Abstract:
This thesis proposes a new LCL pickup topology which improves the efficiency, cost and practicality of high power inductive power transfer (IPT) pickups. IPT is a technology which enables wireless power transfer, over a reasonable air gap, between two electrically isolated systems. It is widely used in a variety of applications from large industrial vehicles to small sensors or devices. The LCL pickup topology improves on the traditional tuning topologies by having zero current switching in the rectifier, only reflecting a real load onto the track, presenting a current source output for easy voltage regulation and minimizing the current in the pickup when it is decoupled. When the regulatory circuitry is placed on the LCL pickup it causes distortion in the output current and a drop in power. The distortion introduces extra inductance into the compensation network, which results in a VAR load being reflected onto the track. To compensate for the extra inductance an extra capacitor is introduced, resulting in the ‘Unity Power Factor’ (UPF) pickup. Analysis of the UPF pickup at the edge of continuous rectifier conduction produced a design strategy which can compensate for the drop in power and maintaining unity DPF. The new design strategy is also applied to Automatic Guided Vehicles (AGV), where the mutual inductance between the pickup and track can change. The UPF pickup can be used to reduce the variation in track inductance due to the reflected load of the pickup. A practical 2kW AGV system and 1.5kW monorail system were constructed to confirm the validity of the UPF design strategy. To further improve the operating efficiency of pickups, self tuning strategies are investigated to counter the effects of mis-tuning due to manufacturing tolerances and long term capacitor degradation. An input phase tuned LCL pickup is proposed which seeks to maintain unity input DPF by varying the effective inductance of Z3. This strategy can theoretically increase the output power of the mis-tuned pickups. A practical lkW input phase tuned pickup was created which proved that the output power and unity power factor can be maintained with a 20% deviation in tuning.