A nuclear power unit partial loop operation optimization control system and an operation method thereof

Abstract

This invention discloses an optimized control system and its operation method for off-loop operation of nuclear power units, belonging to the field of nuclear reactor control technology. It is applicable to multi-loop pressurized water reactor units with switchable off-loop operation, particularly the VVER-1200 unit. The system includes a condition identification module, an off-loop power coordination control module, a nuclear power regulation unit, an electrical power regulation unit, and an execution drive unit, all connected in sequence via communication. The condition identification module enables accurate identification of off-loop operating conditions and calculation of the maximum allowable power. A three-channel nonlinear nuclear power regulation unit achieves precise control of reactor-side power. The electrical power regulation unit constructs a primary and secondary loop linkage coordination mechanism, breaking through the limitations of traditional off-loop operating modes. This invention can achieve smooth power transition during off-loop switching and dynamic grid load response during steady-state operation, effectively suppressing key parameter fluctuations, reducing core operation risks, and significantly improving the unit's operational stability and grid adaptability under off-loop operating conditions.

Description

Technical Field

[0001] This invention belongs to the field of nuclear reactor control technology, specifically relating to an operation optimization control system and its operation method for multi-loop pressurized water reactors (especially suitable for VVER1200 models) to achieve dynamic load adjustment and coordination between primary and secondary loops under switching off-loop operation and off-loop steady-state operation conditions. Background Technology

[0002] The VVER1200 unit, like traditional Siemens-designed KWU and other models, features a redundant multi-loop coolant system. It can maintain unit operation even after the main circulation pumps (based on its design number) stop; this operating condition is defined as off-loop operation. In existing technology, when the VVER1200 unit's main circulation pumps stop, triggering off-loop switching, the unit uses the APP pre-protection control system to reduce reactor power below a safe threshold and forcibly switch to "N mode" (maintaining the neutron flux setpoint mode), strictly prohibiting switching back to "T mode" (maintaining the main steam pipe steam pressure mode).

[0003] This control strategy has significant technical flaws: First, the primary and secondary loop controls are decoupled, and the secondary loop power regulation rate cannot adapt to the heat transfer efficiency changes caused by the decrease in coolant flow in the primary loop, leading to excessive fluctuations in main steam pressure. Second, during off-loop operation, the unit loses its load regulation capability and cannot respond to dynamic load demands from the grid. Third, there is a lack of a precise temperature regulation mechanism for off-loop conditions; local loop temperature deviations can easily mislead the reactor-side regulation logic, increasing the risk of core heat transfer deterioration. Currently, the industry still lacks an integrated coordinated control system that can achieve off-loop condition identification, precise nuclear power regulation, and coordinated power matching. Summary of the Invention

[0004] To address the shortcomings of existing technologies in multi-loop pressurized water reactors, such as decoupling of the primary and secondary loops, load regulation failure, and large fluctuations in key parameters during off-loop operation, this invention aims to provide an optimized control system and its operation method for off-loop operation of nuclear power units. Through an integrated design that incorporates precise operating condition identification, three-channel nonlinear nuclear power regulation, and electrical power linkage adaptation, it achieves smooth power transition during off-loop switching, dynamic load response during steady-state operation, and ensures the stability of primary and secondary loop parameters.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A nuclear power unit off-loop operation optimization control system is applicable to multi-loop pressurized water reactor units with switchable off-loop operation. The system includes an operating condition identification module, an off-loop power coordination control module, a nuclear power regulation unit, an electric power regulation unit, and an execution drive unit that are connected in sequence via communication.

[0007] The operating condition identification module is used to collect core operating parameters such as coolant flow rate and temperature of each loop of the nuclear power unit in real time. Through built-in judgment logic, it accurately identifies the off-loop operating condition of the nuclear power unit. At the same time, based on the decrease in total core flow rate and thermal safety boundary under the off-loop operating condition, it calculates the maximum allowable power of the core under this condition and performs safety verification and upper limit threshold limit on the target load command input from the grid side. It locks the safety boundary of the unit's off-loop operation from the source and eliminates the risk of core over-power operation.

[0008] The off-loop power coordination control module, as the nuclear-electric power matching hub of the system, is used to receive the target load command from the power grid and the operating condition signal and maximum allowable power parameters output by the operating condition identification module. Based on the change in heat transfer efficiency caused by the first loop flow attenuation under the off-loop operating condition, it dynamically adapts the matching relationship between nuclear power and electric power, and generates nuclear power setpoints and electric power setpoints that are fully adapted to the current off-loop operating condition, thus solving the core problems of nuclear power control decoupling and power matching inaccuracy.

