For more than a century it has been known that signals and power can be transferred electromagnetically. This knowledge has motivated substantial research and development into wireless signal transmission which today is competitive with traditional conductive cabling systems. Power transfer across air gaps, however, has seen more modest development and has tended to be restricted to electric machines that have tight magnetic couplings. It is only very recently that a novel technique termed IPT (Inductive Power Transfer) has made power delivery to movable objects across large air gaps a practical reality. A typical IPT system comprises a primary power converter supplying high frequency alternating current to a conductive track loop with multiple secondary power pick-up circuits loosely coupled to it. IPT employs modern power conversion, control, and magnetic coupling techniques to achieve clean and reliable power transfer without direct electrical contact. Many practical applications have been found for IPT in materials handing, lighting, and transportation systems. One of the major constraints, however, is the primary power supply, particularly at high power levels and when power transfer over large distances is required. In this thesis selected resonant converters suitable for IPT power supplies are investigated using mathematical analysis, computer simulations and practical experiments. The basic characteristics and underlying principles of the converters are studied in order to determine their dynamic performance and power transfer capability. Special attention is given to improving existing IPT power supplies while investigating new power converters in order to achieve high efficiency and reliable operation at reduced cost. The current-fed parallel resonant converter power supply has been the basis of most commercial applications to date. It has a high efficiency and produces good voltage and current waveforms. However, both the track length that it can drive and the power level it can operate at are limited and the system may vary in frequency if the track resonant circuit and the pick-up load are not carefully designed. As a result, this supply, in its simple form, is only suitable for short track lengths and low power applications. The voltage-fed series ii quasi-resonant converter power supply controls the frequency directly and is capable of driving longer track lengths as a result of series compensation employed in the track loop. However, its voltage and current waveforms contain more harmonics, and while high efficiency may be achieved with soft switching, the condition is very dependent on the track compensation and is difficult to meet during start-up and shut down transients. In consequence, this supply is suitable for medium track lengths and medium power level applications. Improved current-fed and voltage-fed IPT power supplies are proposed in this thesis. They have the most preferred track current properties, including constant magnitude and nearly pure sine wave characteristics. Despite the circuit complexity and high system cost involved, these supplies are ideally suitable for long track lengths and high power applications. A novel converter based on free oscillation and energy injection control is also presented and shown to be capable of achieving high frequency AC power generation at very low switching frequencies while reducing the system cost. As such it is appealing for long track length, high track current, high frequency, and low voltage source applications. Finally, a very simple converter based on self-sustained oscillation without an external controller is demonstrated at low operating voltages, and a cost-effective option to overcome the start-up problems exhibited by most IPT power supplies at high voltages is shown with excellent dynamic zero voltage switching performance. / Whole document restricted, but available by request, use the feedback form to request access.
| Identifer | oai:union.ndltd.org:AUCKLAND/oai:researchspace.auckland.ac.nz:2292/3 |
| Date | January 2001 |
| Creators | Hu, Aiguo Patrick |
| Contributors | Boys, John T |
| Publisher | ResearchSpace@Auckland |
| Source Sets | University of Auckland |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | Whole document restricted but available by request. Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
| Relation | PhD Thesis - University of Auckland, UoA1013314 |
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