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This article presents a 6.78-MHz wireless power transfer (WPT) system, which is configured to automatically cancel the reactance in primary and secondary. In the WPT system, the detuning caused by the parameter variation, the implementation of the frequency control, and components tolerance will decrease a lot the system performance, especially in very low coupling (k = 0.06) and low power applications. The delivered power is sensitive to the reactance under low coupling and high-frequency conditions, accordingly, a novel self-adaptive WPT system to automatically retune the resonance is proposed. The proposed concept uses a synchronous series compensator (SSC) instead of a capacitor in series with the secondary to tune it, which can automatically cancel the reactance caused by the inductor, nonresistive load or frequency variation, hence increases the system performance in terms of delivered power and efficiency. A prototype has been built and tested experimentally to validate the feasibility of the proposed concept. A constant power of 1.8 W can be transmitted with 50% overall efficiency at a coil separation distance of 1.5 cm between the printed-circuit-board transmitter (3 × 3 cm2) and receiver (1 × 2 cm2) under wide detuning conditions, being 0.95 the ratio between distance and the equivalent diameter of receiver. [ABSTRACT FROM AUTHOR]

In this article, a series–series wireless power transfer (WPT) system combined with an inverse coupled current doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high-current low-voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with full-bridge rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10 kW 400 V/48 V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 and 55 Vdc, and the rated output current is 200 A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220 W energy saving with respect to the traditional diode-rectifier system, when 9.5-kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high-power WPT applications. [ABSTRACT FROM AUTHOR]