As the world transitions towards sustainable transportation, the advancement of electric vehicles (EVs) has become imperative. Wireless power transfer (WPT) technology presents a promising solution to enhance the convenience and efficiency of EV charging while alleviating the challenges associated with traditional wired systems. This paper conducts an in-depth exploration of WPT technologies for EVs, focusing on their theoretical foundations, practical implementation, optimization strategies, development trends, and limitations. The theoretical principles of wireless charging are first elucidated, categorizing them into near-field methods, such as inductive and capacitive charging, and far-field methods, including microwave and laser-based charging. A comparative analysis reveals the advantages and limitations inherent to each technology. The implementation section examines various charging strategies, encompassing stationary, dynamic, and quasi-dynamic wireless charging, assessing their feasibility and effectiveness in practical applications. Furthermore, optimization techniques aimed at enhancing WPT system performance are examined in depth, with particular emphasis on coil structure optimizations, anti-misalignment solutions, compensation topology optimizations, modulation strategy optimizations, and parameter identifications. The discussion section outlines current development trends in wireless charging technologies for EVs, highlighting the limitations that hinder the widespread adoption of wireless charging technologies in the EV market. Finally, potential research directions and the implications of wireless charging technology on the development of EVs are summarized. This critical review aims to provide valuable insights for researchers and practitioners dedicated to advancing the field of wireless charging for EVs.

This brief presents a novel simultaneous wireless power and data transfer (SWPDT) system that combines inductive and capacitive couplings, featuring full-duplex communication with high data transfer rates. Specifically, the power and forward data are transferred through inductive coupling respectively by means of the DD coils and Q coils, while the backward data is transferred through capacitive coupling by means of the stray capacitances. Because of the decoupling characteristic of the DDQ coil structure and the use of two coupling types, the interferences among the power, forward data, and backward data are relatively low. By integrating the two coupling types, a comprehensive circuit model of full-duplex data transfer is established and analyzed. Finally, a 145-W prototype is actualized with 91.4% power transfer efficiency. The forward and backward data transfer rates are 150 kbps and 600 kbps, respectively, demonstrating the feasibility of the proposed system.

Internet-of-Things (IoT) bolts, which incorporate sensors and are embedded within rail fasteners, are used for monitoring environmental and train status in railway. Wireless power transfer (WPT) is a promising solution for powering these sensors due to its maintenance-free and highly reliable characteristics. However, the large number of bolts makes it costly to adopt the traditional approach where every receiver (Rx) coil is paired with its own transmitter (Tx) coil. To charge multiple Rx coils with a single transmitter, a dynamic-Tx-to-static-Rx (DTSR) WPT approach is proposed. Two key challenges remain. First, conductive and ferromagnetic rails might interfere with the coupling between Tx and Rx coils—a phenomenon that has not been explored previously. Second, due to high-speed trains, charging time is limited to milliseconds. This article is the first to quantify rail interference using a third-order circuit model. On this basis, the challenges and design requirements for DTSR-WPT systems are summarized. Multilayer asymmetrical coils and optimized frequency selection are employed to mitigate rail effects and maximize the energy transferred within a given time. A joule-level WPT prototype with capacitive loads is built. Experimental results indicate that capacitive voltage reaches 80% and 95% of steady-state levels within 6.4 and 9.6 ms, respectively.

This paper proposes a novel approach to simultaneously identifying multiple critical parameters in a wireless power transfer (WPT) system, such as the resonant frequency, mutual inductance, and load resistance, solely from the primary side. The key is to adopt a primary-side-switch-controlled capacitor (SCC) to ensure that the imaginary part of the input impedance is only caused by the secondary-side reflected impedance at three predesigned frequencies. The DSP controller then samples and processes the primary voltage and current using a gradient descent algorithm to derive the above parameters. After the identification, the SCC adjusts its equivalent capacitance based on the secondary-side practical resonant frequency to ensure a zero-phase angle (ZPA), thereby significantly improving the compatibility of the WPT system with unknown receivers. Compared to the previous frequency-sweeping method, the proposed approach is simpler and more suitable for deployment on the controller. Finally, experimental results demonstrate that the identification error of mutual inductance and resonant frequency are within 7.5% and 2.68%, respectively.

In a wireless power transfer (WPT) system, maximum efficiency can be achieved at specific load conditions by employing impedance matching (IM). Some researchers employ DC-DC converters or additional inductors and capacitors; however, this inevitably leads to an increase in both system cost and complexity. In this paper, we propose a receiver-side variable capacitor system, which comprises a series-connected switch-controlled capacitor (SCC) and a parallel-connected relay-controlled capacitor (RCC). This system aims to achieve maximum efficiency tracking (MET) for WPT across a wide range of load variations. The proposed system autonomously detects variations in the load and adjusts the equivalent capacitor value to achieve MET. Experimental results demonstrate that the proposed system can enhance system efficiency by approximately 5% to 20% when the load varies from 60 Ω to 180 Ω. Finally, we validate the feasibility of the proposed system through experimental verification.

Matrix converter (MC) and semi-active rectifier (SAR)-based two-stage wireless power transfer (WPT) systems can eliminate electrolytic capacitors while achieving wide-range power regulation and buck-boost capability. However, the cascaded current-source configuration introduces intrinsic system-level instability, which limits the practical feasibility of such capacitor-less architectures. In this paper, the stability characteristics of the cascaded system are systematically investigated using admittance-based modeling. The admittance interaction between the source and load subsystems is analyzed. It is revealed that overall stability cannot be guaranteed even when each subsystem is locally stable. To address this problem, an admittance reconfiguration strategy is proposed. The strategy reshapes the load-subsystem admittance through feedforward compensation. In this way, the closed-loop admittance approximates the open-loop characteristic that favors system-level stability. The experimental results verify that the proposed method effectively enhances the stability margin of the cascaded system while maintaining fast dynamic response.