CN113721674A - Water level control system and method for evaporator of nuclear power plant - Google Patents
Water level control system and method for evaporator of nuclear power plant Download PDFInfo
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Abstract
The invention relates to a water level control system and a method for an evaporator of a nuclear power plant, wherein the water level control system comprises an evaporator, a large valve and a small valve, the large valve and the small valve are arranged in parallel and are connected to a water supply main pipe of the evaporator, and a venturi tube and a pore plate are arranged on the water supply main pipe; at least three feed water flow transmitters are respectively arranged on the Venturi tube; the pore plate is connected to a fourth feedwater flow transmitter through a pressure leading pipe. The invention also relates to a water level control method of the evaporator of the nuclear power plant, which comprises the steps of S1, judging whether the water level control system of the evaporator meets the switching condition, and judging the quality level fault of the fourth water supply flow transmitter; and S2, when the fourth feedwater flow transmitter works normally, the system is switched to a second control mode by controlling the manual switching button, and a second control signal is output to control the opening degrees of the large valve and the small valve. The invention greatly improves the stability and reliability of the water level control system of the evaporator, prevents the occurrence of transient state of a unit or automatic shutdown of a reactor, and ensures nuclear safety.
Description
Technical Field
The invention relates to the field of instrument control, in particular to a water level control system and method for an evaporator of a nuclear power plant.
Background
The evaporator water level control system is one of the most important control systems of the nuclear power unit, and the stability of evaporator water level control is important for safe and stable operation of the nuclear power unit. According to statistics, the automatic shutdown times of nuclear power units caused by the abnormality of evaporator water level control systems at home and abroad are not enumerated. Due to the deviation of venturi tube measurement, the condition that water supply flow measurement is not followed (namely, the change of real flow is not reflected) exists under the condition of low flow, so that the water level adjustment of an evaporator is greatly fluctuated, which is the common problem of multi-base nuclear power units and reflects different conditions in different base nuclear power units.
Disclosure of Invention
The invention aims to solve the technical problem that an evaporator water level control system is abnormal under the condition of low load, and provides a nuclear power plant evaporator water level control system and method for stably controlling and switching low-load feedwater flow, aiming at the defects of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: the water level control system of the nuclear power plant evaporator comprises an evaporator, a large valve and a small valve, wherein the large valve and the small valve are used for controlling the opening degree of the evaporator;
the venturi tube is respectively provided with at least three water supply flow transmitters, the at least three water supply flow transmitters comprise a first water supply flow transmitter, a second water supply flow transmitter and a third water supply flow transmitter, and the venturi tube is respectively connected with the at least three water supply flow transmitters through pressure pipes; and the pore plate is connected to a fourth feedwater flow transmitter for heat balance flow calculation through a pressure guiding pipe.
Preferably, the first feedwater flow transmitter is a narrow range feedwater flow transmitter, and the second and third feedwater flow transmitters are wide range feedwater flow transmitters.
The invention also constructs a water level control method of the nuclear power plant evaporator, aiming at the water level control system of the evaporator, the water level control method comprises the following steps:
s1, judging whether the evaporator water level control system meets a switching condition or not, and judging quality level faults of the fourth water supply flow transmitter; when the evaporator water level control system meets the switching condition, continuing to execute the step S2; when the system does not meet the switching condition, maintaining the first control mode;
s2, when the fourth feedwater flow transmitter works normally, the evaporator water level control system is switched to a second control mode by controlling a manual switching button, and a second control signal is output to control the opening degrees of the large valve and the small valve; and when the fourth feedwater flow transmitter fails, the evaporator water level control system is automatically switched to the first control mode, and outputs a first control signal to control the opening degrees of the large valve and the small valve.
Preferably, in step S1, the quality level fault determining for the fourth feedwater flow transmitter specifically includes determining that the fourth feedwater flow transmitter is faulty when the fourth feedwater flow transmitter has a card fault and/or a network fault.
Preferably, in step S2, the method further comprises switching the system to the first control mode by controlling a manual switch when the fourth feedwater flow transmitter is in an unexpected fluctuation state.
Preferably, the first control signal controls the evaporator water level control system to obtain a third feedwater flow Q measured by the second feedwater flow transmitter and the third feedwater flow transmitter respectivelyW1And a fourth feed water flow rate QW2Controlling; the second control signal controls the evaporator water level control system to obtain a fourth water supply flow QTAnd (5) controlling.
