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an investigation of dual stator winding induction machines

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the modulation index <strong>of</strong> the rectifier <strong>an</strong>d load resist<strong>an</strong>ce are constrained to achieve<br />

converter excitation. For const<strong>an</strong>t total output power condition, a greater load resist<strong>an</strong>ce<br />

requires a smaller modulation index <strong>an</strong>d the power distribution coefficient c<strong>an</strong> be used to<br />

ch<strong>an</strong>ge the power ratios <strong>of</strong> both <strong>stator</strong> <strong>winding</strong>s. Similarly, the effect <strong>of</strong> the magnetizing<br />

induct<strong>an</strong>ce on the magnitudes <strong>of</strong> the modulation indexes is shown in Figure 8.3(b),<br />

assuming a const<strong>an</strong>t rotor speed <strong>of</strong> ω = 400 rad/s <strong>an</strong>d a const<strong>an</strong>t load (RL =100 Ω). The<br />

r<br />

optimal slip is calculated using (8.21). The variation <strong>of</strong> M1 <strong>an</strong>d M2 with the ch<strong>an</strong>ge in the<br />

power distribution factor is also shown in Figure 8.3(b). Because <strong>of</strong> the saturation <strong>of</strong> the<br />

magnetizing induct<strong>an</strong>ce, two corresponding magnetizing flux linkage levels c<strong>an</strong> be found<br />

for a given modulation index value. This implies that two different output dc voltages c<strong>an</strong><br />

be obtained for each <strong>of</strong> the resulting magnetizing flux linkages.<br />

8.4 Input-Output Linearization<br />

It is observed from the machine model that the model equations are nonlinear.<br />

Therefore, it is not easy to see how to control the behaviors <strong>of</strong> the outputs by using the<br />

input signals. If a direct <strong>an</strong>d simple relationship between system inputs <strong>an</strong>d outputs c<strong>an</strong><br />

be found, the difficulty <strong>of</strong> control design will be reduced. The input-output linearization<br />

approach is one <strong>of</strong> the methods for nonlinear control design. The fundamental idea is to<br />

tr<strong>an</strong>sform a nonlinear system into a fully or partly linear one so that traditional linear<br />

control techniques c<strong>an</strong> be applied for control design.<br />

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