Mathematical model of steam generator feed system at power unit of nuclear plant

A mathematical model of a steam generator feed system at a power unit of a nuclear plant with variable values of transfer function coefficients is presented. The model is realized in the MATLAB/Simulink/Stateflow event-driven simulation.     

核动力装置蒸汽发生器水位的分层模糊自适应控制

针对压水堆核动力装置蒸汽发生器的水位控制提出一种分层模糊自适应控制方案，该方案中2个模糊控制器分层连接，每个模糊控制均采用典型模糊控制单元，使得模糊规则个数和可调参数个数大大减少，便于在线学习和实时控制，给出了分层模糊控制器的解析表达式及可调参数的在线学习方法，在快速加负荷和突然甩负荷的仿真实验中，该方案的控制效果明显优于已有的变参数PID控制，验证了该方案的有效性。     

M310核电机组影响蒸汽发生器液位测量通道的因素分析

根据蒸汽发生器（sG）液位测量系统的工作原理和现状,结合检修、运行积累的经验和数据,对影响液位测量通道的因素进行分析及计算,重点剖析了四个窄量程液位变送器在不同功率平台出现指示偏差较大的异常情况及原因,提出了相应的处理意见,以期达到能改善仪表工作现状,减少蒸汽发生器水位控制波动造成严重后果的机率。     

一个直实化工厂蒸汽网络系统的建模与优化

对蒸汽网络系统进行建模与优化,可以在系统配置和操作条件满足公用工程要求的前提下,以最小产汽量为目标,实现化工厂的节能运行.本文利用在一个真实化工厂现场调研得到的实际数据,对该化工厂的蒸汽网络系统进行建模,得到LP(线性规划)和MINLP(混合整数非线性规划)模型,用线性规划算法和改进文化差分算法分别对模型进行求解,并与现场实时数据和LINGO计算结果进行对比.计算结果显示,MINLP模型更好的描述了该蒸汽网络系统,并达到了可观的优化效果,可在满足生产需求的条件下,减小锅炉产汽量和放空量,达到降低成本、提高经济效益的效果.     

Self-tuning control application to a nuclear power plant

The aim of this paper is to investigate the application possibilities of a self-tuning control method to a pressurized-water reactor (PWR) nuclear power plant. A self-tuning control algorithm which incorporates pole assignment into the generalized minimum variance strategy with a particular form of cost function is employed. This algorithm enables closed-loop system stability characteristics to be readily specified and facilitates reference following. The control system design is based on a second-order linear model with unknown, time-varying parameters. To ensure that this low-order model describes the complex real dynamics well enough for control purposes, control parameters are updated on-line with a recursive estimation sequences of the extended least-squares method. Weighting polynomials are also adjusted on-line to keep closed-loop poles at the desired location and to satisfy the zero steady-state condition and disturbance rejection. The purpose of this control system is to hold the average coolant temperature in the reactor as near as possible to a desired but changing reference value in the load-following mode of the nuclear power plant. The position of the control rods is an appropriate control variable. Simulation results are very successful and show the possibilities of the adaptive control application to actual plants.     

炼油企业蒸汽动力系统改造优化研究

针对当前形势下炼油企业蒸汽动力系统存在的巨大改造潜力,提出了蒸汽动力系统改造的优化方法;该方法首先通过运行优化方案分析和系统设备诊断找出系统存在问题,然后通过专家知识系统提出一系列解决的方案,建立系统改造方案的超结构和考虑柔性调节的优化改造混合整数线性规划(MILP)模型,求解模型并确定最优的改造方案;文章最后部分给出了详细的案例分析,结果表明应用本文提出的改造优化策略方法确定的最佳改造方案可以为案例背景炼油企业蒸汽动力系统节约大约6%的运行费用,投资回收期约0.38年;本文提出的优化改造方法为推动炼油企业蒸汽动力系统的节能降耗提供了定的理论指导和技术支持.     

