CN117095842A - Nuclear power unit system - Google Patents

Abstract

The present invention provides a nuclear power unit system including: a high-pressure cylinder; a deaerator, used to deoxygenate the condensed water entering the deaerator through the steam output by the high-pressure cylinder; and a main steam system, used to provide the deaerator with a third An auxiliary steam; an auxiliary steam system, used to provide the second auxiliary steam to the deaerator, so that the deaerator can operate under a no-load constant pressure operating condition; a pressure detection module, used to obtain the pressure of the deaerator; first-stage The hysteresis module is used to determine based on the pressure of the deaerator to send a trigger signal when the load shedding condition occurs in the steam turbine of the nuclear power unit; the adjustment module is used to maintain the pressure of the deaerator at the pressure before load shedding when the trigger signal is received. Decreases at a preset rate after a preset time. The present invention introduces a first-order inertial filter module, so that the pressure change of the deaerator can be accurately identified, and the load shedding condition of the steam turbine can be accurately detected, ensuring the pressure stability of the deaerator, which is beneficial to the long-term stable operation of the nuclear power unit.

Description

Nuclear power unit system

Technical field

The invention relates to the field of nuclear power units, and in particular to a nuclear power unit system.

Background technique

During the operation of a nuclear power unit, due to the failure of the external power grid, main engine or auxiliary system, the unit load drop condition will inevitably occur, that is, the load shedding condition. The load drop of the nuclear power unit often leads to a rapid drop in the deaerator pressure. The drop in deaerator pressure will cause the main feed water to be unable to continue to be heated. After the unit fault is eliminated, the unit cannot quickly return to the original load condition and continue to operate.

At present, a complex combination of steam turbine shutdown signals, reactor shutdown signals, steam turbine islanding operation and other signals is commonly used to identify load shedding conditions. This solution can identify the large-scale load shedding conditions of some units, but it cannot accurately detect the load shedding conditions. Rapid load reduction of other units other than turbine shutdown, reactor shutdown, and turbine island operation will not trigger load shedding conditions in the steam turbine. Therefore, the pressure stability of the deaerator under these conditions cannot be guaranteed, which is not conducive to the long-term stability of the nuclear power unit. Stable operation.

Contents of the invention

In order to solve the above technical problems, the purpose of the present invention is to propose a nuclear power unit system that can accurately detect the load shedding condition of the steam turbine, ensure the pressure stability of the deaerator, and is conducive to the long-term stable operation of the nuclear power unit.

The technical solutions adopted by the present invention are as follows:

The embodiment of the present invention proposes a nuclear power unit system including: a high-pressure cylinder; and a deaerator, which is connected to the exhaust port of the high-pressure cylinder through a first regulating valve, and is used for steam output by the high-pressure cylinder to enter the deaerator. The condensed water of the oxygenator is deoxidized; the main steam system is connected to the deaerator through a second regulating valve and is used to provide the first auxiliary steam to the deaerator to maintain deoxidation under load shedding conditions. The pressure of the deaerator is stable; the auxiliary steam system is connected to the deaerator through the third regulating valve, and is used to provide the second auxiliary steam to the deaerator through the third regulating valve to make the deaerator operate. In the no-load constant pressure operating condition; a pressure detection module is provided on the deaerator to obtain the pressure of the deaerator; a first-order hysteresis module is used to determine the nuclear power plant based on the pressure of the deaerator Whether the steam turbine of the unit is in a load-shedding condition, and sends a trigger signal when it is determined that the steam turbine is in a load-shedding condition; the regulating module is used to control the second regulating valve when receiving the trigger signal to control the second regulating valve. The pressure of the deaerator is maintained at the pressure before load shedding for a preset time and then decreases at a preset rate.

