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0.5
B=0
0.4
B=5
0.3
B=10
0.2
B=15
B=20
0.1
B=25
0
0
2
4
6
8
10
Tip speed ratio
Fig. 3. Relationship between Power coefficient and tip speed ratio at different pitch angle
The mechanical torque (Nm) developed by the wind power is given by (6)
1
(
)
ρπ
R C
2
λ β
,
V
3
P
p
2
(6)
T
==
m
ma
ω
ω
t
t
where
ω
is the turbine speed.
t
2.2
Maximum Power Tracking of Variable Speed Wind Turbine
In the time when the wind speed is in the range of cut-in and rated value, the
maximum aerodynamic power available in the wind can be capture. The maximum
power in a mass of wind can be extracted by varying the turbine speed with the
varying wind speed so that at all times it is on the track of the maximum power curve
[6].
For efficient wind power captured by the variable wind turbine [11],
λλ
=
,
opt
therefore (5) can be re-written as (7)
R
ω
λ
t
V
=
(7)
opt
substituting (7) in (2), optimum power can be obtained as (8) which can be re-written
as (9)
(
)
t
3
ρπ
R C
5
λ
,
β
=
0
ω
1
2
p
opt
P
=
(8)
opt
λ
3
opt
3
Pkt
=
ω
(9)
opt
opt
where,
(
)
5
ρπ
RC
λ
,
β
=
0
1
2
p
opt
k
=
opt
3
λ
opt
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