Pressurizer water level control with estimation of primary circuit coolant mass in nuclear power plants via robust observer based dynamic sliding mode control

Abstract

Pressurizer is one of the most important components in a pressurized water nuclear power plant. Since it is responsible for coolant mass balance and non-boiling heat transfer in the primary circuit. The pressurizer water level control system in a nuclear power plant with the Pressurized Water Reactor (PWR) is responsible for the coolant mass balance. The main control goal is to stabilize the water level at a reference value and to suppress the effect of time-varying disturbances such as the coolant leakage in the primary circuit pipeline system. In the process of PWR power plant operation, the incorrect pressurizer water level may disturb pressure control or may cause damage to electric heaters which could threaten plant security and stability. In modern reactors, standard Proportional–Integral–Derivative (PID) controllers are used to control the water level in a pressurizer. In this paper, for the first time, in order to improve the performance and transient response of the pressurizer control system, an observer-based dynamic sliding mode control using Lyapunov-approach is designed and applied for the level control problem of the pressurizer in a pressurized water nuclear power plant based on the validated nonlinear model. The proposed method exhibits the desired dynamic properties during the entire output tracking process independent of perturbations. The comparison between the Dynamic Sliding Mode Control (DSMC) and the PID controller shows a significant improvement in water set-point tracking and increased ability in disturbance rejection for the proposed observer-based DSMC. Simulation results confirm the improvement in the transient response obtained by using the proposed controller.