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>Direct</strong> <strong>Torque</strong> <strong>Control</strong> <strong>with</strong> <strong>Space</strong> <strong>Vector</strong> <strong>Modulation</strong><br />
5.2.2 Digital torque control loop<br />
The considered torque control loop is shown in Fig. 5.15.<br />
Ψ s _ ref<br />
M e _ ref<br />
−<br />
<strong>Torque</strong><br />
controller<br />
PI<br />
∆δ Ψ<br />
Reference<br />
flux generator<br />
In stator frame<br />
Ψ<br />
s α _ ref<br />
Ψ<br />
s β _ ref<br />
−<br />
∆Ψ sα<br />
−<br />
∆Ψ sβ<br />
Flux<br />
controllers<br />
In stator frame<br />
U<br />
s α _ ref<br />
U<br />
s β _ ref<br />
M e<br />
θ Ψs<br />
Ψ sα<br />
Ψ sβ<br />
Figure 5.15. <strong>Torque</strong> control loop <strong>with</strong> PI controller.<br />
Based on the equation (5.9a-b and 5.10a-b) the stator flux errors in α,<br />
β coordinates can<br />
be calculated as:<br />
∆Ψ<br />
α<br />
= Ψ cos( θ + ∆δ ) − Ψ cos θ = Ψ [cos( θ + ∆δ ) − cos θ ]<br />
s s_ ref Ψs Ψ s_ ref Ψs s_<br />
ref Ψs Ψ Ψs<br />
(5.21a)<br />
∆Ψ<br />
β<br />
= Ψ sin( θ +∆δ ) − Ψ sin θ = Ψ [sin( θ +∆δ ) − sin θ ]<br />
s s_ ref Ψs Ψ s_ ref Ψs s_<br />
ref Ψs Ψ Ψs<br />
(5.21b)<br />
Assuming that for small changes <strong>of</strong> ∆δ Ψ<br />
the cos ∆δ Ψ<br />
≅ 1and sin ∆δ Ψ<br />
≅∆ δ<br />
Ψ<br />
, the equations<br />
(5.21a) and (5.21b) are given by:<br />
∆Ψ<br />
α _<br />
= − Ψ<br />
_<br />
∆ δ sinθ<br />
(5.22a)<br />
s ref s ref Ψ Ψs<br />
∆Ψ<br />
β _<br />
= Ψ<br />
_<br />
∆ δ cosθ<br />
(5.22b)<br />
s ref s ref Ψ Ψs<br />
In order to design the PI torque controller the following assumption are made:<br />
• stator flux vector position θ Ψ s<br />
and rotor flux vector position θ<br />
r<br />
are equal zero. It<br />
correspond to situation, when those two flux vectors lie along theα axis,<br />
• the reference stator flux amplitude is equal value <strong>of</strong> permanent magnet flux<br />
Ψ<br />
s _ ref<br />
=Ψ<br />
PM<br />
,<br />
• stator resistance is neglected.<br />
Therefore, the error stator fluxes in α,<br />
β coordinates are calculated as:<br />
∆Ψ = , (5.23a)<br />
sα<br />
_ ref<br />
0<br />
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