Dynamic behaviour of material states in steam power plant control

The enormous price increase in petroleum and the limited reserves of other fossil fuels have resulted in the increased use of nuclear power plants for the basic load of electricity supply. Consequently, conventional steam power plants have been used to meet the variable and peak loads in electricity generation. The control of fast and large load changes is becoming more and more important for conventional power plant operations. An economical control of the nonstationary operation (start-up, shut-down and large load changes) is possible only by approaching and maintaining the maximum allowable values of the material state variables (temperature θ, strain ? and stress σ) at the critical points of the power plant components. To achieve this primary control goal, the dynamic behaviour of material states must be well understood. A direct measurement of the changes in material states especially due to thermal stresses, caused by temperature gradients, is not possible. The material states can be calculated, however, by means of mathematical models describing the nonstationary temperature distribution. The working fluid temperature, pressure and mass flow rate are the input variables for these mathematical models. This paper presents a linear mathematical model for the investigation of the dynamic behaviour of material states. Another mathematical model is also developed for calculating the thermal stresses for large temperature and load changes. Thus, the steam generator models so far describing only the states of the working fluid can be extended to the material states. The basic idea is demonstrated for an insulated thick wall tube containing a working fluid. The simulation of the mathematical models is performed.     

Development of a digital turbine control system in a nuclear power plant

A digital turbine control system (TCS) has been developed for retrofitting an old analog TCS in a nuclear power plant. The developed TCS, which controls the speed of a turbine and the power load of a generator, is based on a triple modular redundant structure to ensure the system reliability. In addition, a turbine simulator has been developed to verify the perfection of the TCS prior to its actual installation. The simulator is composed of a graphic editor, a component model builder, and a system simulation solver. The tested TCS has been successfully applied to a CANDU type nuclear power plant. This paper describes major features of the developed TCS and the turbine simulator including thermal-hydraulic models. Also, the simulation result in a laboratory is compared with the pre startup simulation and the actual operation result. Recommended by Editor Hyun Seok Yang. In-Kyu Choi was born in Jeonjoo, Korea in 1967. He obtained his Master’s degree in Electrical Engineering from Chungnam National University in 2004. His research interests include control in power plant machines such as boilers, drums, turbines, and generators. He is now a Senior Member of the KEPCO Research Institute. Jong-An Kim received the B.S. degree in Electronic Engineering from Won-Kwang University, Ik-San, Korea in 1985. He joined the Korea Electric Power Corporation (KEPCO) in 1976, and has mainly worked in the control systems engineering areas of power plants. He is now a Principal Engineer in the Korea Electric Power Research Institute (KEPRI) and his research interests include the design of power plant control systems as well as new technology development. Chang-Ki Jeong was born in Daejeon, Korea in 1956. He obtained his Master’s degree in Electrical Engineering from Daejeon Industry College in 1998. His research interests include control in power plant machines such as boilers, drums, turbines, and generators. He is a Principal Member of the KEPCO Research Institute. Joo-Hee Woo was born in Sangjoo, Korea in 1970. He obtained his Master’s degree in Electrical Engineering from Kyungbook National University in 1995. His research interests include control in power plant machines such as boilers, drums, turbines, and generators. He is now a Senior Member of the KEPCO Research Institute. Ji-Young Choi received the B.S. degree in Mechanical Engineering from Sogang University in 2005. He is a graduate student of the Department of Mechanical Engineering at Sogang University in Seoul, Korea. Choi’s research interests are in the areas of heat transfer, PEM fuel cells, and microfluidics. Gihun Son received the B.S. and M.S. degrees in Mechanical Engineering from Seoul National University in 1986 and 1988, respectively. He obtained the Ph.D. degree in Mechanical Engineering from UCLA in 1996. Dr. Son is currently a Professor in the Department of Mechanical Engineering at Sogang University in Seoul, Korea. His research interests are in the areas of multiphase dynamics, heat transfer, and power system simulation.     

