A Hybrid IPT System Implementing Misalignment Tolerance and Constant Current Output With Primary Intermediate Coil

Inductive power transfer (IPT) systems have advantages of safety, flexibility, and convenience compared to plug-in charging systems. However, in practical applications, pad misalignment is still an almost inevitable issue which may cause variation in magnetic couplings, thus affecting the power transmission and reducing the system efficiency. Therefore, IPT systems are usually expected to achieve tolerance for misalignment. To fulfill this feature, a hybrid IPT system is proposed in this article. By adopting two coils compensated by different topologies in receiver side and an additional intermediate coil in transmitter side, load-independent constant output current with improved misalignment tolerance can be achieved. In addition, when the receiver pad is very far away from the transmitter pad, the proposed system can operate safely due to the inherent limitation ability of the primary inverter current. The design process is presented to optimize the misalignment performance. Based on the experimental results of a 3.3-kW prototype, the fluctuation of the output current is less than 5% within ±300-mm misalignment in <inline-formula> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula>-axis, −30- to +60-mm misalignment in <inline-formula> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula>-axis, and −80- to +60-mm misalignment in <inline-formula> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula>-axis. The system efficiency is 96.7% at nominal operating point (NOP) and varies from 94.7% to 97.8% with variable loads and misalignment.