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an investigation of dual stator winding induction machines

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the controllers. Because <strong>of</strong> the good perform<strong>an</strong>ce <strong>an</strong>d simple system hardware<br />

requirement, the indirect rotor field orientation control scheme is adopted in this work.<br />

The full-order observer based on Model Reference Adaptive Scheme (MRAS) is used<br />

to estimate the flux linkages <strong>an</strong>d <strong>stator</strong> currents using the measured <strong>stator</strong> voltage <strong>an</strong>d<br />

<strong>stator</strong> current signals <strong>of</strong> the motor. There are two sets <strong>of</strong> currents in the system, one is the<br />

set <strong>of</strong> measured or actual currents <strong>an</strong>d the other is the set <strong>of</strong> estimated currents. The error<br />

between the actual <strong>stator</strong> currents <strong>an</strong>d the estimated <strong>stator</strong> currents is used in a specialized<br />

error function to calculate <strong>an</strong> estimation error between the observer <strong>an</strong>d the actual<br />

physical system. Then the output <strong>of</strong> the error function is fed to the speed estimator to<br />

estimate the rotor speed. The adaptive mech<strong>an</strong>ism is established when the rotor speed<br />

estimated from this error is used as the feedback. The estimated rotor speed is equal to<br />

the actual speed when this error is reduced to zero. This method is a closed loop<br />

estimation scheme, which is different from flux estimation using the <strong>stator</strong> voltage<br />

equations.<br />

In this chapter, a speed sensorless control scheme based on a full-order flux observer<br />

using MRAS technique has been <strong>an</strong>alyzed. A novel error function has been proposed to<br />

ensure the stability within ultra-low speed r<strong>an</strong>ge. The Butterworth method is used to<br />

design the observer gains. The tr<strong>an</strong>sfer function <strong>of</strong> the estimated <strong>an</strong>d actual speeds is<br />

derived based on the error <strong>an</strong>alysis, <strong>an</strong>d is used to determine the parameters <strong>of</strong> the speed<br />

estimator for the sensorless control. The D-decomposition method is the design<br />

methodology for both speed estimator <strong>an</strong>d speed controller. Both the rotor speed <strong>an</strong>d slip<br />

frequency are varied within the possible operating r<strong>an</strong>ge to ensure the stability <strong>of</strong> the<br />

system based on the selected parameters.<br />

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