Simple critieria to prevent sustained oscillations in nonlinear fluid flow networks

Includes bibliographical references (p. 26-27).J.S. Simon, J.L. Wyatt, and D. Rowell

Minimal realizations of three-port resistive networks

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The robust design of complex systems

Robust Engineering Design has evolved as an important methodology for the integration of quality with the process of design. The methodology encompasses the disciplines of experimental design, model building and optimization. First an experiment is conducted on a system (or a simulation of the system), second a model is built to emulate the system and finally the emulation model is used to optimize the system design. Applying these methods to large problems can be difficult and time-consuming because of the complexity of most design problems. It is the goal of this thesis to introduce methods which reduce problem complexity and so make the application of Robust Engineering Design (RED) methodology easier for large design problems. By drawing from methods used in systems theory and circuit optimization several techniques are presented with the aim of reducing the complexity of performing experiments for Robust Engineering Design. A common framework for experimentation is created by combining a commercial circuit simulator with established methods for experimental design and model building. This provides the basis for experimentation in subsequent chapters. A method of design optimization with respect to quality is presented to complete the model-based Robust Engineering Design cycle. Three approaches to reducing problem complexity are adopted. First a method of system decomposition is applied directly to an electronic circuit to reduce the size of experiment required for RED. Second a method of modelling system response functions is described which integrates the action of the circuit simulator with the model building process. Third information about system topology is used in the design of experiments to enhance the model-building process. Conclusions are drawn about the effectiveness of the approaches described with respect to the impact on problem complexity

Real-time power system security assessment

The increasing complexity of modern power systems has led to a greater dependence on automatic control at all levels of operation. Large scale systems of which a power system is a prime example, is an area in which a wide gap exists between theoretical mathematically based research and engineering practice. The research programme at Durham is directed towards bridging this gap by linking some of the available and new theoretical techniques with the practical requirements of on-line computer control in power systems. This thesis is concerned with the assessment of security of power systems in real-time operation. The main objective of this work was to develop a package to be incorporated in the University of Durham On line Control of Electrical Power Systems (OCEPS) suite to cater for network islanding and analyse the features and the feasibility of a real-time 'security package’ for modern energy control centres. The real-time power systems simulator developed at Durham was used to test the algorithms and numerical results obtained are presented