Abstract:
Inductive Power Transfer (IPT) technology allows electrical energy to be transferred between two loosely coupled inductors over relatively large air gaps. An IPT system can be divided into two sections - a primary supply and one or more secondary pickups and controllers. Currently, IPT applications have been used in a variety of industrial and commercial applications. This thesis proposes a novel AC processing controller which directly regulates power in AC form, hence producing a controllable high-frequency AC source. The pickup has significant advantages in terms of increasing system efficiency and reducing pickup size compared to traditional pickups that also produce a controlled AC output using complex AC-DC-AC conversion circuits. The parallel AC processing pickup employs switches operating under Zero Voltage Switching (ZVS) conditions to clamp parts of the resonant voltage across a parallel tuned LC resonant tank to achieve a controllable AC current source. The derivation of key power electronic specifications such as component ratings, output harmonic content and power factor are shown along with the pickups normalized characteristics. Practical implementation aspects such as a new synchronization scheme using clamp time, series and parallel connection of switching devices to achieve higher ratings and a new PWM control technique to reduce conduction losses are investigated. By adding a rectifier, a controlled DC output can be produced. Practical examples including a lighting system and an EV charging system have shown the pickup to achieve very high operating efficiencies above 96%. The series AC processing pickup uses an AC switch operating in series with a resonant network to produce a controllable AC voltage source. When a rectifier is cascaded onto this pickup, it can also produce a precisely controlled DC voltage. The circuit is analytically analyzed and the maximum efficiency for a 1.2kW prototype is measured to be 93%. A direct AC-AC IPT system which takes 50Hz mains input and has 50Hz mains output without requiring a DC link is also proposed. This technique is based on the AC processing concept with matrix converters giving it the advantage of high efficiency. Other AC-AC systems at the track frequency are also proposed to enable controllable intermediate IPT links suitable for powering separate IPT tracks. Both of these later systems, appear to have significant future potential but need much further study to understand and overcome practical limitations which could form the basis of separate Ph. D. studies in their own right.