As the world shifts toward sustainable transportation, electric vehicles (EVs) have emerged as a key solution to reducing greenhouse gas emissions. However, one major hurdle remains: efficient and convenient charging. While wireless power transfer (WPT) has gained traction, most systems rely on inductive charging, which requires bulky ferrite cores and suffers from misalignment issues.
Enter Capacitive Power Transfer (CPT)—an innovative alternative that uses electric fields instead of magnetic ones to transmit energy. Unlike inductive systems, CPT eliminates the need for heavy ferrite materials, reduces electromagnetic interference, and offers a more cost-effective and lightweight solution. Despite its advantages, CPT faces challenges, including low coupling capacitance over large air gaps and high electric field strength near the plates. This review explores cutting-edge compensation converter topologies designed to overcome these limitations, making CPT a viable option for high-power EV charging.
Recent advancements in CPT compensation circuits have yielded impressive results, addressing key inefficiencies in wireless EV charging. One experimental prototype, based on the Corbin Sparrow EV, demonstrated how optimized compensation networks can significantly improve power transfer. By fine-tuning the converter topology, researchers achieved 97% efficiency at 7 kW power levels—comparable to onboard chargers but without the need for physical connectors.
A major breakthrough came with conformal bumper-based CPT designs, which integrate charging plates into the vehicle's structure. This approach minimizes air gaps, enhances coupling capacitance, and reduces energy losses. Additionally, using dielectric-coated aluminum plates instead of traditional litz wire further cuts costs while improving durability.
One of the biggest challenges in CPT has been maintaining efficiency over standard vehicle ground clearances (around 150 mm). However, advanced resonant compensation circuits have enabled stable power transfer even at these distances, with coupling capacitance values optimized between 9–10 pF. High-frequency inverters and precisely tuned inductors help maintain strong electric fields without excessive leakage, ensuring both efficiency and safety.
The potential of CPT extends beyond stationary charging. Its lightweight and low-cost nature make it ideal for dynamic charging systems, where EVs could recharge while driving over embedded road plates. Future research could focus on multi-plate arrays to improve alignment tolerance and smart phase-shifting techniques to further reduce electromagnetic exposure. Another promising direction is integrating CPT with renewable energy grids, enabling EVs to draw power from solar or wind sources seamlessly. Additionally, advancements in dielectric materials could enhance coupling efficiency, while AI-driven adaptive compensation circuits could optimize power transfer in real time based on vehicle positioning.
Capacitive Power Transfer represents a paradigm shift in wireless EV charging, offering a lighter, cheaper, and more efficient alternative to traditional inductive systems. By refining compensation converter topologies, researchers have unlocked CPT's potential to deliver high-power, high-efficiency charging without the drawbacks of magnetic-based systems. As the automotive industry moves toward a fully electric future, CPT could play a pivotal role in making wireless charging more accessible, sustainable, and user-friendly.
Reference
Mohammad Amir a, Izhar Ahmad Saifi a, Mohammad Waseem b, Mohd Tariq c
Title of original paper: A critical review of compensation converters for capacitive power transfer in wireless electric vehicle charging circuit topologies
Article link: https://doi.org/10.1016/j.geits.2024.100196
Journal: Green Energy and Intelligent Transportation
https://www.sciencedirect.com/science/article/pii/S2773153724000483
DOI: 10.1016/j.geits.2024.100196
Affiliations:
a Department of Electrical Engineering, Jamia Millia Islamia (Central University), Delhi, India
b University Polytechnic, Faculty of Engineering and Technology, Jamia Millia Islamia, New Delhi, India
c Department of Electrical and Computer Engineering, Florida International University, Florida, USA
