Optimization of boiler control to improve the load-following capability ofpower-plant units

The capability to perform fast load changes has been an important issue in the power market, and will become increasingly more so due to the increasin g commercialization of the European power market. An optimizing control sys tem for improving the load-following capability of power-plant units has th erefore been developed. The system is implemented as a complement, producin g control signals to be added to those of the existing boiler control syste m, a concept which has various practical advantages in terms of implementat ion and commissioning. The optimizing control system takes account of the m ultivariable and load-dependent nonlinear characteristics of the boiler pro cess, as a scheduled LQG controller with feedforward action is utilized. Th e LQG controller improves the control of critical process variables, making it possible to increase the load-following capability of a specific plant. Field tests on a 265 MW coal-fired power-plant unit reveals that the maxim um allowable load gradient that can be imposed on the plant, can be increas ed from 4 to 8 MW/min. (C) 1998 Elsevier Science Ltd. All rights reserved.