Environmental Engineering Reference
In-Depth Information
functions yielding the global model of the system. Details about T-S fuzzy
modelling and control can be found in [
44
].
Several reasons lead to satisfaction that a Takagi-Sugeno (T-S) fuzzy non-linear
control can cope with wind turbine control requirements, these are:
• The T-S fuzzy control makes use of a linear control strategy locally to produce
a non-linear controller through fuzzy inference modelling, in terms of fuzzy
multiple-modelling.
• By increasing the number of premise variables, the T-S fuzzy model can cover
a wider range of operation scenarios which cannot be considered with a linear
robust controller. For example, a linear robust controller is designed based on
the linearised model derived at a specific operation point belong to the ideal
operation curve given in Fig.
7.4
. Hence, all other operating regions are con-
sidered as regions with modelling uncertainty, this controller design always
degrades the nominal required performance in order to take good care of the
modelling uncertainty. On the other hand, by considering the wind speed and
the rotor speed as premise variables in the low wind speed range (Region2), the
T-S fuzzy model can approximate the wind turbine model not only during its
ideal operation curve but it can additionally cover the operation scenarios in
which the system inputs and outputs deviated from ideal operation trajectory.
This scenario usually happens during wind turbine operation, specifically for
large inertia wind turbines, since the variation of wind speed is faster than rotor
speed variations.
• The structure of the non-linear state space model given in Eq. (
7.7
) is char-
acterised by its common input (B) and common output (C) matrices. This fact
plays a vital role in simplification and conservatism reduction of T-S fuzzy
x
10
6
8
Region 1
Region 2
Region 3
Region 4
7
6
5
4
3
2
Total wind power
Power harvisted by ideal actuator disc
Ideal power harvisted by wind turbine
1
0
0
5
10
15
20
25
Wind speed (m /s)
Fig. 7.4
Wind turbine region of operation
