CN113721674B - Nuclear power plant evaporator water level control system and method - Google Patents
Nuclear power plant evaporator water level control system and method Download PDFInfo
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- CN113721674B CN113721674B CN202110838271.4A CN202110838271A CN113721674B CN 113721674 B CN113721674 B CN 113721674B CN 202110838271 A CN202110838271 A CN 202110838271A CN 113721674 B CN113721674 B CN 113721674B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
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- G05D9/12—Level control, e.g. controlling quantity of material stored in vessel characterised by the use of electric means
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Abstract
The invention relates to a water level control system and a water level control method for an evaporator of a nuclear power plant, wherein the water level control system comprises an evaporator, a big valve and a small valve, wherein the big valve and the small valve are arranged in parallel and are connected to a water supply main pipe of the evaporator, and a venturi pipe and a pore plate are arranged on the water supply main pipe; at least three water supply flow transmitters are respectively arranged on the venturi tubes; the orifice plate is connected to a fourth feedwater flow transmitter through a pressure inducing tube. The invention also relates to a water level control method of the evaporator of the nuclear power plant, which comprises the following steps of S1, judging whether the water level control system of the evaporator meets the switching condition or not, and judging the quality position fault of a fourth water supply flow transmitter; s2, when the fourth water supply 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 big valve and the small valve. The invention greatly improves the stability and reliability of the water level control system of the evaporator, prevents the transient state of a unit or the automatic shutdown of a reactor, and ensures the nuclear safety.
Description
Technical Field
The invention relates to the field of instrument control, in particular to a system and a method for controlling the water level of an evaporator of a nuclear power plant.
Background
The evaporator water level control system is used as one of the most important control systems of the nuclear power unit, and the stability of the evaporator water level control is important for safe and stable operation of the nuclear power unit. According to statistics, the number of automatic shutdown times of the nuclear power unit caused by the abnormality of the evaporator water level control system at home and abroad is not counted. Due to the deviation of the venturi tube measurement, under the condition of low flow, the water supply flow measurement has the condition of non-follow (namely, the change of the real flow is not reflected), the water level adjustment of the evaporator has the problem of commonality of the multi-base nuclear power unit, and the problem of commonality of the multi-base nuclear power unit is reflected by different conditions of different base nuclear power units.
Disclosure of Invention
The invention aims to solve the technical problem that an abnormality occurs in an evaporator water level control system under a low load condition, and provides a system and a method for controlling and switching the water level of an evaporator of a nuclear power plant under stable control of low load water supply flow aiming at the defects of the prior art.
The technical scheme adopted for solving the technical problems is as follows: the water level control system of the evaporator of the nuclear power plant comprises the evaporator, a big valve and a small valve for controlling the opening degree of the evaporator, wherein the big valve and the small valve are arranged in parallel and are connected to a water supply main pipe of the evaporator, and a venturi pipe and a pore plate are arranged on the water supply main pipe of the evaporator;
At least three water supply flow transmitters are respectively arranged on the venturi tube, each water supply flow transmitter comprises 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 guiding pipes; the orifice plate is connected to a fourth feedwater flow transmitter for heat balance flow calculation through a pressure inducing tube.
Preferably, the first feedwater flow transmitter is a narrow range feedwater flow transmitter, and the second feedwater flow transmitter and the third feedwater flow transmitter are wide range feedwater flow transmitters.
The invention also constructs a water level control method of the evaporator of the nuclear power plant, which aims at the water level control system of the evaporator and controls the water level control system according to the following steps:
S1, judging whether the evaporator water level control system meets a switching condition or not, and judging a quality position fault 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, a first control mode is maintained;
S2, when the fourth water supply 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 of the big valve and the small valve; when the fourth feedwater flow transmitter 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 big valve and the small valve.
Preferably, in the step S1, the mass bit failure determination of the fourth feedwater flow transmitter specifically includes determining that the fourth feedwater flow transmitter is failed when a clamping failure and/or a network failure occurs in the fourth feedwater flow transmitter.
