As a technology that makes power transfer more flexible, wireless power transfer (WPT) technology has become a hot research topic in recent years. However, most of the existing studies are based on a DC–DC WPT system. If applied to AC loads, the traditional system usually contains multiple energy conversion stages, which lead to a low transmission efficiency and therefore higher costs. Besides, the necessary large electrolytic capacitors make the system unreliable and bulky. The goal of this study is to design a reliable and efficient WPT system featuring constant current (CC) and constant voltage (CV) output for AC loads. In this work, an inductor–capacitor–capacitor series (LCC–S) enveloped modulation wireless power transfer (EM–WPT) system is proposed. The design of the proposed system is elaborated in this paper, including the working principle of the system’s power converters, the relationship between CC/CV output characteristics and the input current, and the control strategy of CC/CV output based on an AC–AC boost converter. Lastly, an experimental prototype is configured to verify the CC/CV characteristics. The measured overall efficiency of the system reaches 91% and the power factor of input power supply approaches 1.

The occurrence of high-amplitude magnetizing inrush current during the energization of a transformer without load poses significant challenges to the stable operation of both the transformer and the power grid, potentially leading to malfunctions in relay protection devices. This paper analyzes the underlying mechanisms of transformer inrush current and presents a novel approach utilizing a soft-start-based method for effectively suppressing inrush currents. The proposed method employs an inrush current suppressor comprising anti-parallel thyristors and filters to mitigate the adverse effects caused by the inrush current. A comparative study is conducted to evaluate the filtering efficacy of three types of filters incorporated in the inrush current suppressor: an LCLC damping filter, a high-order single trap filter and a high-order double trap filter. Through careful analysis and optimization, the high-order double trap filter with parallel RC damping damper is selected as the optimal configuration. To ensure effective suppression, it is necessary to incorporate a filter at the termination point of the anti-parallel thyristor. Additionally, a closed-loop control strategy is implemented to ensure a smooth start and actively suppress the magnetizing inrush current. To validate the effectiveness of the proposed method, comprehensive simulations are performed using Matlab/Simulink. The results demonstrate the successful suppression of inrush current and the maintenance of stable operation for the transformer. This inrush suppression method does not require considering the influence of residual magnetism and the grounding mode of the transformer’s neutral point. It is also suitable for various transformer structures and wiring methods, which makes it highly applicable.

In wireless power transfer (WPT) systems for electric vehicles, the detection of the secondary-side coil plays a crucial role in determining whether the vehicle is within the effective charging area. However, most existing detection approaches based on sensors require modifying the vehicle structure, which has several flaws such as limited adaptability to different vehicles, compromised preservation of the original magnetic coupler’s structure, and potential magnetic interferences with the primary-side coil operation. Driven by the mentioned issues, we propose a novel detection approach based on triple-U auxiliary coil with an equilateral triangle structure. This design preserves the integrity of the secondary-side coil and offers flexibility in accommodating different positioning heights. Besides, the triple-U auxiliary coil effectively mitigates interferes with the operation of the primary-side coil due to the reason that magnetic coupling between these two coils is eliminated. Further, a tailored positioning and direction-guided approach are proposed. This approach is capable of reaching the high-precision detection of the secondary-side coil. Meanwhile, it manages to guide the secondary-side coil to the desired area, approaching perfect alignment with the primary-side coil. Finally, A WPT system prototype incorporating the triple-U auxiliary coil is constructed to validate our proposed detection approach. Experiment results indicate that the maximum recognition range reaches 300mm×400mm and 400mm×300mm, when the secondary-side coil is the rectangular and double-D coil, respectively. Moreover, in both situations, the maximum positioning height achieves 250mm and the positioning resolution is refined to 10mm.

Supercapacitors (SCs) are widely used as energy storage devices in many practical applications of wireless power transfer. However, the modeling and analysis of a wireless power transfer system are seldom based on SC load; thus, the effects of the charging process on the wireless power transfer system cannot be analyzed clearly. In this paper, a variable-resistance-based method is proposed for the modeling and analysis of the process of constant current charging. First, how to make an SC equivalent in variable resistance is described, and the relationship between SC and variable resistance is considered. Next, the charging process, including charging current, voltage, power and transfer efficiency, is analyzed in detail. Furthermore, the effects of transmitting side voltage and frequency offset on this system are studied, and the optimal design method for an SC-load WPT system is provided on a preliminary basis. Finally, the theoretical derivation and analysis are verified by means of simulations and experiments.

In response to the issue of large input current ripple and noise, which can cause current shocks and compromise the overall stability in single-tube wireless power transmission systems, a P^# type LCC-S compensation network and a multi-coil phase-shifting control method have been proposed to suppress input current ripple, improve input current waveform, reduce input current total harmonic distortion (THD), and ultimately enhance system efficiency and stability. Firstly, the working mode and waveform of the P^# type LCC-S compensation network are analyzed, and the calculation method for its parameters is provided. Secondly, the analytical relationship between input current, input voltage, coil mutual inductance, and load impedance of the multi-coil array is derived. Additionally, Fourier transform is used to analyze the input current composition, and the phase shift suppression method is employed to reduce the input current ripple. Finally, a test platform is constructed to verify the relevant experiments. The experimental results demonstrate that the input current ripple is significantly suppressed at the rated transmission power, and the system efficiency is improved to 88.2%, which validates the effectiveness of the proposed method.

In multi-load wireless power transfer (WPT) systems, when multiple loads simultaneously charge using the same transmitter, the unpredictable spatial positions of the loads and the presence of cross-coupling make it challenging to achieve complete system decoupling, thereby limiting the effective power reception area. To address this issue, this paper investigates a one-to-multiple WPT system based on a single-transistor P^#-type LCC-S compensation network. Air-core coils are employed at the receiving end to mitigate cross-coupling, and the effective power reception area is analyzed. First, the operating principle of the system is examined and the parameter configuration conditions for the resonant circuit are derived. Then, MATLAB/Simulink R2022b is used to establish simulation circuit models for both single-transmitter single-receiver and single-transmitter dual-receiver WPT systems. The results indicate that for an effective output power of 5 W, the mutual inductance ranges are (3.5, 6) μH and (3, 6.5) μH, respectively. Next, finite element simulations are conducted to analyze the mutual inductance variations caused by spatial misalignment of the coils. For the single-transmitter single-receiver system, when the transmission distance is 5–12.5 mm, the effective power reception area corresponds to an X- and Y-axis misalignment of ±15 mm, while at a transmission distance of 10 mm, the effective reception area is ±10 mm along both axes. In the single-transmitter dual-receiver system, for a transmission distance of 5–14 mm, the maximum reception area is ±15 mm along the X-axis and ±10 mm along the Y-axis. Finally, an experimental platform is built to verify that multiple loads at different positions can achieve effective power reception for charging.