Adaptive control of a PWR core power using neural networks

Reactor power control is important because of safety concerns and the call for regular and appropriate operation of nuclear power plants. It seems that the load-follow operation of these plants will be unavoidable in the future. Discrepancies between the real plant and the model used in controller design for load-follow operation encourage one to use auto-tuning and/or adaptive techniques. Neural network technology shows great promise for addressing many problems in non-model-based adaptive control methods. Also, there has been a great attention to inverse control especially in the neural and fuzzy control context. Fortunately, online adaptation eliminates some limitations of inverse control and its shortcomings for real world applications. We use a neural adaptive inverse controller to control the power of a PWR reactor. The stability of the system and convergence of the controller parameters are guaranteed during online adaptation phase provided the controller is near the plant’s real inverse after offline training period. The performance of the controller is verified using nonlinear simulations in diverse operating conditions.     

核反应堆堆芯功率模糊切换控制系统开发及应用

为利用不同类型控制器的性能优势,基于堆芯模糊多模型,利用比例-积分-微分(PID)控制器和模糊控制器,结合T-S型模糊规则设计模糊切换控制器。以三里岛核电站压水堆堆型堆芯为例,建立一套堆芯功率模糊切换控制系统并开展仿真研究。结果表明,与传统PID控制器相比,所设计的堆芯模糊切换控制器更适用于堆芯反应性阶跃扰动和堆芯冷却剂进口温度阶跃扰动下的堆芯功率控制。     

A fuzzy controller design for nuclear research reactors using the particle swarm optimization algorithm

In this paper, a closed-loop fuzzy logic controller based on the particle swarm optimization algorithm is proposed for controlling the power level of nuclear research reactors. The principle of the fuzzy logic controller is based on the rules constructed from numerical experiments made by means of a computer code for the core dynamics calculation and from human operator's experience and knowledge. In addition to these intuitive and experimental design efforts, consequent parts of the fuzzy rules are optimally (or near optimally) determined using the particle swarm optimization algorithm. The contribution of the proposed algorithm to a reactor control system is investigated in details. The performance of the controller is also tested with numerical simulations in numerous operating conditions from various initial power levels to desired power levels, as well as under disturbance. It is shown that the proposed control system performs satisfactorily under almost all operating conditions, even in the case of very small initial power levels.     

Xenon-induced axial power oscillations in the 400 MW PBMR

The redistribution of the spatial xenon concentration in the 400 MW Pebble Bed Modular Reactor (PBMR) core has a non-linear, time-dependent feedback effect on the spatial power density during several types of operational transient events. Due to the inherent weak coupling that exists between the iodine and xenon formation and destruction rates, as well as the complicating effect of spatial variance in the thermal flux field, reactor cores have been analyzed for a number of decades for the occurrence and severity of xenon-induced axial power oscillations. Of specific importance is the degree of oscillation damping exhibited by the core during transients, which involves axial variations in the local power density. In this paper the TINTE reactor dynamics code is used to assess the stability of the current 400 MW PBMR core design with regard to axial xenon oscillations.The focus is mainly on the determination of the inherent xenon and power oscillation damping properties by utilizing a set of hypothetical control rod insertion transients at various power levels. The oscillation damping properties of two 100%-50%-100% load-follow transients, one of which includes the de-stabilizing axial effects of moving control rods, are also discussed in some detail.The study shows that, although first axial mode oscillations do occur in the 400 MW PBMR core, the inherent damping of these oscillations is high, and that none of the investigated load-follow transients resulted in diverging oscillations. It is also shown that the PBMR core exhibits no radial oscillation components for these xenon-induced axial power oscillations.     