[0009] The nuclear power regulation unit, as the core execution unit of reactor-side power control, is used to receive the nuclear power setpoint output by the off-loop power coordination control module, and combine it with the real-time operating parameters of the nuclear power unit to complete multi-dimensional closed-loop regulation calculations, generate precise control rod adjustment commands, realize stable and disturbance-free control of core power under off-loop conditions, and effectively suppress large fluctuations in core power and coolant temperature.

[0010] The electric power regulation unit, as the core of the secondary loop side coordinated control, is used to receive the electric power setpoint output by the secondary loop power coordination control module, synchronously collect secondary loop unit operating parameters such as turbine speed, main steam pressure, and flow rate, construct coordinated control logic for primary and secondary loop linkage, generate main steam valve adjustment commands adapted to the current operating conditions, and realize dynamic coordinated matching between secondary loop electric power and primary loop core power.

[0011] The execution drive unit, as the final actuator of the system, receives control rod adjustment commands from the nuclear power regulation unit and main steam valve adjustment commands from the electric power regulation unit, respectively, and completes the core control rod position adjustment and the opening adjustment of the secondary loop main steam regulating valve, thereby achieving coordinated and stable control of the first and second loops under the off-loop condition, ensuring parameter stability during the unit's operating condition switching process and steady-state operation.

[0012] Furthermore, the operating condition identification module has a built-in off-loop operating condition judgment model. The off-loop operating condition judgment model uses the deviation rate between the real-time flow rate of each loop and the rated operating flow rate under the current load as the core judgment basis. When the flow deviation rate of any loop meets the preset threshold and the duration of the deviation state reaches the set time, the model determines that the nuclear power unit has entered the off-loop operating condition and synchronously outputs the operating condition marking signal to the power coordination control module, the nuclear power regulation unit, and the electric power regulation unit.

[0013] Furthermore, the operating condition identification unit also incorporates a flow-weighted temperature calculation module and a power limit calculation module. The flow-weighted temperature calculation module calculates the effective average coolant temperature based on the real-time flow weight of each loop under off-loop operating conditions. The flow weight of abnormal loops is automatically adjusted downwards as the flow decreases, solving the problem in traditional solutions where local temperature deviations in shut-down / low-flow loops mislead the reactor-side regulation logic, thus preventing malfunctions from the outset. The power limit calculation module calculates the maximum permissible power of the reactor core under the current off-loop operating condition based on the decrease in the total core flow under off-loop operating conditions, combined with the core thermal limit parameters and the safety margin required by nuclear safety regulations. It then uses low-selection logic to apply threshold limits to the grid target load command, ensuring that the nuclear power unit's operating power is always within the safety boundary.

[0014] Furthermore, the off-loop power coordination control module incorporates a nuclear-electric power matching coefficient correction unit, which dynamically corrects the abnormal flow deviation rate under off-loop operating conditions to accurately adapt to changes in core heat transfer efficiency caused by primary loop flow attenuation. Based on the corrected matching coefficient, the grid target load command, and the maximum allowable power output by the operating condition identification unit, the power coordination control module outputs the nuclear power setpoint and electric power setpoint for the current off-loop operating condition through low-select logic, maximizing the satisfaction of grid load regulation requirements while ensuring core operation safety.

[0015] The nuclear power regulation unit adopts a three-channel nonlinear controller structure, including a coolant average temperature regulation channel, a load setting regulation channel, and a nuclear power feedback regulation channel. The coolant average temperature regulation channel uses the maximum average temperature of the coolant across the entire loop as the regulation input under normal operating conditions, and automatically switches to the flow-weighted effective average temperature output by the operating condition identification module under off-loop conditions. The load setting regulation channel has a built-in matching coefficient correction module that is linked to the off-loop power coordination control module, which can synchronously adapt to the core heat transfer characteristics under off-loop conditions, ensuring accurate matching between the load setting value and the actual heat transfer capacity of the core. The nuclear power feedback regulation channel is configured with a nonlinear gain unit adapted to off-loop conditions. The gain of the nonlinear gain unit is dynamically adjusted according to the total core flow rate and core power level. When the core power exceeds the maximum allowable power, the maximum gain output is triggered, realizing rapid power reduction under abnormal operating conditions and ensuring core operation safety.

