Observer-Based Spatial Control of Advanced Heavy Water Reactor Using Time-Scale Decoupling

The 90th-order system of advanced heavy water reactor (AHWR) exhibits a three-time-scale structure with 38 slow, 35 fast, and 17 fastest state variables. Consequently, an effective controller is needed to regulate the spatial power. If the controller is based on state feedback, its realization needs an accurate and precise state observer. The regular design of a full or even reduced-order observer for such a three-time-scale system is a challenging task which, however, can be addressed by time-scale decoupling. In this paper, full- and reduced-order observers are proposed for the singularly perturbed three-time-scale system by a novel method. The novelty lies in the fact that the presented multistage observer designs help to reduce design complexity and computational time without losing the freedom to design independent observer gains for slow, fast, and fastest subsystems. These observers are then employed for the state estimation of AHWR, which are fed to the feedback controller for spatial stabilization. Performances of these observers, evaluated on the nonlinear model of AHWR in the presence of transients, are compared with the controller without an observer and fast output sampling-based controller. It is seen that the estimated values are in close agreement with the actual values due to which the controller performance is found to be satisfactory with the observers.