In addition, the nuclear power unit system proposed according to the present invention may also have the following additional technical features:

According to an embodiment of the present invention, the pressure detection module includes a first pressure transmitter, a second pressure transmitter and a third pressure transmitter, and the pressure detection module is specifically used to: when the first pressure When the transmitter, the second pressure transmitter and the third pressure transmitter are all faultless, the first pressure transmitter, the second pressure transmitter and the third pressure transmitter detect The pressure of the deaerator is obtained from the median value of the pressure; when any one of the first pressure transmitter, the second pressure transmitter and the third pressure transmitter When a fault occurs, the pressure of the deaerator is obtained based on the average of the pressures detected by the two pressure transmitters that have not failed; when the first pressure transmitter, the second pressure transmitter and When any two pressure transmitters in the third pressure transmitter fail, the pressure of the deaerator is obtained based on the pressure detected by the pressure transmitter that has not failed; when the first pressure transmitter fails, the pressure of the deaerator is obtained. When the transmitter, the second pressure transmitter and the third pressure transmitter all fail, according to the first pressure transmitter, the second pressure transmitter and the third pressure transmitter, The pressure of the deaerator is obtained from the last effective value detected in the transmitter. By setting up three pressure transmitters, it is possible to avoid failure of a single pressure transmitter causing the deaerator pressure to be unobtainable, so that the deaerator pressure can be obtained continuously and stably.

According to an embodiment of the present invention, the transfer function of the first-order lag module is obtained according to the following formula: Among them, τ is the filtering time and s is the variable. The first-order lag module calculates the pressure of the deaerator based on the transfer function, which can better suppress the periodic interference signal of the deaerator pressure signal. The obtained pressure value of the deaerator is accurate and suitable for the pressure fluctuation of the deaerator. Higher frequency occasions.

According to an embodiment of the invention, τ=10s. When the filtering time is set to 10s, the first-order lag module can adapt to rapid changes in deaerator pressure, and its filtering results can be output in time with high sensitivity. It can also prevent misidentification of load shedding conditions due to being too sensitive and unable to effectively filter out interference. happened.

According to an embodiment of the present invention, the first-order hysteresis module is specifically used to determine that the steam turbine is in a load shedding condition when it is detected that the pressure reduction rate of the deaerator reaches 80KPa/10s or the pressure step drops by 80KPa.

According to an embodiment of the present invention, the adjustment module specifically includes: a given function generator, configured to generate a pressure maintaining curve based on the pressure of the deaerator before load shedding when the trigger signal is received. The pressure change of the curve is: first maintain the pressure of the deaerator before load shedding for 300 seconds, and then reduce it to 0 at 0.1MPa/min; PID regulator (ProportionIntegration Differentiation, proportional-integral-derivative regulator) is used according to the required The pressure maintaining curve controls the second regulating valve so that the pressure of the deaerator changes according to the pressure maintaining curve. When load shedding occurs in the steam turbine, the given function generator and PID regulator control the pressure change of the deaerator according to the pressure maintaining curve, which can effectively prevent the safety valve of the auxiliary steam system from opening over pressure due to a sudden reduction in gas consumption. Ensure the safe operation of the deaerator.

Beneficial effects of the present invention:

According to the nuclear power unit system of the embodiment of the present invention, the pressure change of the deaerator is obtained through the pressure detection module, and a first-order lag module is set to determine whether the load shedding condition occurs in the steam turbine according to the pressure change of the deaerator, and when the load shedding condition is The adjustment module controls the pressure of the deaerator to be maintained at the pressure before load shedding for a period of time. This allows the load shedding condition of the turbine to be accurately detected, ensuring the stability of the deaerator pressure, which is conducive to the long-term stable operation of the nuclear power unit.

Description of the drawings

Figure 1 is a block diagram of a nuclear power unit system according to an embodiment of the present invention;

Figure 2 is a block diagram of a pressure detection module according to an embodiment of the present invention;

Figure 3 is a schematic diagram of a pressure holding curve according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

As shown in Figure 1, the nuclear power unit system according to the embodiment of the present invention includes a high-pressure cylinder 100, a deaerator 200, a main steam system 300, an auxiliary steam system 400, a pressure detection module 500, a first-order hysteresis module 600, an adjustment module 700, and a A regulating valve 800, a second regulating valve 900 and a third regulating valve 1000. Among them, the deaerator 200 is connected to the exhaust port of the high-pressure cylinder 100 through the first regulating valve 800. The deaerator 200 is used to deoxygenate the condensed water entering the deaerator through the steam output by the high-pressure cylinder 100; the main steam The system 300 is connected to the deaerator 200 through the second regulating valve 900. The main steam system 300 is used to provide the first auxiliary steam to the deaerator 200 to maintain a stable pressure of the deaerator 200 under load shedding conditions; the auxiliary steam system 400 The third regulating valve 1000 is connected to the deaerator 200, and the auxiliary steam system 400 is used to provide the second auxiliary steam to the deaerator 200 through the third regulating valve 1000, so that the deaerator 200 can operate at no load and constant pressure. The pressure detection module 500 is set on the deaerator 200, and the pressure detection module 500 is used to obtain the pressure of the deaerator 200; the first-order lag module 600 is used to determine whether the steam turbine of the nuclear power unit is spinning based on the pressure of the deaerator 200. load condition, and sends a trigger signal when it is judged that the load rejection condition occurs in the steam turbine; the adjustment module 700 is used to control the second control valve 900 when receiving the trigger signal, so that the pressure of the deaerator 200 is maintained at the load rejection level. The pressure in front decreases at a preset rate after a preset time.