[0016] The power regulation unit includes a speed control module, an inlet steam pressure and flow limiting module, a load control module, and a weight dynamic allocation module. The speed control module receives real-time speed signals from the turbine generator set and outputs a speed regulation signal when the unit speed deviation exceeds the allowable range to ensure stable unit speed. The inlet steam pressure and flow limiting module collects real-time pressure and flow signals from the main steam pipeline and outputs a valve opening limiting signal when the main steam parameters deviate from the allowable range to prevent large fluctuations in main steam pressure from triggering unit protection actions. The load control module receives the power setpoint output from the off-loop power coordination control module and outputs a main steam valve opening adjustment signal to respond to the load regulation needs of the power grid. The weight dynamic allocation module dynamically adjusts the regulation weights of speed control, main steam pressure limiting, and load control during the initial stage of off-loop switching and the steady-state operation phase, balancing parameter stability during the operating condition switching process and load response capability during the steady-state operation phase.

[0017] The power regulation unit has a built-in primary circuit temperature interlock protection module. When the primary circuit coolant temperature exceeds the set value and shows a continuous upward trend, the temperature interlock protection module triggers the main steam valve operation restriction and regulation rate restriction. The specific triggering logic is as follows: when the primary circuit coolant temperature is higher than the set value and shows a continuous upward trend, the main steam valve is prohibited from being closed slightly, and the valve regulation rate is limited to avoid the regulation action on the secondary circuit side from aggravating the risk of primary circuit overheating, thus constructing an interlock protection mechanism linking the primary and secondary circuits.

[0018] The execution drive unit includes a control rod drive mechanism and a main steam valve electro-hydraulic drive system. The control rod drive mechanism receives control rod adjustment commands from the nuclear power regulation unit, drives the control rods to move up and down to complete core reactivity regulation, and has a built-in automatic rod drop protection module to ensure core safety under abnormal operating conditions. The main steam valve electro-hydraulic drive system receives main steam valve adjustment commands from the electric power regulation unit, precisely adjusts the main steam valve opening to complete secondary loop electric power regulation, and has a built-in valve position feedback and fault diagnosis module to ensure adjustment accuracy and operational reliability of the actuator.

[0019] The present invention also provides an operation method based on the above-mentioned nuclear power unit off-loop operation optimization control system, the method comprising the following steps: The first step is operating condition identification: real-time acquisition of operating parameters such as coolant flow and temperature in each loop of the nuclear power unit, identification of the off-loop operating condition of the nuclear power unit through the built-in off-loop operating condition judgment model, simultaneous calculation of the maximum allowable power of the reactor core under the current off-loop operating condition, safety verification and threshold limitation of the target load command input from the grid side, output of valid target load command, and locking of the safe boundary of unit operation. The second step, power coordination and matching: Based on the identified off-loop operating condition signal and the verified valid target load command, the nuclear-electric power matching coefficient is dynamically corrected to adapt to the core heat transfer efficiency changes under off-loop operating conditions, and nuclear power setpoints and electric power setpoints that are fully adapted to the current operating conditions are generated to achieve coordinated matching of nuclear power and electric power. The third step is closed-loop regulation of nuclear power: Based on the generated nuclear power setpoint and the real-time operating parameters of the nuclear power unit, multi-dimensional closed-loop regulation calculations are completed through three-channel nonlinear control logic to generate control rod adjustment commands and achieve precise closed-loop control of core power under off-loop conditions. The fourth step is the linkage adjustment of electric power: Based on the generated electric power setpoint and the real-time operating parameters of the second loop, the main steam valve adjustment command is generated through the multi-module weight dynamic allocation logic, which synchronously triggers the temperature interlock protection logic of the first loop, and constructs a linkage coordination mechanism between the first and second loops to realize the dynamic adaptation of the electric power of the second loop and the nuclear power of the first loop. The fifth step is execution drive: the execution drive unit executes the control rod adjustment command and the main steam valve adjustment command respectively, which respectively completes the core reactivity adjustment and the secondary loop power adjustment, and finally realizes the stable operation of the unit and the dynamic response of the grid load under the off-loop condition.

[0020] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: 1. Construct an integrated off-loop collaborative control architecture. Through a five-layer linkage structure of operating condition identification, power coordination, nuclear power regulation, electric power regulation, and execution drive, it realizes full-process collaborative control of the reactor and the turbine under off-loop conditions, replacing the limitations of the traditional mode. It can stably achieve "reactor-follower" operation under off-loop conditions, significantly improving the unit's adaptability and continuous operation capability.

[0021] 2. By using the operating condition identification module to perform flow-weighted temperature calculation under partial loop operation, abnormal loop interference is eliminated, the reliability of regulation is improved, the problem of temperature deviation in low flow / shutdown loops misleading the regulation logic is solved, and malfunctions in regulation are avoided.

[0022] 3. By dynamically correcting the nuclear power-electricity power matching coefficient during the operation of the off-loop through the off-loop power coordination control module, the heat transfer efficiency changes caused by the primary loop flow attenuation are adapted, enabling the nuclear power to be matched accurately in real time. Within the safety boundary, it can respond to the grid load demand, solve the pain point of losing load regulation capability under the traditional off-loop operating condition, and realize effective load tracking under the off-loop.

