Executive Summary : | Wireless power transfer (WPT) has the potential to reduce onboard storage requirements and charging time for electric vehicles (EVs). Capacitive WPT is an attractive alternative due to its lightweight, less expensive, and easier embedding in roadways. However, recent advances in capacitive WPT have shown potential for high power transfer densities, but still suffer from poor thermal stability of GaN transistors, high fringing electric field levels, and the need for large compensating inductors. This proposal aims to improve large air-gap kilowatt-level capacitive WPT systems by employing a modular approach. Distributing power among multiple modules allows for scalability without adding thermal stress on high-frequency GaN devices. Operating adjacent modules in opposite phases allows their fringing electric fields to cancel each other, reducing overall field levels and making adjacent areas safer without compromising power transfer. Integrating all modules' inductors into a single air-core magnetic structure can bring a favorable trade-off between efficiency and size. The proposed modular system can achieve improved tolerance to misalignments and air-gap variations. The project will analyze theoretically, use circuit and FEA-based simulations, and validate using a GaN-based 6.78-MHz 3.7-kW 15-cm air-gap modular capacitive WPT prototype. The design and implementation will also include mitigation of inter-module parasitic interaction and closed loop control of modules for equal power sharing. The proposed modular approach can scale up power transfer levels in capacitive WPT systems while ensuring low thermal stress on GaN transistors, low fringing electric field levels, and a favorable trade-off between efficiency and size. This will lead to successful deployment of an efficient, small, and cost-effective capacitive WPT system in eMobility applications. |