Automation Drum-boiler dynamics.pdf

Automatica 36 (2000) 363}378 Drum-boiler dynamicsq K.J. As stroK m!,*, R.D. Bell !Department of Automatic Control, Lund Institute of Technology, Box 118, S-221 00 Lund, Sweden Department of Computing, School of Mathematics, Physics, Computing and Electronics, Macquarie University, New South Wales 2109, Australia Received 2 October 1998; revised 7 March 1999; received in nal form 8 June 1999 Abstract A nonlinear dynamic model for natural circulation drum-boilers is presented. The model describes the complicated dynamics of the drum, downcomer, and riser components. It is derived from rst principles, and is characterized by a few physical parameters. A strong e!ort has been made to strike a balance between delity and simplicity. Results from validation of the model against unique plant data are presented. The model describes the behavior of the system over a wide operating range. ( 2000 Elsevier Science Ltd. All rights reserved. 1. Introduction There are dramatic changes in the power industry because of deregulation. One consequence of this is that the demands for rapid changes in power generation is increasing. This leads to more stringent requirements on the control systems for the processes. It is required to keep the processes operating well for large changes in the operating conditions. One way to achieve this is to incor- porate more process knowledge into the systems. There has also been a signicant development of methods for model-based control, see Garcia, Prett and Morari (1989), Qin and Badgwell (1997) and Mayne, Rawlings and Rao (1999). Lack of good nonlinear process models is a bottleneck for using model-based controllers. For many industrial processes there are good static models used for process design and steady-state operation. By using system identication techniques it is possible to obtain black box models of reasonable complexity that describe the system well in specic operating conditions. Neither static models nor black box models are suitable fo