Environmental Engineering Reference
In-Depth Information
Wind power
(
theoretical limit
)
C
p
= 1
Wind power
(
theoretical limit
)
C
p
= 1
Wind
speed
Wind
speed
v
cut-off
v
cut-off
v
cut-in
v
cut-in
v
rmax
v
rmax
v
rated
v
rated
Constant speed,
variable
TSR
Constant speed,
variable
TSR
Variable speed,
constant power
Variable speed,
constant power
Variable speed, optimum
TSR
Variable speed, optimum
TSR
Wind
speed
Wind
speed
v
cut-off
v
cut-off
v
cut-in
v
cut-in
v
rmax
v
rmax
v
rated
v
rated
C
p
C
p
Wind
speed
Wind
speed
v
cut-in
v
cut-in
v
rmax
v
rmax
v
rated
v
rated
v
cut-off
v
cut-off
Fig. 2.4
Wind turbine control regions
methods come at the price of poor system performance and low reliability. Hence, the
need for nonlinear and robust control to take into account these control problems.
Although many modern techniques can be used for this purpose [
13
], sliding mode
control has proved to be especially appropriate for nonlinear systems, presenting
robust features with respect to system parameter uncertainties and external distur-
bances. For wind turbine control, sliding mode should provide a suitable compromise
between conversion efficiency and torque oscillation smoothing [
7
,
14
,
15
].
Sliding mode control copes with system uncertainty keeping a properly chosen
constraint by means of high-frequency control switching. Featuring robustness and
high accuracy, the standard (first-order) sliding mode usage is, however, restricted
due to the chattering effect caused by the control switching, and the equality of the
constraint relative degree to 1. High-order sliding mode approach suggests treating
the chattering effect using a time derivative of control as a new control, thus
integrating the switching [
16
].
2.3.2 High-Order Sliding Modes Control Design
As the chattering phenomenon is the major drawback of practical implementation
of sliding mode control, the most efficient ways to cope with this problem is higher
