Environmental Engineering Reference
In-Depth Information
P S grid
V S d
V R ∠0
X grid
Grid
ref
S gen
P
ref
S grid
P X grid
V S V R
δ
PWM
δ =
V R
V S (= V R )
ref
S gri Q
grid
ref
S grid
Q
=
0
V S
=
V R
+
V S
Figure 3.30
Load angle control of the grid-side converter
Note: The Betz Limit
Kinetic energy in the wind
Consider an airstream flowing at velocity V through an area A . If the air density is
r , the kinetic energy per unit volume is
1
2 r V 2
The wind power P over area A is the rate at which kinetic energy flows
through it
1
2 mV 2
E ¼
¼
1
2 r AV 3
Taking 1.2 kg/m 3 , a wind speed of 10 m/s would appear to be able to
produce 600 W/m 2 . However, there is a theoretical limit.
P ¼ EAV ¼
Turbine air flow
From Figure 3.31, the mass flow rate is given by
m ¼ r AV ¼ r A 0 V 0
Turbine energy capture
A turbine will slow the upstream free air velocity V to V 0 downstream. The mass
flow rate through the turbine is
m ¼ r A V þ V 0
2                                                                              Search WWH ::

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