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

Sensorless Speed Direct Torque Control with Space Vector Modulation (DTC-SVM)
The stator current trajectory can be divided in to eight sectors (see Fig. 6.5a).
7π
8
o
157 .5
Sector 4
− +
5π
8
o
112 .5
Sector 3
− −
3π
8
+ −
o
67 .5
Sector 2
I s
o
22.5
π
8
+ +
Sector 5
o
202 .5
9π
8
Sector 6
+ −
o
247 .5
11π
8
− −
Sector 7
− +
o
292 .5
13π
8
+ +
Sector 8
Sector 1
15π
8 π
−
8
o
337 .5
Figure 6.5. Stator current trajectory.
Based on the measured response of phase currents in α,
β coordinates, the
( ) sign I s
+ and sign( I s
)
− is calculated from following formulas:
sign( I )
+ = I + I − I
(6.1)
s sα
sβ
s
sign( I )
− = I −I − I
(6.2)
s sα
sβ
s
The possible combinations of sign( I s
)
+ and sign( I s
)
− are shown in Fig. 6.6:
Figure 6.6. Possible combination of sign( I s
)
+
sign( I s
) + + − −
−
sign( I s
) + − − +
+ and sign( I s
)
− under short pulse supply.
Let us assuming, for example, the case where the sign( I s
)
+ and sign( I s
)
− have positive
π π
sign. The position γ m
exist in the domain of − ~ or 7 π 9 π
~ and two estimated
8 8 8 8
position can be obtained.
The mathematical analysis of I , I
sα
sβ waveforms leads to following equations:
I = I +∆ I cos 2γ
(6.3)
sα
s s m
125