Power curves for wind turbines - Wind Power Generation and Wind Turbine Design - page 607

Figure 9: Langevin power curve (dots + error bars) and IEC power curve (line) for
a multi-MW wind turbine (same as Fig. 8). The power output is normalized
by its rated value P r .
dependency of the power on the wind speed. The results are therefore site indepen-
dent because effects of turbulence have no infl uence on the dynamical power
curve. An interesting feature of this approach is the ability to show also additional
characteristics of the investigated system. Examples are regions where the system
is close to stability, as mentioned above, or multiple stable states, see also [17, 18].
Because of these features the dynamical power curve is a promising tool for mon-
itoring the power output of wind turbines.
3 P erspectives
Different tools have been defi ned in the previous section to estimate power perfor-
mance. The IEC power curve, in spite of being a good introduction to the topic,
cannot characterize the conversion process of a wind turbine objectively, i.e. the
result depends on the wind condition. The Langevin power curve, on the other
hand, provides robust results that can be applied to determine and monitor the
dynamical behavior of a wind turbine. Rather than competing against each other,
these two power curves, when plotted together, can quickly bring useful insights
on the health of any (horizontal-axis) wind turbine.
An overview of the available applications will be presented in this section.
3.1 Characterizing wind turbines
A striking feature is that the Langevin power curve offers new, complementary
information to the IEC power curve. The two power curves are presented together
in Fig. 9.