Decoupling Compensation Design for Multi-Load Inductive Power Transfer Utilizing Unipolar Coils

In the previous inductive power transfer (IPT) system with repeater coils for multiple loads, bipolar coils were usually adopted to reduce the cross-coupling between different units. However, the bipolar coil has a complex structure and features a short energy transmission distance. Thus, unipolar coils rather than bipolar coils are adopted in the proposed multi-load IPT system in this paper. Compared to bipolar coils, unipolar coils cause cross-coupling between any two coils, not only those inside the same unit but also those among different units. To compensate for the cross-coupling inside the same unit, capacitor compensation based on the T-type decoupling principle is adopted. Then, to achieve better constant current characteristics, the cross-couplings between coils in constant voltage (CV) loops of different units are compensated according to their proportional current characteristics. Moreover, this paper analyzes the factors affecting the load current attenuation and provides guidance for achieving better constant current characteristics. Finally, a three-load IPT system is fabricated, and the capacitance compensation effect and constant current characteristics of the system are verified. The maximum reachable system efficiency is about 86.8% through measurement.