Specifically, the first regulating valve can be a pneumatic on-off valve, and the deaerator 200 can use steam to heat and disperse the condensate water entering the deaerator, and finally remove the oxygen in the condensate water to achieve the deoxygenation effect. The steam can come from high pressure. Cylinder 100, main steam system 300 and auxiliary steam system 400. The adjustment module 700 can control the opening of the second adjustment valve 900 and the third adjustment valve 1000 to use auxiliary steam to adjust the pressure of the deaerator 200 according to actual needs and maintain the pressure of the deaerator at a set pressure. . When the water level in the deaerator is too high, the second regulating valve 900 and the third regulating valve 1000 are automatically closed to prevent water intrusion accidents in the steam turbine.

As shown in Figure 1, according to the different working conditions of the steam turbine of the nuclear power unit system, the operation modes of the deaerator 200 can be divided into the following four types:

The first operation mode: when the steam turbine of the nuclear power unit is in no-load condition, the deaerator 200 operates at constant pressure. When the steam turbine is in no-load condition, during the startup phase, the auxiliary steam system 400 and the third regulating valve 1000 are used to provide the second auxiliary steam for the deaerator 200 to maintain the deaerator 200 operating at a constant pressure. Among them, the reference value of pressure one is 0.12MPa(a), which can be adjusted according to specific conditions.

The second operating mode: when the steam turbine of the nuclear power unit is in low load condition, the deaerator 200 operates at a constant pressure. When the steam turbine load is at a low level and gradually increases, the main steam system 300 and the steady-pressure steam regulating valve, that is, the second regulating valve 900, are used to provide the first auxiliary steam for the deaerator 200 to maintain the deaerator 200 at Run at constant pressure under pressure 2. Among them, the reference value of pressure two is 0.17MPa(a), which can be adjusted according to specific conditions.

The third operating mode: when the steam turbine of the nuclear power unit is in normal operating conditions, the deaerator 200 operates under sliding pressure. When the steam turbine is operating normally, if the exhaust steam pressure from the high-pressure cylinder 100 to the deaerator 200 is greater than pressure 2, the deaerator 200 can deoxygenate the steam output from the high-pressure cylinder 100, and the deaerator 200 can also pass the first adjustment The valve 800 supplies exhaust steam to the high-pressure cylinder 100 so that the deaerator 200 can operate according to the exhaust steam pressure from the high-pressure cylinder 100 to the deaerator 200 . Among them, the exhaust pressure from the high-pressure cylinder 100 to the deaerator 200 (the pressure of the deaerator) is a function of the turbine load. The first-order lag module 600 calculates the load change in real time according to the pressure of the deaerator to determine whether it occurs. Load shedding conditions.

The fourth operating mode: when the steam turbine of the nuclear power unit is in load shedding mode, the deaerator 200 performs pressure control. When load shedding occurs in the steam turbine, the second regulating valve 900 is controlled by the regulating module 700 to adjust the pressure of the deaerator 200, thereby controlling the steam volume of the deaerator 200 to ensure that the feed water continues to be heated and cavitation of the feed water pump does not occur.

When the first-order lag module 600 tracks the ramp signal in a steady state, the change rates of the input and output signals of the system are completely equal. However, due to the inertia of the system, when the input signal c(t) rises from 0 to 1, the corresponding output signal is Numerically, it lags behind the input signal by a constant T, so it can also be called a first-order lag link.

