Simulation And Parameter Estimation Of Natural Circulation Drum Boiler Steam-water System

Drum-boiler is a crucial part of power plants, the dynamical properties of drum-boiler have a direct impact on the whole power plants. One of the most important parameters of drum-boiler is water level, which is the sign of whether the steam-water system is balanced. In current market driven electricity industry, power plants are frequently changing load subject to sudden load disturbances, this leads to the shrink-and-swell phenomenon of steam below the liquid level, creating a nonminimum phase behavior which changes significantly with the operating conditions, and makes the control of water level difficult. Thus, analyse a moderately complex nonlinear model based on physical principles that capture the key dynamical properties over a wide operating range is of much importance.So far one of the most representative of the Drum Boiler Steam-Water System models is the Astrom-Bell model which is suitable for model-based control, developed in2000, has four states; two account for storage of total energy and total mass, one characterizes steam distribution in the risers and another the steam distribution in the drum. The model can be characterized by steam tables and a few physical parameters. The related studies described in this paper are based on the model developed by Astrom and Bell.The main research contents and contributions are as follows:●The Astrom-Bell model is perfected according to IAPWS-IF97and simulation model is built in MATLAB/SIMULINK. To illustrate the dynamic behavior of the model, we validated open loop, simulated responses to a step change in the inputs at three working points and studied dynamic of false level in different situation. At last, problems existed in SIMULINK implementation are discussed.●Applied simultaneous method to Astrom-Bell model. Simultaneous model of steam-water system is developed, steady state properties and dynamic of typical working points are validated. The results of simultaneous method and nested sequential method are compared on accuracy and efficiency. ●A steady process model of steam-water system is built according to dynamic model and freedom of steady model is analyzed. In order to estimate parameters, key parameters are choosed, also sensitivity and feasibility are studied.Conducted parameter estimation when model parameters are mismatched. Selected three steady working points from factory data, estimated parameters based on process data, dynamic test showed that parameters estimation is effective.