Preferably, in the step S1, the method specifically includes the following steps:
s1-1, judging quality level faults of the fourth feedwater flow transmitter;
s1-2, obtaining a fourth water supply flow Q measured by the fourth water supply flow transmitterTAnd judging the fourth water supply flow QTWhether the water flow is within the preset water supply flow range or not;
s1-3, acquiring the nuclear power of the nuclear power plant, and judging whether the nuclear power is smaller than a preset nuclear power range;
s1-4, when the fourth water supply flow QTIf the nuclear power is smaller than the preset nuclear power range within the preset feedwater flow range, the switching condition is met, and the step S2 is continuously executed; otherwise, the switching condition is not satisfied, and the first control mode is maintained.
Preferably, the preset water supply flow range is more than or equal to 150 and less than or equal to QT≤550。
Preferably, the preset nuclear power range is less than 30%.
Preferably, in the step S2, the first control signal and the second control signal control the opening degrees of the large valve and the small valve through PID adjustment.
The implementation of the invention has the following beneficial effects: the stability and the reliability of the water level control system of the nuclear power unit evaporator are greatly improved, the phenomenon that the nuclear power unit is in a transient state or the reactor is automatically stopped due to the abnormal control system is prevented, and the nuclear safety is guaranteed.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of a nuclear power plant evaporator water level control system according to the present invention;
FIG. 2 is a control schematic of the nuclear power plant evaporator water level control method of the present invention;
FIG. 3 is a flow chart of a first embodiment of a nuclear power plant evaporator water level control method of the present invention;
FIG. 4 is a flow chart of a nuclear power plant evaporator water level control method according to a second embodiment of the present invention;
FIG. 5 is a block flow diagram of a nuclear power plant evaporator water level control method of the present invention;
FIG. 6 is a schematic diagram of the nuclear power plant evaporator water level control method of step S1;
FIG. 7 is a logic circuit diagram of a nuclear power plant evaporator water level control method of the present invention;
fig. 8 is a control circuit diagram of the nuclear power plant evaporator water level control method of the present invention.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, it is to be understood that the orientations and positional relationships indicated by "front", "rear", "upper", "lower", "left", "right", "longitudinal", "lateral", "vertical", "horizontal", "top", "bottom", "inner", "outer", "leading", "trailing", and the like are configured and operated in specific orientations based on the orientations and positional relationships shown in the drawings, and are only for convenience of describing the present invention, and do not indicate that the device or element referred to must have a specific orientation, and thus, are not to be construed as limiting the present invention.
It is also noted that, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," "disposed," and the like are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. When an element is referred to as being "on" or "under" another element, it can be "directly" or "indirectly" on the other element or intervening elements may also be present. The terms "first", "second", "third", etc. are only for convenience in describing the present technical solution, and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated, whereby the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
As shown in fig. 1, the water level control system for the evaporator of the nuclear power plant of the present invention comprises an evaporator 1, a large valve 2 and a small valve 3 for controlling the opening degree of the evaporator 1, wherein the large valve 2 and the small valve 3 are respectively arranged in parallel on two branch pipes and are connected to a water supply main pipe 11 of the evaporator 1 together, and a venturi tube 4 and an orifice plate 5 are installed on the water supply main pipe 11 between the evaporator 1 and the large valve 2 and the small valve 3;
the venturi tube 4 is respectively provided with at least three water supply flow transmitters for detecting the flow of the venturi tube 4, the at least three water supply flow transmitters comprise a first water supply flow transmitter 41, a second water supply flow transmitter 42 and a third water supply flow transmitter 43, and the venturi tube 4 is respectively connected with the at least three water supply flow transmitters through pressure pipes; the orifice plate 5 is connected by a lead pipe to a fourth feedwater flow transmitter 51 for heat balance flow calculation.
Further, the first feedwater flow transmitter 41 is a narrow-range feedwater flow transmitter, and the second and third feedwater flow transmitters 42 and 43 are wide-range feedwater flow transmitters.
During the control process, the differential pressure of the measuring element Venturi tube 4 may not follow the abnormity at low flow, which is mainly reflected in that the sensitivity of the measuring element Venturi tube 4 to the pressure at low flow is poor at one time under the low power condition. The evaporator 1 water supply main pipe 11 is provided with a throttling element Venturi tube 4, the Venturi tube 4 is respectively provided with a narrow range water supply flow transmitter and two wide range water supply flow transmitters, and at the moment, the water supply flow Q participating in water level control of the evaporator 1FWIs the second toWide range Q measured by the water flow rate transmitter 42 and the third feed water flow rate transmitter 43, respectivelyW1、QW2But actually, the process value of the wide-range feed water flow transmitter is greatly deviated from the theoretical value due to the poor pressure sensing sensitivity of the Venturi tube 4 under the low flow condition.
