Environmental Engineering Reference
In-Depth Information
The principle of furling is illustrated in Fig. 5.24, where (a) is for normal wind
speeds (no furling); (b) indicates starting of furling action and (c) is for the end
position at high wind speeds [Wha05].
For systems of ratings 1 kW and above, available market data allow a view on
practical values of turbine diameter and upper operational speed in dependence of
power. Figure 5.25 covers the range up to 20 kW; see also [BWE07].
Inverter circuits to couple generator and dc (and battery) side may be selected
from the types indicated in Fig. 5.26 where (a) stands for the active front-end in-
verter, (b) shows a diode rectifier, (c) is the rectifier and step-up inverter combina-
tion, and (d) is a reduced version of (c) applicable for use with a generator of high
inductance [Wha05].
A comparison can be deduced from Table 5.2: The features determining the cost
is the semiconductor count and the complexity of control equipment. It is seen that
(a) is the most advanced but costly solution; (b) will not meet requirements of a
VSI circuit with controlled dc side voltage; (c) has the advantage of using only
1 switch (transistor) and a simple control; (d) is only suitable with generators of
unconventional design.
For systems rated some kW the rectifier and step-up inverter combination (in-
dicated by c) in Fig. 5.26 and Table 5.2 is a good compromise regarding cost and
performance.
Fig. 5.26 Typical inverter circuits for small ratings
Table 5.2 Comparison of inverter circuits in Fig. 5.26
Inverter type
Diode
count
Switch
count
Control
Relative cost
a
6
6
complex
high
b
6
0
none
low
c
7
1
simple
medium
d
7
1
simple
medium
 
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