Fractional Order Modeling of a PHWR Under Step-Back Condition and Control of Its Global Power with a Robust PI{\lambda}D{\mu} Controller

TL;DR

This paper develops a fractional order model of a CANDU reactor for step-back power control, demonstrating that a robust PIλDμ controller outperforms classical PID in achieving active, stable power reduction under varying conditions.

Contribution

Introduces a novel fractional order modeling and reduction technique for a nuclear reactor, enhancing control robustness and response accuracy with a PIλDμ controller.

Findings

Fractional order model improves robustness against parameter variations.

PIλDμ controller achieves dead-beat response during power step-back.

Enhanced stability and performance over classical PID controllers.

Abstract

Bulk reduction of reactor power within a small finite time interval under abnormal conditions is referred to as step-back. In this paper, a 500MWe Canadian Deuterium Uranium (CANDU) type Pressurized Heavy Water Reactor (PHWR) is modeled using few variants of Least Square Estimator (LSE) from practical test data under a control rod drop scenario in order to design a control system to achieve a dead-beat response during a stepped reduction of its global power. A new fractional order (FO) model reduction technique is attempted which increases the parametric robustness of the control loop due to lesser modeling error and ensures iso-damped closed loop response with a PI{\lambda}D{\mu} or FOPID controller. Such a controller can, therefore, be used to achieve active step-back under varying load conditions for which the system dynamics change significantly. For closed loop active control of the reduced FO reactor models, the PI{\lambda}D{\mu} controller is shown to perform better than the classical integer order PID controllers and present operating Reactor Regulating System (RRS) due to its robustness against shift in system parameters.