Guanxi Li

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 power transmission and reducing 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 paper. 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. Besides, 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 3.3kW prototype, the fluctuation of the output current is less than 5% within ±300mm misalignment in Y-axis, -30mm to +60mm misalignment in Z-axis and -80mm to +60mm misalignment in Xaxis. The system efficiency is 96.7% at nominal operating point (NOP) and varies from 94.7% to 97.8% with variable loads and misalignment.

Inductive power transfer (IPT) systems are appropriate for electric vehicles (EVs) charging applications because of the advantages of safety and convenience. However, due to the considerable influence of pad misalignment, improving misalignment tolerance is important for IPT systems. Besides, constant current (CC) and constant voltage (CV) output characteristics are usually required for EVs battery charging. Therefore, to fulfill both features, a hybrid IPT system implementing high misalignment tolerance with inherent CC–CV output is proposed for EVs charging applications in this article. Two coils connected reversely in series are applied on the transmitter side while two coils, respectively, compensated by a capacitor and an inductor–capacitor–capacitor are applied on the receiver side. Hence, without an extra dc–dc converter or complicated control strategy and corresponding circuits, CC–CV output can be naturally achieved with high misalignment tolerance, which obviously increases the system reliability. Besides, zero-voltage switching and zero-phase angle condition can be easily achieved. A 1-kW experimental prototype is built. The experimental results show that the fluctuations of the constant charging current and the constant charging voltage are less than 5% when the proposed system operates within the predetermined misalignment range.