Inductive Power Transfer Systems for Charging of Electric Vehicles

In this dissertation I present novel topologies, design procedures, and models of transmitters, receivers, and coupled coils of systems for wireless inductive power transfer (IPT) used for charging of electric vehicles. The research presented addresses important deficiencies of the state-of-the-art solutions: limited efficiency and range of transferred power, and lack of reliable control over the power delivery from the transmitter (source) to the receiver (pickup). The dissertation consists of five contributions that diagnose the problem, offer the solution and demonstrate the improvements of WIPT subsystems or the system as a whole.;As the first topic, a system-level analysis that investigates the concept of the dynamic charging of electric vehicles is presented and a methodology for optimal placement of the IPT infrastructure to eliminate the problem of limited driving range is suggested. The second topic addresses the problem of high switching losses of a full-bridge converter at a transmitter by redesigning the transmitter's resonant tank to take into account the harmonics of the inverter currents and create soft-switching conditions for the inverter switches.;The power flow between transmitter and receiver coils is often limited by the detuning of the receiver's resonant circuit, especially when the quality factor of the receiver's coil is high. The conceptual framework for this problem is presented in the third part and a tri-state-boost based solution is suggested that tunes a parallel resonant circuit by emulating the missing reactance. This solution provides real-time bi-directional tuning with minimum additional components and its effectiveness is demonstrated through numerous experiments and for different sources of detuning---capacitance variation, signal frequency fluctuation, or detuning caused by parasitic coupling with surrounding metal objects.;Tubular-conductor based coils for wireless power transfer are usually overlooked compared with Litz-wire based ones, partially due to the lack of an accurate frequency model of the coil resistances and a quality factor for an arbitrary layout of the coil turns. Therefore, a new model of the tubular coil is presented in the dissertation that effectively quantifies the skin and proximity effects and their influence on current redistribution and equivalent resistance. An analytical model is tested through numerous FEM simulations and experimental measurements.;The last contribution of this dissertation is the proposal of a new IPT concept that uses multiple frequencies to deliver power. This frequency multiplex is achieved by using LC ladder-based, multi-resonant tanks at both the transmitter and the receiver to amplify and extract power at multiple frequencies. At the same time, low switching frequency is preserved at the primary, since the voltage harmonics are used to excite resonant modes of compensation which may lead to higher overall efficiency. Additionally, emission standards may become easier to meet by spreading the power transfer over a spectrum of frequencies. In this dissertation, an analytical framework is presented for a dual-frequency design, while the case in which the fundamental and the third harmonic are used is verified through simulations and a prototype design.