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Title: Low speed encoderless control of permanent magnet AC machines for automotive applications
Author: Curson, Adam Stefan
ISNI:       0000 0004 2746 5414
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2010
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This thesis presents an analysis of low speed sensorless control techniques for low voltage permanent magnet motor drives. The specific application of these drives is for power steering in small to medium sized cars. The focus of the project is to create a low speed sensorless drive with minimum current distortion, such that any additional torque ripple or audible noise is acceptable for the steering application. A comparison of two sensorless control methods is made, in terms of their benefits and drawbacks. The first method uses a measurement of the motor current derivative in response to the normally applied PWM switching vectors, to obtain a position estimate. The second method uses the high frequency current response to an injected high frequency voltage in the d-axis of the machine. Both methods track the variation of inductance in the machine due to local saturation as the machine rotates. The quality of the position estimate, current distortion and audible noise generated by the methods are investigated and compared. Experimental results show that the position quality of the current derivative method is better and is quieter than the d-axis method. However it produces a larger current distortion compared to the d-axis method. The d-axis method requires a large injection voltage (10% of rated) to be applied due to the poor quality of the estimated position signal below this voltage. For the current derivative method it was found experimentally that increas- ing the vector extension time (tmin) up to 1OJ.L3 gave an improved position es- timation performance. at the cost of increased current distortion and audible noise. For the d-axis method increasing the injection frequency from 1.5kHz to 2kHz causes a decrease in position estimation quality, an increase in audible noise but a decrease in current distortion.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available