This paper is about start-up costs of hydro power units. In the introduction we address three questions about startups of hydro power units:What causes the costs in the start-up? How much does a start-up cost? How do start-ups effect the short-term scheduling strategies of power producers in Sweden? In order to answer these questions, we have interviewed employees working with generation planing at the eight largest power producers in Sweden.
0Loss of water during maintenance. * Wear and tear of the windings due to temperature changes dur-0 Wear and tear of mechanical equipment during the start-up. * Malfunctions in the control equipment during the start-up. * Loss of water during the start up. The aspects causing the largest costs are maintenance due to the wear and tear and the unavailability and personnel costs due to malfunctions in the control equipment. The cost of lost water is usually small. * Start ups cost. The cost will depend on the nominal power of the * The majority of the power producers consider start-ups in their * There is a need for better knowledge about start-up cost. * There is a need for planning software which considers start-up We found five aspects causing start-up costs:ing the start-up.Our conclusions are the following:unit and the unit model.
planning.costs of hydro units.
Abstruct-In this paper a mixed-integer hydro electric power model for short-term planning is presented. The advantage of this model is that the schedules only include points with good effi-of values and there has to be a minimum delay between two variations of the discharge. For the hydro system studied in this work, it is appropriate to allow discharges on a continuous part ciency. The planning problem is decomposed into a for each hydro plant. In order to get smooth schedules the model of production characteristic for high flows. Furthermore, the head dependency has to be modelled explicitly, since it will includes start-up costs for hydro aggregates. The main mathematical methods used in this work are Lagrange relaxation, dynamic programming and network programming. The model is illussystem.
aggregates.affect the operation of the system. This leads to a mixed-integer model to avoid discharges at forbidden areas. To get smooth trated by a numerical example from a part of the Swedish power schedules the includes a start-up cost for hydro
In short term power system scheduling, reserve margins are kept in order to maintain the security of the system if a non-forecasted event occur;s. The security is maintained by re-dispatch of the generators in ithe system. During the first seconds of the disturbance it is only possible to re-dispatch the on-line units. The maximal increase of the generation during these first seconds of the disturbance is called the spinning reserve. In hydro dominated power systems the spinning reserve is kept in the hydro system, since hydro units arc: easy to re-dispatch. For an on-line hydro unit the spinning rc:serve is the marginal between maximum generation and the actual generation. If a hydro plant has several units, only the on-line units will contribute to the spinning reserve. This means that we need to introduce integer variables to model the spinning reserve contribution from a hydro plant with several units. In the literature there are several examples of integer models for representation of the generation of hydro plants. The contribution of this paper is that it incorporates the integer representation of the spinning reserve into an integer model of generation scheduling.To this model we apply variable splitting and Lagrange relaxation to decompose the problem into one subproblem for the hydrological constraints and one subproblem for each hydro plant. In order to find feasible solutions we use a combination of network programming and heuristic search. The dual problem constructed by the decomposition is solved by a subgradient method. In the paper we apply the proposed method to a numerical example.
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