In order to ensure the accuracy of the measurement of the water supply flow of the evaporator 1 under the condition of low flow, a pore plate 5 can be installed on a water supply main pipe 11 of the evaporator 1, the pore plate 5 is connected to a water supply flow transmitter for heat balance flow calculation through a pressure leading pipe, the pore plate 5 and a fourth water supply flow transmitter 51 passing through the pressure leading pipe are led to a non-safety-level DCS system to participate in the control of a large water level valve and a small water level valve of the evaporator.
As shown in fig. 2, the present embodiment uses a non-safety level DCS system to control the evaporator water level large valve 2 and the small valve 3. The water level control of the evaporator adopts cascade regulation and comprises a feed water flow signal QFWSteam flow signal QSTEvaporator water level signal LSGLoad signal (wide range) P of two loopsPWLoad signal (narrow range) P of two loopsPN. Evaporator water level signal L obtained through actual measurementSGAnd two-loop load signal (wide range) PPWInput to a PID main regulator, wherein a two-loop load signal (wide range) PPWIs a constant value signal. The output signal of the PID main regulator and the steam flow signal QSTAnd feed water flow signal QFWThe steam-water deviation signal is input to a PI auxiliary regulator, and the output signal of the PI auxiliary regulator controls a big valve 2 of the evaporator. The output signal of PID main regulator and two-loop load signal (narrow range) PPNThe signal is input into a P auxiliary regulator, and the output signal of the P auxiliary regulator controls a small valve 3 of the evaporator, thereby realizing the opening degree V of a water level control valve of the evaporatorOControl and regulation of.
The main reason for generating the abnormal water level control of the evaporator is that large deviation exists between steam and water, and under the condition of low load, the abnormal virtual high of the water supply flow does not follow the deviation amount of the advanced adjustment. Therefore, the water supply flow signal Q can be obtained through the comparisonFWSignal selection to reduce abnormal water level control of evaporator。
As shown in fig. 3 to 5, a method for controlling a water level of an evaporator in a nuclear power plant according to the present invention includes the following steps:
s1, judging whether the evaporator water level control system meets the switching condition, and judging the quality level fault of the fourth water supply flow transmitter 51; when the evaporator water level control system meets the switching condition, continuing to execute the step S2; when the system does not meet the switching condition, maintaining the first control mode;
as shown in fig. 6, further, in step S1, the method specifically includes the following steps:
s1-1, judging quality level faults of the fourth feedwater flow transmitter 51;
further, when the fourth feedwater flow transmitter 51 has a card failure and/or a network failure, it is determined that the fourth feedwater flow transmitter 51 has a failure. Specifically, QTThe conditions for triggering the Q mode (quality failure) mainly include card failure, network failure, signal short circuit, signal open circuit, signal over-range, signal power down, etc.
S1-2, obtaining a fourth water supply flow Q measured by the fourth water supply flow transmitter 51TJudging the fourth water supply flow QTWhether the water flow is within the preset water supply flow range or not;
s1-3, acquiring the nuclear power of the nuclear power plant, and judging whether the nuclear power is smaller than a preset nuclear power range;
s1-4, when the fourth water supply flow rate QTIf the nuclear power is smaller than the preset nuclear power range within the preset feedwater flow range, the switching condition is met, and the step S2 is continuously executed; otherwise, the switching condition is not satisfied, and the first control mode is maintained.
S2, when the fourth feed water flow transmitter 51 works normally, the evaporator water level control system is switched to a second control mode by controlling the manual switching button, and a second control signal is output to control the opening degrees of the large valve 2 and the small valve 3; when the fourth feed water flow transmitter 51 fails, the evaporator water level control system automatically switches to the first control mode and outputs a first control signal to control the opening degrees of the large valve 2 and the small valve 3. Further, when the fourth feedwater flow transmitter 51 is in an unexpected surge condition, the system can be switched to the first control mode by controlling the manual diverter switch.
