Abstracts:Pulse density modulation (PDM) enables continuous output power regulation and zero-voltage switching (ZVS) in wireless power transfer (WPT) systems. However, abrupt voltage transitions inherent to PDM often induce severe current oscillations, critically threatening system stability and operational safety. This article systematically analyzes the theoretical mechanisms underlying current oscillations, and a multilevel pulse magnitude modulation (ML-PMM) method based on a three-level full-bridge inverter is proposed. The ML-PMM can achieve wide-range flexible power regulation and ZVS operation while effectively suppressing current oscillations across most pulse density ranges. Furthermore, to address persistent oscillations at specific critical pulse densities, a hybrid modulation strategy integrating ML-PMM with asymmetrical voltage cancellation is developed. This hybrid asymmetrical ML-PMM can mitigate severe current oscillations during continuous power adjustment while preserving ZVS without requiring frequency control. Meanwhile, a switching-state-based multiflying-capacitor voltage balancing method is proposed, ensuring stable capacitor voltage balancing for both modulation schemes. Experimental validation on a hardware prototype of 1.06 kW proves the efficacy of the proposed methods.

Abstracts:Matrix converter-based wireless power transfer (WPT) systems inherently exhibit dual-frequency coupling between the 50-Hz grid-side stage and the 85-kHz high-frequency resonant stage due to the absence of high-capacity electrolytic capacitors. This coupling leads to significant grid current distortion under nonideal grid conditions. In this article, a dual-frequency state-space model is developed for the electrolytic capacitorless WPT system, enabling a quantitative analysis of grid current distortion caused by grid harmonics and unbalance. To solve this problem, a proportional-integral-resonant composited sixth-harmonic repetitive controller in the rotating frame is proposed. Furthermore, the error convergence characteristics are analyzed for the composite controller. Based on this, the controller parameters are designed in the discrete domain to ensure stability and great transient performance. Finally, the correctness of the theoretical analysis and the feasibility of the proposed method are verified by experimental verification.

Abstracts:Wireless Power Transfer Network (WPTN), with their multidimensional dynamic magnetic coupling capabilities, address the limitations of traditional wireless power transfer (WPT) technologies in terms of degrees of freedom, thus advancing the development and application of WPT technologies. Accurate mutual inductance identification is essential for establishing and optimizing paths in WPTN systems. However, the dynamic nature of the network causes frequent changes in mutual inductance parameters as nodes join or leave. This makes traditional calculation methods inadequate for complex multinode network. To address this challenge, this article proposes a dynamic mutual inductance identification method based on the gradient descent algorithm. The method effectively handles simultaneous changes in multiple mutual inductance parameters caused by network topology variations. By constructing a mathematical model of the WPTN system and designing a gradient descent algorithm with adaptive learning rates, the method achieves synchronous identification of multiple mutual inductance parameters. It does not require pretraining or extensive computational resources, and supports both online and offline identification. Experimental results on a four-node system platform show that the proposed method can identify three new mutual inductances in real time during node switching, while dynamically selecting the most efficient transmission path.

Abstracts:Inductive power transfer (IPT) technology is well-suited for wireless charging of electric vehicles due to its convenience, inherent safety, and resilience to weather conditions. Maintaining a constant output current across varying coupling coefficients and load resistances is a critical feature of IPT systems. This article proposes a dual-switch hybrid LCC-S inverter with a novel topology featuring reverse-coupled primary and secondary compensation coils integrated into a new dual D-quadrature-dual D magnetic coupler. This design eliminates cross-circuit mutual inductance and enhances system stability under mismatched conditions. The proposed two-switch topology replaces the conventional full-bridge inverter, eliminating ac switches in the resonance network and the need for an active rectifier on the receiver side, thereby reducing losses, component count, gate drive circuits, and additional control signals. By relocating inductors from the printed circuit board (PCB) to the magnetic couplers, the PCB size is significantly reduced, while the obtained tolerant system eliminates the need for complex control methods. A 1 kW prototype operating in zero voltage switching mode has been designed and tested, achieving output current regulation with less than 9% deviation across varying load and coupling conditions, with system efficiency maintained between 88% and 92% .

