Study On Fault Tolerant Control Method For Reactor Control System

The reactor control system includes a large number of sensors and actuators. It is oneof the important systems which can ensure the nuclear power plant to secure and stableoperation. At present, the nuclear power plant mainly makes use of the hardwareredundancy fault-tolerant control technology to ensure that system can still run normally inthe control equipment failure occurs. This technology not only needs a lot of money, butalso will pruduce a lot of problems about reliability and safety in design and constructionstage. When the intelligent control technology such as artificial neural network technologyand fuzzy logic control technology is used to carry through fault-tolerant control for thereactor control system, it will greatly improve the defects of using the hardware redundancymethod. So studying the fault diagnosis and fault-tolerant control methods for the reactorcontrol system, it is the very vital significance that improve safety, reliability and economyof the nuclear power plant.In this paper, the reactor control system will be as the research object. Against thecontrol equipment fault in different power operating condition, the fault-tolerant controltechnology and method of the reactor control system will be analyzed and studied from thefollowing aspects.Firstly, the reactor control system is studied. Respectively on the pressurizer pressurecontrol system, the pressurizer water level control system and the steam generator water levelcontrol system are analyzed, and studied the function and characteristics of the control system,the relationship among various parameters and the change law of various parameters.Meanwhile, the sensor and actuator is studied in typical fault model, and analyzes the requiredconditions of the fault model mutual transformation between the two control equipment.Secondly, several kinds of fault-tolerant comtrol design methods are studied. Severalcommon types of the passive fault-tolerant control method and the active fault tolerantcontrol method are analyzed. It will respectively study the fault-tolerant design methodbased on the Riccati equation, the fault-tolerant design method based on the control ratereconfiguration and the fault-tolerant design method based on the state feedback controller.It mainly analyzes their application condition, the design process of fault-tolerant controland points out its shortcomings. On this basis, the fault-tolerant control method based on BP neural network is studied. Inview of the standard BP neural network algorithm has the slower convergence speed, easy tofall into local minimum point and can not get the global optimal, the BP neural networkalgorithm will be improved by increasing the momentum, improving the transform function,improving the error signal and changing the learning rate. Through simulation experiment, itis shown that the improved BP neural network algorithm can effectively improve theconvergence speed and obtain the global optimal. And then, it determines the fault-tolerantcontrol scheme and establishes the dynamic model library. For the known fault, the systemcan automatically identify fault model, at the same time carry through fault-tolerant control bythe control rate reconfiguration unit. For the unknown fault, the system will use the modelidentification method, and the new fault model will be stored into the dynamic model libraryto continuously improve on it. The pressurizer pressure measuring sensor will be as theresearch object in the simulation experiment. In three kinds of power operating condition (theoperating condition of power at100%，the operating condition of power from100%to90%and the operating condition of power from100%to90%), the simulation experimentsimulates the sensor fault of the locked and the constant deviation. The simulationexperimental results show that the fault-tolerant control method based on the improved BPneural network algorithm can effectively correct the pressurizer pressure measuring sensorfault. The steam generator pressure measuring sensor will be as the research object to validatethe method. The simulation experimental results show that this metnod is equally effective tocorrect the steam generator pressure measuring sensor fault.Finally, the fault-tolerant control method based on fuzzy neural network is studied. Inview of the physical meaning of the artificial neural network connection weights is not clear,and its knowledge to explain difficultly, the fuzzy neural network method will be used forfault-tolerant control by combining with the artificial neural network and fuzzy logic control.The simulation experimental will adopt the pressurizer water level measuring sensor as theresearch object. The simulation experimental results show that using this method can get thecredibility of sensor in real time, and the method can effectively correct the pressurizerwater level measuring sensor fault.