Specifically, the first control signal controls the evaporator water level control system to obtain a third feedwater flow Q measured by the second feedwater flow transmitter 42 and the third feedwater flow transmitter 43 respectivelyW1And a fourth feed water flow rate QW2As the feed water flow QFWControlling; the second control signal controls the evaporator water level control system to obtain a fourth water supply flow QTAs the feed water flow QFWAnd (5) controlling.
Further, the first control signal and the second control signal control the opening degrees of the large valve 2 and the small valve 3 by PID adjustment.
In the present embodiment, whether or not the switching condition is satisfied is mainly determined from two aspects, including the fourth water supply flow rate QTWhether the water supply flow is within a preset water supply flow range and the nuclear power meets a preset nuclear power range, and if the two conditions are met simultaneously, the switching condition is met; if any one of the control modes is not met, the switching condition is not met, and the system keeps the first control mode for control. When the quality bit fault is judged to be normal and the switching condition is met, the control mode of the system can be switched into the second control mode by controlling the manual switching button.
Wherein, in the first control mode, the water supply flow signal Q isFWAutomatic obtaining wide-range water supply flow QW1、QW2And (4) performing water level control, and when the system is in an initial state, performing control by default in a first control mode. In the second control mode, the water supply flow signal QFWAutomatically acquiring fourth water supply flow QTAnd controlling the water level. Understandably, the first control mode and the second control mode can be respectively set according to different conditions, and different control modes can be obtained by adjusting different data acquisition objects.
Furthermore, the preset water supply flow range is more than or equal to Q of 150TLess than or equal to 550. Understandably, the preset water supply flow range can be adjusted according to the actual situation. 150 ≦ Q in the formal configurationTThe return difference of 20t/h is designed less than or equal to 550, and the logic is prevented from switching back and forth at a critical constant value.
Further, the preset nuclear power range is less than 30%. Understandably, the preset core power range can be adjusted according to actual conditions.
As shown in FIG. 7, in order to logically control the water level control method of the evaporator of the nuclear power plant, the fourth water supply transmitter quality level fault judgment signal is inverted to obtain an inverted signal and a fourth water supply flow QTThe judgment signal and the system nuclear power judgment signal are respectively input to the input end of the first logic AND gate; the output signal of the first logic AND gate and the output signal of the O end of the manual switching button are transmitted to the input end of a second logic AND gate together, and the output signal of the second logic AND gate is transmitted to the S end of the RS trigger;
meanwhile, the output signal of the first logic AND gate is inverted and then transmitted to the logic OR gate together with the output signal of the C end of the manual switching button, the output signal of the logic OR gate is transmitted to the R end of the RS trigger, so that the RS trigger outputs a signal to control the switching switch to switch and select the control mode of the system, and the switched control signal is output to the water supply flow signal QFWEntering the DSC system.
The signal of the manual switching button is a pulse quantity, the manual switching button is divided into an O end and a C end, when the manual switching button is pressed, the O end outputs a high level, and the C end outputs a low level.
As shown in FIG. 8, when the evaporator water level control system satisfies the switching condition and the fourth feed water flow rate transmitter 51 determines that the quality level fault is normal, the mode is switched to switch the control mode of the system to the second control mode, that is, Q is the timeFWObtaining QW1、QW2Outputting the water flow as the feed water flow to a DCS and controlling a large valve and a small valve through PID regulation; when the system does not satisfy the switching condition, the first control mode is maintained, i.e. Q at this timeFWObtaining QTAnd outputting the water flow to a DCS (distributed control system) as the feed water flow, and controlling a large valve and a small valve through PID (proportion integration differentiation) regulation.
