H∞-based LQR water level control for nuclear u-tube steam generators

The water level of the U-tube steam generator (UTSG) in a nuclear power unit, which is an important process parameter, must be maintained in a safe range whether the unit is working under fixed or variable conditions. But it is a challenging job to accurately control the water level, for its dynamic responses vary significantly when the load changes and its non-minimum phase characteristic, especially at the lower load. In this paper, an H_∞-based linear-quadratic regulator (LQR) control scheme is proposed. In this scheme, the H_∞ approach is used to design the water level controller to ensure the stable and the tracking ability of the system at deferent loads, and, to accommodate the constraint of the feed-water flow, the LQR method is adopted. Case studies, based on an actual nuclear UTSG model, show the effectiveness of this control scheme.