Spatial control of a large PHWR by piecewise constant periodic output feedback

The paper presents the design of piecewise constant periodic output feedbac k control for a discrete-time singularly perturbed system resulting from th e discretization of a continuous-time standard singularly perturbed system, By a suitable linear transformation of state variables, the given continuo us-time singularly perturbed model is converted into a block triangular for m in which the fast subsystem is decoupled. Tbe discrete-time model corresp onding to the transformed model also exhibits a two time scale property if sampling period is larger than the parameter a, Newt an output injection ma trix is found that stabilizes the slow subsystem. The periodic output feedb ack gain is then calculated only for the slow subsystem and the same for th e fast subsystem is set equal to zero. Finally the periodic output feedback gain for the composite system is obtained using the periodic output feedba ck gains computed separately for the slow and fast subsystems, An approach has been suggested whereby the determination of periodic output feedback ga in for the slow subsystem can be converted into an optimization problem. By minimization of the suggested performance index the closed loop system beh avior is improved. The method has been applied to a large pressurized heavy water reactor (PHW R) for control of xenon-induced spatial oscillations. A particular grouping of state variables has, been suggested for obtaining the model in standard singularly perturbed form. The periodic output feedback gain Is then calcu lated. The efficacy of control has been demonstrated by simulation of trans ient behavior of the nonlinear model of the PHWR.