Wind Power in Power Systems

Wind Power in Power Systems 359
I n / I 1 (%)
1.0
0.8
0.6
0.4
0.2
0.0
1250 1255 1260 1265 1270 1275 1280 1285 1290 1295 1300
converter, the emission of harmonic currents during continuous operation has to be
specified. The emission of the individual harmonics for frequencies of up to 50 times the
fundamental grid frequency are to be specified, as well as the total harmonic distortion.
According to IEC 61000-4-7, the following equation has to be applied to determine the
harmonic currents that originate from more than one source connected to a common
point:
In ¼ X
Frequency (Hz)
Figure 16.12 Current interharmonic content between 1250 Hz and 1300 Hz. Note: In ¼ harmonic
current of order n
k
I n; k
! 1=
; ð16:2Þ
where In is the harmonic current of order n; In, k is the harmonic current of order n from
source k; and is an exponent, chosen from Table 16.1. This recommendation is valid
for wind farm applications.
Figure 16.13 shows the harmonic content of two Type D1 wind turbine equipped with
forced-commutated inverters. The harmonic content is obtained in two different ways. One
way is to use Equation (16.2) and the measured time series from each wind turbine. The
other way is to use the measured time series of the total current from both wind turbines.
Table 16.1 Exponent, , for harmonics
Harmonic number, n
1 n < 5
1.4 5 n 10
2 n > 10
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