Compact and Modularized Design of High-frequency Wireless Power Transfer Systems

Date:2023/02/15 - 2023/02/15

Dissertation Title: Compact and Modularized Design of High-frequency Wireless Power Transfer Systems

Speaker: Huan Zhang, Ph.D. candidate at UM-SJTU Joint Institute

Time: 10:00 a.m., Februray 15th, 2023 ( Beijing Time)

Location: Room 454, Longbin Building

Abstract

Wireless power transfer (WPT) systems with high operation frequency (e.g., 6.78MHz) can achieve light coupling structure and high spatial freedom, which is very friendly for electric devices, such as cell phones, implantable medical devices and motion robots. However, the high operation frequency enlarges the components' parasitics and thus decreases the system's robustness. In order to improve system performance, an impedance matching network (IMN) with a bulky ac inductor will be necessary for system design, which decreases the compactness of the final high-frequency WPT system. Meanwhile, the design of the WPT system operating at high frequency is usually complicated. It requires an intensive effort on simulation and impedance analysis, which limits the usage and development of high-frequency WPT technology.

In this dissertation, the complex impedance characteristics caused by component parasitics are first analyzed. Based on that, effective reactance compression is achieved through receiving-side parameters design. Then, new converter topologies are applied or designed to reduce the requirement of the ac inductor while maintaining the robustness of the high-frequency system.

The design of a modified Class E power amplifier with a novel edge inductor decreases the prototype's height nearly three times. And a novel inductor-less topology with a flexible printed circuit (FPC) coil enables an ultra-thin and bendable WPT prototype. Furthermore, a vertically modularized and reconfigurable WPT design concept is proposed in this dissertation to reduce the design complexity and maintenance cost of a high-frequency WPT system. In order to decrease the proximity effect in vertically stacking UM coils, a novel interleaved coil design is proposed based on the electromagnetic field analysis, which improves power balance among UMs and increases the dc-dc efficiency of the final system.

This dissertation contributes to enhancing the compactness and modularization of high-frequency WPT systems. Compared with the classical high-frequency WPT system with IMN, the proposed design methodology of edge inductor and inductor-less WPT topology increases the power density about 8 times while maintaining the system robustness against the load variation, misalignment or bending FPC coil. Thanks to the modularized design concept, the prototype demonstrates the desired scalability in both power levels (4~116 W) and transfer distance (30~90 mm) with high dc-dc efficiency (over 80% in most transfer distance), which is conducive to the promotion and application of high-frequency WPT technology.

Biography

Huan Zhang received the B.S. degree in electrical engineering from Shandong University, Jinan, China, in 2016, and the M.S. degree in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 2019. He is currently working toward the Ph.D. degree in electrical and computer engineering at the UM-SJTU Joint Institute, supervised by Prof. Chengbin Ma. His research interests include high-frequency power electronics and its applications in megahertz wireless power transfer and energy routers.Mr. Zhang received 2022 National Scholarship for Doctoral Students, the Top 10 1st Stage Proposal Award at the Inaugural IEEE Global Student Wireless Power Competition in 2022, and the Best Paper Award at the IEEE Energy Conversion Congress and Exposition-Asia in 2020.