T-S型模糊切换控制器在堆芯功率控制中的应用#br# #br#

The traditional PID controller is used to control the core power, which has the problems of large overshoot and long regulating time in the control process. In order to solve this problem, based on the core transfer function model, the PD controller, the PID controller and the fuzzy controller are weighted and switched by T-S fuzzy rules, and T-S fuzzy switching controller is designed. Taking the core power control of a lead cooled fast reactor as an example, a T-S fuzzy switching control system of the core power is established to simulate the relative power setpoint value step and the core inlet coolant temperature disturbance. The results show that the T-S fuzzy switching controller designed based on the core transfer function model can achieve a good control of the core power.     

稳压器水位控制改进研究

现代的反应堆稳压器的水位控制大都采用的是传统的PI调节器,对于这样一个非线性和时变性的复杂控制系统,PI调节器表现出来的常常是超调量大、调节时间长等并不理想的效果.本文提出以智能模糊控制器取代原有常规PI控制器的改进方案,并以大亚湾一期工程反应堆控制系统的稳压器水位控制为研究对象,着重阐述智能模糊控制原理在具体实践中的使用方法,最后对改造前后的系统输出进行LabVIEW仿真比较.仿真结果表明,模糊PI调节器不但克服了常规PI调节器的缺点,而且还提高了控制系统的实时性和抗干扰能力,值得广泛采用.     

固态燃料熔盐堆自适应功率控制器设计及分析

钍基熔盐堆核能系统(Thorium-based Molten Salt Reactor,TMSR)是中国科学院首批启动实施的战略性先导科技专项,旨在研发第四代反应堆核能系统。固态燃料钍基熔盐实验堆(The Solid Fuel Thorium-based Molten Salt Experimental Reactor,TMSR-SF1)是一个10 MW热功率的氟盐冷却球床堆,目前已经完成方案设计和初步工程设计。功率控制系统是反应堆一个关键控制系统,实现反应堆正常启动、功率运行和正常停堆功能,对保证反应堆安全和稳定运行起着极其重要的作用。根据TMSR-SF1运行控制要求,结合自适应控制理论,基于Lyapunov稳定性理论设计了一种TMSR-SF1模型参考自适应功率控制器。基于TMSR仿真平台,使用MATLAB/Simulink建立了自适应功率控制系统模型,并开展了控制器特性分析。结果表明,自适应功率控制器具备良好的负荷跟随能力,抗干扰能力强、稳定性好、可靠性高,能够满足TMSR-SF1功率控制的要求,确保堆芯的输出功率与功率设定值相匹配。     

基于变论域模糊PID的液态熔盐堆堆芯功率控制

液态熔盐堆堆芯系统具有非线性、时变性等特点,模糊比例积分微分(PID)控制技术因初始论域不能跟随误差变化而伸缩,使得系统的控制精度降低,故设计了一种基于变论域模糊PID控制器的堆芯功率控制策略。以熔盐增殖堆MSBR堆芯为例,在堆芯入口温度扰动或堆芯反应性扰动下,使用Matlab/Simulink对PID控制、模糊PID控制与变论域模糊PID控制下的效果进行仿真对比。结果表明,基于变论域模糊PID控制器建立的堆芯功率控制系统响应速度更快,超调量更小,控制效果更佳。     

Comparison between a continuous and a discrete method for the aggregation and deffuzification stages of a TRIGA reactor power fuzzy controller

This paper presents a comparison of the performance of two different methods to realize the aggregation and the centre of gravity stages of a fuzzy controller that is under development for its integration, as an alternative power control algorithm, in the control console of the TRIGA Mark III reactor of the Mexican Nuclear Centre. In one case, an innovative method determines, in every control cycle, the group of lines that define the fuzzy aggregated set of the rule base in the continuous domain of the output variable. Likewise, the centre of gravity of this aggregated set is analytically obtained, and the corresponding controller is named exact or continuous. In the other case, a method is used to determine, in one step, both the aggregated set and its centre of gravity using the classical discretization of the universe of discourse of the output variable, thus leading to the discrete fuzzy controller. These methods were simulated in the ascent and regulation of neutron power in a TRIGA Mark III reactor. The performance parameters used for the comparison between the two methods were: The required number of floating point operations, the time required to attain a certain power level, the neutron power time response, and the reactor period values.     

