Study On Fault Tolerant Control Method For The Control System Of Water Level In Steam Generator

Steam generator is the important heat exchanger in nuclear power plant, whose water level directly affects the safe and reliable operation of nuclear power plant. There are plenty of sensors and actuators in the control system of water level in steam generator, which will malfunction inevitably due to the fatigue of equipment and the changes of internal and external circumstances during the long-term operation. At present,the method of hardware redundancy is generally used in fault tolerant processing in nuclear power plant, which not only demands substantial capital investment, but also leads to security and reliability problems in the design and construction phase. However, the development of fault tolerant control technology to a great degree improves the defects caused by hardware redundancy. So,it is of great value for improving the security, reliability and economy of the nuclear power plant that researching on the fault tolerant control methods for steam generator water level control system.The steam generator of nuclear power plant is taken as the research object, the fault diagnosis and fault tolerant control technology for the control system of water level in steam generator is studied and the corresponding graphical user interface is developed according to each kind of fault of water level sensor in different cases.Firstly, the steam generator model was built by analyzing the operation principle of steam generator, using the piecewise linear mathematical model proposed by E.Irving.Meanwhile, the classical three impulses water level control system was built and realized effective control of water level by studying the characteristics of water level in steam generator.Secondly, the fault diagnosis system for water level sensor was built by using BP neural network, basing on the analysis of sensor fault mode and research on water level response characteristics under each kind of water level sensor fault condition. Multiple neural networks were trained by fault data of simulation model in this paper, whose outputs were integrated and processed to realize state detection and fault diagnosis for steam generator water level control system.Lastly, the fault tolerant design method based on state feedback controller was researched, by which the control law reconfiguration method of cascade control system was derived. According to different fault feature, the fault tolerant control system of water level in steam generator was built by using the control law reconfiguration method of cascade control system and the fault tolerant control method based on active compensation, which is not necessary to get the mathematical model of research object, and overcomes the bottleneck that the traditional method based on observer or filter is over dependent on mathematical model,and is generally applicable to other nonlinear system, and has good anti-interference ability after fault. At the same time, a friendly and concise interface was developed, which can organize and display the information of fault tolerant control system effectively, and improve the system efficiency greatly.