The invention controls the process asThe following: when the quality level of the fourth water supply transmitter is judged to be normal, outputting a low level, inverting the low level, and inputting the high level serving as a high level to a first logic AND gate; when the fourth feed water flow satisfies the condition that Q is more than or equal to 150TWhen the voltage is less than or equal to 550, outputting a high level to a first logic AND gate; when the core power is less than 30%, outputting a high level to a first logic AND gate; at this time, the first and gate outputs a high level to the second and gate and a low level to the or gate after the inversion process. Meanwhile, a pulse signal is obtained by pressing the manual switching button, namely, the O end of the manual switching button outputs a high level to the second logic AND gate, and the C end of the manual switching button outputs a low level to the logic OR gate. At this time, the second logical and gate outputs a high level to the S terminal of the RS flip-flop, and the logical or gate outputs a low level to the R terminal of the RS flip-flop, according to the basic RS flip-flop operating principle, when R is 1 and S is 0, Q is 1, and the flip-flop is set to 1, so that the flip-flop is set, and the control switch is switched to the fourth water supply flow QTControl, i.e. obtaining feed water flow Q at this timeFW＝QT。
When the quality level of the fourth water supply transmitter is judged to be a fault, outputting a high level, and inputting the high level serving as a low level to a first logic AND gate after inversion processing; when the fourth feed water flow satisfies the condition that Q is more than or equal to 150TWhen the voltage is less than or equal to 550, outputting a high level to a first logic AND gate; when the core power is less than 30%, outputting a high level to a first logic AND gate; at this time, the first logical and gate outputs a low level to the second logical and gate and outputs a high level to the logical or gate after the negation processing, so that no matter what state the manual switching button is in, the logical or gate must output a high level, at this time, the second logical and gate outputs a low level to the S terminal of the RS flip-flop, the logical or gate outputs a high level to the R terminal of the RS flip-flop, according to the basic RS flip-flop working principle, when R is 0 and S is 1, Q is 0, the flip-flop is 0, thereby resetting the flip-flop and controlling the switch to QW1、QW2Control, i.e. obtaining feed water flow Q at this timeFWComprising QW1And QW2。
In the embodiment, the simulation control of the system can be realized by designing the DCS picture, the DCS picture is optimized and improved, the manual switching button is designed to be a pulse instruction, after the pulse instruction is triggered, the pulse instruction is triggered and kept for 2s and disappears, and the pulse instruction is fed back to be a long signal which is displayed as a KC icon to remind an operator. Water supply flow Q with newly-increased measuring range on pictureW1、QW2And a fourth feed water flow rate QTA switch; increase the fourth feed water flow rate QTAnd a flow display window.
In order to ensure the effectiveness and feasibility of the method in field application and implementation of the nuclear power unit, a complete risk control scheme is firstly formulated to predict possible risks, effective countermeasures are implemented to ensure that additional risks are not introduced into newly added equipment, and meanwhile, the method can still effectively cope with emergency situations. And thirdly, establishing a perfect field implementation scheme and re-authentication measures, reliably managing and controlling the field implementation process, ensuring the quality of the implementation process and realizing effective landing of the optimized improvement scheme.
The risk control scheme mainly comprises the following parts:
1. fourth feed water flow transducer QTAnd (4) offline, taking measures: will QTPutting operation into the machine set up and down file packet, confirming the opening Q of the machine set down operationTAn upstream primary isolation valve.
2. Fourth feed water flow transducer QTAnd (3) faults occur during participation in water level control of the evaporator, and measures are as follows: reserve the manual switch to QW1/QW2Control function, timely switching to Q when the water level control of the evaporator is abnormalW1/QW2And (5) controlling.
3. Newly-added fourth feed water flow transmitter QTAnd the pipeline may have leakage after the primary valve, and the measures are as follows: after the transmitter needs to be installed, the pipeline is subjected to tightness inspection, and technical positions are required to perform penetration inspection on all welded junctions.
The field embodiment mainly comprises the following parts:
1. fourth water supply transducer QTInstallation, termination, internal parameter setting and verification ofSelecting the range and the model of the device;
2. laying a newly-added cable, including setting a cable path;
3, the end connection of the AI clamping piece and the selection and the arrangement of the channel and the wiring terminal;
4. newly-added analog quantity point device QTPoint definition, database setting, configuration, compiling and downloading of newly added logic (including GD);
5. the configuration of the water level control frame of the new evaporator comprises QTA display and KG switching block;
6. detailed full re-identification protocol: newly-added flow transmitter QTChannel re-identification, QTDifferential pressure flow conversion logic verification, switching function logic verification, manual switching logic verification, nuclear power switching logic verification and QTQuality bit switching logic verification, QTThe flow restriction logic validates.
The invention uses the high-precision orifice plate as the accurate measurement of the flow under the condition of low flow, and uses the water supply flow as the process quantity of the water level control of the evaporator, thereby ensuring the accuracy of the process quantity participating in the control. The switching logic of the newly added water supply flow is effectively formulated, so that the stability of low-load control is ensured, high load is taken into account, and the continuity and stability of the water level control of the evaporator in the whole process are realized; and reliably perfects field implementation scheme formulation and risk control. The stability and the reliability of the water level control system of the nuclear power unit evaporator are greatly improved, the phenomenon that the nuclear power unit is in a transient state or the reactor is automatically stopped due to the abnormal control system is prevented, and the nuclear safety is guaranteed.
