CN111535879B - Control method for bypass system of gas-steam combined cycle unit - Google Patents
Control method for bypass system of gas-steam combined cycle unit Download PDFInfo
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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
- F01D17/00—Regulating or controlling by varying flow
- F01D17/10—Final actuators
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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
- F01D17/00—Regulating or controlling by varying flow
- F01D17/10—Final actuators
- F01D17/12—Final actuators arranged in stator parts
- F01D17/14—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits
- F01D17/141—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of shiftable members or valves obturating part of the flow path
- F01D17/145—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of shiftable members or valves obturating part of the flow path by means of valves, e.g. for steam turbines
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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
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D27/00—Simultaneous control of variables covered by two or more of main groups G05D1/00 - G05D25/00
- G05D27/02—Simultaneous control of variables covered by two or more of main groups G05D1/00 - G05D25/00 characterised by the use of electric means
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Abstract
The invention discloses a control method of a bypass system of a gas-steam combined cycle unit, which comprises the steps of simulating the operation condition of a steam turbine in the whole process, dynamically calculating the preset opening of a valve by combining a characteristic function of a bypass valve and an energy conservation law, outputting a pulse signal of the preset opening of the valve at intervals, triggering a valve opening instruction immediately after a tripping signal of the steam turbine is triggered and the pulse signal of the preset opening of an upper valve, and quickly responding and opening each bypass valve to the preset opening. The method can effectively realize accurate dynamic control of the bypass valve system, well stabilize steam system parameters, ensure that the gas turbine can independently operate with the bypass system under the condition of tripping of the steam turbine from the technical aspect, ensure that system equipment is safe and reliable, and avoid economic loss and social influence on a power grid and a power plant caused by non-stop accidents of the gas turbine.
Description
Technical Field
The invention relates to a control method for a bypass system of a gas-steam combined cycle unit, and belongs to the technical field of debugging of the gas-steam combined cycle unit.
Background
The invention aims at the research of a bypass system of a domestic introduced large-scale gas-steam combined cycle unit, the load of the combined cycle unit is distributed into a 300MW gas turbine and a 140MW steam turbine, the gas turbine and the steam turbine are respectively provided with an independent power generation and transformation unit system to operate, the conventional steam turbine generator device protects the action, and the gas turbine system still has the independent operation function. The steam turbine adopts high and medium pressure cylinder, low pressure cylinder double current to arrange, and the steam turbine bypass adopts high pressure bypass and medium pressure bypass to establish ties and sets up, and the low pressure bypass is steam turbine low pressure steam supplement pipeline bypass, directly gets into the condenser. The bypass system device comprises a bypass valve (comprising a desuperheater), a water spray adjusting valve, a water spray isolation valve and the like, and three-pressure bypasses are all designed with 100% capacity.
The steam turbine bypass system is a steam temperature and pressure reducing system connected with the steam turbine in parallel, in the gas-steam combined cycle unit, the gas turbine and the steam turbine are matched with each other under the control of unit coordination, and the bypass system can coordinate steam parameters of an outlet of the waste heat boiler when the steam turbine is quickly started, so that the steam-water circulation is accelerated, and the cold-state or hot-state starting time of the unit is shortened; meanwhile, the function of ensuring that the fuel can independently operate with a bypass system and the exhaust-heat boiler does not stop after the steam turbine accident trip is realized.
The operation condition of the steam turbine bypass system of the same type of gas power plants in China is comprehensively researched, full-range automatic control is basically realized by the bypass system in the start-stop stage, when the steam turbine trips in an accident, the bypass valve takes pressure as an adjusting object, after a tripping signal is received, the bypass valve is quickly and fully opened, then the steam pressure of the system is adjusted, a temperature reducing water adjusting valve takes temperature as a control object, the response time is slow in the accident condition, the adjusting control mode is simple in design, but the fluctuation of steam parameters of the system is large, the system protection action is easy to interlock and trip the gas turbine, and the operation function of the steam turbine tripping combustion engine independent belt bypass system cannot be. There are mainly the following problems:
a. when the steam turbine trips, the steam pressure of the system rises rapidly, the response time and the opening degree of the bypass valve are not appropriate, and the steam pressure of the system fluctuates greatly, so that the high steam pressure protection action is directly caused.
b. The steam pressure fluctuation directly influences the stability of the water level of the boiler drum, and the water level protection action is caused by large-amplitude disturbance.
c. The response time and flow control of the bypass desuperheating water are improper, so that the steam temperature behind the bypass valve is too high or too low, the bypass valve with high temperature is closed in a locking way, and the boiler protection action is interlocked with the tripping of the combustion engine. The excessive low temperature causes water hammer of accumulated water in the pipeline behind the valve, which causes serious safety accidents of the pipeline equipment.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and the control method can effectively stabilize system operation parameters and ensure that the gas turbine can independently carry out stable operation of a steam bypass system by accurately processing the control mode of the bypass system valve when the gas turbine trips.