Abstracts:Wireless power transfer (WPT) is an essential technology for powering implantable medical devices. The significant distance between the transmitter and the receiver of the inductive link, relative to their small size, requires the use of high frequencies (HFs), hence increasing the complexity of the system design. This article proposes a method to model an HF inductive link based on artificial neural networks (ANNs), capable of estimating its electrical variables with an average error of 1.5% compared to finite element analysis data. This ANN is integrated into a multiobjective optimization process to enhance system efficiency under nominal conditions, taking into account electromagnetic safety assessment through the computation of the specific absorption rate. This method is validated through the design of four WPT topologies, based on combinations of two inverters (class D ZVS and class E) and two rectifiers (current-fed class E and compact voltage-fed class E). The designs are experimentally validated under various loads, distances, misalignments, and the use of biologic tissues as transmission media. All four topologies are capable of transmitting 0.48 W of power with efficiencies of 70% at a distance of 15 mm, achieving higher power density and efficiencies compared to state-of-the-art studies.

Abstracts:In the domain of electric vehicle (EV) charging applications, single-stage solutions are constantly gaining prominence due to their compactness and high power density. On the other hand, increase in charger power level, naturally leads to increase in the number of phases, as the distributed power transfer allows for lower current and voltage stress on the semiconductors and passive components of each of the phases individually. In this article, a single-stage, three-phase, inductive power transfer charger for EV applications is considered. Coils of the system are based on the DD2Q topology. For each of the phases, a three-phase to single-phase matrix converter is employed as the interface between the grid and the inductive link. Modulation of the given converter is proposed and outlined, allowing for stable power transfer, and by that means low distortion of the grid currents and high power factor, thus complying with the required grid code. Power distribution problem caused by misalignment is discussed in-detail, and solution that equalizes power levels per phase is proposed. An experimental prototype was built and several different tests were conducted in order to verify the proposed ideas, with the power transfer of up to 24 kW and system efficiencies of up to 86.42%. The proposed modulation of the employed converter results in THD of the grid currents less than 3% and the power factor higher than 0.98.

Abstracts:Multiphase parallel converters are widely used in electric vehicle (EV) charging, portable electronic power supply for high-power operation and inherent redundancy. However, conventional designs face magnetic integration challenges, requiring careful interphase magnetic coupling and flux balancing, and uncanceled inductor current ripples further increase losses. To address these limitations, this article proposes a multiphase dual-output-type converter employing distributed wireless coils to replace conventional inductors. The topology repurposes inductor current ripples as wireless ac energy, enabling simultaneous wired and wireless power delivery. By optimizing intercoil coupling, equivalent inductance is enhanced without enlarging magnetic components, reducing current ripples compared to traditional designs. A proportional-integral perturbation-and-observation algorithm dynamically adjusts phase duty cycles, suppressing parasitic-induced efficiency deviations while ensuring voltage stability. Experimental results demonstrate 93% peak efficiency with dual-output regulation. The proposed system achieves 5% efficiency gains over wired-only symmetric configurations and 3% improvement versus uniformly coupled three-phase systems, validating its effectiveness in balancing power density, efficiency, and multifunctional energy delivery for next-generation charging applications.

Abstracts:The proportion of electric-field power (EFP) in existing hybrid wireless power transfer (HWPT) systems is constrained by dielectric constant limitations, resulting in a narrow EFP transmission channel. This article addresses this limitation by proposing a novel Tri-SS HWPT system incorporating a multichannel integrated coupler that simultaneously enables EFP and magnetic-field power (MFP) transmission. A synchronized regulation mechanism has been implemented through series-connected power distribution, achieving capacity coordination between transmission channels. The complementary characteristics of different transmission channels are leveraged to achieve synergistic power transfer under varying coupling conditions. Resonance maintenance and performance optimization are ensured via enhanced misalignment tolerance within the specified range. Experimental validation on a 550 W platform demonstrates 81.4% power transfer efficiency at 60% misalignment, with improvements in EFP channel width and power density compared with conventional systems. The Tri-SS architecture establishes a robust HWPT framework that effectively enhances both power density and misalignment tolerance, thereby expanding the potential application domains of such HWPT systems.

Abstracts:Achieving efficient power regulation without communication in wireless power transfer (WPT) systems remains a significant challenge, particularly under varying load and coupling conditions. This article proposes a dual-frequency dual-channel WPT system by introducing a third harmonic resonant channel alongside the fundamental power channel. The third harmonic current serves multiple roles: it enables communication-free synchronization via implicit phase feedback, contributes actively to power transfer, and extends the zero-voltage switching (ZVS) range of the primary-side inverter without increasing the switching frequency. A two-stage synchronous control strategy is developed to regulate power based solely on local measurements, avoiding complex sensing, parameters estimation, or digital modulation-demodulation. To control the overall size of the coupler, a compact coil design is adopted, while maintaining a competitive power density. The proposed system is validated on a 1.7 kW experimental platform. Results confirm the system’s wide ZVS range and its ability to maintain stable control without communication. The system achieves a peak efficiency of 94.39%, and remains above 93.5% when the output power exceeds 50% .