韶关发电厂#8机组DCS系统网络优化

针对韶关发电厂#8机组DCS系统所存在的DPU离线和MMI站死机或自动重启问题进行研究,通过网络升级改造,将原有的FDDI／CDDI网络移植到FE（快速以太网）网络,最终解决了DCS系统的DPU离线、MMI站死机或自动重启这一顽症。     

Improving power network stability and unit stress with adaptive generator control

The ‘steady state stability’ of the French power transmission system has been greatly improved by supplying additional signals to the voltage regulator. The control system parameters, including the additional signals, have been chosen in order to cover all the possible operating conditions and network configurations. These additional signals lead to an increase in the ‘steady state stability’ domain even with a regulator having constant parameters. Better results have been obtained using the model reference adaptive control method with an adjustable regulator. A method based on the ‘hyperstability’ approach has been used for the design of the adaptive control system because of its efficiency. Moreover, the adaptive control of generator excitation, using voltage, speed and active power as input signals, reduces the oscillations of the H.P. turbine valves when the generator is affected by network perturbations. Therefore, the wear of the units, in particular of nuclear units, could be reduced. The principles of this new type regulator are discussed and experimental results are presented.     

Soft computing based multi-objective optimization of steam cycle power plant using NSGA-II and ANN

In this paper a steam turbine power plant is thermo-economically modeled and optimized. For this purpose, the data for actual running power plant are used for modeling, verifying the results and optimization. Turbine inlet temperature, boiler pressure, turbines extraction pressures, turbines and pumps isentropic efficiency, reheat pressure as well as condenser pressure are selected as fifteen design variables. Then, the fast and elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) is applied to maximize the thermal efficiency and minimize the total cost rate (sum of investment cost, fuel cost, and maintenance cost) simultaneously. The results of the optimal design are a set of multiple optimum solutions, called ‘Pareto optimal solutions’. The optimization results in some points show 3.76% increase in efficiency and 3.84% decrease in total cost rate simultaneously, when it compared with the actual data of the running power plant. Finally as a short cut to choose the system optimal design parameters a correlation between two objectives and fifteen decision variables with acceptable precision are presented using Artificial Neural Network (ANN).     

Developing a taxonomy of coordination behaviours in nuclear power plant control rooms during emergencies

Abstract

This study aims to develop a taxonomy of coordination behaviours during emergencies in nuclear power plants (NPPs). We summarised basic coordination behaviours from literature in aviation, health care and nuclear field and identified coordination behaviours specific to the nuclear domain by interviewing and surveying control crew operators. The established taxonomy includes 7 workflow stages and 24 basic coordination behaviours. To evaluate the reliability and feasibility of the taxonomy, we analysed 12 videos of operators’ training sessions by coding coordination behaviours with the taxonomy and the inter-rater reliability was acceptable. Further analysis of the frequency, the duration and the direction of the coordination behaviours revealed four coordination problems. This taxonomy provides a foundation of systematic observation of coordination behaviours among NPP crews, advances researchers’ understanding of the coordination mechanism during emergencies in NPPs and facilitate the possibility to deepen the understanding of the relationships between coordination behaviours and team performance.

Practitioner Summary: A taxonomy of coordination behaviours during emergencies in nuclear power plants was developed. Reliability and feasibility of the taxonomy was verified through the analysis of 12 training sessions. The taxonomy can serve as an observation system for analysis of coordination behaviours and help to identify coordination problems of control crews.     

Real-time optimization of a hydroelectric power plant

An optimal control problem modelling a hydroelectric power plant was developed and discussed by Hj. Wacker and his co-workers in [1]. In the present paper, this problem is treated within a more general framework of “non-differentiable” optimal control problems. Necessary conditions of optimality are derived and it is proven that the restricted class of controls considered in [1] indeed contains the optimal control. Furthermore, a decoupling technique is established that allows the full problem to be split into several small subproblems. Based on the new results, an efficient algorithm is developed. This algorithm allows the optimal control to be computed for more general problems with greater accuracy and for a longer time period. Numerical results are given both for the model described in [1] and for the more refined model presented in this paper.     