[0023] 4. It provides a complete and reproducible off-loop operation method, from operating condition identification, power coordination, nuclear power regulation, electromechanical linkage to execution drive, which can be directly applied to the off-loop operation control of multi-loop pressurized water reactors and has strong engineering applicability. Attached Figure Description

[0024] Figure 1 This is a flowchart of the nuclear power unit eccentric loop operation optimization control system described in this invention; Figure 2 This is the control logic diagram of the working condition identification module described in this invention; Figure 3 This is the control logic diagram of the power coordination control module described in this invention; Figure 4 This is a comparison curve of the nuclear power response of nuclear power units using embodiments of the present invention and conventional control strategies; Figure 5 This is a comparison curve of the main steam pressure response of a nuclear power unit under the embodiment of the present invention and the conventional control strategy. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings, specific embodiments and specific examples. This example is based on the design of the VVER-1200 four-loop pressurized water reactor unit.

[0026] Please see Figure 1 The present invention is an optimized control system for the off-loop operation of a nuclear power unit and its operation method. The control system includes a condition identification module, an off-loop power coordination control module, a nuclear power regulation unit, an electric power regulation unit and an execution drive unit that are connected in sequence via communication.

[0027] Please see Figure 2 The operating condition identification module is used to collect core operating parameters such as coolant flow rate and temperature of each loop of the nuclear power unit in real time. It calculates the deviation rate between the loop flow rate and the rated operating flow rate of the loop under the current load in real time, and the calculated deviation rate signal is synchronously input to a 3-second anti-jitter timer (corresponding to...). Figure 2The TON timer module (in the middle loop) triggers a signal when the flow deviation in any loop reaches the limit for entering off-loop operation and lasts for 3 seconds. The model determines that the unit has entered off-loop operation and calculates the maximum allowable power of the core under this condition based on the decrease in total core flow and the thermal safety boundary. It also performs safety verification and upper limit threshold restrictions on the target load command input from the grid side, locking the safety boundary of the unit's off-loop operation from the source and eliminating the risk of core over-power operation. After the unit enters off-loop operation, the operating condition identification module switches the coolant average temperature calculation to a weighted calculation mode. Based on the real-time flow weight of each loop, it calculates the effective coolant average temperature and outputs it to the nuclear power regulation unit. After the unit enters off-loop operation, the module collects the total core flow signal and inputs it to the power regulation gain function to calculate the flow gain value adapted to the current flow condition. The adjustment range is 1.0 to 4.0 times, used for the nonlinear gain unit of the nuclear power regulation unit during off-loop operation. When the flow deviation rate of all loops is ≤20% and the duration is ≥10 s, the model determines that the unit exits the off-loop operating condition, and the system automatically switches back to the rated operating condition control logic.

[0028] Please see Figure 3 The off-loop power coordination control module, serving as the nuclear-electric power matching hub of the system, receives the grid target load command and the operating condition signal and maximum allowable power parameters output by the operating condition identification module. Based on the change in heat transfer efficiency caused by the first loop flow attenuation under off-loop operating conditions, it calculates the matching coefficient for off-loop operation and converts the grid target load command into an initial nuclear power setpoint. Simultaneously, it inputs the initial nuclear power setpoint and the maximum allowable power output by the operating condition identification module to the low-select logic unit, taking the smaller of the two as the final output nuclear power setpoint to ensure that the nuclear power setpoint never exceeds the core safety boundary. Simultaneously, based on the final nuclear power setpoint and the corrected matching coefficient, it calculates the corresponding electric power setpoint and outputs it synchronously to the nuclear power regulation unit and the electric power regulation unit. This module dynamically adapts the matching relationship between nuclear power and electric power, generating nuclear power setpoints and electric power setpoints that are fully adapted to the current off-loop operating conditions, solving the core problems of nuclear power control decoupling and power matching inaccuracy.

[0029] The nuclear power regulation unit, as the core execution unit of reactor-side power control, is used to receive the nuclear power setpoint output by the off-loop power coordination control module, and combine it with the real-time operating parameters of the nuclear power unit to complete multi-dimensional closed-loop regulation calculations, generate precise control rod adjustment commands, realize stable and disturbance-free control of core power under off-loop conditions, and effectively suppress large fluctuations in core power and coolant temperature.

