Compact Z-Impedance Compensation for Inductive Power Transfer and Its Capacitance Tuning Method

This paper proposes a Z-impedance compensation for inductive power transfer (IPT). There are three contributions. First, a Z impedance-S compensated IPT topology is developed to achieve constant transmitting current, load-independent constant-voltage (CV) output, and zero-phase angle (ZPA) property, which is an alternative to the conventional LCC-S topology. Second, compared to an LCC circuit, the Z-impedance compensation burdens much smaller current/voltage stress and shows lower sensitivity to compensation capacitance drift, contributing to high-power applications. Third, a capacitance tuning method is proposed to regulate power, which improves the misalignment tolerance. Two 5 kW Z impedance-S and LCC-S IPT prototypes are implemented. Experiments show that the Z impedance-S IPT system achieves comparable power and efficiency with an LCC-S IPT system with smaller current/voltage stress and lower sensitivity. The proposed capacitance tuning method is effective to maintain a rated 3 kW output within a horizontal misalignment of [0 100mm] with zero-voltage-switching (ZVS) and ZPA operation. Meantime, A peak dc-dc efficiency of 96.88% is realized in the Z impedance-S IPT system at 3.47 kW.