Timothy Wyatt (Power and Water Systems Consultants)

Modelling and optimising the operation and development of water resource and hydro-thermal power systems: past experience and future requirements
Wednesday 12 January 2005 at 16.00, JCMB 5327


This talk will focus on the application of mathematical programming techniques for the analysis of water resource and hydro-thermal power systems. The author has been involved in the modelling of such systems since graduating from Edinburgh University in 1969 with a BSc in Civil Engineering. Initial experience was gained in developing simulation and direct (gradient) search techniques for optimising long-term operating policies for water resource systems. The importance of adequately modelling hydrological time series, and benefits from integrated use of simulation and mathematical programming techniques for operating policy optimisation, will be emphasised. The concept of 'equivalent reservoirs' will be introduced for dealing with multi-reservoir systems, together with the use of heuristic procedures for reservoir balancing.

The application of similar techniques to hydro-thermal systems, with the additional requirement to model daily variations in electricity demand, will be described. A simulation model of the Uruguayan hydro-thermal system will be outlined, featuring a simple 'maximise hydro/maximise thermal' operating policy and Jacoby's Integrated Load Duration curve method for load dispatch simulation. The practical importance of incorporating supply restriction options will be stressed, and the concept of 'multiple regime' operating policies introduced.

The desirability of implementing simulation models prior to attempting operating policy optimisation will be argued, and the continuing absence of adequate models in many countries noted. Development of the MOSPA program for optimising the operation of water resource/supply systems will be described, and attention drawn to the need for daily simulation time steps when modelling river abstractions. The stochastic value iteration Dynamic Programming algorithm incorporated in MOSPA will be outlined, and the program's use to model major water resource and supply systems in North West England. discussed.

Development of Program SYSIM and its applications to the national irrigation and hydro-thermal system in Sri Lanka will be described, and references made to programs such as WASP for optimising generation system expansion plans. The development of such programs will be placed in the context of available computer hardware and the limitations imposed e.g. time steps, lack of transmission modelling, load dispatch simulation techniques.

Additional requirements associated with modelling the operation of privatised electricity supply systems will be outlined, with particular reference to the Brazilian system. The hierarchy of models for long, medium and short term operations planning will be briefly described, together with issues that arise with respect to time steps, heuristic operating rules, software validation and auditing. The importance of correct problem formulation will be emphasised, as will the dangers of an overreliance on statistics when generating flow sequences and attempting to predict future inflows.

Finally, two new computer programs, EPSIM and AQUARIUS will be described. Building on experience gained with MOSPA and SYSIM, and facilitated by the increases in computer storage and processor speeds, AQUARIUS seeks to provide a highly 'user-friendly' and flexible modelling tool suitable for application to a wide variety of systems. Main features include the on-screen definition of system configuration, template data entry, variable time steps, LP optimisation of system operation within each time step, database storage and the graphical presentation of results.

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