Research On Fuzzy-I Control System Of Steam Generator Level And It's Semi-physical Simulation

Steam Generator (SG), an important heat exchanger that connects pressured water reactor's primary circuit with secondary circuit, is considered the intersection of primary circuit and secondary circuit. SG level control system, a kind of multi-input single-output system with the character of nonlinearity and time varying, is one of the most complex systems of nuclear power plant. Due to the existence of so-called "fake level", it is hard to control SG level satisfactorily by traditional PID methods. The fuzzy control technology does not rely on the mathematic model and has excellent robustness characteristics. It is fit for the control of SG level.On the basis of study SG's operating rules, a two layers fuzzy controller includes the "fake level" identifying process and the three-dimensional water control process for SG level is proposed according to domain expert's knowledge and the characteristics of "fake level" during different phases. In the course of "fake level", the influence of the level error is weakened to maintain the stabilization of the feedwater flux. Then change the feedwater flux according to the level error if the "fake level" course is ending.The change of steam flux and the changing rate of steam flux are designed as the inputs of the first fuzzy layer to identify the "fake level", while the changing trend of water level that affected by the change of steam flux is designed as the output of the first fuzzy layer. Subsequently, the output of the first fuzzy layer, the level error, and the error rate are the inputs of the fuzzy controller's secondary layer. The final output of the fuzzy controller is the feedwater flux. The output range of the feedwater flux is centering on the steam flux, with the aim to realize the rapidly control of the dynamic process and maintain the stability of SG Because of the intrinsic disadvantage of fuzzy controller, it can hardly eliminate the static error. So a kind of FUZZY-I controller which combines fuzzy controller with traditional three parameters integral controller are constructed to improve the capability of the control system.In addition, based on the analysis of different parameters which have effect on the character of the system, this paper proposed a revising function for online parameter self-adjustment of the level error and the error rate in order to meet the request of fuzzy control system towards Ke and Kc during different level phases. To get self-adaptability, a revising function is also designed to dynamically adjust the integral factor according to the secondary level excess of the system.The FUZZY-I controller for SG is put into effect on the hardware structure based on the Digital Signal Processor. The fuzzy system and the fuzzy controller's algorithmic subprograms are developed utilize the Computer-Aided fuzzy system designing tool FuzzyTECH. The other subprograms and the main program are developed by C language and assemble language under the professional TDS EMUEX DSP hardware simulation environment. The framework of the main program and the filtering subprogram are presented, and the steps to design the fuzzy system with FuzzyTECH software are described.The semi-physical simulation system of SG level is constructed. It consists of the FUZZY-I controller of SG level, digital simulating model, data sampling board, signal transforming circuit board, switching circuit board, electric executer, etc. The interfacing program of the data sampling board is designed at the same time. A lot of experiments about the disturbance of steam flux, the disturbance of feedwater flux and the frequency disturbance of steam flux have been done under various working states utilizing the parameter self-adjustment integral controller, two layers fuzzy controller and FUZZY-I controller separately. The results of the experiments show that the FUZZY-I controller combines good qualities of integral controller and fuzzy controller and meets the requirement of the system.