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CHAPTER 3: HF MODELLING STRATEGY
Figure 3.3: HF Motor model in Simulink with topology toggling resistors
It is clear that it will take quite some time when the number of variables is more than
10, as in the case of the HF model of an induction motor. Furthermore, in the case that
a different circuit topology needs to be considered, the equations need to be re-written
all over again even if just a single component has to be added or removed.
A good compromise solution finally adopted was to use the Simulink tool PowerSim
to implement the HF circuit and, rather than recalling iteratively the simulink circuit
simulations, theÐÒÑÓcommand has been used in the GA script. This method pro-
duces the state space matrices of the network between an input and an output port.
Therefore adding to this network a voltage controlled source as input and measuring
a current as an output, and eventually using Ohm’s law, will generate exactly the required
transfer function that represents the impedance of a function of frequency (Fig.
ÑÔ×ÖÕ℄Ó ℄ÐÒÑÓÅÓÐÆÑ ×ØØ×Ô×× Ø×ØØ×ÔÖ Ô
3.3). So, providing that the HF circuit model is in a simulink file, the following three
lines of code will implement the procedure previously described:
Here the ss function initializes the "statespace" variable with the state-space model ob-
tained from the four matrices and the tf function transforms again this model into a
transfer-function one. This latter model, together with the frequency reference "Fref",
is eventually passed to the bode function giving three vectors as results: magnitude
and phase of the impedance and a vector with the values of frequency for each of the
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