Design and Optimization of a Three Phase Inductive Power Transfer System

• DIRECTORS: Haritza Camblong and Irma Villar 
• UNIVERSITY: Euskal Herriko Unibertsitatea / Universidad del País Vasco

Abstract:

The concept of a sustainable transportation system within cities must be reconsidered in order to achieve healthier urban areas. Many cities are currently suffering from significant pollution problems. Mainly, due to the fact that private motor vehicles, with large CO2 emissions, represent over the 50 % of the modal share. Thus, it is clear that public transportation must be stimulated. Particularly talking, railway conveyance is very attractive, as no direct emissions are produced.

Railway transportation systems, such as trams and metros, are very advantageous in efficiency, user price, safety and comfort. However, compared to a vehicle, the initial and maintenances costs are very high. The high initial cost is mainly due to the high price of the batteries. On the other hand, the maintenance is enormously affected due to corrosion and environmental exposure that suffers part the power supply system, the pantograph and the catenaries, being these the most critical components. In addition in big cities with many tram lines, the overhead catenaries have a great visual impact. In order to ease these problems, one of the most promising solutions is to endow the railway vehicle with an Inductive Power Transfer (IPT) system. This way the catenary could be removed and the charing will be done wirelessly with the transmitter coils buried in the ground.

Between different possible IPT systems, this work is focused on Dynamic Inductive Power Transfer (DIPT) systems, i.e charging while the vehicle is moving. Particularly taking, this thesis delves in the design of meander type coils. The objective of this work is to propose a method for designing three-phase inductive charging systems. For that purpose, the fundamental working principles of IPT system is introduced in the first part of this thesis. The equations are presented and the pole-splitting limit are calculated. Validating them with a 3.3 Kw prototype.

Afterwards, the meander type coil working principles are described. The equations that model this coils are shown and the possibility of achieving constant coupling with multiple phases is highlighted. Moreover, with the presented modifications, the multi-phase system can be modeled by an equivalent single-phase system. Thank to this, the polesplitting limit can easily be calculated. Using this limit a design procedure is described and experimentally validated in a 50 W prototype. This prototype shows the potential of this type of coils, achieving constant power transmission with an efficiency of 70 %.

Based on this design procedure an optimization methodology is proposed, so as to improve the size, weight and cost of the DIPT. The trade-offs between these performance indicators are highlighted. Finally, this optimization is applied for a 9 kW system and is validated in a real test bench with an efficiency of 90 %, for any position and output power with a coil separation of 100 mm.