It is to be understood that the foregoing examples, while indicating the preferred embodiments of the invention, are given by way of illustration and description, and are not to be construed as limiting the scope of the invention; it should be noted that, for those skilled in the art, the above technical features can be freely combined, and several changes and modifications can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention; therefore, all equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.
Claims (10)
1. The water level control system of the nuclear power plant evaporator is characterized by comprising an evaporator (1), a large valve (2) and a small valve (3) which are used for controlling the opening degree of the evaporator (1), wherein the large valve (2) and the small valve (3) are arranged in parallel and are connected to a water supply main pipe (11) of the evaporator (1), and a venturi tube (4) and a pore plate are installed on the water supply main pipe (11) of the evaporator (1);
at least three water supply flow transmitters are respectively installed on the Venturi tube (4), the at least three water supply flow transmitters comprise a first water supply flow transmitter (41), a second water supply flow transmitter (42) and a third water supply flow transmitter (43), and the Venturi tube (4) is respectively connected with the at least three water supply flow transmitters through pressure pipes; the orifice plate is connected to a fourth feedwater flow transmitter (51) for heat balance flow calculation through a pressure lead pipe.
2. The nuclear power plant evaporator water level control system of claim 1 wherein the first feedwater flow transmitter (41) is a narrow range feedwater flow transmitter and the second and third feedwater flow transmitters (42, 43) are wide range feedwater flow transmitters.
3.A method for controlling the water level of an evaporator of a nuclear power plant, which is characterized by comprising the following steps of:
s1, judging whether the evaporator water level control system meets a switching condition or not, and judging quality level faults of the fourth water supply flow transmitter (51); when the evaporator water level control system meets the switching condition, continuing to execute the step S2; when the system does not meet the switching condition, maintaining the first control mode;
s2, when the fourth feed water flow transmitter (51) works normally, the evaporator water level control system is switched to a second control mode by controlling a manual switching button, and a second control signal is output to control the opening degrees of the large valve (2) and the small valve (3); when the fourth feed water flow transmitter (51) breaks down, the evaporator water level control system is automatically switched to the first control mode, and outputs a first control signal to control the opening degrees of the large valve (2) and the small valve (3).
4. The nuclear power plant evaporator water level control method according to claim 3, wherein in the step S1, the quality level fault judgment of the fourth feedwater flow transmitter (51) specifically comprises judging that the fourth feedwater flow transmitter (51) is in fault when a card fault and/or a network fault occurs in the fourth feedwater flow transmitter (51).
5. The nuclear power plant evaporator water level control method according to claim 3, further comprising switching the system to the first control mode by controlling a manual switch when the fourth feedwater flow transmitter (51) is in an unexpected surge state in step S2.
6. The nuclear power plant evaporator water level control method according to claim 3, wherein the first control signal controls the evaporator water level control system to obtain a third feedwater flow Q measured by the second feedwater flow transmitter (42) and the third feedwater flow transmitter (43), respectivelyW1And a fourth feed water flow rate QW2Controlling; the second control signal controls the evaporator water level control system to obtain a fourth water supply flow QTAnd (5) controlling.
7. The nuclear power plant evaporator water level control method according to claim 3, wherein in the step S1, the method specifically comprises the following steps:
s1-1, judging quality level fault of the fourth feedwater flow transmitter (51);
s1-2, obtaining a fourth feedwater flow Q measured by the fourth feedwater flow transmitter (51)TAnd judging the fourth water supply flow QTWhether the water flow is within the preset water supply flow range or not;
s1-3, acquiring the nuclear power of the nuclear power plant, and judging whether the nuclear power is smaller than a preset nuclear power range;
s1-4, when the fourth water supply flow QTIf the nuclear power is smaller than the preset nuclear power range within the preset feedwater flow range, the switching condition is met, and the step S2 is continuously executed; otherwise, the switching condition is not satisfied, and the first control mode is maintained.
8. The nuclear power plant evaporator water level control method of claim 7, wherein the preset feedwater flow range is 150 ≤ QT≤550。
9. The nuclear power plant evaporator water level control method of claim 7, wherein the preset nuclear power range is less than 30%.
10. The nuclear power plant evaporator water level control method according to claim 3, wherein in the step S2, the first and second control signals control the opening degrees of the large valve (2) and the small valve (3) through PID adjustment.
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