The pressure detection module 500 obtains the pressure of the deaerator 200 in real time, that is, the exhaust pressure from the high-pressure cylinder 100 to the deaerator 200. The first-order lag module 600 determines whether the steam turbine has a load shedding condition based on the pressure of the deaerator 200, and When it is determined that a load shedding condition occurs in the steam turbine, a trigger signal is sent to the adjustment module 700 . When receiving the trigger signal, the regulating module 700 controls the opening of the second regulating valve 900 so that the pressure of the deaerator 200 is maintained at the pressure before load shedding for a preset time (for example, 300s) and then decreases at a preset rate. Therefore, multi-signal combination logic is not used, and the load shedding condition determination logic is simplified. Only the most direct signal of the deaerator pressure is used, so that the deaerator pressure change can be accurately identified, and the turbine load shedding can be accurately detected. Load conditions, and when it is recognized that load shedding occurs in the steam turbine, the pressure of the deaerator is controlled to maintain the pressure before load shedding for a period of time and then decrease, so as to meet the requirements of the suction head of the main feed water pump and ensure that the condensate water continues to be Heating, so that the unit can quickly return to the original load setting value and continue to operate after troubleshooting, thereby maintaining the continuous and stable operation of the unit. As shown in FIG. 2 , in one embodiment of the present invention, the pressure detection module 500 may include a first pressure transmitter 510 , a second pressure transmitter 520 and a third pressure transmitter 530 . When the first pressure transmitter 510 , the second pressure transmitter 520 and the third pressure transmitter 530 are all faultless, the pressure detection module 500 detects the first pressure transmitter 510 , the second pressure transmitter 520 and the third pressure transmitter 530 according to the The median value of the pressure detected by the third pressure transmitter 530 obtains the pressure of the deaerator 200; when any one of the first pressure transmitter 510, the second pressure transmitter 520 and the third pressure transmitter 530 When the pressure transmitter fails, the pressure detection module 500 obtains the pressure of the deaerator 200 based on the average of the pressures detected by the two pressure transmitters that have not failed; when the first pressure transmitter 510 and the second pressure transmitter When any two pressure transmitters in the transmitter 520 and the third pressure transmitter 530 fail, the pressure detection module 500 obtains the pressure of the deaerator 200 based on the pressure detected by the pressure transmitter that has not failed; When the first pressure transmitter 510 , the second pressure transmitter 520 and the third pressure transmitter 530 all fail, the pressure detection module 500 determines whether the first pressure transmitter 510 , the second pressure transmitter 520 and the third pressure transmitter 530 The last detected effective value in the third pressure transmitter 530 obtains the pressure of the deaerator 200 .

Specifically, the deaerator 200 detects the pressure of the deaerator 200 through the pressure detection module 500, and adopts the logical method of taking the three out of three. The specific processing logic is as follows: when none of the transmitters are faulty, the output is the median out of the three; When one transmitter fails, the output is the average value of the other two normally working transmitters; when two transmitters fail, the output is the value of the remaining normal working transmitter; when all three transmitters fail , the output maintains the last effective value; the pressure detection module 500 outputs a transmitter fault signal while outputting the pressure signal of the deaerator 200 .

The pressure signal of the deaerator 200 output by the pressure detection module 500 will be used as the adjusted variable when the deaerator 200 is running. When two of the three pressure transmitters fail, the pressure control of the deaerator 200 is switched to manual control. When the pressure value of the deaerator 200 is too high, an alarm is issued on the DCS (Distributed Control System) operator station.

In one embodiment of the present invention, the transfer function of the first-order lag module 600 can be obtained according to the following formula: Among them, τ is the filtering time, for example, τ = 10s, and s is a variable.

In one embodiment of the present invention, the first-order hysteresis module 600 can determine that the load shedding condition of the steam turbine occurs when it detects that the pressure reduction rate of the deaerator 200 reaches 80KPa/10s or the pressure step drops by 80KPa. The pressure of the deaerator 200 is the exhaust pressure from the high-pressure cylinder 100 to the deaerator 200 .