Preferably, in said step S2, further comprising switching the system to said first control mode by controlling a manual switch when said fourth feedwater flow transmitter is in an unexpected surge condition.
Preferably, the first control signal controls the evaporator water level control system to acquire and control the third water supply flow Q W1 and the fourth water supply flow Q W2 measured by the second water supply flow transmitter and the third water supply flow transmitter respectively; the second control signal controls the evaporator water level control system to acquire the fourth water supply flow Q T for control.
Preferably, in the step S1, the method specifically includes the following steps:
s1-1, judging quality bit faults of the fourth water supply flow transmitter;
S1-2, acquiring a fourth water supply flow Q T measured by the fourth water supply flow transmitter, and judging whether the fourth water supply flow Q T is in a preset water supply flow range;
s1-3, acquiring nuclear power of a 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 Q T is in the preset water supply flow range and the nuclear power is smaller than a preset nuclear power 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 flow rate range is 150- T -550.
Preferably, the preset core power range is less than 30%.
Preferably, in the step S2, the opening degrees of the large valve and the small valve are controlled by the first control signal and the second control signal 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 evaporator of the nuclear power unit are greatly improved, the occurrence of transient state or automatic reactor shutdown due to abnormal units of the control system is prevented, and the nuclear safety is ensured.
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 system for controlling water level in an evaporator of a nuclear power plant according to the present invention;
FIG. 2 is a control schematic diagram of the method for controlling water level in an evaporator of a nuclear power plant according to the present invention;
FIG. 3 is a flow chart of a first embodiment of a method for controlling water level in an evaporator of a nuclear power plant in accordance with the present invention;
FIG. 4 is a flow chart of a second embodiment of a method for controlling water level in an evaporator of a nuclear power plant in accordance with the present invention;
FIG. 5 is a flow chart of a method for controlling water level in an evaporator of a nuclear power plant according to the present invention;
FIG. 6 is a schematic diagram of a method for controlling water level in an evaporator of a nuclear power plant according to the present invention at step S1;
FIG. 7 is a logic circuit diagram of a method of controlling water level in an evaporator of a nuclear power plant according to the present invention;
Fig. 8 is a control circuit diagram of the method for controlling the water level of the evaporator of the nuclear power plant according to the present invention.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "rear", "upper", "lower", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", "tail", etc. are configured and operated in specific directions based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention, and do not indicate that the apparatus or element to be referred to must have specific directions, and thus should not be construed as limiting the present invention.
It should also be noted that unless explicitly stated or limited otherwise, terms such as "mounted," "connected," "secured," "disposed," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. When an element is referred to as being "on" or "under" another element, it can be "directly" or "indirectly" on the other element or one or more intervening elements may also be present. The terms "first," "second," "third," and the like are used merely for convenience in describing the present invention and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, whereby features defining "first," "second," "third," etc. may explicitly or implicitly include one or more such features. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present 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 comprises an evaporator 1, a big valve 2 and a small valve 3 for controlling the opening degree of the evaporator 1, wherein the big valve 2 and the small valve 3 are respectively arranged on two branch pipes in parallel and are connected to a water supply pipe 11 of the evaporator 1 together, and a venturi tube 4 and a pore plate 5 are arranged on the water supply pipe 11 between the evaporator 1 and the big 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 guiding pipes; the orifice plate 5 is connected by a pilot tube 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 feedwater flow transmitter 42 and the third feedwater flow transmitter 43 are wide range feedwater flow transmitters.
During control, the measuring element venturi 4 may not follow an abnormality in the differential pressure at low flow rates, and the primary measuring element venturi 4 has poor pressure sensitivity at low flow rates. The venturi tube 4 of the throttling element is installed on the water supply mother tube 11 of the evaporator 1, the venturi tube 4 is respectively provided with a narrow-range water supply flow transmitter and two wide-range water supply flow transmitters, at this time, the water supply flow Q FW participating in the water level control of the evaporator 1 is the wide-range Q W1、QW2 respectively measured by the second water supply flow transmitter 42 and the third water supply flow transmitter 43, but in practice, the pressure sensitivity of the venturi tube 4 is poor under the condition of low flow, so that the deviation of the process value of the wide-range water supply flow transmitter from the theoretical value is large.
