of the 660MW supercritical unit bypass control system is carried out according to the following steps:

the control method comprises step opening control of the No. 2 valve when load shedding or FCB occurs, wherein the opening of the No. 2 valve is as follows:

through a steam flow calculation book, a bypass steam enthalpy value and steam balance during load shedding, undisturbed switching of a steam channel during load shedding is realized, public duty balance of the unit is maintained, and the integral stability of the unit is kept;

the steam flow balance relationship is as described in equation (1):

Q₁＝Q₂(1)

wherein Q₁The steam flow (t/h) and Q passing through the No. 1 pipeline before load shedding₂The steam flow (t/h) passing through the No. 2 pipeline after load shedding; q₁The relationship with load and regulated stage pressure is shown in table 1: q₁Can be regulated by stage pressure p₁Obtained by calculation, f (p)₁) The main steam flow rate without temperature correction is shown in formula (2);

and steam flow Q after the high pressure bypass valve₂(T/h) and the opening degree kn (%) of opening of the No. 2 valve and the steam temperature T before the No. 2 valve₂(K) Due to adjacent ducts, T₂With main steam temperature T₁Equal value, front steam pressure p of No. 2 valve₂(MPa), vapor enthalpy E (J/kg) through valve No. 2 through T₂(K)、p₂The pressure is inquired and obtained, and the delta P is the front-back differential pressure of the No. 2 valve;

the relationship shown in equation (2) is written according to valve flow calculation No. 2:

Q₂＝kn*ΔP*p₂*[507*(0.03*E(T₂,p₂)-18.7)](3)

when the unit normally operates, the No. 2 valve is closed, steam enters from the No. 1 and No. 1.1 valves, and the operation of the steam turbine is maintained; when the unit is unloaded, the valves 1 and 1.1 are quickly closed instantly, and the valve 2 is quickly opened;

in order to ensure the safe operation of the unit during the load shedding period, avoid the severe fluctuation of the unit and maintain the balance of working media, the opening degree of instantaneous step opening of the No. 2 valve during the load shedding period can be accurately calculated by the above notations (1), (2) and (3), as shown in a formula (4):

p₁(MPa) is the steam pressure behind the valve V1.1, the pressure of the regulating stage, p₂(MPa) is the pressure of steam before the valve V2₁(K) Is the pre-valve steam temperature, f (p), of V2₁) For the main steam flow corresponding to the pressure of the regulating stage, without temperature correction, the steam enthalpy E (J/kg) is passed through T₁(K)、p₂(MPa) the pressure difference is obtained by inquiring, wherein the delta P is the front-back differential pressure of the valve V2;

for more precise calculation of the opening of the No. 2 valve, f (p) is paired₁) And (3) making a piecewise broken line function:

when p is₁When f is less than or equal to 5.8, f (p)₁)＝600；

When 5.8<p₁When f is less than or equal to 7.5, f (p)₁)＝600+(p₁-5.8)*88.23,

When 7.5<p₁When f is less than or equal to 9.43, f (p)₁)＝750+(p₁-7.5)*129.53,

When 9.43<p₁When f is less than or equal to 11.18, f (p)₁)＝1000+(p₁-9.43)*114.28,

When 11.18<p₁When f is less than or equal to 12.52, f (p)₁)＝1200+(p₁-11.18)*111.94,

When 12.52<p₁When f is less than or equal to 13.56, f (p)₁)＝1350+(p₁-12.52)*144.23,

When 13.56<p₁When f is less than or equal to 16.8, f (p)₁)＝1500+(p₁-13.56)*133.93,

When 16.8 is used<p₁When f is less than or equal to 17.64, f (p)₁)＝1800+(p₁-16.8)*119.05,

When 17.64<p₁When f is less than or equal to 18.73, f (p)₁)＝1900+(p₁-17.64)*90.1,

Preferably, the control method further includes a method for generating a control target pressure of valve No. 2, and the set value of the steam pressure control is:

after the No. 2 valve is opened to the opening degree calculated by the formula (4) in a step mode, entering an automatic control mode, and automatically adjusting the main steam pressure; testing steam pressure at each stable point of boiler load, and taking stable time after testingMean value as a pressure target set value p corresponding to the pressure load₄；p₄The value is determined by the size of the boiler load, is a related function of the boiler load, and is used as a set value for controlling the pressure of the high-pressure bypass valve after passing through a first-order inertia link:

p₄＝f(L)*(1-e^-t/20) (5)

t in the display (5) is time.

The target pressure boiler load test data is shown in the following table:

in order to obtain a more accurate target pressure, the target pressure p is in a linear relationship to the load₄Performing accurate calculation in a segmented manner; the calculated value is used as a set value of a target pressure value for automatic control after the high-pressure bypass is opened after load shedding:

when L is less than or equal to 30; p is a radical of₄＝10.33*(1-e^-t/20)

When 30 is turned into<When L is less than or equal to 40, p₄＝(10.33+0.305*(L-30))*(1-e^-t/20)；

When 40<When L is less than or equal to 50, p₄＝(13.38+0.282*(L-40))*(1-e^-t/20)；

When 50 is turned on<When L is less than or equal to 60, p₄＝(16.2+0.273*(L-50))*(1-e^-t/20)；

When 60 is turned on<When L is less than or equal to 70, p₄＝(18.93+0.302*(L-60))*(1-e^-t/20)；

When 70<When L is less than or equal to 80, p₄＝(21.95+0.186*(L-70))*(1-e^-t/20)；

When 80<When L is less than or equal to 90, p₄＝(23.81+0.019*(L-80))*(1-e^-t/20)；

When 90 is reached<When L is less than or equal to 100, p₄＝24；

The deviation between the pressure set value and the actual steam pressure enters a No. 2 valve PID control module for operation, the opening of the high-pressure bypass regulating valve is directly controlled through an operation output instruction, and the steam pressure is controlled to correspond to the load shedding load or the boiler combustion load after the FCB action.

The invention can achieve the following effects:

according to the invention, during load shedding of the boiler, the opening of the high-pressure bypass step opening is directly and accurately calculated by using the current steam temperature and pressure through a steam flow calculation formula and a steam balance principle, so that the unit and a steam through-flow channel are accurately switched when the load is shed under any working condition, the action of a safety valve is avoided, and the working medium balance of the unit is realized. And (3) putting into an automatic control mode of the high-pressure bypass valve, automatically setting a control target value of the high-pressure bypass valve according to the combustion load of the boiler, and automatically adjusting to enable the opening degree of the bypass to be matched with the combustion working condition of the unit. By the invention, the high-side bypass control system automatically adapts to the load shedding or FCB working condition under any load, avoids the rapid change of unit parameters caused by the large fluctuation of the load, meets the requirements of the load shedding and FCB working condition, and has high safety, good reliability and simple structure.

Drawings

FIG. 1 is a schematic view of the connection structure of the present invention;

FIG. 2 is a logic flow diagram of the high pressure bypass control of the present invention;

FIG. 3 is a schematic logic flow diagram for the control of the low pressure regulator valve of the present invention;

FIG. 4 is a depiction of the meaning of the symbols in FIGS. 2-3 in accordance with the present invention;

fig. 5 is a schematic block diagram of the circuit schematic connection structure of the present invention.

Shown in the figure: l1 is No. 1 pipeline, L2 is No. 2 pipeline, L3 is No. 3 pipeline, L4 is No. 4 pipeline, V1 is No. 1 valve, V1.1 is No. 1 valve, V2 is No. 2 valve, V3 is No. 3 valve, V3.1 is No. 3.1 valve.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings.