A novel hierarchical approach to plant-wide control of a thermal power unit

This paper presents a novel hierarchical approach to plant-wide control by making effective use of a physical plant model. It incorporates a two-level control structure consisting of lower-level conventional PI regulators and a higher-level non-linear model predictive controller (NMPC). The lower-level PZ loops help stabilise the unstable drum-boiler dynamics and allow faster governor valve action for power and grid-frequency regulation. The higher-level NMPC provides an optimal load demand (or set-point) transition by effective handling of plant-wide interactions and system disturbances. The strategy has been tested on a simulation of a 200 MW oil-fired power plant at Ballylumford in N. Ireland. Impressive results have been obtained during large system disturbances and extremely high rate of load changes. These results compare favourably with those from a non-linear, state-space generalised predictive control (GPC) method designed under similar conditions. Copyright (C) 2000 IFAC.