In order to ensure the accuracy of the measurement of the feed water flow of the evaporator 1 under the condition of low flow, an orifice plate 5 can be arranged on the feed water main pipe 11 of the evaporator 1, the orifice plate 5 is connected to a feed water flow transmitter for calculating the heat balance flow through a pressure guiding pipe, and the control of the non-safety level DCS system participating in the evaporator water level big valve and the small valve is introduced through the orifice plate 5 and a fourth feed water flow transmitter 51 of the pressure guiding pipe.
As shown in fig. 2, the embodiment adopts a non-safety level DCS system to control the evaporator water level large valve 2 and the small valve 3. The evaporator water level control adopts cascade adjustment, and comprises a water supply flow signal Q FW, a steam flow signal Q ST, an evaporator water level signal L SG, a two-loop load signal (wide range) P PW and a two-loop load signal (narrow range) P PN. The measured evaporator water level signal L SG and the two-circuit load signal (wide range) signal P PW are input to the PID main regulator, wherein the two-circuit load signal (wide range) signal P PW is a constant value signal. The output signal of the PID main regulator, the steam-water deviation signal of the steam flow signal Q ST and the water supply flow signal Q FW are input to the PI auxiliary regulator, and the output signal of the PI auxiliary regulator controls the big valve 2 of the evaporator. The output signal of the PID main regulator and a two-loop load signal (narrow range) P PN are input into the P auxiliary regulator, and the output signal of the P auxiliary regulator controls the small valve 3 of the evaporator, so that the control and regulation of the opening V O of the water level control valve of the evaporator are realized.
The main reason for the abnormality of the water level control of the evaporator is that a large deviation exists between the steam and water, and under the condition of low load, the abnormal deficiency of the water supply flow is not followed, so that the advanced adjustment deviation amount is generated. Therefore, the abnormal water level control phenomenon of the evaporator can be reduced by selecting the signal of the water supply flow rate signal Q FW.
As shown in fig. 3 to 5, the method for controlling the water level of the evaporator of the nuclear power plant according to the present invention is characterized in that the following steps are performed with respect to the above-mentioned water level control system of the evaporator:
s1, judging whether the evaporator water level control system meets a switching condition or not, and judging a quality position fault of a 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, a first control mode is maintained;
As shown in fig. 6, further, in step S1, the method specifically includes the following steps:
s1-1, judging quality bit faults of a fourth water supply flow transmitter 51;
further, when the fourth feedwater flow transmitter 51 fails in a stuck and/or network, the fourth feedwater flow transmitter 51 is judged to be failed. Specifically, the Q T conditions of triggering the Q mode (quality fault) mainly include card fault, network fault, signal short circuit, signal open circuit, signal over-range, signal power failure, etc.
S1-2, acquiring a fourth water supply flow Q T measured by a fourth water supply flow transmitter 51, and judging whether the fourth water supply flow Q T is in a preset water supply flow range;
s1-3, acquiring nuclear power of a 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 Q T is in the preset water supply flow range and the nuclear power is smaller than the preset nuclear power 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 water supply 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 of the big valve 2 and the small valve 3; when the fourth feedwater flow transducer 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 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 switch.
Specifically, the first control signal controls the evaporator water level control system to acquire the third water supply flow Q W1 and the fourth water supply flow Q W2 measured by the second water supply flow transmitter 42 and the third water supply flow transmitter 43 respectively as the water supply flow Q FW for control; the second control signal controls the evaporator water level control system to acquire the fourth feedwater flow Q T as the feedwater flow Q FW for control.
