Modelling
A simple Matlab/SIMULINK simulation model is developed in
this section, based on the equations provided in Ref. [9]. This
simplified model is the control design model exploited for
designing the controllers in Sections 3 and 4. Research is still being
conducted to develop more detailed models to predict wind turbines'
response and performance more accurately [13,14], but the
controllers are still designed based on simplified models similar to
the one reported in this section [15e17]. In fact, it is recommended
that the control design model be kept not too complex since it
could cause the controllers to be active at high frequencies and to
lack robustness. A high fidelity aero-elastic model (of the same
turbine) in Bladed is thus utilised to simulate the plant in Section 3.
This model produces additional dynamics enabling further results
to be obtained, including all significant variables and loads and
lifetime equivalent fatigue load estimates.
The model employs the parameters of the 5MWexemplar wind
turbine of Supergen. As the size of a cluster increases, each wind
turbine would experience greater drive-train load transients and
fluctuations in generated power in above rated wind speed as a
result of increasing differences in the wind speed each turbine
experiences. In order to ameliorate these effects to an extent, the
model replaces the existing synchronous generator with an asynchronous
induction generator since the latter would provide
considerably greater damping.