热采锅炉配风自动控制系统

分析了国产热采锅炉配风系统存在的问题,设计了烟气含氧量自动控制系统,实现热采锅炉最佳配风,并取得了满意的应用效果。     

Sensor fault detection and isolation in a thermal power plant steam separator

A fault detection and isolation approach, specially designed for steam separators in thermal power plants, is presented in the paper. The first step of the proposed algorithm is to identify the process. Because of the presence of sporadic high-intensity measurement noise (outliers), the paper proposes a robust version of recursive identification. Starting from the parameter vector of the identified model, the second step of the proposed procedure has the form of a data-driven fault detector. This particular fault detection and isolation approach was implemented at TEKOB1 Kostolac Thermal Power Plant in Serbia, whose nominal power output is 330 MW.     

Robust controller design for simultaneous control of throttle pressure and megawatt output in a power plant unit

This paper presents an application of H_∞ and μ-synthesis controller design methods to a coal-fired power generation unit and compares the closed-loop performance and robustness of H_∞ and μ-synthesis control laws with those of an H₂ control law. The model which relates firing rate and turbine valve position inputs to throttle pressure and megawatt outputs presented by Ollat and Smoak in an earlier work is modified to match the test data from a Tennessee Valley Authority (TVA) power generation unit. All three controller synthesis procedures are applied to a two-input two-output plant model which has time delay, differential part, colored noise output disturbance, and sensor noise disturbance. Application of the procedures to the model shows that when the shape of the closed loop control signals of all three designs is closely matched, in the low-frequency range the μ-synthesis and H_∞ control laws have robustness much better than that of H₂ control law, while providing adequate robustness in the high-frequency range. H_∞ control law gives the best performance, and H₂ – the worst of the three designs, exhibiting the largest overshoot. The balancing procedure permits significant reduction of the order of the controllers without degradation in performance and robustness. The comparative evaluation of three designs shows that in power plant control problem H_∞ and μ-synthesis designs provide much more consistent and convenient performance/robustness trade-off than H₂ design. Copyright © 1999 John Wiley & Sons, Ltd.     

Modal control of a nuclear power reactor

The control scheme developed is based on a nonlinear axial model of the reactor using the diffusion theory of neutrons. The model is valid for a time period in which the reactor changes from one power level to another. The controlled variable is the axial distribution of the neutron density; the control variables are the positions of several partly or fully absorbing (generating) control rods. The control scheme is designed to control the eigenfunctions of the reactor. It is able to control the total power as well as the axial power distribution in the core of the reactor. Because the controller is developed using the nonlinear system equations, it is independent of the operating power level of the reactor. Furthermore the control scheme is very simple and relatively insensitive to parameter changes of the plant, so that it is well suited for practical use.     

核电站仪表控制系统检修平台的开发

Bailey系列模块是广东核电集团的100万千瓦级核电站一回路过程仪表控制和保护系统的主体。核安全的重要责任和安全生产的任务,都要求Bailey模块可靠、稳定和安全运行。但是,由于备件、老化以及产品升级等原因使得Bailey模块的维护存在不小的困难。本文阐述了如何设计一种集信号的采集、发生、数据的分析处理、参数的校正、自动选择跳线功能于一身的小型专用的校验设备-Bailey系列模块综合试验台。该设备主要设计在实验室使用(也可用于现场操作),可以自动(也可以选择手动方式)实时地控制Bailey9020系列模块的输入信号,并对Bailey9020系列模块输出数据的进行实时显示、分析和处理,可记录测试数据和打印规定格式的报表。Bailey系列模块综合试验台作为一种小型化多功能的专用校验设备,在设计思想上具有独到之处。同时它作为适用性强的国产专用设备,在生产实践以及实现广核国产化方面作出了贡献。