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an investigation of dual stator winding induction machines

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σ<br />

= 3<br />

1+<br />

K<br />

( Vqs1iqs1<br />

+ Vds1<br />

ds1)<br />

= σ dc1<br />

dc i<br />

( Vqs2iqs2<br />

+ Vds2<br />

ds2<br />

) = σ dc2<br />

Kσ<br />

dc = 3<br />

i<br />

1+<br />

K<br />

297<br />

(8.35)<br />

(8.36)<br />

K is the power distribution coefficient which is used to vary the output power <strong>of</strong> each<br />

<strong>winding</strong> set. If a const<strong>an</strong>t power load is desired, the value <strong>of</strong> K c<strong>an</strong> be varied to ch<strong>an</strong>ge<br />

the power generated by each <strong>winding</strong> in order to further improve the generator efficiency.<br />

Only the control design for the 2-pole ABC <strong>winding</strong> set is undertaken below. Similar<br />

<strong>an</strong>alysis is done for the 6-pole XYZ <strong>winding</strong>. From (8.3-8.4), the slip frequency <strong>an</strong>d the<br />

reference <strong>stator</strong> d-axis current <strong>of</strong> the 2-pole ABC <strong>winding</strong> set are :<br />

σ r L I qs1<br />

− (8.37)<br />

λ<br />

( ω )<br />

qr1<br />

r1<br />

m1<br />

ωe1 r1<br />

= − + ⋅<br />

λdr1<br />

Lr1<br />

[ σ − ( ω −ω<br />

) ]<br />

I λ<br />

L<br />

dr1<br />

*<br />

r1<br />

ds1<br />

= dr1<br />

e1<br />

r1<br />

qr1<br />

(8.38)<br />

rr1Lm<br />

1<br />

Since the optimal slip is determined by (8.21), equation (8.37) is used to calculate the<br />

reference rotor flux linkage value. The comm<strong>an</strong>d (reference) q <strong>an</strong>d d axis <strong>stator</strong> voltages<br />

<strong>of</strong> the 2-pole ABC <strong>winding</strong> set from (8.1-8.2) are expressed as :<br />

r L L<br />

V = λ<br />

(8.39)<br />

*<br />

r1<br />

m1<br />

m1<br />

qs1<br />

σ qs1<br />

+ ωe1Lσ<br />

1I<br />

ds1<br />

− λ 2 qr1<br />

+ ωr1<br />

dr1<br />

Lr1<br />

Lr1<br />

r L L<br />

V = λ<br />

(8.40)<br />

*<br />

r1<br />

m1<br />

m1<br />

ds1<br />

σ ds1<br />

− ωe1Lσ<br />

1I<br />

qs1<br />

− λ 2 dr1<br />

− ωr1<br />

qr1<br />

Lr1<br />

Lr1<br />

The unknown qu<strong>an</strong>tities σ qs1<br />

, σ ds1<br />

, σ qr1,<br />

dr1<br />

σ <strong>an</strong>d σ dc are the outputs <strong>of</strong> controllers <strong>of</strong><br />

the 2-pole <strong>winding</strong> set which are defined from (8.1-8.4, 8.9). If the traditional PI<br />

controllers are used <strong>an</strong>d the parameters <strong>of</strong> the controllers are given as defined below (i.e.

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