Emotional learning based intelligent controller for a PWR nuclear reactor core during load following operation

The design and evaluation of a novel approach to reactor core power control based on emotional learning is described. The controller includes a neuro-fuzzy system with power error and its derivative as inputs. A fuzzy critic evaluates the present situation, and provides the emotional signal (stress). The controller modifies its characteristics so that the critic’s stress is reduced. Simulation results show that the controller has good convergence and performance robustness characteristics over a wide range of operational parameters.     

核反应堆模糊PID控制的实验模拟系统

在核反应堆实验模拟系统上进行了核反应堆模糊ＰＩＤ控制的研究,研究结果表明：采用模糊ＰＩＤ控制器控制核反应堆系统,在负载改变时能较快抑制冷却剂温度变化,稳态精度高,可以达到很好的控制效果。     

压水堆负荷跟踪的模糊控制系统

模糊控制理论的发展促进了模糊控制器在压水堆负荷跟踪中的应用。用模糊逻辑控制器和常规ＰＩＤ（比例－积分－微分）控制器相结合，并以输出增闪随功率调整的策略，解决了反应堆负荷跟踪问题，本方法解决了时变非线性对象的闭环控制并克服了基于模型的控制方法的不足，仿真结果显示本文提出的方案不但具有优良的动态特性，而且具有很高的稳态精度，使负荷跟踪控制的自动化程度大为提高。     

T-S型模糊切换控制器在堆芯功率控制中的应用

采用传统比例-积分-微分(PID)控制器开展堆芯功率控制,控制过程中存在超调量大、调节时间长的问题。为解决这一问题,基于堆芯传递函数模型,采用T-S型模糊规则对比例-微分(PD)控制器、PID控制器、模糊控制器进行加权及切换,设计T-S型模糊切换控制器。以铅冷快堆堆芯功率控制为例,建立堆芯功率T-S型模糊切换控制系统,开展堆芯相对功率设定值阶跃、堆芯冷却剂进口温度扰动仿真。结果表明,基于堆芯传递函数模型设计的T-S型模糊切换控制器可以实现对堆芯功率的良好控制。     

Design of an intelligent fuzzy logic controller for a nuclear research reactor

The main objective of this paper is to design an intelligent controller system based on the concepts of fuzzy logic. This latter will be used to control the power of a nuclear reactor. The principle of this controller is based on rules established from experiments used with a classical controller and from the knowledge and the expertise of the operators of the reactor. This intelligent controller could be used in parallel with the actual system, which is semiautomatic, as a decision aided system to assist the operators in the control room.     

Fuzzy Logic Control Application for BWR Recirculation Flow Control System

There has been increasing necessity for load following and/or AFC (Automatic Frequency Control) operation along with the growth in the share of nuclear power generation in the electric power network. Fuzzy logic control was investigated for application to a BWR recirculation flow control system, in order to obtain a rapid generator power response within an allowable neutron flux overshoot. The proposed controller has two control loops, generator power and neutron flux loop. The fuzzy logic is utilized for weighing these control loops and for controlling the neutron flux. By evaluating the controller performance by numerical simulations on the step response for generator power demand with the model BWR recirculation flow system, more rapid response was obtained than that for conventional proportional plus integral controllers with no neutron flux overshoot beyond alarm activation level.     

A neuro-fuzzy controller for axial power distribution an nuclear reactors

A neuro-fuzzy control algorithm is applied for the core power distribution in a pressurized water reactor. The inputs of the neural fuzzy system are composed of data from each region of the reactor core. Rule outputs consist of linear combinations of their inputs (first-order Sugeno-Takagi type). The consequent and antecedent parameters of the fuzzy rules are updated by the backpropagation method. The reactor model used for computer simulations is a two-point xenon oscillation model based on the nonlinear xenon and iodine balance equations and the one group, one-dimensional neutron diffusion equation having nonlinear power reactivity feedback. The reactor core is axially divided into two regions, and each region has one input and one output and is coupled with the other region. The interaction between the regions of the reactor core is treated by a decoupling scheme. This proposed control method exhibits very fast response to a step or a ramp change of target axial offset without any residual flux oscillations between the upper and lower halves of the reactor core.     

