Robust optimal-integral sliding mode control for a pressurized water nuclear reactor in load following mode of operation

•A hybrid LQG/LTR-ISMC control system for a PWR reactor core is presented.•Core model is Point kinetics equation with thermal and Xenon reactivity feedbacks.•The load following and stability of the hybrid control system is demonstrated.•The robustness of the control system against a matched disturbance is demonstrated.•The robustness of the controller against parametric variation is demonstrated.•The study revealed that the hybrid controller is the most effective. A nuclear reactor is a complex, nonlinear, and time-varying system. External disturbances and uncertainty due to neutronic and thermal-hydraulics parameters variation contribute to reactor control challenges and safe operations. Thus, this paper presents a hybrid control system for a nuclear reactor core power control in the presence of a matched disturbance and uncertainties. The hybrid controller combines Linear Quadratic Gaussian/Loop Transfer Recovery (LQG/LTR) optimal control and a nonlinear Integral sliding mode control (ISMC). The nonlinear system of the reactor, which is based on point kinetics equations with three delayed neutron group is linearized to design the LQG/LTR. The Lyapunov theory is used to prove the finite-time convergence of the Integral sliding mode control. Furthermore, a comparative analysis of the hybrid control scheme, LQG/LTR, PID, and an ISMC is conducted with the nonlinear model. Simulation experiments reveal that the closed-loop hybrid control system is stable and achieves the best performance specifications in the presence of external disturbance and uncertainties.