[0030] The power regulation unit, as the core of the secondary loop coordinated control, receives the power setpoint output by the partial loop power coordination control module and synchronously collects secondary loop unit operating parameters such as turbine speed and main steam pressure / flow. The main steam valve generates three signals: a speed regulation opening signal based on the speed deviation value through incremental PI calculation; a pressure limit opening signal based on the main steam pressure PI control; and a load regulation opening signal based on the power setpoint output by the partial loop power coordination control module through incremental PI calculation of the power deviation value. These signals are then linearly summed with their respective weights to obtain the integrated main steam regulating valve opening signal. In conjunction with the primary loop temperature interlock protection module, when the primary loop coolant temperature exceeds the setpoint by 5°C and shows a continuous upward trend, the primary loop temperature interlock protection is immediately triggered, prohibiting the main steam valve from closing and limiting the valve regulation rate. This constructs a coordinated control logic linking the primary and secondary loops, generating a main steam valve regulation command adapted to the current operating conditions, and achieving dynamic coordinated matching between the secondary loop power and the primary loop core power. The weighting of the three signals controlling the main steam valve opening is dynamically determined based on the unit's operating phase. In the initial stage of the off-loop switching, priority is given to ensuring the stability of unit parameters to avoid triggering protection due to parameter exceeding limits during the switching process. The weights are set as follows: pressure limit opening signal weight 60%, speed regulation opening signal weight 30%, and load regulation opening signal weight 10%. In the steady-state operation phase of the off-loop, priority is given to ensuring the grid load tracking capability to achieve dynamic load response under off-loop conditions. The weights are set as follows: load regulation opening signal weight 60%, pressure limit opening signal weight 25%, and speed regulation opening signal weight 15%.

[0031] The execution drive unit, as the final actuator of the system, receives control rod adjustment commands from the nuclear power regulation unit and main steam valve adjustment commands from the electric power regulation unit, respectively, and completes the core control rod position adjustment and the opening adjustment of the secondary loop main steam regulating valve, thereby achieving coordinated and stable control of the first and second loops under the off-loop condition, ensuring parameter stability during the unit's operating condition switching process and steady-state operation.

[0032] Furthermore, the operating condition identification module incorporates a loop-biased operating condition judgment model. This model uses the deviation rate between the real-time flow rate of each loop and the rated operating flow rate under the current load as the core judgment criterion. Compared to lagging parameters such as temperature and pressure, flow rate parameters can reflect the true operating status of the loop more quickly and accurately. When the flow deviation rate of any loop meets a preset threshold, and the duration of this deviation reaches the set anti-shake time, the model determines that the nuclear power unit has entered a loop-biased operating condition. It synchronously outputs an operating condition marking signal to the power coordination control module, nuclear power regulation unit, and electric power regulation unit, realizing the synchronous switching of the control mode of the entire system. At the same time, it can effectively avoid misjudgment of operating conditions caused by normal fluctuations in loop flow. Specifically, the preset threshold of the judgment model is: flow deviation rate of any loop > 35%, duration ≥ 3s. When this condition is met, the loop-biased operating condition judgment is triggered.

[0033] Furthermore, the operating condition identification unit also incorporates a flow-weighted temperature calculation module and a power limit calculation module. The flow-weighted temperature calculation module calculates the effective average coolant temperature based on the real-time flow weight of each loop under off-loop operating conditions. The flow weight of abnormal loops is automatically adjusted downwards as the flow decreases, solving the problem in traditional solutions where local temperature deviations in shut-down / low-flow loops mislead the reactor-side regulation logic, thus preventing malfunctions at the source. The power limit calculation module calculates the maximum permissible power of the reactor core under the current off-loop operating condition based on the total core flow decrease under off-loop operating conditions, combined with the core thermal limit parameters and the 1.3 times DNBR (deviation from nucleo-boiling ratio) safety margin required by nuclear safety regulations. It then uses low-select logic to apply threshold limits to the grid target load command, ensuring that the nuclear power unit's operating power is always within the safety boundary.

[0034] Furthermore, the off-loop power coordination control module incorporates a nuclear-electric power matching coefficient correction unit. This matching coefficient is dynamically corrected based on the flow deviation rate of the abnormal loop under off-loop operating conditions (the example described in this invention uses an empirical function derived from the simulation of the unit's off-loop operating conditions). This is used to accurately adapt to the core heat transfer efficiency changes caused by the primary loop flow decay, correcting the nuclear-electric power mismatch problem caused by the fixed matching coefficient under traditional rated operating conditions. Based on the corrected matching coefficient, the grid target load command, and the maximum allowable power output by the operating condition identification unit, the power coordination control module outputs the nuclear power setpoint and the electric power setpoint for the current off-loop operating conditions through low-select logic, maximizing the satisfaction of the grid load regulation requirements while ensuring the safe operation of the core.

