Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...

Direct Torque Control with Space Vector Modulation
K
K Ψ A ( K + K )( z− )( z−1)
pM
pΨ
PM M _ d pM iM
KpM
+ KiM
3 2
M _ d M _ d pM iM M _ d M _ d pM
= =
[ z − B z + [ A ( K + K ) + C ] z− A K ]( z−1)
K
K Ψ A ( K + K )( z−
)
pM
pΨ
PM M _ d pM iM
KpM
+ KiM
3 2
−
M _ d
+ [
M _ d( pM
+
iM) +
M _ d]
−
M _ d pM
z B z A K K C z A K
(5.35)
Selecting
K Ψ
, K Ψ
will influence poles placement of closed torque control loop and as
p
i
a consequence also torque step responses can be selected.
The transfer function of closed torque control loop is more complicated than flux
control loop (see design of P-flux controller – section 5.2.1). One possibility is use to
the SISO tools from Matlab package to tune parameters of PI torque controller [106].
a) b)
Figure 5.18. a) Torque step response for sampling time T = 200µ
s, b) with denoted rise time,
overshoot and settling time.
As can be observed in (Fig. 5.18) torque response is characterized by overshoot about
40%, rise time 4 samples and settling time 17 samples.
s
To eliminate high overshoot it is recommended to insert at the input prefilter (see
Fig.5.19 ) with transfer function:
z−
b z−
0.6878
PM
( z)
= K = K
K
pM z − 0.855
( z − )
K + K
1
where K =
=0.466 is gain of the prefilter.
z − 0.6878
lim
z→1
z − 0.855
pM
iM
(5.36)
83