Environmental Engineering Reference
In-Depth Information
Rotor
Reactive-power
compensation
ASG
Gearbox
Transformer
Generator
Grid
Figure 5.33
Asynchronous Generator with Direct Mains Coupling
With
, the approximation for
c
P
of a certain wind generator is:
(see also Equation 5.45)
and with
,
the dependence of rotor power
P
on the speed
n
for a constant wind speed
v
can be calculated (see Figure 5.35). However, the asynchronous generator
allows only relatively small fluctuations in speed. The stator frequency and the
gearbox define the rotor speed, and this can only be varied by the slip that
increases with the power. Asynchronous generators with variable slip can
increase the slip at higher powers. This can cushion high power fluctuations
and high strains to the mains.
Figure 5.35 shows also that the rotor speed has an important influence on
the usable wind energy. If the rotor speed is nearly constant, the wind generator
Figure 5.34
Torque Characteristics as a Function of Slip
s
with Variation of
the Rotor Resistance
R
R