[0035] Furthermore, the nuclear power regulation unit adopts a three-channel nonlinear controller structure, including a coolant average temperature regulation channel, a load setting regulation channel, and a nuclear power feedback regulation channel. The regulation deviation signals output from the three channels are summed to obtain the total regulation deviation signal of the regulator, and a control rod regulation command is generated based on this signal and the control rod displacement rate function. The coolant average temperature regulation channel uses the maximum value of the full-loop coolant average temperature as the regulation input under normal operating conditions, and automatically switches to the flow-weighted effective average temperature output by the operating condition identification module under off-loop conditions, fully adapting to the temperature acquisition and regulation logic under off-loop conditions. The load setting regulation channel has a built-in matching coefficient correction module linked with the off-loop power coordination control module, which can synchronously adapt to the core heat transfer characteristics under off-loop conditions, ensuring accurate matching between the load setpoint and the actual core heat transfer capacity. The nuclear power feedback regulation channel is configured with appropriate... The nonlinear gain unit for the biased loop operation dynamically adjusts its gain according to the total core flow and core power level. Specifically, the flow gain decreases linearly as the total core flow decreases, with an adjustment range of 1.2 to 2.0 times. When the core power is below 0.25 times the rated power, the power gain is 4. Within the range of core power from 0.25 times to 1 times the rated power, the power gain changes linearly from 4 to 1. When the core power is above the maximum allowable power, the maximum gain output is triggered to achieve rapid power reduction under abnormal operating conditions and ensure the safe operation of the core.

[0036] Furthermore, the electric power regulation unit includes a speed control module, an inlet steam pressure and flow limiting module, a load control module, and a weight dynamic allocation module. The speed control module receives real-time speed signals from the turbine generator set. When the unit speed deviation exceeds ±5 r / min, it outputs a speed adjustment signal to ensure stable unit speed and meet the primary frequency regulation requirements of the power grid. The steam inlet pressure and flow limiting module collects real-time pressure and flow signals from the main steam pipeline. When the main steam pressure deviates from the rated value by more than ±0.15 MPa, it outputs a valve opening limiting signal to prevent large fluctuations in main steam pressure from triggering unit protection actions. The load control module receives the power setpoint output from the off-loop power coordination control module and outputs a main steam valve opening adjustment signal to respond to the load regulation needs of the power grid. The weight dynamic allocation module dynamically adjusts the adjustment weights of speed control, main steam pressure limiting, and load control during the initial stage of off-loop switching (0~60s) and the steady-state operation phase. During the initial switching phase, priority is given to ensuring the stability of main steam pressure and unit speed. During the steady-state operation phase, priority is given to ensuring load tracking capability, taking into account both parameter stability during the operating condition switching process and load response capability during the steady-state operation phase.

[0037] Furthermore, the power regulation unit has a built-in primary circuit temperature interlock protection module. When the primary circuit coolant temperature exceeds the set value and shows a continuous upward trend, the temperature interlock protection module triggers the main steam valve operation restriction and regulation rate restriction. Specifically, when the primary circuit coolant temperature is 5°C higher than the set value and shows a continuous upward trend, the main steam valve is prohibited from being closed slightly, and the valve regulation rate is limited to ≤1% of the rated opening per second. This avoids the regulation action on the secondary circuit side from exacerbating the risk of primary circuit overheating, thus constructing an interlock protection mechanism linking the primary and secondary circuits.

[0038] Furthermore, the execution drive unit includes a control rod drive mechanism and a main steam valve electro-hydraulic drive system. The control rod drive mechanism receives control rod adjustment commands from the nuclear power regulation unit, drives the control rods to move up and down to complete core reactivity regulation, with a displacement control accuracy of ±1 mm and a response time ≤0.5 s. It has a built-in automatic rod drop protection module to ensure core safety under abnormal operating conditions. The main steam valve electro-hydraulic drive system receives main steam valve adjustment commands from the electric power regulation unit, precisely adjusts the main steam valve opening to complete secondary loop electric power regulation, with an opening adjustment range of 0~100% of rated opening and an adjustment accuracy of ±0.1% of rated opening. It has a built-in valve position feedback and fault diagnosis module to ensure adjustment accuracy and the operational reliability of the actuator.

