Advanced Control Method for Forced-Natural Cycle Switching Process in Small Pressurized Water Reactors

The combination of natural circulation at low power levels and forced circulation at medium-high power levels can enhance the passive safety features and has been proposed as a promising operation scheme for small pressurized water reactors (SPWRs). The control effect of the traditional Proportional-Integral-Derivative (PID) control method in the forced-natural circulation transition process with drastic parameter changes needs to be improved, so it is necessary to carry out the research on advanced control methods. Under such a control demand, evolutionary control systems and fuzzy control systems become an effective supplement to the traditional PID control method. In this paper, first, the transfer function model of SPWRs under forced-natural circulation transition process is obtained by using the system identification method. Second, the evaluation function is constructed by using the reactor power deviation signal, and the parameters of the temperature controller and power controller in the reactor power dual feedback control system are optimized by using genetic algorithm. Finally, an online fuzzy tuning system for reactor power setpoint is established to realize the dynamic adjustment of reactor power setpoint. The results show that at a 20% power level, the advanced control strategy by using the online fuzzy tuning system can significantly reduce the overshooting amount of each key parameter and make the transition process faster and smoother.