Wireless Power Transfer (WPT) for autonomous underwater vehicles (AUVs) has been a research focus in recent years. This paper studies the inductor-capacitor-capacitor and parallel (LCC-P) compensation topology to achieve a compact receiver for AUVs. Unlike the series-series (SS) compensation topology, the LCC-P topology retains the advantages of the double-sided LCC topology and has a more compact receiver than the double-sided LCC topology with fewer elements used on the receiver side. The analytical model of such a WPT system is established to analyze the output power and transfer efficiency. The LCC-P topology has a higher efficiency compared to the SS topology due to the smaller conduction loss of the inverter. Moreover, a method of eliminating the DC filter inductor L0 is proposed to further decrease the size and weight of the receiver. The amplitude of the withstanding voltage on the receiver compensation capacitor without L0 is approximately decreased by 40% compared to that with L0. Both cases of with and without L0 have a constant current output and the peak efficiency without L0 is about 94%, which is 1% lower than that with L0. A prototype was built and the experimental results verified the theoretical analysis.

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Underwater wireless power transfer (WPT) technology can enhance the endurance of the autonomous underwater vehicles (AUV). WPT that based on electromagnetic theory will generate eddy current loss (ECL) in seawater. In this paper, we make use of shielding coils to weaken the electromagnetic field (EMF) in seawater, which can reduce ECL and improve the transfer efficiency. Simplified circuit models were proposed to provide an intuitive and comprehensive analysis of the transfer efficiency and the finite element analysis (FEA) was used to simulate the distribution of EMF. We learn that the system with shielding coils performs better when the operating frequency is relatively high by comparing the power transfer efficiency of the underwater WPT systems with and without the shielding, and its maximum efficiency is higher than the system without shielding. The effect of the shielding coils has the similar influence when compared with the metallic plate. While considering the efficiency and weight of coils, the results show that the shielding coils can be used in the underwater WPT system to improve the power transfer efficiency.

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This paper introduces the working principle of the inductive power transfer (IPT) system from the perspective of the electromagnetic field. Using Maxwell's equations, the analytical solution for the electromagnetic field, synthesized by the primary and secondary circular coils in an IPT system, is deduced in detail to obtain the electric field in the IPT system, and the derivation process is easy to understand for researchers engaged in IPT. The final solutions are obtained by combining analytical derivation and the numerical integration method to find the induced voltage in the secondary coil. Finally, by comparison, the simulation results from the finite element software are in a good agreement with those from the analytical analysis. Moreover, an IPT system is set up to validate the analytical and simulation results, and the maximal relative error is under 6% in different working conditions, which shows that it is feasible to understand the working principle of IPT systems from the viewpoint of the electromagnetic field.

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