[0039] The operation method based on the above-mentioned nuclear power unit off-loop operation optimization control system provided by the present invention includes the following steps: The first step is operating condition identification: real-time acquisition of operating parameters such as coolant flow and temperature in each loop of the nuclear power unit, identification of the off-loop operating condition of the nuclear power unit through the built-in off-loop operating condition judgment model, simultaneous calculation of the maximum allowable power of the reactor core under the current off-loop operating condition, safety verification and threshold limitation of the target load command input from the grid side, output of valid target load command, and locking of the safe boundary of unit operation. The second step, power coordination and matching: Based on the identified off-loop operating condition signal and the verified valid target load command, the nuclear-electric power matching coefficient is dynamically corrected to adapt to the core heat transfer efficiency changes under off-loop operating conditions, and nuclear power setpoints and electric power setpoints that are fully adapted to the current operating conditions are generated to achieve coordinated matching of nuclear power and electric power. The third step is closed-loop regulation of nuclear power: Based on the generated nuclear power setpoint and the real-time operating parameters of the nuclear power unit, the independent deviation signals output from the three channels are linearly integrated by summation to obtain the total regulation deviation signal of the regulator. The deviation signal is then converted into a control rod displacement rate command through the control rod displacement rate function to achieve precise closed-loop control of the core power under the off-loop condition. The fourth step is the linkage adjustment of electrical power: Based on the generated electrical power setpoint and the real-time operating parameters of the second loop, the main steam valve adjustment command is generated through the multi-module weight dynamic allocation logic. The primary loop temperature interlock protection logic is triggered simultaneously. When the primary loop coolant temperature is 5°C higher than the setpoint and shows a continuous heating trend, the primary loop temperature interlock protection is immediately triggered, prohibiting the main steam valve from closing and limiting the valve adjustment rate. This establishes a linkage and coordination mechanism between the primary and secondary loops, realizing the dynamic adaptation of the electrical power of the second loop and the nuclear power of the primary loop. The fifth step is execution drive: the execution drive unit executes the control rod adjustment command and the main steam valve adjustment command respectively, which respectively completes the core reactivity adjustment and the secondary loop power adjustment, and finally realizes the stable operation of the unit and the dynamic response of the grid load under the off-loop condition.

[0040] To verify the control effect of the present invention, this embodiment uses APROS thermal-hydraulic simulation software to build a thermal-hydraulic model of the VVER-1200 unit. Simulation verification is performed on a partial loop condition with the main pump shut down in a single loop. The simulation duration is 1400 seconds. Simultaneously, a comparative simulation is conducted using the unit's traditional partial loop control strategy (forced power reduction + switching and locking "N" mode). Figure 4 and Figure 5 The comparison results. Figure 4 As can be seen from the comparison curves of the unit's nuclear power response, when using the traditional control strategy, the fluctuation amplitude of nuclear power and electrical power is large during the off-loop switching process, and the stabilization time after switching is long. However, the present invention can ensure stable and rapid switching of nuclear power and electrical power. Figure 5 As can be seen from the main steam pressure response curve, the control process of this invention can ensure the stability of the main steam pressure during the off-loop switching process, avoid the unit from triggering overpressure protection, and ensure the operational stability of the unit under off-loop conditions.

Claims

1. A nuclear power plant partial loop operation optimization control system, suitable for a multi-loop pressurized water reactor plant capable of switchable partial loop operation, characterized in that, The nuclear power unit's off-loop operation optimization control system includes, in sequence, an operating condition identification module, an off-loop power coordination control module, a nuclear power regulation unit, an electric power regulation unit, and an execution drive unit, all connected in communication. The operating condition identification module is used to collect the operating parameters of each loop of the nuclear power unit, identify the off-loop operating condition, calculate the maximum allowable power of the reactor core under the off-loop operating condition, and perform safety verification and threshold limit on the input power grid target load command. The off-loop power coordination control module is used to receive the grid target load command and the operating condition signal output by the operating condition identification module, and generate core power setting value and electric power setting value adapted to the off-loop operating condition. The nuclear power adjustment unit is used to receive the nuclear power setpoint output by the off-loop power coordination control module after being verified by the operating condition identification module, and generate control rod adjustment commands. The electric power regulation unit is used to receive the electric power setpoint output by the off-loop power coordination control module after being verified by the operating condition identification module, collect the operating parameters of the secondary loop unit, and generate the main steam valve regulation command. The execution drive unit receives control rod adjustment commands and main steam valve adjustment commands respectively, and completes core reactivity adjustment and secondary loop power adjustment accordingly, realizing coordinated control of the primary and secondary loops under the off-loop condition.

2. The nuclear power plant control system of claim 1, wherein, The operating condition identification module has a built-in off-loop condition judgment model. The off-loop condition judgment model uses the deviation rate between the real-time flow rate of each loop and the rated operating flow rate under the current load as the core judgment basis. When the deviation rate meets the preset threshold and the duration reaches the set time, it is judged as an off-loop condition and the signal is output to the power coordination control module, the core power adjustment unit, and the electric power adjustment unit.

