The wireless power transfer (WPT) system is widely applied in the underwater environment. A multitransmitter multireceiver WPT system is proposed in this article for the application of the submerged buoy, and numbers of beacons can be charged at the same time to send more data. Both series and parallel connection structures of several coils are analyzed in detail. In order to increase the system efficiency at ultracapacitors charging process, a maximum efficiency tracking with a primary current controller and an optimal resistance controller is studied and designed. All mentioned above analyses are verified in a three-receiver WPT system prototype. When ultracapacitors are charged from 10 to 25 V, the system efficiency is achieved at almost 70.5%, and the charging voltage of all three receivers can be stabled.

The power supply of underwater devices can be realized by the non-electrical contact wireless power transfer (WPT) technology. The diversity and flexibility of devices carried by the remote operated vehicle (ROV) can be increased by the WPT which can achieve convenient and safe device switching. Power independent regulation is a key for the underwater wireless power connector (UWPC) with multi-load, and a superimposed dual-frequency modulation (SDFM) method is proposed in this article to achieve the load power independent regulation. The equal-area rule is first applied to SDFM, which can use one inverter to generate SDFM current at the transmitter. The theory of decoupled power transfer is analyzed in detail for the SDFM UWPC with dual-load. All above analyses are verified in a dual-load UWPC system prototype. The experimental results show that the SDFM current is generated using one inverter, and the load power can be independently regulated by adjusting the output voltage of the inverter. Furthermore, the load power is still independent and controllable under the conditions of load switching and mutual inductances changing. The dual-load UWPC system power can reach 50 W and DC-DC efficiency is about 68.73 %.

This paper proposes a wireless power transfer (WPT) system with quasi-uniform magnetic coupling to satisfy the Unmanned Aerial Vehicle (UAV) lightweight constant current (CC) charging without secondary feedback control. The traditional wired charging for UAVs is less automated and not portable. WPT as a new way of energy supply has shown great potential for charging UAVs with safety and automation. However, some actual challenges still exist due to the UAV's special structure and lightweight requirements. Accordingly, a coupler with a lightweight receiving coil and double transmitting coils to satisfy the CC wireless charge of the UAV without communication and control is proposed in this paper. The power transfer and CC charging theory analysis are carried out, and the structure of the coupler is designed. A simulation model and a prototype are built, as well as the simulation and experimental results are given to verify the performance of the proposed UAV CC charging system. In the experiment, 23.8 Wh of power is charged to the UAV's lithium battery pack with CC in two hours. This paper provides a reference to the design of the UAV wireless charging stations.

Inductively coupled power transfer (ICPT) is a new technology used in mooring buoy for underwater sensors power supply. In this paper, an ICPT system with a mooring cable to power double ultracapacitor chargers is proposed. Firstly, the system model is analyzed in detail, including the primary side of abovewater system, the mooring cable, and the secondary side of underwater system. Secondly, to reduce the torque between buoy and mooring cable, a non-contact rotary magnetic coupler, which can provide two degrees of freedom, is designed. Thirdly, considering that the charging voltage is difficult to feedback directly, indirect closed-loop control using current in the mooring cable is applied to achieve constant current and voltage charging. Finally, the proposed analyses are verified in experiments. As gap of the abovewater magnetic coupler changes, two ultracapacitor modules are charged in 1A, and the maximum efficiency is 65.75% respectively.

This paper proposes a multiple transmitting array wireless power transfer (MTA-WPT) system with constant output power charging for consumer electronics, such as tablets and mobile phones. Compared to conventional WPT systems, this proposed system can achieve constant output power by controlling the current phase shift of the transmitting (Tx) coils when the receive (Rx) coil is located at different positions and directions. The detailed circuit topology of the proposed system is modeled and analyzed to obtain the correspondence between the current phase shift and load output power. Furthermore, the excitation current distribution strategies for a system of three and four Tx coils at optimized efficiency are theoretically analyzed. The simulation demonstrates that the proposed system can achieve constant output power with modulating the phase shift at various Rx sites. Finally, an experimental prototype with four Tx coils is designed and carried out to prove the effectiveness of the phase shift modulation method and current distribution strategy. Besides, the superiority of the proposed MTA-WPT system is verified by comparison with other methodologies. The experimental results show that the output power of Rx at different positions is kept at roughly 41W with the transmission efficiency over 80% by the Tx current phase shift modulation.

Batteries are commonly used as the power source of present underwater sensors of ocean buoys. However, batteries need to be frequently replaced, which is costly. To implement the real-time power supply for a buoy’s underwater sensor, a new inductively coupled power transfer (ICPT) system that consists of two couplers and a closed cable is proposed in this paper. The special closed cable, which is the both mooring cable and transmission media, is designed to diminish the influence of changes on impedance. A model of the particular ICPT system is established. Optimization of system parameters are carried out based on the model and verified by means of the simulations. Resonant compensation is used to improve the power transfer performance. Finally, many experiments are implemented to compare with the original prototype. It is confirmed that this system can help solve the difficulty of the energy limit to a buoy’s underwater sensor.