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 this embodiment, whether the switching condition is satisfied is mainly determined from two aspects, including whether the fourth water supply flow Q T is within a preset water supply flow range and whether the core power accords with a preset core power range, and if the two conditions are satisfied at the same time, the switching condition is satisfied; if any one of the control modes does not meet the switching condition, the system keeps the first control mode for control. When the quality bit fault judgment is normal and the switching condition is met, the control mode of the system can be switched to the second control mode by controlling the manual switching button.
In the first control mode, the water level control is performed by automatically acquiring the wide-range water supply flow Q W1、QW2 for the water supply flow signal Q FW, and the system is controlled by default in the first control mode in the initial state. In the second control mode, the feedwater flow signal Q FW automatically acquires the fourth feedwater flow Q T for water level control. It is understood that the first control mode and the second control mode may be set according to different situations, and different control modes may be obtained by adjusting different data acquisition objects.
Further, the preset water flow range is 150- T -550. It is understood that the preset feedwater flow range can be adjusted according to practical conditions. In the formal configuration, Q T is less than or equal to 150 and less than or equal to 550, and 20t/h return difference is designed, so that logic is prevented from switching back and forth at a critical fixed value.
Further, the preset core power range is less than 30%. Understandably, the preset core power range can be adjusted according to practical situations.
As shown in fig. 7, in the logic control process of the method for controlling water level of an evaporator in a nuclear power plant according to the present invention, a reverse signal obtained by reversing a quality bit fault determination signal of a fourth water supply transmitter, a fourth water supply flow Q T determination signal, and a system nuclear power determination signal are respectively input to an input end of a first logic and gate; the output signal of the first logic AND gate and the output signal of the manual switching button O end are transmitted to the input end of the second logic AND gate, 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 is 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, and accordingly the output signal of the RS trigger controls 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 Q FW to enter the DSC system.
The manual switching button signal is 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 high level, and the C end outputs low level.
As shown in fig. 8, when the evaporator water level control system satisfies the switching condition and the fourth feedwater flow transmitter 51 determines that the quality bit fault is normal, performing mode switching to switch the control mode of the system to the second control mode, that is, at this time, Q FW acquires Q W1、QW2 as feedwater flow to output to the DCS system and controls the large valve and the small valve through PID adjustment; when the system does not meet the switching condition, the first control mode is kept, namely, at the moment, Q FW obtains Q T as water supply flow to be output to the DCS system, and the big valve and the small valve are controlled through PID regulation.
The control process of the invention is as follows: when the quality bit of the fourth water supply transmitter is judged to be normal, outputting a low level, and taking the low level as a high level to be input to a first logic AND gate after the inversion treatment; when the fourth water supply flow rate is more than or equal to 150 and less than or equal to 550 and Q T, outputting a high level to the first logic AND gate; outputting a high level to a first logic AND gate when the core power is less than 30%; at this time, the first logical AND gate outputs high level to the second logical AND gate and outputs low level to the logical OR gate after the inverting process. Meanwhile, a pulse signal is obtained by pressing a manual switching button, namely, the O end of the manual switching button outputs a high level to a second logic AND gate, and the C end of the manual switching button outputs a low level to a logic OR gate. At this time, the second logic and gate outputs a high level to the S end of the RS flip-flop, the logic or gate outputs a low level to the R end of the RS flip-flop, and according to the basic RS flip-flop operating principle, when r=1 and s=0, q=0 and q=1 are provided, and the flip-flop is set, so that the flip-flop is set, and the switch is controlled to switch to the fourth feedwater flow Q T for control, that is, the feedwater flow Q FW＝QT is obtained at this time.
