POLITECHNIKA WARSZAWSKA

6. ANN sensorless Field Oriented Conrol of IM
6.3.4.2 Design of current loop with internal model approach
In the case of induction motor, after decoupling the open loop transfer function is
defined by equation Eq. 6.20. If we substitute this formula to equation Eq. 6.21 and
assume the closed loop system defined by equation Eq. 6.24, we can obtain
⎡ 1 ⎤
Gr
( s)
=
⎢
I − I
⎣ 1+
τs
⎥
⎦
−1
G
−1
o
1 sx r
s
σ +
( ) =
1+
τs
τs
im
I
(6.25)
or in different form
⎡ ⎤
x ⎢ ⎥
Gr
s =
σ 1
( )
⎢
1+
I
x ⎥
(6.26)
τ σ
⎢ s
⎣ r im
⎥
⎦
It means that to control i sx and i sy currents we should use the PI controllers with the
same parameters
K pc
=
xσ
x
, Tic
= σ TN
(6.27)
τ
rim
where the K pc is the gain factor of the PI controller, and T ic is the time constants of this
controller.
Note that in this case we have the desired transfer function of the closed loop system
(Eq. 6.24) which is useful in tuning of the speed control part. Furthermore because of
this that decoupled system is the first order system, we do not need to use more
complicated regulators. As result the design of PI controller is unique.
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