Four-Coil Wireless Charging for EMVs: Topologies, Optimization Strategies, Deployment Readiness, and Future Directions

There is a growing trend toward employing two-coil and three-coil systems in magnetically coupled resonance wireless power-transfer (MCR-WPT) technology. However, these configurations have limitations at longer transmission distances and are sensitive to load variations. This paper provides a comprehensive review of four-coil WPT systems, focusing on their design, optimization, and applications. The reviewed literature indicates that four-coil configurations generally maintain higher power-transfer efficiency (PTE) over longer transmission distances, exhibit greater tolerance to misalignment, and show reduced sensitivity to load variations. The literature review indicates that while symmetric designs are easier to analyze, asymmetric configurations may provide higher efficiency and extended transmission range. The review also discusses how four-coil technology can be used in medical implants, sensors, and consumer electronics. It also addresses the current challenges of power and compliance in the electric vehicle (EV) industry. Finally, this paper identifies important areas of research that need to be addressed. Future research should aim to optimize power and efficiency together, explore multi-receiver systems for public charging, and investigate the potential of four-coil technology for Electric Micromobility Vehicles (EMVs).