It should be noted that the first-order lag module 600 is based on the direct signal of the exhaust pressure from the high-pressure cylinder 100 to the deaerator 200, and can determine the load shedding operation by judging the change rate of the exhaust pressure from the high-pressure cylinder 100 to the deaerator 200. occurrence of the situation. Since the pressure signal detected by the pressure detection module 500 itself has the characteristics of jitter, by setting the transfer function, the first-order lag module 600 can suppress the periodic interference of the pressure signal and obtain accurate exhaust pressure from the high-pressure cylinder 100 to the deaerator 200 Changes. The selection of the filter time τ is very critical to the accuracy of the judgment of the first-order lag module 600. The filter time τ must be able to adapt to the rapid changes in the exhaust pressure from the high-pressure cylinder 100 to the deaerator 200, so that the filter results can keep up with enough in time. The sensitivity must be high, and it is necessary to prevent misidentification of load shedding conditions due to being too sensitive and unable to effectively filter out interference. Therefore, according to the characteristics of the steam turbine load shedding, that is, the greater the exhaust pressure reduction rate from the high-pressure cylinder 100 to the deaerator 200, the shorter the time required for the exhaust pressure to decrease. The filter time τ = 10s is selected to set the critical value for the trigger signal. The exhaust pressure reduction rate from the high-pressure cylinder 100 to the deaerator 200 is set to 80KPa/10s. When the first-order lag module 600 detects that the exhaust steam pressure reduction rate from the high-pressure cylinder 100 to the deaerator 200 reaches 80KPa/10s or the pressure step drops by 80KPa, it is determined that the steam turbine is in a load shedding condition.

In one embodiment of the invention, the adjustment module 700 may include a given function generator and a PID regulator. Among them, the given function generator is used to generate a pressure-maintaining curve according to the pressure of the deaerator 200 before load shedding when receiving the trigger signal; the PID regulator is used to control the second regulating valve 900 according to the pressure-maintaining curve to make the deaerator The pressure of the oxygenator 200 changes according to the pressure holding curve. As an example, as shown in Figure 3, the pressure change of the pressure holding curve can be: first maintain the pressure of the deaerator 200 before load shedding for 300 seconds, and then reduce it to 0 at 0.1MPa/min, where, Figure 3 The horizontal axis is time, and the vertical axis is deaerator pressure.

Specifically, when a failure of the unit causes the steam turbine to undergo a load rejection condition, the first-order lag module 600 determines that the steam turbine has a load rejection condition and outputs a trigger signal. The given function generator of the adjustment module 700 receives the trigger signal according to the load rejection condition. The pressure of the deaerator 200 before load generates a pressure holding curve. The regulating module 700 controls the second regulating valve 900 to open quickly according to the pressure holding curve through the PID regulator. A large amount of first auxiliary steam in the main steam system 300 is provided to the deaerator 200 The pressure of the deaerator 200 before load shedding occurs in the steam turbine is maintained to meet the requirements of the suction head of the main feedwater pump and to ensure that the condensate water is continuously heated. The reference setting holding time is 300s, and the holding time can be adjusted according to specific conditions. If the unit failure is resolved during the pressure maintaining time, the stable pressure of the deaerator 200 can create conditions for the unit to restore the load and return to the original unit state, so that the unit can achieve the goal of continuous and stable operation. After a pressure holding time of 300s, the PID regulator controls the second regulating valve 900 to slowly close, so that the pressure of the deaerator 200 drops to 0 at a rate of 0.1MPa/min, which can effectively avoid the second regulating valve 900 due to gas consumption. suddenly decreases and the overpressure opens. Subsequently, the setpoint function generator output tracks the deaerator pressure and the PID regulator output is zero.

According to the nuclear power unit system of the embodiment of the present invention, the pressure change of the deaerator is obtained through the pressure detection module, and a first-order lag module is set to determine whether the load shedding condition occurs in the steam turbine according to the pressure change of the deaerator, and when the load shedding condition is The adjustment module controls the pressure of the deaerator to be maintained at the pressure before load shedding for a period of time. This allows the load shedding condition of the turbine to be accurately detected, ensuring the stability of the deaerator pressure, which is conducive to the long-term stable operation of the nuclear power unit.

In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of these features. "Plural" means two or more, unless otherwise expressly and specifically limited.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "an example," "specific examples," or "some examples" or the like means that specific features are described in connection with the embodiment or example. , structures, materials or features are included in at least one embodiment or example of the invention. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other. In the description of this specification, reference to the terms "one embodiment," "some embodiments," "an example," "specific examples," or "some examples" or the like means that specific features are described in connection with the embodiment or example. , structures, materials or features are included in at least one embodiment or example of the invention. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other.