In order to achieve the purpose, aiming at the fully-closed working condition of the unit combined cycle steam bypass system valve, the invention provides the technical scheme that:
a control method for a bypass system of a gas-steam combined cycle unit comprises the steps of simulating the operation condition of a steam turbine in the whole process, collecting relevant steam parameters in real time, and dynamically calculating the preset opening of each valve according to a valve characteristic function and through system control logic operation.
The invention quantizes the quick opening degree of each steam bypass valve, sends out a preset opening degree pulse signal at intervals through the calculation of a valve characteristic function, immediately triggers a valve opening instruction when a tripping signal of a steam turbine is triggered, and quickly opens the bypass valve until the pulse signal corresponds to the preset opening degree.
Further, the steam bypass temperature-reducing water regulating valve is regulated and controlled: the control mode of the high-pressure and medium-pressure temperature-reducing water regulating valve is more complicated than that of the conventional control mode, wherein the control strategy of the high-pressure and medium-pressure temperature-reducing water regulating valve adopts an enthalpy value control mode, the preset opening degree of the valve is calculated through the law of energy conservation and the flow characteristic function of the regulating valve, a preset opening degree pulse signal is triggered once at intervals, when the high-pressure and medium-pressure bypass valve is triggered by a quick opening signal and the analog quantity signal of the opening degree of the valve is more than 5%, an opening instruction of the temperature-reducing water regulating valve is triggered immediately, and the temperature-reducing water regulating.
Preferably, the interval time of triggering the preset opening pulse signals by the high and middle side temperature-reducing water regulating valves is consistent with the interval time of sending out dynamic valve opening pulse signals by each bypass valve, and the interval time is set to be 2 s.
Wherein, the steam bypass valve comprises a high-pressure bypass valve, a medium-pressure bypass valve and a low-pressure bypass valve.
Further, after each bypass valve is quickly opened, the system is stably operated for a period of time and is switched to a pressure control mode; after the bypass temperature-reducing water regulating valve is quickly opened, the steam temperature after the bypass temperature-reducing water regulating valve is stably operated for a period of time and is converted into closed-loop regulation control for the bypass valve.
The dynamic valve opening theta 1 corresponding to the dynamic valve opening pulse signal sent by the high-pressure bypass valve is determined by the real-time main steam flow Q1, the main steam pressure P1, the main steam enthalpy value H1 and the pressure difference delta P1 of two sides when the high-pressure bypass valve is fully opened, and the specific calculation formula is as follows:
the dynamic valve opening theta 2 corresponding to a dynamic valve opening pulse signal sent by the medium-pressure bypass valve is determined by the main reheat steam flow Q2 when being triggered, the enthalpy value H2 of the reheat steam and the pressure difference delta P2 of two sides when the medium-pressure bypass valve is fully opened, and the specific calculation formula is as follows:
the dynamic valve opening theta 3 corresponding to the dynamic valve opening pulse signal sent by the low-pressure bypass valve is determined by the low-pressure steam flow Q3 when triggered, the low-pressure steam enthalpy value H3 and the pressure difference delta P3 at two sides when the low-pressure bypass valve is fully opened, and the specific calculation formula is as follows:
the preset opening of the high side temperature-reducing water regulating valve is calculated according to the high side temperature-reducing water flow in a linear relation with the high side temperature-reducing water regulating valve; the flow rate Q1 of the high-side desuperheating water is determined by real-time main steam flow rate Q1, main steam enthalpy value H1, desuperheating water enthalpy value H1 and steam enthalpy value H1' after desuperheating and depressurization during triggering, and the specific calculation formula is as follows:
the preset opening degree of the medium-side desuperheating water regulating valve is calculated according to the medium-side desuperheating water flow in a linear relation with the medium-side desuperheating water regulating valve; the flow rate Q2 of the intermediate side desuperheating water is determined by the real-time reheated steam flow rate Q2, the enthalpy value H2 of the reheated steam, the enthalpy value H2 of the desuperheating water and the enthalpy value H2' of the steam after desuperheating and pressure reduction, and the specific calculation formula is as follows:
when the steam turbine trips, the low-side valve quickly opens the interlocking fully-opened temperature-reducing water regulating valve, and the temperature after the control valve is regulated in a switching closed-loop mode after 30s of stabilization.
