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an investigation of dual stator winding induction machines

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The tr<strong>an</strong>sfer function <strong>of</strong> rotor speed is given as:<br />

ˆ ω<br />

ω<br />

rm<br />

rm<br />

4 3 2<br />

A4i<br />

p + A3i<br />

p + A2i<br />

p + A1i<br />

p + A0i<br />

= 5 4 3 2<br />

p + B p + B p + B p + B p + B<br />

4i<br />

3i<br />

The condition that satisfies the first condition is:<br />

B<br />

0i<br />

= 0 ⇒ a<br />

− ω ⋅ t<br />

ei<br />

2bi<br />

0i<br />

= 0 ⇒<br />

+ k ⋅ω<br />

⋅ t<br />

i<br />

ei<br />

1bi<br />

= 0<br />

2i<br />

1i<br />

0i<br />

399<br />

(10.145)<br />

Equation (10.145) is a function <strong>of</strong> the observer gains, machine parameters <strong>an</strong>d the<br />

error function partition coefficient <strong>of</strong> active <strong>an</strong>d reactive power. Since the observer gains<br />

have been determined in the previous section <strong>an</strong>d the machine parameters are all known<br />

<strong>an</strong>d assumed to be const<strong>an</strong>t here, (10.138) becomes the function <strong>of</strong> error function<br />

partition coefficients ( k , 1 k <strong>an</strong>d 2<br />

k ).<br />

Substituting (10.144) into the denominator <strong>of</strong> (10.140), the expression satisfying the<br />

second condition is given as:<br />

4<br />

2<br />

⎧ ω0<br />

− B3i<br />

⋅ω0<br />

+ B1i<br />

= 0<br />

⎨ 4<br />

2<br />

⎩B4i<br />

⋅ω0<br />

− B2i<br />

⋅ω0<br />

+ B0i<br />

= 0<br />

(10.146)<br />

Since all the B coefficients in (10.146) are functions <strong>of</strong> the controller parameters G pi<br />

<strong>an</strong>d G ii , the boundary <strong>of</strong> the controller parameters c<strong>an</strong> be obtained when ω 0 is ch<strong>an</strong>ged.<br />

The boundaries <strong>of</strong> the controller parameters should be found under different slip<br />

conditions <strong>an</strong>d different values <strong>of</strong> factor k i so that the controller parameters chosen<br />

guar<strong>an</strong>tee stability under all operating conditions.<br />

The stability issue using only active power has been studied by plotting the zeros <strong>an</strong>d<br />

poles <strong>of</strong> the tr<strong>an</strong>sfer function for speed estimation. The observer gains <strong>an</strong>d parameters <strong>of</strong><br />

the speed estimator are kept to be const<strong>an</strong>t <strong>an</strong>d factor k i is set equal to zero, the poles <strong>an</strong>d

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