Rodney D. Bell

Simple Drum-Boiler Models

Abstract This paper describes a simple nonlinear models for a drum-boiler. The models are derived from first principles. They can be characterized by a few physical parameters that are easily obtained from construction data. The models also require steam tables for a limited operating range, which can be approximated by polynomials. The models have been validated against experimental data. A complete simulation program is provided.

A Nonlinear Model for Steam Generation Process

Abstract A nonlinear model for steam generation processes is derived from first principles. The model is of third order. It is characterized by a few physical parameters that are easily obtained from construction data. Results of validation of the model from unique plant experiments show that it describes the behaviour of the system quite well. It also indicates how the model can be improved further.

A Fourth Order Non-Linear Model for Drum-Boiler Dynamics

Abstract This paper describes a nonlinear model for a drum-boiler. The model is derived from first principles. It can be characterized by a few physical parameters that are easily obtained from construction data and steam tables. Results of validating this model against experimental data covering a large operating range for a plant are given.

Models of Large Boiler-Turbine Plant

Summary During the next decade the demand on power system generating units will increase as loading patterns require more and more flexible operation. To meet this need for improved performance a much better knowledge of the dynamics of the units will be needed both at the design stage and for control studies. In this paper models of a 500MW unit of the Electricity Commission of N.S.W. at their Liddell Power Station are developed. To obtain these models, data has been collected using a Leeds & Northrup LN5200 digital computer logging 124 variables around the plant at various sampling rates (6, 12, 30 secs.). The logged variables have been chosen to allow mass, energy, and momentum balances to be written for each of 11 subsections that make up the plant. Two types of models have been developed. The first is a nonlinear model requiring only steady-state operating and design data to fix parameters and the second is a linear statistical model with parameters estimated from dynamic data obtained from field testing with the data collected when the plant is operating under closed loop conditions. The advantages and disadvantages of both models is discussed including ease of producing the model, usefulness for design, usefulness for control and so on. The transient responses are compared with the actual plant operating data for both small and large disturbances so that the simulation capabilities can be judged.

Predictive Constrained Policy Generation for Macroeconomic Systems

Abstract This paper examines the generation of optimal control policies where there are explicit constraints upon the control values and their rates of change, and there is limited knowledge of the complex economic system. The paper develops a methodology using quadratic programming where the constrained optimal control policies are based upon a learning model that predicts the policy targets for the economic system. A subset of the control policies is applied to the economic system and from the response of the system a new predictive model and resultant optimal controls are generated. The methodology is then repeated. A numeric example of the methodology as applied to a macroeconomic model is presented in the paper.

Scheduling control of a deaerator plant

Abstract The deaerator of a power plant may experience severe two phase steam/water problems especially during re-start of the power plant following a unit trip. Unless suitable control strategies are adopted, cavitation in the suction area and choking in the deaerator can occur. Cavitation can cause expensive damage to the feedwater pumps while choking will interrupt the operation of the deaerator. We have developed a model which can predict the transient behaviour of the deaerator plant for possible cavitation and choking. In this paper we propose a scheduling control for deaerator operation based on this model. This scheme utilises operational status and process variables to predict possible cavitation or choking, then takes the necessary action to avoid the loss of head in the suction area and high velocity of steam in the deaerator equaliser. The simulation results show that the control scheme will ensure safe operation even during re-starts of the power plant.

Scheduling Control of Deaerator Plant

Abstract The deaerator of a power plant may experience severe two phase steam/water problems especially during re-start of the power plant following a unit trip. Unless suitable control strategies are adopted, cavitation in the suction area and choking in the deaerator can occur. Cavitation can cause expensive damage to the feedwater pumps while choking will interrupt the operation of the deaerator. We have developed a model which can predict the transient behaviour of the deaerator plant for possible cavitation and choking. In this paper we propose a scheduling control for deaerator operation based on this model. This scheme utilises operational status and process variables to predict possible cavitation or choking, then takes the necessary action to avoid the loss of head in the suction area and high velocity of steam in the deaerator equaliser. The simulation results show that the control scheme will ensure safe operation even during re-starts of the power plant.

Transient Analysis of Power Plant Deaerators

A mathematical model suitable for predicting the transient behaviour of deaerator plant is presented. The model is based on energy and mass balance equations applied to the deaerator, storage tank and feed pump suction pipe. The model parameters are based entirely on the physical characteristics of the plant, and hence the model can be easily adapted to plants of different size. A comparison with data collected from a deaerator plant operating on a 500 MW unit indicates that the model gives good transient responses and can be used to predict accurately the onset of cavitation in the feed pump.

A natural approach to modeling physical systems

Models are useful for design of control systems and they are also an integral part of high performance controllers. Although modeling is an important aspect of most engineering activities, the control engineer faces special problems because he has to deal with strongly heterogeneous systems which have mechanical, electrical, and chemical parts. This paper describes a general approach that can be applied to a wide range of systems. It is based on constraints and object orientation and leads naturally to behavioral systems. The approach is in this paper illustrated with modeling of a thermal boiler.

Model-algorithmic adaptive control for nonlinear systems

A model-algorithmic adaptive control algorithm is proposed for nonlinear systems. The model can be assumed to be very crude and the adaption serves to improve the model and also to correct for any slight variations in the actual system parameters.