Position Offset Tolerance Design Considering Variations of Both Self and Mutual Inductance of Inductive-Power-Transfer Systems for Optimal Constant Current Outputs

Current research on position offset tolerance designs of inductive-power-transfer (IPT) systems mainly focuses on how to maintain the stability of mutual inductance. In fact, position offset between transmitters and receivers would not only change the mutual inductance but also the inductance of the magnetic coupled structure, which would deteriorate the tuned resonant condition and further affect output powers, system efficiency, and zero voltage switching (ZVS). To achieve constant-current (CC) charging with optimal efficiency, this article attempts to design a position offset tolerance control that considers variations of both self-inductance and mutual inductance simultaneously for a typical S-S compensation IPT system. First of all, a fast frequency searching scheme is proposed to track the system resonant frequency and further identify the self-inductance of the magnetically coupled coils. Then, the steady-state mathematical models of IPT systems are reconstructed based on the identified parameters. Furthermore, the mutual inductance can be further identified by sampling the peak current of the secondary side. The optimal control parameters for CC outputs with ZVS and minimum conduction losses could be calculated. Finally, the effectiveness of the designed method is verified by experimental results. The estimated errors of system resonate frequency, self, and mutual inductances are all less than 3%. Meanwhile, CC outputs with ZVS and minimum conduction loss can be well achieved under different position offsets.