Design, analysis, and optimization of self-resonant wireless power transfer systems

Abstract

This dissertation establishes a unified electromagnetic design methodology for low-frequency, capacitor-free Self-Resonant Wireless Power Transfer (SRWPT) systems. Unlike conventional resonant WPT architectures that rely on discrete compensation capacitors, thereby introducing voltage magnification, dielectric stress, parasitic losses, and long-term reliability constraints, the proposed approach embeds resonance directly within the coil structure through deliberate control of distributed inductance and capacitance. The primary limitation of planar self-resonant coils, namely insufficient intrinsic capacitance that shifts the natural resonant frequency toward the MHz range, is systematically resolved through a parallel-stacked multilayer PCB architecture that enhances effective interlayer capacitance while concurrently reducing equivalent resistance via current sharing. To sustain high efficiency under medium-power, under150 kHz operation, layout-level electromagnetic optimization using Track-Width Ratio (TWR) and Track-Gap Ratio (TGR) is introduced as a structured loss-reduction strategy that mitigates AC resistance arising from skin and proximity effects, thereby preserving a high-quality factor. In parallel, a comprehensive geometry-driven analysis reveals how coil shape intrinsically governs inductance, distributed capacitance, coupling behavior, loss distribution, and misalignment tolerance through strongly interdependent electromagnetic mechanisms. By transforming parasitic effects into controllable design parameters, this work demonstrates that low-frequency intrinsic resonance, high-Q performance, and compact PCB implementation can be achieved simultaneously within a rigorous structural framework. To address efficiency degradation under weak magnetic coupling and extended air gaps, the dissertation further advances self-resonant three-coil architectures that enhance reflected impedance and stabilize power transfer without reintroducing discrete reactive components. Through coordinated mutual inductance–capacitance interaction and intrinsic impedance shaping, the proposed multi-coil configurations strengthen effective coupling and improve robustness against distance variation and misalignment. A series–series self-resonant three-coil topology is developed to extend transfer range beyond the practical limits of conventional two-coil systems, while maintaining structural simplicity and capacitor-free operation. For size constrained biomedical platforms, a compact receiver architecture is introduced in which interconnected multilayer PCB coils increase effective inductance without enlarging physical dimensions, enabling improved voltage gain and transfer efficiency under strict geometric constraints. Experimental results obtained under both medium and low power operating conditions demonstrate that multilayer structuring, geometry driven design, and intrinsic multicoil coupling strategies collectively establish a scalable and integration ready foundation for high-efficiency, structurally robust wireless power transfer systems suitable for industrial platforms, automated guided vehicle (AGV) charging applications, and biomedical devices.

Date	23 Apr 2026
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Qingsong Wang (Supervisor) & Ambrish Chandra (Co-supervisor)