The Fuzzy Variable Structure Control For The Once-Through Stream Generator

A once-through stream generator is important equipment in nuclear power plant, so its control level is higher. In this paper, the mathematics model of some spiral once-through stream generator is studied, and according to the model and the dynamic characteristic two control systems are devised: the cascade feedforward-feedback control system and the fuzzy variable structure control system. These main jobs completed are included:The cascade feedforward-feedback control system of the once-through stream generator is advised. The feedforward-feedback control can quickly and timely overcome some main disturbance, and the feedback control can overcome others, so the controlled value can quickly and accurately reach to the given one. Thus we adapt the cascade feedforward-feedback controller.The fuzzy variable structure control system is advised. A fuzzy variable structure controller inherits the robust characteristics of sliding mode control and interpolation property of fuzzy logic control. The robustness property of variable structure system makes the control system insensitive for different burthen variety and different outside disturbance. Fuzzy control predigests the device of control system and alleviates the chattering which variable structure system causes .So the control system can be made more ideal. The paper describes the design method of sliding mode fuzzy controller without its system model for the once-through stream generator.The simulation results of several control methods, such as cascade PID, cascade feedforward-feedback control, fuzzy control and fuzzy variable structure control, for the once-through stream generator, under different typical load disturbances, are carried on the comparison. The simulation results show that the cascade feedforward-feedback controller is more valid than the PID controller, and the fuzzy variable structure controller is the most valid.