Wireless electric vehicle charging via capacitive power transfer through a conformal bumper

Abstract

Wireless power transfer (WPT) is emerging as a practical means for electric vehicle (EV) charging. Of the three main approaches to WPT, resonant inductive, inductive, and capacitive coupling, capacitive power transfer (CPT) is proposed herein to charge an EV at a kilowatt scale power level. CPT implementation replaces copper coils and ferrous core focusing/shield materials of inductive approaches with foil surfaces making CPT cost effective and structurally simple to implement, while maintaining efficient power transfer capability. This paper addresses each facet of kilowatt scale CPT system development, namely achieving high coupling capacitance between the vehicle and charging station and the associated drive power electronics. High capacitive coupling is achieved through a conformal (flexible and compressive) foam transmitter bumper that molds and contours itself to the vehicle to minimize air gap during charging. An experimental docking station to charge a Corbin Sparrow EV 156V battery pack was built and measured throughput power is demonstrated at >1kW with a coupling capacitance of 10nF operating at 540kHz.

Optimal Analytical Solution for a Capacitive Wireless Power Transfer System with One Transmitter and Two Receivers

“…Applications are the charging of, for example, electric vehicles [8], automatic guided vehicles [9], biomedical implants [10], integrated circuits [11] and low-power consumer applications [12]. Compared to IWPT, it has several advantages, such as a reduced cost and weight and the ability to transfer energy through metal [13,14].…”

Design of Capacitive Power Transfer Using a Class-E Resonant Inverter

“…However, they may have speed-dependent coupling capacitance, and the circuit must be auto-tuned. Additionally, conformal pads have been developed for CPT [17]. The pads shape and mold themselves to surfaces for maximum coupling.…”

“…Consequently, power can be transferred to the load without direct electrical contact while allowing some freedom of movement between the primary and secondary plates. The capacitive coupling structure can be of various configurations according to different applications; it may be rectangular, cylinder, disk [15], matrix [16], conformal surface [17], and hydrodynamic capacitive coupling [18], [19]. The receiver unit regulates the captured power and drives the load according to demand.…”

“…Other types of high frequency resonant inverters must be investigated further. Generally, high frequency inverters, such as Class-D or Class-E inverters, are the most suitable candidates for WPT systems because of their high efficiency that approaches 100% theoretical efficiency [17], [22], [23]. Jiejian Dai et al proposed four types of single active switch power electronics (i.e., Cuk, SEPIC, Zeta, and buck-boost) for a kW scale CPT system with over 90% efficiency [9].…”

An Interference Isolation Method for Wireless Power and Signal Parallel Transmissions on CPT Systems

“…As a kind of transmission mode, capacitive power transfer (CPT, or capacitively coupled power transfer, CCPT) technologies [5], [6] are attracting a growing number of researchers due to their advantages such as design flexibility, reduced volume and weight of the coupling structure and metal penetration capability [7], [8] because capacitive plates are utilized as the coupling structure. CPT technologies have been used in rotating devices [9], mobile robots [10], biological implants [11], cell phones [12], and electric vehicles [13], [14].…”