Robust Active Tuning for Wireless Power Transfer to Support Misalignments and Variable Load

Wireless power transfer has been employed in several applications where the use of cables for powering remote devices are not suitable or feasible. However, such devices work in a tuned frequency and thus the transferred power is set to make the system operate under resonant conditions. These conditions and, in turn the transferred power, are highly dependent on the parameters of an equivalent electrical circuit. Such power can drop abruptly with variations of the relative position between the transmitter and receiver coils as well as the variations of the output load. This work presents a multi-variable with method for maximizing the output power in a wireless power transfer system to make it robust to misalignments and load variations. The described method monitors the magnitude and phase of the input current of the inductive link and proposes an automatic control algorithm by controlling both, the source frequency and a variable matching network. Preliminary results showed that the power delivered to the load can be hold approximately constant over a large range of magnetic coupling coefficient and the load values. These results are a significant improvement of the results obtained by controlling only the source frequency or only the matching network.