Environmental Engineering Reference
In-Depth Information
Fig. 14.7 a DC generator with gearbox (E-motor), b Actuator (NXT-motor), c Angle sensor
(Glide-Wheel-AS), d CurrentMeter for NXT, e VoltMeter for NXT
induced to move by an applied voltage. The linear characteristics of the E-motor/
generator are calculated based on [
8
], so that:
P
mec
¼
T
r
X
r
;
P
elec
¼
u
gen
i
gen
;
P
elec
¼
P
mec
g
g
ð
14
:
1
Þ
T
g
¼
K
T
i
gen
;
where K
T
¼
0
:
0609 Nm
=
A
ð
14
:
2
Þ
P
losses
¼
P
cu
þ
P
rotation
; P
cu
¼
i
gen
R
a
;
R
a
¼
21
:
95 ohm;
P
rotation
¼
0
:
1508 W
ð
14
:
3
Þ
being P
mec
the mechanical power at the generator shaft (in watts), T
r
the
mechanical torque at the shaft (in Nm), X
r
the rotor speed (in rad/s), P
elec
the
electrical power produced by the generator (in watts), u
gen
the voltage at the output
of the generator (in volts), i
gen
the generator current (in A), g
g
the generator
efficiency, T
g
the electrical torque (in Nm), and P
losses
the generator losses (in
watts) due to the Joule effect P
cu
and friction P
rotation
.
The generator is connected to the grid system through an actuator able to
change the current i
gen
—see Fig.
14.2
, element (9)- and therefore the electrical
generator torque T
g
, which is opposite to the mechanical torque T
r
in Fig.
14.12
,
Table
14.1
and Eqs. (
14.24
), (
14.27
), (
14.43
) and (
14.44
).
14.2.1.4 Sensors: Rotor Speed, Pitch and Yaw Angles, Voltage,
Currents, Torque, Power, Wind
There are various electronics on each wind turbine, falling into two categories:
actuators and sensors. There are three kinds of sensors on the wind turbine. On the
nacelle there is a glide wheel angle sensor—see Fig.
14.2
, number (6), Fig.
14.7
c
and Ref. [
6
], which is configured to record the rotor velocity. This sensor has a one
degree resolution and very low resistance as it has almost exactly the same surface
area as the generator, so it does not strongly affect the mechanics or aerodynamics
