Croatia: Integration of wind farms into the Croatian power system

, SEE Energy News

The biggest obstacle to the wind farm power system integration is the inability to provide additional reserves for secondary and tertiary P/f regulation.

Past experience shows that the wind farms over a longer period of time are a relatively stable source of energy, but with significant intraday generation variations, necessitating additional secondary and tertiary regulation reserve, which is the main limiting factor for their significant integration into the power system. So far, inside the Croatian power system, a total of 346.45 MW of installed capacity in 16 wind farms has been developed. The first 5.95 MW wind farm was built in 2004 on the island of Pag. However, from 2007, more intensive integration of wind power plants began by adopting a comprehensive legal framework. From 2011 to 2014 wind turbines generated a total of 1.7 TWh, or about 10% of the total annual electricity consumption in Croatia.

To activate the control reserves of power and frequency (P/f regulation) generation deviations defined as the difference between the forecasted and realized generation of electricity generated in a given unit of time should be used as competent. The average error in the 2011 generation forecasts amounted to 11.8% of the total installed capacity in 2012, 13.1% and 9.8% in 2013. The ideal solution would be if the system had a secondary reserve large enough to cover all the imbalances of generation and consumption, as well as the extremely large ones, but it was never realized due to high costs of maintaining such large reserves.

The biggest obstacle to the integration of wind farms into the power system is the inability to provide additional reserves for secondary and tertiary P/f regulation. Secondary regulation is provided by three hydropower plants, whose generation depends on current hydrologic conditions. These hydropower plants are mainly out of operation during the night, just when significant variations in wind farm generation occur. Fast tertiary regulation generally may be ensured. However, the problems are the low load periods when surplus generation occurs inside the system, while the downward regulation may not be ensured, transmits