Sinha, Sreyam2021-03-122021-03-122020-08Sinha_cornellgrad_0058F_12271http://dissertations.umi.com/cornellgrad:12271https://hdl.handle.net/1813/103061202 pagesDynamic wireless power transfer (WPT) systems that effectively charge electric vehicles (EVs) while in motion can reduce EV costs, eliminate charging time, and enable unlimited range. This thesis introduces innovative architectures, circuit topologies, design techniques, and control methodologies for large air-gap kW-scale high power-transfer-density efficient dynamic capacitive WPT systems that maintain constant power across wide variations in misalignment and air-gap. A new design approach for large air-gap capacitive WPT systems is proposed that utilizes split-inductor matching networks to absorb the parasitic capacitances of the charging environment that can otherwise severely degrade power transfer and efficiency. This approach also enhances the system’s reliability by eliminating the need for discrete high-voltage capacitors. Two 6.78-MHz 12-cm air-gap prototype capacitive WPT systems are designed using this approach, with the first prototype achieving an efficiency of 88.4% and the second prototype achieving a power transfer density of 51.6 kW/m2. This thesis also presents a new approach to designing multistage matching networks in capacitive WPT systems which maximizes the network efficiency while providing the required overall gain and compensation. Compared to the conventional approach to designing matching networks, the proposed approach offers a better trade-off between efficiency and power transfer density while meeting electric field safety requirements. The proposed design approach is validated using three capacitive WPT prototypes, one of which is also demonstrated to achieve substantially higher efficiency than a conventionally designed prototype. Furthermore, this thesis introduces a novel variable compensation technique – the active variable reactance (AVR) rectifier – that enables WPT systems to maintain a constant power transfer for widely varying coupling conditions expected in a dynamic charging scenario. A 13.56-MHz 12-cm air-gap prototype capacitive WPT system incorporating the AVR rectifier is demonstrated to achieve constant power transfer for up to 45% misalignment between the charging pads and up to 45% increase in the air-gap. A control strategy for the AVR rectifier is developed that can dynamically compensate for coupling variations without the need for high-frequency sensing, and is experimentally demonstrated. Finally, capacitive WPT systems are compared with inductive WPT systems in terms of the theoretical limits on their power transfer capabilities and efficiencies.endissertation or thesishttps://doi.org/10.7298/hyv3-jb35