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Abstract
This thesis investigates the dynamic control performances of a 14-pole/18-slot fractional slot concentrated winding (FSCW) interior permanent magnet synchronous machine (FSCW IPMSM). The machine was run with two commonly used control techniques: Field Oriented Control (FOC) and Direct Torque and Flux Control (DTFC). The FSCW IPMSM under consideration was previously designed and constructed at the University of New South Wales (UNSW) to achieve a high torque/high power density, high efficiency, a very wide (> 10:1) constant power speed range and very low cogging torque. The key favourable characteristic of an FSCW is the short end windings, which results in low copper loss and more compact design compared to its distributed winding counterpart. The other benefit of this particular 14-pole/18-slot FSCW IPMSM design includes some saliency ratio, which is desirable for sensorless control, compared to other CW permanent magnet machines. Nevertheless, this type of machine has so far been only investigated in terms of steady state performance; the dynamic control performance has not been studied yet. The major objective of this study is to investigate the dynamic control performances of the 14/18 FSCW IPMSM machine while running with model based controllers such as the FOC and DTFC, to study their limitations and to propose improvements of these controllers.
The FOC was first implemented in the prototype FSCW machine using standard distributed windings IPMSM mathematical model. A number of issues associated with the FSCW IPMSM under FOC were detected and investigated thoroughly. The issues were resolved by implementing a closed-loop rotor position compensator and a new voltage compensation scheme.
It is believed that this thesis, for the first time, applied the Sensorless Direct Torque and Flux Control (DTFC) to a FSCW IPMSM. The performances of the FSCW-IPMSM under DTFC at very low speed, however, were not satisfactory. To improve the performance of the DTFC at low speed operation, a closed-loop extended flux linkage model is proposed. Although it was proven that the proposed closed-loop extended flux linkage DTFC is superior to the open-loop DTFC, the extremely low speed operation still is not achieved.
To elevate the performance of the sensorless DTFC drive in extremely low speed religion, including standstill, a sensorless DTFC based on high frequency injection method for the FSCW IPMSM is implemented in this thesis.