Power control for wind turbines in weak grids: Project summary

Abstract In many parts of the world and certainly in Europe large areas exist where the wind resources are good or very good and the grid is relatively weak due to a small population. In these areas the capacity of the grid can very often be a limiting factor for the exploitation of the wind resource. There are two main problems concerned with wind power and weak grids. The first is the steady state voltage level. When the power consumption is low e.g. during the night the voltage of the grid can increase to levels above the limits if the wind power input is high. The other main problem is voltage fluctuations. Because the wind is fluctuating the output from the wind turbines is also fluctuating. This to-gether with wind turbine cut-ins can result in voltage fluctuations that are above the flicker limit. Some or all of the these problems can be avoided if a so-called power control concept is applied together with the wind farm. The idea behind the power control concept is to eliminate the violations of the steady state voltage level by buffering the power from the wind turbines in periods where the voltage limits might be violated and then release it when the voltage leve