Application of Dual Cycloconverters to a Double Fed Motor for Traction Drives
| Autor: | Brown, Murray Gerald |
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| Rok vydání: | 2010 |
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| Druh dokumentu: | Diplomová práce |
| Popis: | Variable speed AC drives have become the new standard for high performance drive systems. Very high power traction drives present a particular challenge for AC drive technology because of the simultaneous need for high-torque vibration-free operation at standstill, traction-limited dynamic braking, and high speed operation. In this work, two independently controlled cycloconverters are used with a wound rotor machine to provide a double fed drive system that overcomes the frequency limitations of the cycloconverters and provides a stable high power drive, with potential for rapid torque response and power factor control. A new 'Jitter' control method is derived for the firing angle control of the cycloconverter. This method effectively spreads the cycloconverter output harmonics over a broader spectrum and thus minimizes the filtering requirements. The double fed motor (DFM) equations are applied to the DFM circle diagram and a simulation program has been written to plot the circle diagram and give a geometric interpretation of the developed torque. A new algorithm is proposed using δν, the pseudo torque angle, to give direct control of the torque using only position feed-back. A novel frequency hopping algorithm is also derived that allows the cycloconverters to be operated at high frequencies without generating harmonic torques. A dual cycloconverter drive was built to verify the stability and torque-speed performance of such a system. Reliable operation was achieved by using bank switching sensors based on detecting the reverse bias across a series connected diode, and by short circuit detection circuits with automatic reset facilities. The control software displays system status information on the screen, with on-line parameter modification, and provides a complete range of manual and automatic modes of operation to facilitate system development and testing. Doctor of Philosophy (PhD) |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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