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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]

A multi-level boost topology based on a flying capacitor is compared in this work with the hybrid, multi-level, partial power processing topology already presented in the literature for use as a highly efficient and compact dc/dc stage in 1500-V, two-stage, grid-connected PV systems. Different variations of the resonant stage of the hybrid topology are analyzed and compared in terms of losses, volume and complexity. Full multivariable optimization is conducted for the multi-level boost topology with different number of levels and for all the analyzed variations of the resonant stage of the hybrid topology. Appropriately rated new classes of 650-V and 900-V WBG devices are included in the optimization algorithm. It is concluded that due to the dominant conduction losses and gap in the voltage rating of the commercially available WBG devices between 650V and 200V, increase of the number of levels over 4 leads to the deteriorated loss and volume performances. All the analysis related to the resonant stage of the hybrid topology is confirmed by detailed and comprehensive measurements of two prototypes of 4kW of nominal and 7kW of maximal power. Additionally, all the loss models applied in the optimization algorithms presented in this paper are confirmed by detailed measurements, thermal calibration and finite element thermal simulations of the wide bandgap devices and inductor designs employed in this work. [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]