Demonstrating Dynamic Wireless Charging of an Electric Vehicle: The Benefit of Electrochemical Capacitor Smoothing

TLDR

Wireless charging of an electric vehicle while it moves faces challenges such as low‑latency communication for coil excitation sequencing, maintaining lateral alignment, and the need for power‑flow smoothing. The article reports experimental results on in‑motion wireless EV charging at Oak Ridge National Laboratory, evaluating power smoothing using various electrochemical capacitors on both the grid side and in the vehicle. The authors employed symmetric carbon‑carbon electrochemical capacitors from Maxwell Technologies for in‑vehicle current smoothing and a passive/active parallel lithium‑capacitor unit from Electro Standards Laboratories to smooth grid‑side power. Power pulsation was reduced by 81 % on the grid with the lithium‑capacitor and by 84 % on the vehicle when using both the lithium‑capacitor and carbon ultracapacitors.

Abstract

The wireless charging of an electric vehicle (EV) while it is in motion presents challenges in terms of low-latency communications for roadway coil excitation sequencing and maintenance of lateral alignment, plus the need for power-flow smoothing. This article summarizes the experimental results on power smoothing of in-motion wireless EV charging performed at the Oak Ridge National Laboratory (ORNL) using various combinations of electrochemical capacitors at the grid side and in the vehicle. Electrochemical capacitors of the symmetric carbon-carbon type from Maxwell Technologies comprised the in-vehicle smoothing of wireless charging current to the EV battery pack. Electro Standards Laboratories (ESL) fabricated the passive and active parallel lithium-capacitor (LiC) unit used to smooth the grid-side power. The power pulsation reduction was 81% on the grid by the LiC, and 84% on the vehicle for both the LiC and the carbon ultracapacitors (UCs).