Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
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<strong>Control</strong> methods <strong>of</strong> PM Synchronous motor<br />
For many years the CTA control ( I<br />
_<br />
= 0 ) method has been a popular technique for a<br />
sd<br />
ref<br />
long time because <strong>of</strong> simple control. This method was dedicated for surface permanent<br />
magnet synchronous motor (SPMSM), where the magnetic saliency does not exist<br />
[126]. So the maximum torque per ampere is obtained, when stator current vector is<br />
shifted in respect to rotor flux vector 90 degree. However, in IPMSM, maximum torque<br />
per ampere is obtained <strong>with</strong> torque angle more than 90 degree. This is because <strong>of</strong><br />
existence <strong>of</strong> reluctance torque component due to magnetic saliency (see subchapter<br />
2.2.2). Therefore, the I<br />
sd_<br />
ref<br />
should be negative value [44].<br />
The main question is how or in which manner produce the reference currents in d-q<br />
frame. Its leads to many realization <strong>of</strong> current control structure. Among them generally<br />
we can distinguish two structures <strong>of</strong> current control loop. One <strong>of</strong> them is hysteresis<br />
based control (Fig.4.7a) [3,52] and the second one is PI based current controllers<br />
(Fig.4.7b).<br />
Hysteresis based current control has following disadvantage such as [3]:<br />
• measurement <strong>of</strong> three phase currents are required,<br />
• three independent hysteresis current controllers are required,<br />
• variable switching frequency is achieved,<br />
• fast sampling time is required.<br />
All this listed above disadvantage can be eliminate, when the PI current control are<br />
used. This structure are mostly used in industrial application (Fig. 4.7b).<br />
a)<br />
U DC<br />
M e _ ref<br />
Fig. 4.5<br />
I d _ ref<br />
I q _ ref<br />
d,q/ABC<br />
I A _ ref<br />
I B _ ref<br />
I C _ ref<br />
−<br />
−<br />
S A<br />
S B<br />
S C<br />
Inverter<br />
current<br />
feedback<br />
−<br />
I A current<br />
I<br />
sensors<br />
B<br />
I C<br />
rotor<br />
position<br />
sensor<br />
PMSM<br />
56