Abstract
The possibility of increasing the transmission efficiency in mid-range wireless power transfer (WPT) applications can be achieved by inserting resonant relay coils between the transmitting and receiving sides of the device, forming an array of magnetically coupled resonant circuits, over which a receiver can be placed. This is a very cheap solution for improving the performance of the WPT apparatus, even if the complexity of the system increases, requiring a complete and detailed investigation for a smart design and control of the apparatus. The presented study investigates the current distribution in the coils of the array, which revealed strong peaks in magnitude depending on the load and receiver position. The analysis is carried out with the transmission line (TL) theory and it is performed for different positions of the receiver, as well as for different load conditions. Furthermore, a real application is considered and discussed, which includes the presence of a power converter as power supply and a battery charging system as load. Each resonant circuit resonates at 150 kHz and the whole apparatus is capable to transmit power up to 1 kW with an efficiency around 70%. The theoretical results have been validated with experimental measurements.
Highlights
In recent years, wireless power transfer (WPT) has received increasing attention for the prospects of use that it offers, ranging from powering portable electronic devices to electric vehicle (EV) charging
High-frequency inductive power transfer (IPT) systems are usually the most popular candidates, allowing the size of the components to be limited with an acceptable transmission distance, even if the electromagnetic radiation may become hazardous as the frequency increases
The analysis is developed considering phasor quantities for the voltages and currents involved in the system, which can be determined solving the Kirchhoff voltage law (KVL) equations written for each cell
Summary
Wireless power transfer (WPT) has received increasing attention for the prospects of use that it offers, ranging from powering portable electronic devices to electric vehicle (EV) charging. They can be sized for a limited amount of power, resulting in WPT systems suitable for portable electronics or medical devices only [6,7] Through the theory of magneto-inductive (MI) waves [19,20,21] that is exploited in order to provide a satisfactory description of the operation and useful insights into the design The efficiency of this kind of systems has been deeply investigated [12,16,18,21], while the behaviour of the resonator currents requires a more in-depth research due to power reflection phenomena that can occur [21].
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