DESIGN OF DYNAMIC CAPACITIVE WIRELESS POWER TRANSFER SYSTEMS FOR ELECTRIC VEHICLE CHARGING

Dynamic wireless power transfer (WPT) systems can potentially accelerate the penetration of electric vehicles (EVs) in the market by enabling stationary, semi-dynamic, and dynamic charging, thereby reducing EV costs, eliminating charging time, and enabling unlimited range. Furthermore, dynamic WPT systems can also prove revolutionary in autonomizing warehouses by charging autonomous material handling vehicles while they are in motion, enabling increased productivity by reducing downtime. This thesis introduces innovative architectures, circuit topologies, design techniques, and control methodologies for large air-gap kW-scale high power-transfer-density efficient dynamic capacitive WPT systems operating at multi-MHz frequencies that maintain constant power across wide misalignments and varying air-gaps. This thesis proposes an innovative design for roadway-embeddable charging pads that minimizes the effect of parasitic capacitances present in the charging environment while maintaining a favorable cost-performance tradeoff. Furthermore, a novel technique using metasurface-based coupling plates (referred to as ‘metacoupler’) to reduce the fringing electricfields outside the charging pads is also proposed. Different physical implementations of the metacoupler that enable significant fringing field reduction while maintaining a high system efficiency are investigated. A prototype 13.56-MHz 12-cm air-gap prototype capacitive WPT system that utilizes the charging pads and metacouplers is designed and built, and is experimentally shown to maintain 92% dc-ac power transfer efficiency while achieving a 40% reduction in fringing fields. State-of-the-art high-frequency capacitive wireless power transfer (WPT) systems are limited in their power transfer capability due to the limited power rating of the semiconductor devices used in their inverters. This thesis presents several passive power-combining architectures to operate multiple high-frequency inverters in parallel while ensuring balanced current sharing between them. A comprehensive methodology to design each of these power combining architectures anda systematic comparison between them is also presented. The analytical results are validated using a 6.78-MHz 4.2-kW experimental prototype, which transfers 2x power relative to a single inverter-based system. An alternate approach to power scaling, that uses a frequency multiplier inverter to maximize the power processing capability of high-frequency capacitive WPT systems is also presented. The proposed architecture can reduce the inverter transistor’s switching frequency by any desired factor compared to the system’s resonant frequency, thereby improving transistor switching performance and reducing high-frequency-dependent losses. Two frequency multiplier architectures, one using a stacked inverter and other using a parallel-in series-out transformer are proposed and are compared in terms of their efficiency and harmonic quality. The analytical findings are validated using experimental results. Finally, this thesis proposes an improved design of an active variable reactance (AVR) rectifier that enables WPT systems to maintain a constant power transfer for widely varying coupling conditions. This improved design enables a wider misalignment tolerance range. A control strategy for the AVR rectifier and the inverter is developed that can dynamically compensate for coupling variations and also enable EV detection and soft-start.

Name thesis:degree_name

Ph. D., Electrical and Computer Engineering

Level thesis:degree_level

Doctor of Philosophy

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Grantor

Cornell University

Year dc:date.issued

2024

Author dc:creator

• Maji, Sounak

Committee members dc:contributor.committeemember

• Molnar, Alyosha
• Monticone, Francesco

• Capacitive Wireless Power Transfer
• EV charging
• Frequency Multipliers
• High-Frequency
• Power Combining
• WPT

Language dc:language.iso

en

DOI

https://doi.org/10.7298/gmff-zq19

Dc Identifier Other

ProQuest Submission ID: 14637
ProQuest Publication ID: 31489630

OAI identifier oai:identifier

oai:ecommons.cornell.edu:1813/116524