Aiming at the rapid decrease of coupling coefficient and transfer efficiency caused by misalignment during static wireless charging of electric vehicle, a high misalignment tolerance wireless power transfer (WPT) system based on magnetic field control of Double-layer Quadrature DD (DQDD) coil is proposed. Firstly, the excitation scheme of the two sets of DD coils on the primary side for a different magnetic field distribution is elaborated. Accordingly, the principle of high misalignment tolerance by matching the position of the secondary coils with the magnetic field distribution is explained. Secondly, the equivalent circuit model of the WPT system with dual path LCC-S compensation network is constructed, and the parameter configuration for constant excitation current of primary coil and output voltage are deduced. Then, a magnetic-field control strategy and the coil positioning method without additional auxiliary detection are proposed. Finally, a 1-kW experimental prototype was built to verify the feasibility, and the experimental results indicate that the power transfer efficiency, from DC input to DC output, of 87% is achieved with the longitudinal and lateral misalignment as high as 120mm in the meantime.

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.

Recently, an extended-duty-ratio (EDR) boost converter has attracted great attention of many scholars. However, the EDR boost converter with fix phase shifts is difficult to achieve phase-to-phase current sharing over a wide range of duty ratio. In this article, a variable phase-shift control strategy is proposed to further expand its current sharing range for the EDR boost converter. Under the proposed control strategy, the EDR boost converter can operate in wide range of duty ratio varying from 0.5 to 1 with automatic current sharing between phases since two adjacent phase shifts can be adjusted to guarantee that the energy stored in certain inductor is only transferred to the next phase capacitor step by step for generating high step-up output voltage. Next, the steady-state analysis of the EDR boost converter under the proposed control strategy is discussed thoroughly, and the switch voltage stresses and current stresses are also analyzed. Finally, a 300 W, 3.3 V to 38.9 V, four-phase EDR boost hardware prototype has been built. The effectiveness of the proposed control strategy is verified by the experimental results of the built prototype.

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.

An important area of research in electric vehicle wireless power transfer systems is the detection of the secondary pad, which is vital evidence to determine whether the vehicle is in the effective charging area. However, the detection based on sensors mostly will reconstruct the vehicle structure and has a limit on versatility in all kinds of vehicles and the applicability of magnetic couplers and the influence on the primary pad. Therefore, an auxiliary pad structure and corresponding positioning method for offset estimation utilizing the existing inverter and secondary pad in the vehicle system are proposed. Firstly, to satisfy the needs of different positioning heights and avoid the effect on the primary pad, a triple-U positioning auxiliary pad is designed to assist positioning. Secondly, the direction-guided trajectory and detection algorithm are proposed to modify the vehicle location in real-time after analyzing the corresponding equivalent mutual inductance feature trajectory, according to the magnetic field characteristics of various typical magnetic couplers intervened by the proposed triple-U auxiliary pad. Finally, a prototype system is built to validate the applicability and feasibility of the triple-U auxiliary pad, where the positioning accuracy is within 10 mm, and the maximum recognizable recognition range can reach 300 mm × 300 mm, and the direction-guided trajectory is accurate, which can satisfy the actual positioning requirements of electric vehicles.