The influence of wind generation on the definition of reserve margins in a hydro-thermoelectric system

The last few years have seen a strong increase in installed capacity from wind sources, with further substantial developments expected for next years. Such an increase entails technical problems that have not been completely solved yet, such as those related with reserve dimensioning and voltage regulation. Assuming, for instance, to add new wind generation units to an existing hydro-thermoelectric system, the volatility of the production associated with the wind farms requires an over sizing of the secondary and tertiary power reserve margins. This effect could lead to incur additional costs, to ensure auxiliary system services, that could even exceed the benefits provided by the use of the renewable source. The problem is, therefore, to estimate which is the relationship between the required operating reserve of the system and the new installed capacity from wind source, with an equal overall reliability of the production system. Note that a large number of variables are involved in this problem, many of which are affected by aleatory events, such as wind speed or accidental faults of the units, and the solution depends on many parameters as the daily and seasonal cycles of the load, the scheduled maintenance, etc. Furthermore, a competitive market environment has to be considered. For this kind of problems, a probabilistic approach, based on sequential Montecarlo techniques, which have been largely applied in the past for studying the behavior of large electric power systems [1,2], can be very useful. The aim of this study is to simulate the impact of non-programmable wind generation on the system reliability and management, with special reference to operating reserve dimensioning.