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

Direct Torque Control with Space Vector Modulation
Finally, the discrete transfer function of controlled plant G ( z ) can be written as:
M
Where:
C
M _ d
⎛ A ⎞
Md
GM
( z) = ( z−1) ⎜ 2
⎟
⎝ z − BMd
z+
CMd
⎠
2
A
BM
A = e sin( T C − ) ,
4
BM
− T
M
s
2
M _ d
2
s M
BM
CM
−
4
BM
Ts
= e − and T
s
is sampling time.
(5.78)
BM
2
− Ts
B
2
M
BM _ d
= 2e cos( Ts CM
− )
4
Hence, the transfer function of closed torque control loop is obtained as:
G
M _ closed
( z)
M ( z) C ( z) G ( z) D( z)
M ( z) 1 + C ( z) G ( z) D( z)
e_
ref M M
= = =
e M M
K
A ( K + K )( z−
)
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
(5.79)
Selecting
K Ψ
, K Ψ
will influence poles placement of closed torque control loop and as a
p
i
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 PI-flux controller – section 5.3.1). One possibility is use to the SISO tools from
Matlab package to tune parameters of PI torque controller [106].
a) b)
Figure 5.37. a) Torque step response for sampling time T = 200µ
s, b) with denoted rise time,
overshoot and settling time.
As can be observed the response is characterized by overshoot about 40%, rise time 4 samples
and settling time 17 samples.
s
103