It should be understood that various parts of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if it is implemented in hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: discrete logic gate circuits with logic functions for implementing data signals; Logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

Those of ordinary skill in the art can understand that all or part of the steps involved in implementing the methods of the above embodiments can be completed by instructing relevant hardware through a program. The program can be stored in a computer-readable storage medium. The program can be stored in a computer-readable storage medium. When executed, one of the steps of the method embodiment or a combination thereof is included.

In addition, each functional unit in various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically alone, or two or more units can be integrated into one module. The above integrated modules can be implemented in the form of hardware or software function modules. If the integrated module is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

The storage media mentioned above can be read-only memory, magnetic disks or optical disks, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are illustrative and should not be construed as limitations of the present invention. Those of ordinary skill in the art can make modifications to the above-mentioned embodiments within the scope of the present invention. The embodiments are subject to changes, modifications, substitutions and variations.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principles and spirit of the invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (6)

1. A nuclear power unit system, characterized by including: high pressure cylinder; Deaerator, the deaerator is connected to the exhaust port of the high-pressure cylinder through a first regulating valve, and the deaerator is used to deoxygenate the condensed water entering the deaerator through the steam output by the high-pressure cylinder. deal with; A main steam system, the main steam system is connected to the deaerator through a second regulating valve, and the main steam system is used to provide first auxiliary steam to the deaerator; Auxiliary steam system, the auxiliary steam system is connected to the deaerator through a third regulating valve, and the auxiliary steam system is used to provide second auxiliary steam to the deaerator through the third regulating valve, so that The deaerator operates under no-load and constant-pressure operation conditions; A pressure detection module, the pressure detection module is arranged on the deaerator, and the pressure detection module is used to obtain the pressure of the deaerator; A first-order lag module, the first-order lag module is used to determine whether the steam turbine of the nuclear power unit is in a load-shedding condition based on the pressure of the deaerator, and to send a trigger signal when it is determined that the steam turbine is in a load-shedding condition. ; A regulating module, the regulating module is used to control the second regulating valve when receiving the trigger signal, so that the pressure of the deaerator is maintained at the pressure before load shedding for a preset time. rate decreases. 2. The nuclear power unit system according to claim 1, wherein the pressure detection module includes a first pressure transmitter, a second pressure transmitter and a third pressure transmitter, and the pressure detection module body Used for: When the first pressure transmitter, the second pressure transmitter and the third pressure transmitter are all faultless, according to the first pressure transmitter, the second pressure transmitter and the third pressure transmitter, The pressure of the deaerator is obtained from the median value of the pressures detected by the three pressure transmitters; When any one of the first pressure transmitter, the second pressure transmitter and the third pressure transmitter fails, according to the two pressure transmitters that have not failed, The pressure of the deaerator is obtained by averaging the detected pressures; When any two pressure transmitters among the first pressure transmitter, the second pressure transmitter and the third pressure transmitter fail, the detection method is based on the pressure transmitter that has not failed. The pressure obtained is the pressure of the deaerator; When the first pressure transmitter, the second pressure transmitter and the third pressure transmitter all fail, according to the first pressure transmitter, the second pressure transmitter and the last detected effective value in the third pressure transmitter to obtain the pressure of the deaerator. 3. The nuclear power unit system according to claim 1, characterized in that the transfer function of the first-order lag module is obtained according to the following formula: Among them, τ is the filtering time and s is the variable. 4. The nuclear power unit system according to claim 3, characterized in that τ=10s. 5. The nuclear power unit system according to claim 4, characterized in that the first-order lag module is specifically used for: When it is detected that the pressure reduction rate of the deaerator reaches 80KPa/10s or the pressure step drops by 80KPa, it is determined that the steam turbine has a load shedding condition. 6. The nuclear power unit system according to claim 1, characterized in that the adjustment module specifically includes: A given function generator is used to generate a pressure-holding curve according to the pressure of the deaerator before load shedding when receiving the trigger signal. The pressure change of the pressure-holding curve is: first The pressure of the deaerator is maintained for 300 seconds before load, and then reduced to 0 at 0.1MPa/min; PID regulator, the PID regulator is used to control the second regulating valve according to the pressure maintaining curve, so that the pressure of the deaerator changes according to the pressure maintaining curve.