Compared with the prior art, the invention has the following advantages:
1. the bypass system control method of the invention has accurately designed the bypass system control under the condition of turbine tripping, the unit enters the gas-steam combined cycle working condition, the steam bypass system valve is totally closed and is in the tracking standby state, through specially processing the bypass system control logic, after the turbine tripping signal is triggered, the bypass valve immediately implements the quick opening function module, the function module is divided into a high, middle and low pressure bypass valve and a temperature reduction water regulating valve, and the control block of accurate calculation can effectively control the steam bypass valve system.
The control method includes the steps of simulating the operation condition of the steam turbine in the whole process, immediately acquiring system steam parameter signals when the unit operates, calculating preset opening degrees of the bypass valve and the temperature reduction water regulating valve according to a valve characteristic function and an energy conservation law, immediately outputting the preset opening degree signals of the bypass valve by setting a certain time pulse amount, immediately executing a preset opening degree instruction by the bypass valve when a tripping signal of the steam turbine is triggered, and further adjusting system steam pressure and temperature according to a unit slip pressure curve after system parameters are stable. The method can realize the refined dynamic control of the bypass valve system, well stabilize the steam system parameters, ensure the independent operation of the gas turbine with the bypass system under the condition of the trip of the gas turbine from the technical aspect, ensure the safety and the reliability of system equipment and avoid the economic loss and the social influence on a power grid and a power plant caused by the non-stop accident of the gas turbine.
Drawings
FIG. 1 is a schematic view of the construction of a steam bypass according to the present invention;
FIG. 2 is a high pressure bypass valve logic control diagram;
FIG. 3 is a logic control diagram of a high side desuperheating water regulating valve.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
As shown in fig. 1, in this embodiment, a bypass valve system adopted by a combined cycle unit with load distribution of 300MW gas turbine and 140MW turbine is taken as an example, the control method is a refined design for bypass system control under turbine trip condition, the unit enters a gas-steam combined cycle working condition, the steam bypass system valve is fully closed and is in a tracking standby state, special processing is performed on the bypass system control logic, after the turbine trip signal is triggered, the bypass valve immediately implements a quick opening function module, the function module is divided into a high-pressure bypass valve, a medium-pressure bypass valve and a low-pressure bypass valve and a temperature reduction water regulating valve, the precisely calculated control block can effectively control the steam bypass valve system, after the bypass valve is opened and stabilized, the bypass valve is converted into a pressure control mode, and the pressure is the pressure of a sliding pressure curve corresponding to the load. The fluctuation of system parameters is stabilized to a great extent, and the gas turbine can independently operate stably with a bypass system under the condition of tripping of the steam turbine.
The specific implementation process is as follows:
1. control of a high pressure bypass valve (hereinafter referred to as a high bypass valve) of a steam system:
as shown in fig. 2, the high bypass valve control module: under any load, the operation of a high-pressure cylinder of the steam turbine is completely simulated, the preset opening degree of the high bypass valve is fitted on line through control logic operation according to the characteristic function of the bypass valve and steam parameters, and a pulse signal is set to be sent every 2 seconds. Steam is sampled and input to control system immediately when the unit is operated, and the main steam parameters of collection include: main steam flow, pressure, temperature. After the tripping signal of the steam turbine is triggered, a valve quick opening instruction is immediately triggered by a pulse signal with the preset opening of the upper side bypass valve, the high side bypass valve is opened to the preset opening and stably runs for a certain time, and then the operation mode is switched to a pressure control mode, wherein the pressure is a sliding pressure curve corresponding to the load of the gas turbine.
