Direct Power and Torque Control of AC/DC/AC Converter-Fed ...

3. Vector Control Methods of AC/DC/AC Converter-Fed IM Drives – A Review
VF-DPC
P
Q
γ ΨL
Power
& Virtual Flux
Estimation
I L
VM
U L
Ω mc
U dcc
+
U dc
DTC
+
Ω m
−
−
e U
dc
e Ω m
PI
PI
P c
+
M ec
−
Q c
+
+
Ψ Sc
= 0
−
e p
e ψ
−
e Q
e M
S Q
S P
S Ψ
S M
Sector
Selection
Switching
Table
Switching
Table
Sector
Selection
U dc
S 1
S 2
VSR
C 1
C 2
VSI
γ ΨS
I S
Ψ S
M e
Torque
& Stator Flux
Estimation
Ωm
U
dc
IM
Fig. 3. 8. Conventional switching table based direct power control – DPC and direct torque
control – DTC
3.2.3. Direct Torque Control with Space Vector Modulation – DTC-SVM
To avoid the drawbacks of switching table based DTC (described in Section 3.2.2)
instead of hysteresis controllers and switching table the PI controllers with the SVM
block were introduced like in IFOC (described in Section 3.2.1). Therefore, DTC
with SVM (DTC-SVM) joins DTC and IFOC features in one control structure as in
Fig. 3. 10.
For needs of the DTC-SVM method a mathematical model of IM in a xy rotating
system of coordinates are chosen ( Ω = Ω ). In this case the coordinate system is
oriented with x stator flux linkage component (Fig. 3. 9) such as:
K
Ψ
S
43