Wind Energy

94 H. Kantz et al.
relative frequency
[arbitrary units]
160
120
80
40
0 2
4
6
8
0
0 2 4 6 8 10 12 −6−4−2 fluctuation
14 16 −8 around minute mean [m/s]
minute mean [m/s]
standard deviation of c-pdf [m/s]
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0 2 4 6 8 10 12 14 16
minute mean [m/s]
Fig. 16.1. Conditional pdfs p(vt − ¯vt|¯vt), where ¯vt is the moving 1-minute mean,
of data of three different days and the standard deviations of conditional pdfs as a
function of ¯vt for all 10 days
grow linearly with ¯vt Fig. 16.1, so that the noise amplitude of the supposed
stochastic process is a function of the state (multiplicative noise). In summary,
the very simplest model for wind speeds could read vt+1 = αvt + βvtξt, where
0