When the quality bit of the fourth water supply transmitter is judged to be faulty, outputting a high level, and taking the high level as a low level to be input to a first logic AND gate after the inverse processing; when the fourth water supply flow rate is more than or equal to 150 and less than or equal to 550 and Q T, outputting a high level to the first logic AND gate; outputting a high level to a first logic AND gate when the core power is less than 30%; at this time, the first logic and gate outputs a low level to the second logic and gate and outputs a high level to the logic or gate after the inversion processing, so no matter what state the manual switching button is, the logic or gate must output a high level, at this time, the second logic and gate outputs a low level to the S end of the RS trigger, the logic or gate outputs a high level to the R end of the RS trigger, according to the basic RS trigger working principle, when r=0 and s=1, q=1 and q=0 are provided, the trigger is set to 0, so that the trigger is reset, and the control switch is switched to Q W1、QW2 to control, i.e. the water supply flow Q FW is obtained at this time and includes Q W1 and Q W2.
According to the embodiment, the DCS picture can be designed to carry out simulation control on the system, meanwhile, the DCS picture is optimized and improved, the manual switching button is designed to be a pulse command, after triggering, the command is triggered and disappears after 2s is kept, the command is fed back to be a long signal, and the long signal is displayed as a KC icon to remind an operator. A switch is switched between the water supply flow Q W1、QW2 with the wide range and the fourth water supply flow Q T newly increased on the picture; and adding a fourth water supply flow Q T flow display window.
In order to ensure the effectiveness and feasibility of the method in the field application and implementation of the nuclear power unit, a complete risk control scheme is firstly established, possible risks are expected, effective countermeasures are implemented, the fact that additional risks are not introduced into newly-added equipment is ensured, and meanwhile, the method can still be effectively applied to emergency situations. And thirdly, formulating perfect field implementation and re-identification measures, reliably controlling the field implementation process, ensuring the quality of the implementation process and realizing the effective landing of the optimized improvement scheme.
The risk control scheme mainly comprises the following parts:
1. The fourth feedwater flow transmitter Q T is not on-line, measure: and adding the Q T operation into an up-down file packet of the unit, and confirming the down-down operation of the unit to open the upstream primary isolation valve of Q T.
2. The fourth feedwater flow transmitter Q T is involved in the evaporator water level control and fails, measures: the control function of the manual switch Q W1/QW2 is reserved, and the control is switched to the control of the Q W1/QW2 in time when the water level control of the evaporator is abnormal.
3. The newly added fourth water supply flow transmitter Q T has the advantages that after one valve, the pipeline can have leakage, and measures are taken: after the transmitter is installed, the pipeline is subjected to tightness inspection, and all welded junctions are subjected to penetration inspection at the technical position.
The field implementation mainly comprises the following parts:
1. The installation, termination, internal parameter setting and verification of the fourth water supply transmitter Q T, and the range and model selection of the transmitter;
2. The laying of the newly added cable comprises the setting of a cable path;
Termination of AI card, channel and binding post selection and setting;
4. The method comprises the steps of defining a point of a newly added analog quantity point device Q T, setting a database, and configuring, compiling and downloading newly added logic (including GD);
5. The newly added evaporator water level control picture configuration comprises a Q T indication display and a KG switching block;
6. Detailed complete re-identification scheme: the newly added flow transmitter Q T channel re-authentication, Q T differential pressure flow conversion logic verification, switching function logic verification, manual switching logic verification, core power switching logic verification, Q T quality bit switching logic verification and Q T flow limiting logic verification.
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 evaporator water level control, thereby ensuring the accuracy of the process quantity involved in the control. The switching logic of the newly added water flow is effectively formulated, so that the stability of low-load control is ensured, meanwhile, the high load is considered, and the continuity and stability of the water level control of the whole process evaporator are realized; and reliably perfects field implementation formulation and risk control. The stability and the reliability of the water level control system of the evaporator of the nuclear power unit are greatly improved, the occurrence of transient state or automatic reactor shutdown due to abnormal units of the control system is prevented, and the nuclear safety is ensured.
