In a wireless power transfer (WPT) system, in order to reduce the leakage of the magnetic field in the space and to improve the transmission efficiency of the system, a magnetic shielding mechanism is usually added to the coupling coil. However, the commonly used ferrite material has defects of brittleness, easy cracking, and a low saturation limit. Therefore, a novel magnetic shielding mechanism based on a quartz fiber and nanocrystalline reinforced resin matrix composite material was proposed, and epoxy resin and cross-laminate-splicing processes were used to improve the resistivity of the nanocrystalline material and to improve the eddy current loss. A discretized geometric model was designed for quartz fiber, and the effects of different shielding structures on the space magnetic field and the power loss were simulated and analyzed. In the experiment, a space magnetic field measurement system was built, and the transmission efficiency was analyzed. The results showed that the new magnetic shielding mechanism has a good shielding effect, can effectively suppress leakage of the magnetic field in space, reduce the weight, and improve the mechanical performance while also achieving a high transmission efficiency of 85.6%.

This paper proposes an M-ary amplitude shift keying (MASK) power and information synchronous transmission system based on phase-shifted full-bridge (PSFB) for applications in wireless power transmission (WPT). The Pulse Width Modulation (PWM) waveform uses different phases to control the MOSFET in the full-bridge inverter for MASK modulation. The inverter voltage generates M amplitude transformation, forming a comprehensive power information flow. The demodulation circuit processes the information transmitted to the secondary side, following the power supply with a differential amplifier, to realize synchronous transmission of power supply and information. Compared with conventional amplitude modulation, the system’s volume is significantly reduced, and the DC-DC modulation circuit has no filtering effect. It transmits comprehensive high-level data and improves the information transmission rate from the perspective of bit width. In the experiment, 16-bit width data are transmitted, and the bit rate is increased by four times compared to conventional amplitude modulation. Combined with DSP, the designed demodulation circuit reduces the voltage amplitude fluctuation at the receiving end to 5% and minimizes the impact of amplitude modulation voltage fluctuation on the system.

Aiming at the problem of the unavoidable phase-tracking error of the wireless power transfer (WPT) system caused by dead time, MOSFET drive and other factors, this paper proposes a frequency-tracking method with high accuracy based on a Field-Programmable Gate Array (FPGA) to track the current and voltage phase differences on the transmitting side. Compared with fixed-phase systems, the proposed method accurately controls the phase difference between voltage and current. It detects the phase difference in real time and adjusts the phase compensation angle dynamically to ensure that the system always operates under the optimal zero-voltage switching (ZVS) state, which reduces system loss. Experiments under operating conditions of varying transmission distances and load resistance values are carried out on a prototype. The experimental results show that the proposed method achieves a desired phase difference of 11.5° under the conditions of varying transmission distances and load resistance values, which meets the expectation of a phase difference between 10.5° and 13° to achieve ZVS. Within the range of over-coupling conditions, the output power and transmission efficiency of the WPT system are more significantly improved than those of the fixed-frequency system, which verifies the feasibility of the proposed method.