Hybrid Feedforward and Feedback Control of Steam Temperature in a Once-Through Direct Cycle Canadian SCWR

Abstract

Supercritical Water-cooled Reactor (SCWR) is the only water cooled reactor proposed for Generation IV potential nuclear reactors. Canadian SCWR is a pressure-tube type SCWR under development in Canada. A linearized dynamic model of the Canadian SCWR is developed based on the lumped-parameter method to investigate its dynamic characteristics. Through dynamic analysis, the Canadian SCWR can be modelled as a three-input and three-output system with high power-to-flow ratio and strong cross-coupling. Among the three outputs, the dynamics of the steam temperature are the most complex and vulnerable to disturbances, especially those from the reactor power. It is difficult and challenging to control the steam temperature. In this paper, a hybrid feedforward and feedback control strategy is adopted for control system design of the steam temperature. Feedforward control can reduce the effect of the measured disturbance on the steam temperature. It starts to act before the disturbance actually affects the steam temperature. Feedback control is used to track the setpoint change and suppress unmeasured disturbances. The uncompensated effects from the feedforward control can also be eliminated by the feedback control. Combined feedforward and feedback control scheme can significantly improve performance. The feedforward controller and feedback controller are designed based on the linearized dynamic model. The control performance is verified using nonlinear dynamic model. Through simulation, the steam temperature variation using designed control system satisfies its limit to a typical load pattern.