This work considers the sensorless control of AC machines for the low and zero speed operation range. Two novel techniques have been developed that use the inherit nature of the inverter PWM to estimate the rotor position of the machine. The inherent back EMF and the saliency of AC machines can be utilized to identify the rotor/flux position. The zero vector current derivative (ZVCD) technique for permanent magnet synchronous machines (PMSM) utilizes both of these effects. No additional test signals are injected into the machine and the difficulty in sensing the machine terminal voltage at low speed is eased. Only three standard current transducers are used in the drive system. For the position/ speed estimator only the machine current derivative during the relatively long (at low speed) zero voltage vectors is used for obtaining the rotor position. Practical results show the operation of the drive at several torque and speed conditions including stand still. A further method has been developed for the sensorless control of induction machines. The high frequency harmonics present in a PWM inverter drive system can be used to detect an equivalent impendence saliency that shows modulation due to rotor/ flux position saliency. The proposed method focuses particularly on the extraction of spatial saliency modulation due to rotor bar slotting effect, which can be used to determine the mechanical rotor position. No additional signal injection is required; the method simply employs some of the inherent PWM carrier harmonics.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:514859 |
| Date | January 2009 |
| Creators | Raute, Reiko |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/10930/ |
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