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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 />

M e _ ref<br />

U sy<br />

C () M<br />

s GM<br />

() s<br />

M e<br />

Figure 5.35. Block diagram <strong>of</strong> torque control loop in s-domain.<br />

The transfer function <strong>of</strong> torque control loop is obtained as:<br />

G<br />

M _ closed<br />

() s<br />

M () s C () s G () s<br />

e_<br />

ref M M<br />

= = (5.73)<br />

M<br />

e() s 1 + CM() z GM()<br />

s<br />

Substituting in equation (5.73) transfer function for CM<br />

( s)<br />

-Eq.5.28 and GM<br />

( s)<br />

- Eq.5.72 we<br />

may calculate:<br />

KiM<br />

AMKpM( s+<br />

)<br />

K<br />

pM<br />

GM<br />

_ closed()<br />

s = =<br />

2<br />

s + ( B + K A ) s+ C + K A<br />

M pM M M iM M<br />

(5.74)<br />

Discrete design<br />

z −1<br />

Using backward difference method for discretization process ( s = ) the transfer function<br />

Tz<br />

for discrete PI controller is expressed as:<br />

s<br />

K<br />

pM<br />

( z − )<br />

Tz<br />

KpM<br />

+ K<br />

s<br />

iM<br />

CM( z) = KpM(1 + ) = ( KpM + KiM)<br />

T ( z−1) ( z−1)<br />

iM<br />

(5.75)<br />

Where:<br />

K<br />

iM<br />

K<br />

pM<br />

= Ts<br />

- integration gain;<br />

s<br />

TiM<br />

T - sampling time<br />

101

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