It is to be understood that the above examples only represent preferred embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the invention; it should be noted that, for a person skilled in the art, the above technical features can be freely combined, and several variations and modifications can be made without departing from the scope of the invention; therefore, all changes and modifications that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Claims (9)
1. The water level control system of the evaporator of the nuclear power plant is characterized by comprising an evaporator (1), a big valve (2) and a small valve (3) for controlling the opening degree of the evaporator (1), wherein the big 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 arranged on the water supply main pipe (11) of the evaporator (1);
At least three water supply flow transmitters are respectively arranged on the venturi tube (4), each water supply flow transmitter comprises 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 guiding pipes; the orifice plate is connected to a fourth feedwater flow transmitter (51) for heat balance flow calculation through a pressure inducing tube;
wherein the big valve (2) and the small valve (3) are controlled according to a PI auxiliary regulator connected with the big valve (2) and a P auxiliary regulator connected with the small valve (3); the PID main regulator is connected with the PI auxiliary regulator and the P auxiliary regulator which are connected in parallel;
the evaporator water level control adopts cascade adjustment, comprising water supply flow signal Steam flow Signal/>Evaporator Water level Signal/>Two-loop load wide-range signal/>Two-loop load narrow range signal/>；
The evaporator water level signalAnd the two loops load wide range signal/>Input to the PID main regulator, and the two-loop load wide-range signal/>Is a constant value signal;
the output signal of the PID main regulator and the steam flow signal And the feedwater flow signal/>The steam-water deviation signal of the evaporator is input to the PI auxiliary regulator, and the output signal of the PI auxiliary regulator controls the big valve (2) of the evaporator;
The output signal of the PID main regulator and the two-loop load narrow-range signal Is input to the P auxiliary regulator, and the output signal of the P auxiliary regulator controls the small valve (3) of the evaporator, thereby realizing the opening/>, of the evaporator water level control valveControl and regulation of (2);
the first water supply flow transmitter (41) is a narrow range water supply flow transmitter, and the second water supply flow transmitter (42) and the third water supply flow transmitter (43) are wide range water supply flow transmitters.
2. A method for controlling water level of an evaporator in a nuclear power plant, wherein the water level control system for the evaporator according to claim 1 is controlled by:
S1, judging whether the evaporator water level control system meets a switching condition or not, and judging a quality bit 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, a first control mode is maintained;
S2, when the fourth water supply 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 of the big valve (2) and the small valve (3); when the fourth feedwater 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 big valve (2) and the small valve (3).
3. The method according to claim 2, wherein in the step S1, the quality fault determination of the fourth feedwater flow transmitter (51) specifically includes determining that the fourth feedwater flow transmitter (51) is faulty when a clamping fault and/or a network fault occurs in the fourth feedwater flow transmitter (51).
4. The method according to claim 2, characterized in that in said step S2, it further comprises switching the system to said first control mode by controlling a manual change-over switch when said fourth feedwater flow transmitter (51) is in an unexpected wave state.
5. The method of controlling water level in an evaporator of a nuclear power plant according to claim 2, wherein the first control signal controls the evaporator water level control system to acquire the second feedwater flow measured by the second feedwater flow transmitter (42) and the third feedwater flow transmitter (43), respectivelyAnd third water supply flow/>Performing control; the second control signal controls the evaporator water level control system to obtain fourth water supply flow/>And controlling.
6. The method according to claim 2, characterized in that in step S1, it comprises the following steps:
S1-1, judging quality bit faults of the fourth water supply flow transmitter (51);
s1-2, obtaining the fourth water supply flow measured by the fourth water supply flow transmitter (51) Judging the fourth water supply flow/>Whether within a preset feedwater flow range;
s1-3, acquiring nuclear power of the nuclear power plant, and judging Whether the power range is smaller than a preset nuclear power range;
S1-4, when the fourth water supply flow rate is If the nuclear power is smaller than the preset nuclear power range and within the preset water supply 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.
7. The method of claim 6, wherein the predetermined feedwater flow range is。
8. The method of claim 6, wherein the predetermined nuclear power range is less than 30%.
9. The method according to claim 2, characterized in that in the step S2, the first control signal and the second control signal control the opening degree of the large valve (2) and the small valve (3) by PID adjustment.
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