3. The nuclear power plant control system of claim 2, wherein, The operating condition identification module also has a built-in flow-weighted temperature calculation module and a power limit calculation module; The flow-weighted temperature calculation module is used to calculate the effective average temperature of the coolant based on the real-time flow weight of each loop under the condition of partial loop operation. The flow weight of abnormal loops is automatically reduced as the flow decreases. The power limit calculation module is used to calculate the maximum allowable power of the reactor core based on the attenuation of the total flow rate of the reactor core under the off-loop condition, combined with the thermal limit parameters of the reactor core and the safety margin, and to impose threshold limits on the target load command of the power grid through low selection logic.

4. The nuclear power plant control system of claim 1, wherein, The off-loop power coordination control module has a built-in nuclear-electric power matching coefficient correction unit. The matching coefficient is dynamically corrected based on the flow deviation rate of the abnormal loop under the off-loop operating condition, and is used to adapt to the heat transfer efficiency change caused by the flow decay of the primary loop. The off-loop power coordination control module outputs the nuclear power setting value and electric power setting value matching the off-loop operating condition based on the corrected matching coefficient, the grid target load command and the maximum allowable power.

5. The nuclear power plant control system of claim 1, wherein, The nuclear power regulation unit includes a coolant average temperature regulation channel, a load setting regulation channel and a nuclear power feedback regulation channel. The coolant average temperature regulation channel uses the maximum value of the full-loop coolant average temperature as the regulation input under normal operating conditions, and switches to the flow-weighted effective average temperature output by the operating condition identification module under partial loop operating conditions. The load setting and adjustment channel has a built-in matching coefficient value correction module that is linked with the off-loop power coordination control module, which is used to adapt to the heat transfer characteristics under off-loop conditions. The nuclear power feedback regulation channel is configured with a nonlinear gain unit adapted to the off-loop operating condition. The gain of the nonlinear gain unit is dynamically adjusted with the total core flow and core power level. When the core power is higher than the maximum allowable power, the maximum gain output is triggered.

6. The nuclear power plant control system of claim 1, wherein, The electric power regulation unit includes a speed control module, an inlet steam pressure and flow limiting module, a load control module, and a weight dynamic allocation module. The speed control module is used to receive the speed signal of the steam turbine generator set and output the speed adjustment signal; The steam inlet pressure and flow rate limiting module is used to collect the pressure and flow rate signals of the main steam pipeline and output the valve opening limit signal. The load control module is used to receive the set value of electrical power and output the main steam valve opening adjustment signal; The weight dynamic allocation module is used to dynamically adjust the adjustment weights of speed control, main steam pressure limit and load control during the initial stage of the off-loop switching and the steady-state operation stage.

7. The nuclear power plant control system of claim 6, wherein, The electric power regulation unit has a built-in primary circuit temperature interlock protection module. When the primary circuit coolant temperature exceeds the limit and shows a continuous upward trend, the temperature interlock protection module triggers the main steam valve operation limit and regulation rate limit.

8. The nuclear power plant control system of claim 1, wherein, The execution drive unit includes a control rod drive mechanism and a main steam valve electro-hydraulic drive system; The control rod drive mechanism is used to receive control rod adjustment commands and drive the control rod to complete core reactivity adjustment, and has a built-in automatic rod drop protection module in case of power failure. The main steam valve electro-hydraulic drive system is used to receive the main steam valve adjustment command, adjust the main steam valve opening to complete the second-circuit electric power adjustment, and has a built-in valve position feedback and fault diagnosis module.

9. The method of claim 1 to 8 for operating a nuclear power plant control system for optimizing the operation of a nuclear power plant control system, characterized in that Includes the following steps: Operating condition identification: Real-time acquisition of flow and temperature parameters of each loop of the nuclear power unit, identification of off-loop operating conditions, calculation of the maximum allowable core power under off-loop conditions, and safety verification and threshold limit of the target load command of the power grid; Power coordination and matching: Based on the identified off-loop operating conditions and the verified target load command, the nuclear power-electric power matching coefficient is dynamically corrected to generate nuclear power setpoints and electric power setpoints that are adapted to the off-loop operating conditions. Nuclear power closed-loop regulation: Based on the nuclear power setpoint and the real-time operating parameters of the nuclear power unit, control rod adjustment commands are generated through three-channel nonlinear control logic to achieve precise closed-loop control of the core power; Electric power linkage regulation: Based on the electric power setpoint and the real-time operating parameters of the second loop, the main steam valve regulation command is generated through the multi-module weight dynamic allocation logic to build a linkage and coordination mechanism between the primary and secondary loops. Execution drive: The execution drive unit completes the coordinated regulation of core reactivity and secondary loop power to achieve stable operation and dynamic load response of the unit under off-loop conditions.

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