Design of optimal fractional order fuzzy PID controller based on cuckoo search algorithm for core power control in molten salt reactors

Abstract

In case of the adverse effects of unforeseeable or uncertain disturbances on control systems, stability robustness of control performance is crucial for controller design. Accordingly, in this study, an optimal design scheme for Fractional Order Fuzzy Proportional Integral Derivative (FOFPID) controller with adoption of Cuckoo Search (CS) optimization algorithm is presented in order to examine the application of the FOFPID in the core power control of molten salt reactors (MSRs) as an example. By using the proposed scheme, PID, FOPID and fuzzy PID controllers are also designed by the CS for the purpose of showing the superiority of the FOFPID controller. Firstly, a nonlinear dynamic model of the MSR system is introduced by means of point kinetic equations considering the time delay in the fluid's transit connecting the core and the heat exchanger. Then, the nonlinear model is linearized for obtaining a linear model of MSR core system. Also, for the purpose of performing the sensitivity analysis, transit behaviors for both the linear and nonlinear approaches are shown and compared for different reactivity inputs. The core power control of molten salt reactor system is examined for each tuned controller in terms of stability, time domain and the robustness analysis under instantaneous and continuous disturbances. The results showed that the proposed CS based FOFPID controller has better control performance as compared to the PID, FOPID and fuzzy PID controllers tuned by the CS, especially in point of capability of disturbance suppression, improving tracking performance, and robustness against parameter uncertainty.