Taking a high-pressure bypass valve adopted by a combined cycle unit with load distribution of a 300MW gas turbine and a 140MW steam turbine as an example:
in the formula, Q1 is high side steam flow, and the high side steam flow is equal to the high pressure main steam flow; the opening degree of the high bypass valve is set; Δ P1 is the differential pressure between the two sides when the high side valve is fully opened, and is a constant; p1 is the main steam pressure; h1 is the main steam enthalpy.
Under a specific load, the preset opening degree of the high bypass quick opening can be fitted by the main steam flow, the main steam pressure and the temperature, and the calculation formula is as follows:
2. control of the high bypass temperature-reducing water regulating valve:
as shown in fig. 3, the high-side temperature-reducing water regulating valve can quickly respond to the action of the high-side valve, quickly opens to a preset opening degree after receiving a high-side quick opening signal, and then is automatically controlled to regulate the temperature behind the high-side valve to prevent overtemperature. After the high side valve is opened quickly in an emergency, in order to ensure that the temperature of steam behind the high side valve is not over-temperature and avoid closing the high side valve by high locking of the temperature behind the valve, the preset opening signal of the temperature reduction water regulating valve is also a pulse signal (synchronous with the high side valve) triggered every 2 seconds. The preset opening degree of the high-side temperature-reducing water regulating valve is as follows: collecting the steam and desuperheating water parameter signals related to the operation of the bypass system, and obtaining the signals through the online control operation of the mass and energy conservation law.
According to the law of conservation of mass and energy, the following relationships are obtained:
Q1×H1+q1×h1＝Q1"H1"
Q1×H1+q1×h1＝(Q1+q1)×H1"
the required high side temperature-reducing water flow is as follows:
wherein the main steam flow is Q1, the main steam enthalpy is H1, the desuperheating water flow is Q1, the desuperheating water enthalpy is H1, the steam flow after desuperheating and depressurizing is Q1", and the steam enthalpy after desuperheating and depressurizing is H1" (the reheater steam pressure P2 is known, and the steam temperature after valve T2 is a fixed value, so that the steam enthalpy H1 can be obtained).
The flow of the high-side temperature-reducing water and the opening of the high-side temperature-reducing water regulating valve are basically in a linear relationship, so that in the actual process, the steam flow function under the current working condition is used as the instantaneous opening value of the high-side temperature-reducing water when the bypass is quickly opened. After the high-side temperature-reducing water regulating valve is opened to a preset opening degree, the high-side temperature-reducing water regulating valve stably operates for 5 seconds (can be adjusted in the operation process within specific time), and then the high-side temperature-reducing water regulating valve is converted into closed-loop adjustment to control the steam temperature behind the high-side valve.
3. Control of a medium pressure bypass valve (hereinafter referred to as a mid-bypass valve) in a steam system:
a middle bypass valve control module: under any load, the operation of the steam turbine intermediate pressure cylinder is completely simulated, the preset opening degree of the intermediate side valve is fitted on line through control logic operation according to the characteristic function of the bypass valve and steam parameters, and a pulse signal is set to be sent every 2 seconds. Steam is sampled and input to the control system immediately when the unit operates, and the collected steam parameters comprise: reheat steam flow, reheat steam pressure, and temperature. After the tripping signal of the steam turbine is triggered, a valve quick opening instruction is immediately triggered by a pulse signal with the preset opening of the upper valve, the bypass valve is opened to the preset opening and stably runs for a certain time, and then the operation is switched to a pressure control mode, wherein the pressure is a reheat steam sliding pressure curve corresponding to the load of the steam turbine.
Taking the medium-pressure bypass valve adopted by the combined cycle unit with the load distribution of a 300MW gas turbine and a 140MW steam turbine as an example:
in the formula, Q2 is the flow rate of medium-side steam, and the flow rate of the medium-side steam is the sum of the flow rate of medium-pressure superheater steam and the flow rate of reheater steam; θ 2 is the opening of the intermediate bypass valve; Δ P2 is the differential pressure between the two sides when the intermediate bypass valve is fully opened, and is a constant; p2 is the medium pressure main steam pressure; h2 is the medium pressure main steam enthalpy.
