(A) study of fuzzy logic controller for water level control of the PWR steam generator

Abstract

In nuclear power plants, the fault-tolerant controller has been sought to operate components as means of over coming barriers confronting automation, especially in augmenting safely functions. In this paper, a new aproach of the controller, fuzzy controller, is proposed here for the steam generator water level control. The fuzzy control is composed of four elements;Fuzzification, Fuzzy control rule, Decision making and Defuzzification. In fuzzification, nonfuzzy variables are fuzzified into fuzzy variables. In this study, the fuzzy singleton variables are used, because of the facility of implementation and wide use in fuzzy control approach. In the fuzzy control rule part, the control rule is made using th fuzzy set theory, the expert knowledge-base and the control engineer knowledge. That control rule is standard of control action in the fuzzy controller. In this study, the control rule design method is proposed in steam generator water level control. In the decision making part, decision is made using fuzzy control rule, fuzzified controller input, fuzzy set theory and the membership of states. In the defuzzification part, the nonfuzzy output is made using the decision making output. The output is transported into the controlled system input. For plant simulation, the model of steam generator is based on a simplified transfer function. However, the simplified model has the same magnitude of swell and shrink effects. In this study, the steam generator model is redesigned so that the swell magnitude may be larger than that of shrink. From the simulation results, the fuzzy control shows that the fuzzy controller can reduce the swell and shrink and be robust at any power. Using fuzzy logics, the knowledge which an expert and a control engineer have about a system model through their experience, training and learning of system operation, is implemented as a controller.