The Improvement And Validation Of The RCV Letdown Temperature Control Of Daya Bay

Based on the information fed back from Daya Bay and Ling’ao-I nuclearpower plants, the RCV letdown temperature control circuit takes on seriouslag and feeble repellence characters when the letdown temperature acutelyfluctuates or the outside disturbs. By analysis it we may make a conclusionthat the cause lies in the PI controller and the intrinsic delay of the valve andthe heat exchanger.In this paper, to abstract the transfer functions of different parts in thecontrol loop is the first task, and then, the improvement of the circuit isdivided into three steps, the first step is to improve the controller, the secondstep is to improve the whole control loop and the third is to realize theself-adjust of the PID parameters by intelligence control.By comparison, a more advanced technique is put forward to resolve the lagand enhance the resistibility to the disturb in this paper after manyexperiments and research, concretely, the improved circuit combines theSmith predictive control, adaptive fuzzy control and PID control, thepredictive control is used to repair the pure delay which may cause the systemunstable, the fuzzy control is used to self-adjust the PID parameters so that itwould be real-time optimal. The whole scheme could give the control system agood static dynamic and a better robustness so as to overcome the shortagesreferred before.Because of the different influence factors, the heat exchanger has twodifferent transfer functions. In this paper, we simulate both of the two tovalidate the great efficiency of the improved circuit.With MATLAB, we validate the shortage of the exist circuit and the effectof the improved one, including the effect of different parameters of thecontroller, the importance of improved controller, the predictive control andfuzzy control. In a word, we could approve the success of improvement byMATLAB. In addition, there are many simulation codes and model drawingsboth of which could be used to simulate in the end of this paper.Eventually, the improved arithmetic’s validity is verified in the validationplatform of the nuclear instrument and control in ICD, CNPDC, so it has greatapplication value.