Under specific load, the middle-pressure steam flow, the pressure and the temperature can be fitted to form the preset opening of the middle bypass valve, and the calculation formula is as follows:
4. control of the bypass temperature-reducing water regulating valve:
the middle side temperature-reducing water regulating valve can quickly respond to the action of the middle side valve, quickly opens to a preset opening after receiving a quick opening signal of the middle side valve, then automatically controls to regulate the temperature behind the high side valve, avoids closing the middle side valve due to high temperature behind the valve, and triggers a pulse signal (synchronous with the middle side valve) every 2 seconds according to the preset opening signal of the temperature-reducing water regulating valve. The control strategy of the middle-side temperature-reducing water regulating valve adopts an enthalpy value control mode, and the preset opening degree of the valve is calculated through an energy conservation law and a regulating valve flow characteristic function.
Q2×H2+q2×h2＝Q2"×H2"
Q2×H2+q2×h2＝(Q2+q2)×H2"
The required high side temperature-reducing water flow is as follows:
wherein the medium pressure steam flow is Q2, the medium pressure steam enthalpy value is H2, the desuperheating water flow is Q2, the desuperheating water enthalpy value is H2, the steam flow after desuperheating and depressurizing is Q2", and the steam enthalpy value after desuperheating and depressurizing is H2" (the reheater steam pressure P2 is known, and the steam temperature T2 after the valve is a fixed value, so that the steam enthalpy value H2 can be obtained).
The enthalpy value of the condenser inlet is calculated according to the designed pressure and temperature, and the steam flow at the condenser inlet is equal to the sum of the flow of the desuperheating steam and the flow of the reheating steam.
The flow of the middle-side desuperheating water and the opening of the middle-side desuperheating water regulating valve are basically in a linear relation, so that in the actual process, a steam flow function under the current working condition is used as a preset opening value of the middle-side desuperheating water when the bypass is opened quickly. And (3) opening the middle side temperature-reducing water regulating valve to a preset opening degree, stably operating for 30 seconds, and then converting the opening degree into the steam temperature behind the middle side valve in closed-loop regulation control (which can be adjusted in the optimal time test process).
5. The control idea of the low-pressure bypass valve is the same as that of the high-pressure bypass valve and the medium-pressure bypass valve, the preset opening degree of the bypass valve is accurately calculated through the characteristic function corresponding to the valve, the pressure control mode is switched after the valve is stabilized for a certain time, and the steam pressure of the system and the water level of a steam drum of the boiler are further stabilized.
Taking the low-pressure bypass valve adopted by the combined cycle unit with the load distribution of a 300MW gas turbine and a 140MW steam turbine as an example:
in the formula, Q3 is the flow rate of low-pressure steam; θ 3 is the low bypass valve opening; Δ P3 is a differential pressure between both sides when the low side valve is fully opened, and is a constant; p3 is low pressure steam pressure; h3 vapor enthalpy.
Under specific load, the low-side quick-opening preset opening degree can be fitted by the low-pressure steam flow, the steam pressure and the temperature, and the calculation formula is as follows:
6. the low-pressure bypass steam directly returns to the condenser, the steam temperature control behind the bypass valve is relatively easy, as long as the steam temperature does not exceed the high-temperature locked closed middle and low-pressure bypass valve values, so when the steam turbine trips, the low bypass valve quickly opens the interlocked fully-opened desuperheating water regulating valve, the capacity of the condensate pump designed by the system can meet the requirement of desuperheating water, and the temperature behind the control valve is regulated in a post-conversion closed loop mode.
The technical solutions of the present invention are not limited to the above embodiments, and all technical solutions obtained by using equivalent substitution modes fall within the scope of the present invention.
Claims (9)
1. A control method for a bypass system of a gas-steam combined cycle unit is characterized by comprising the following steps: the control method includes the steps that the operation condition of the steam turbine is simulated in the whole process, relevant steam parameters are collected in real time, and the preset opening degree of each bypass valve is dynamically calculated through system control logic operation according to the characteristic function of the bypass valve; the bypass valve sends out a preset opening pulse signal at intervals, after the tripping signal of the steam turbine is triggered, the bypass valve is triggered to quickly open a command after the steam turbine and the preset opening pulse signal of the upper bypass valve, and each bypass valve is quickly opened to the corresponding preset opening of the bypass valve; triggering a preset opening pulse signal once every a period of time by the high-side temperature-reducing water regulating valve, when a tripping signal of a steam turbine is triggered and the opening analog quantity of the high-pressure bypass valve is more than 5%, and presetting an opening pulse signal with the high-side temperature-reducing water regulating valve, immediately triggering an opening instruction of the high-side temperature-reducing water regulating valve, and quickly opening the high-side temperature-reducing water regulating valve to the preset opening; the middle-side desuperheating water regulating valve controls the preset opening pulse signal to be triggered once at intervals, when the tripping signal of the steam turbine is triggered and the opening analog quantity of the middle-pressure bypass valve is larger than 5%, the opening pulse signal is preset with the upper middle-side desuperheating water regulating valve, the opening instruction of the middle-side desuperheating water regulating valve is triggered immediately, and the middle-side desuperheating water regulating valve is quickly opened to the preset opening.
