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  • Low power digital VLSI design
    (1998) Choe, Swee Yew
    Thesis
  • A new method for optimising the operation of remote area power supply (RAPS) systems
    (1995) Hancock, Mark
    Thesis
    Stand-alone power systems, also known as Remote Area Power Supply (RAPS) systems, are increasingly being used as an alternative to the extension of reticulated electricity supply in many areas of the world. State-of-the-art Hybrid RAPS systems consisting of one or more diesel/petrol engine generators, photovoltaic generation, battery storage and associated power conditioning equipment, are considered in this thesis. Typical applications of Hybrid RAPS systems include the supply of electricity to isolated communities or homesteads, and power for remote telecommunications sites. This thesis describes a new method for optimising the operation of Hybrid RAPS systems. Previous approaches to the RAPS operation optimisation problem are described. An existing mathematical optimisation method, based on linear programming and dynamic programming techniques, is selected and modified to allow incorporation of diesel generator on/off state and diesel generator start-up costs. The new optimisation method is applied to a Hybrid RAPS model for a deterministic future, and implemented on a computer. It is compared to a discrete dynamic programming method, previously representing the best approach to the RAPS operation optimisation problem, and shown to provide superior performance characteristics, in particular giving a faster solution time and higher solution accuracy. Example RAPS control actions produced by the new optimisation method are presented and discussed. The optimisation method is compared to a conventional RAPS control algorithm, implemented in a RAPS simulation program. The comparison has identified that the new method has a potential to reduce system operating costs. At present, the new method is most effectively used as a benchmark for other RAPS control algorithms. It could be extended to model the stochastic nature of future load demand and photovoltaic power, which would increase its practical value.
  • Integrated silicon flow sensors
    (1996) Lin, Kwang-Ming
    Thesis
  • Risk averse operation of an electricity plant in an electricity market
    (1995) Ranatunga, R. A. Shantha Kumara
    Thesis
    New methods are required to make optimal operation decisions for electricity generating and consuming plants in market-based electricity industries. Since wholesale electricity is traded on a spot price basis, both generators and consumers face uncertainty in their future income. Operating plants with inter-temporal links are particularly difficult since operation decisions at one instant affect the available operation decisions after that, and hence affect future income. Operation decision making with a risk-averse attitude is a method to handle uncertainty, however, some form of financial instruments, such as forward contracts, are required to allocate risk. Since electricity markets operate on a discrete time basis, a multi-stage decision making method is required to operate an electricity plant with inter-temporal links. Although risk-averse decision making has been used in other contexts, few attempts have been made to use these techniques for multi-stage problems. In this thesis, a new multi-stage risk-averse decision making algorithm is proposed and applied to make operation and forward contract trading decisions for a plant in an electricity market. In the proposed algorithm, risk aversion is incorporated in sequential decision making using the expected utility method with a von Neumann-Morgenstern utility function. Decisions are taken to maximise the utility of total financial income. Since utility functions have a concave shape, the marginal utility of income diminishes with increased income, giving risk aversion. A solution structure similar to dynamic programming is proposed for the risk management algorithm by introducing a state variable to represent past behaviour. The proposed algorithm is applied to make decisions for electricity plant and market models. Simulation results for different plant models show a clear reduction in financial risk when compared with risk-neutral operation. Any reduction in risk is shown to be sensitive to the decision maker s attitude toward risk used in the algorithm. Simulation results suggest that forward contracts play a major role in minimising risk when starting plants with high start up costs. Forward contracts ensure financial security even under unfavourable market conditions. It is shown that, plants employing a risk-averse attitude which do not commit to start, do so after securing their future financial position using forward contracts. In general, the proposed risk management algorithm shows potential for use in electricity markets.