Due to the further expansion and development of wind power generating plants, the electric performance and the power production systems in individual turbines and of entire wind farms become increasingly important; especially for areas with a high wind power penetration. In some countries, there are regions where wind power production—at certain times—exceeds load, thus creating a special challenge for grid owners, grid operators, wind farm operation and wind turbine performance. In order to handle such situations, transmission system operators in several countries have developed special grid codes for wind turbines.
Grid codes define requirements and operating performance regarding both single wind turbines and large wind farms of several hundreds of megawatts. In this context—grid codes, increased rated power of wind turbines, wind farm size, penetration levels, cost of wind power generation—the electric system of wind turbines/wind farms and their integration with the grid become an important issue. Wind farm control is part of that development. Today's control systems have to be able to support the voltage and frequency control of the grid in order to achieve an improved power system integration, for instance.
There is a clear trend regarding wind turbine development: away from the ‘Danish concept’ with an induction generator directly connected to the grid towards full power electronic converter wind turbines. This way leads via wind turbines with double-fed induction generators and partial power electronic converters; the currently most widely used concept. There are other possible developments, such as the renaissance of turbines without or with limited power electronic components—in cases where a high voltage direct current (HVDC) link is used to connect the wind farm to the main grid, for instance. Such HVDC links may further lead to DC-based internal grids in wind farms.
The Nordic Wind Power Conference focussed on the electric aspects of wind power. Conference papers covered, among others, generator design, power electronic converter design and operation, transients in wind farm cable grids, integration of wind power, power system operation, protection in power systems and grid codes. This special issue of Wind Energy comprises reviewed and updated versions of the most relevant and interesting papers of the Nordic Wind Power Conference.