2. The control method of the bypass system of the gas-steam combined cycle unit according to claim 1, wherein the interval time for triggering the preset opening pulse signals by the high and middle bypass temperature-reducing water regulating valves is consistent with the interval time for sending the preset opening pulse signals by each bypass valve, and is 2 s.
3. The gas-steam combined cycle unit bypass system control method according to claim 2, wherein the bypass valve includes a high pressure bypass valve, an intermediate pressure bypass valve, a low pressure bypass valve; after each bypass valve is quickly opened, stably running for a period of time and switching to a pressure control mode; after the high-side temperature-reducing water regulating valve is quickly opened, the high-side temperature-reducing water regulating valve stably operates for a period of time and is converted into closed-loop regulation to control the steam temperature of the high-pressure side-by-pass valve.
4. The gas-steam combined cycle unit bypass system of claim 3The system control method is characterized in that the dynamic valve opening corresponding to the preset opening pulse signal sent by the high-pressure bypass valve
The system is determined by real-time main steam flow Q1, main steam pressure P1, main steam enthalpy H1 and pressure difference delta P1 of two sides when the high-pressure bypass valve is fully opened during triggering, and the specific calculation formula is as follows:
5. the control method of the bypass system of the gas-steam combined cycle unit according to claim 3, wherein the dynamic valve opening corresponding to the preset opening pulse signal sent by the medium-pressure bypass valve is the dynamic valve opening corresponding to the preset opening pulse signal sent by the medium-pressure bypass valve
The control method is determined by the reheat steam flow Q2, the enthalpy value H2 and the pressure difference delta P2 between two sides when the medium-pressure bypass valve is fully opened when triggered, and the specific calculation formula is as follows:
wherein P2 is reheat steam pressure.
6. The control method of the bypass system of the gas-steam combined cycle unit according to claim 3, wherein the dynamic valve opening corresponding to the preset opening pulse signal sent by the low-pressure bypass valve is set to be smaller than the dynamic valve opening corresponding to the preset opening pulse signal sent by the low-pressure bypass valve
The low-pressure steam flow Q3, the low-pressure steam enthalpy value H3 and the pressure difference delta P3 of two sides when the low-pressure bypass valve is fully opened are used for determining, and the specific calculation formula is as follows:
wherein P3 is a low pressure steam pressure.
7. The gas-steam combined cycle unit bypass system control method according to claim 1, wherein the preset opening of the high bypass desuperheating water regulating valve is calculated according to a high bypass desuperheating water flow rate in a linear relationship therewith; the flow rate Q1 of the high-side desuperheating water is determined by real-time main steam flow rate Q1, main steam enthalpy value H1, desuperheating water enthalpy value H1 and steam enthalpy value H1' after desuperheating and depressurization during triggering, and the specific calculation formula is as follows:
8. the control method of the gas-steam combined cycle unit bypass system according to claim 1, wherein the preset opening degree of the intermediate side desuperheating water regulating valve is calculated according to intermediate side desuperheating water flow rate in a linear relation with the intermediate side desuperheating water regulating valve; the flow rate Q2 of the intermediate side desuperheating water is determined by the real-time reheated steam flow rate Q2, the enthalpy value H2 of the reheated steam, the enthalpy value H2 of the desuperheating water and the enthalpy value H2' of the steam after desuperheating and pressure reduction, and the specific calculation formula is as follows:
9. the control method of the gas-steam combined cycle unit bypass system according to claim 3, characterized in that when the steam turbine is tripped, the low-pressure bypass valve is quickly opened and interlocked to fully open the low-pressure bypass temperature-reducing water regulating valve, and the temperature after the closed-loop low-pressure bypass valve is converted after 30s is stabilized.
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