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an investigation of dual stator winding induction machines

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generally the case to get a good perform<strong>an</strong>ce from the LPF. Hence the following gain<br />

( G i ) <strong>an</strong>d phase compensations ( P i ) are proposed to solve the problem:<br />

G<br />

P<br />

i<br />

i<br />

=<br />

= exp<br />

ω + a<br />

2<br />

ei<br />

ω<br />

ei<br />

2<br />

i<br />

( − jϕ<br />

)<br />

i<br />

−1⎛<br />

a ⎞ i<br />

where, ϕ =<br />

⎜<br />

⎟<br />

i t<strong>an</strong> <strong>an</strong>d ω ei is the synchronous <strong>an</strong>gular frequency.<br />

⎝ ωei<br />

⎠<br />

These two compensations c<strong>an</strong> be combined to be:<br />

1<br />

Gi ⋅ Pi<br />

= ωei<br />

⋅<br />

ω<br />

ei<br />

( − j a )<br />

i<br />

303<br />

(8.48)<br />

(8.49)<br />

If the pole <strong>of</strong> a LPF a is varied proportionally to the synchronous motor speed, the<br />

ratio <strong>of</strong> the motor frequency to the cut<strong>of</strong>f frequency is const<strong>an</strong>t. Then (8.49) is converted<br />

to a compensation with const<strong>an</strong>t coefficients. If the const<strong>an</strong>t coefficient is assumed to be<br />

k<br />

a<br />

i<br />

i = , the compensation expression <strong>an</strong>d the compensated flux linkages are given as:<br />

ωei<br />

λ<br />

λ<br />

λ<br />

qsi<br />

qsi<br />

dsi<br />

dsi<br />

qsip<br />

dsip<br />

( λ + jλ<br />

) ⋅ ( − j ⋅ k )<br />

+ jλ<br />

=<br />

1<br />

= λ<br />

= λ<br />

i<br />

i<br />

qsip<br />

+ k ⋅ λ<br />

− k ⋅ λ<br />

dsip<br />

qsip<br />

dsip<br />

i<br />

(8.50)<br />

where, λ qsip <strong>an</strong>d λ dsip are the estimated flux linkages using the Low Pass Filter (LPF);<br />

λ qsi <strong>an</strong>d λ dsi are the flux linkages after compensation.<br />

If the <strong>stator</strong> resist<strong>an</strong>ce is ignored, the complete model <strong>of</strong> the <strong>stator</strong> flux estimation is<br />

given as:<br />

λ<br />

ω + a<br />

2 2<br />

qdsi 1 ei i<br />

= ⋅ ⋅exp<br />

si s + ai<br />

ωei<br />

V<br />

( − jϕ<br />

)<br />

i<br />

(8.51)

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