Dynamic Receiver Characterisation in HF-IPT Systems

This paper expands on our previous work on an induced voltage estimation technique of an HF-IPT system, with the specific purpose of live system monitoring and rectifier characterisation. With this method it is possible to track changes in rectifier behavior depending on loading conditions and coupling factor, while only using primary-side measurements in real time. This technique can be particularly useful for live monitoring of the system, foreign object detection and optimal tuning of the resonant tanks for variable coupling by minimising the reflected reactance from the rectifier to the primary side. The implementation presented in this work is achieved using a Class EF inverter operating at 13.56 MHz and a prediction model with a root mean square error lower than 1.5%. The experimental results are obtained using four rectifiers, three of which are characterised at a fixed coupling factor of 4%, while varying the load. The fourth rectifier is mounted on a batteryless drone that uses a copper-plated propeller guard as the receiver coil. This last setup is tested under different throttle conditions and for a range of coupling factors from 5% to 16%.