Minimizing Current in Inductive Power Transfer Systems with an Asymmetrical Factor for Misalignment Tolerance and Wide Load Range

In inductive power transfer (IPT) systems, misalignment and wide load range can lead to high current and control complexity. This can affect the performance of high-power systems. In this article, a method to minimize converter and primary resonant circuit currents based on an asymmetrical factor is proposed to improve IPT system performance over wide misalignment and load ranges. The proposed asymmetrical factor incorporates two design variables: an asymmetrical voltage factor and an asymmetrical compensation factor. These help to minimize current from two perspectives. First, they tend to redistribute zeroes and poles for power versus frequency characteristics. The power characteristic can be asymmetrical and monotonic over the working switching frequency range. Second, the input impedance angle can become insensitive to coupling factor and to load by adjusting the frequency that corresponds to the minimum input impedance angle. The current increases by only 15% over a 2:1 coupling coefficient variation range at rated load. Analysis and design guidelines are presented for the proposed method. A 2.1-kW prototype has been prepared to verify the approach.