高温气冷堆核蒸汽供应系统出口蒸汽温度的T-S模糊控制方法

高温气冷堆（HTGR）是国际核能界公认的一种具有良好安全特性的堆型,具有第四代核能系统的技术特征,其核蒸汽供应系统（NSSS）复杂的非线性特性,对控制策略的设计提出了挑战。另一方面,T-S模糊控制方法在复杂非线性系统的控制方面存在巨大优势,因此在高温气冷堆核蒸汽供应系统中应用T-S模糊控制方法,可能会获得较传统线性控制方法更好的控制性能。本文提出了一种T-S模糊控制器的系统化设计方法,首先建立高温气冷堆核蒸汽供应系统出口蒸汽温度的T-S模糊控制系统模型;然后基于李雅普诺夫方法,得到T-S模糊控制系统的双线性矩阵不等式（BMI）形式的全局渐近稳定条件;最后通过局部最小化算法求解双线性矩阵不等式,得到T-S模糊控制器的参数。仿真结果表明,按照这一系统化方法设计的T-S模糊控制器较传统的线性PI控制器表现出更好的控制特性。     

Design and optimization of fuzzy-PID controller for the nuclear reactor power control

This paper introduces a fuzzy proportional-integral-derivative (fuzzy-PID) control strategy, and applies it to the nuclear reactor power control system. At the fuzzy-PID control strategy, the fuzzy logic controller (FLC) is exploited to extend the finite sets of PID gains to the possible combinations of PID gains in stable region and the genetic algorithm to improve the ‘extending’ precision through quadratic optimization for the membership function (MF) of the FLC. Thus the FLC tunes the gains of PID controller to adapt the model changing with the power. The fuzzy-PID has been designed and simulated to control the reactor power. The simulation results show the favorable performance of the fuzzy-PID controller.     

核电厂低功率时蒸汽发生器水位的模糊控制

本文针对压水堆核电厂在低功率运行时蒸汽发生器水位控制容易造成停堆的实际情况，提出了蒸汽流量的估算方法，设计了以模糊控制为核心的水位控制器。模糊控制器的输入信号是水位偏差，以及通过对核电厂中所测得的具有一定精度的变量进行综合计算得出的流量偏差，它们的隶属度函数分别由流量偏差和水位偏差决定。分析表明，该控制器在核电厂低功率运行时能够有效的控制蒸汽发生器水位．可避免水位的大幅度脉动与紧急停堆，对提高的可用性、减少不必要的停堆有积极的意义与工程实用价值。     

液态熔盐堆堆芯功率模糊PID控制

液态熔盐堆采用熔融氟化盐为燃料,燃料熔盐出口温度是衡量熔盐堆安全的重要指标。通过堆芯功率控制可实现燃料熔盐出口温度控制。将液态熔盐堆堆芯划分成内区和外区,并基于能量守恒原理建立堆芯非线性模型,采用微扰理论对非线性模型进行线性化。基于堆芯线性化模型,采用模糊比例-积分-微分(PID)控制器设计堆芯功率控制系统。以熔盐增殖堆(MSBR)为例,开展堆芯功率控制仿真。结果表明,引入10^-3、2×10^-3阶跃反应性时,模糊PID控制器可以减小系统响应的上冲幅度和超调量,并且在堆芯功率发生了较大的负荷变化时,模糊PID控制器可以对堆芯功率的变化实现良好跟踪。故所采用的模糊PID控制器具有良好的动态性能,可实现对堆芯功率的良好控制。