Power curves for wind turbines - Wind Power Generation and Wind Turbine Design - page 595

CHAPTER 18
Power curves for wind turbines
Patrick Milan , Matthias Wächter , Stephan Barth & Joachim Peinke
ForWind Center for Wind Energy Research of the Universities
of Oldenburg, Bremen and Hannover, Oldenburg, Germany.
The concept of a power curve is introduced, as well as the principles of the power
conversion performed by a wind turbine. As an appropriate approach for the
estimation of the annual power production of a wind turbine, the procedure to
determine the power curve after the international standard IEC 61400 of the Inter-
national Electrotechnical Commission (IEC) is discussed. As another approach
is introduced a stochastic defi nition of a power curve which is based on high fre-
quency measurement data and on the dynamic response of the wind turbine to
wind fl uctuations. The latter approach should be seen as a completion to the IEC
defi nition which provides further insight into the dynamic performance of a wind
turbine and may be used as a monitoring tool for wind turbines.
1 Introduction
The overall purpose of a wind turbine is to produce electrical power from wind.
Quantifying this power output is necessary, on the one hand, for the fi nancial plan-
ning of any wind energy project. On the other hand, besides the pure amount of
energy production, also the dynamics of the power conversion contains essential
information about, e.g. mechanical and electrical performance of the turbine and
power quality. Following the turbulent behavior of the wind, the power produc-
tion of a wind turbine fl uctuates on short-time scales [1]. While exploiting the
free, uncontrolled input that is the wind, it is of primary importance to control
the stability of the power output of wind turbines. A large integration into energy
networks supposes a good command of the power production, in terms of quantity,
quality and availability.
To achieve such control, it is necessary to understand the behavior of wind turbines
and quantify it. This is the scope of power performance techniques. This chapter