In recent years, the Wireless Power Transfer (WPT) system has become more and more popular due to its prominent advantages, especially for Electrical Vehicle (EV) charging. The WPT systems are required to follow the EV battery charging profiles, thus more and more voltage control methods with distinctive characteristics are proposed and studied. The goal of this thesis report is to conduct a comprehensive benchmark of the front-end voltage control solutions.

This thesis report focuses on the front-end voltage control solutions including the front-end buck converter and the phase shift control based on the primary inverter. Six different front-end voltage control scenarios are designed and compared in terms of system efficiency. There are four scenarios of the front-end buck converters including the single-phase buck converter working in Continuous Conduction Mode (CCM), the single-phase buck converter working in Triangular Current Mode (TCM), the two-phase interleaved buck converter working in CCM and the two-phase interleaved buck converter working in TCM. There are also two scenarios of primary inverter-based phase shift controls including phase shift with and without phase delay. The single-phase buck converter working in TCM has the highest efficiency reaching 95.5% at a light load. The phase shift control scenario with phase delay has the highest efficiency exceeding 96.5% at a heavy load.

Different from previous research on phase shift control, this thesis report conducts an in-depth harmonic analysis and compares the accuracy of harmonics analysis with the accuracy of fundamental wave analysis. The conclusion not only proves that fundamental wave analysis is reliable and accurate enough to calculate the phase shift parameters for the S-S compensation but also improves the calculation accuracy at a light load by harmonics calibration.

The compensation network in wireless power transfer (WPT) system has many functions, including increasing efficiency, providing constant voltage/current output, reducing volt-ampere rating, etc. With the popularity of wireless charging for electric vehicles, more and more compensation topologies with distinctive characteristics are proposed. Therefore, a comprehensive comparison among various com-pensation topologies under rated operating condition is necessary for the selection of compensation topology for WPT. In this thesis, eight compensation topologies are selected for benchmark and com-pared in terms of efficiency, component voltage/current stress, design freedom, misalignment be-haviour, etc. under the rated operating condition set based on SAE J2954 [1] standard. Given the analytical comparison results, the S-S compensation and LCC-S compensation are selected for further analysis and experimental verification.
In the practical design process of the compensation, the voltage/current stress on each compo-nent and the implementation of zero voltage switching (ZVS) on switches are two critical issues to be considered. For the calculation of components’ peak voltage/current, the fundamental-frequency analysis is the most widely used calculation method, which is inaccurate in some inductors’ voltage peak calculation. Therefore, a new resonant inductor voltage peak calculation method is proposed in this thesis, which is proved to be more accurate in both simulation and experiments in S-S and LCC-S compensations. For the implementation of ZVS, few studies have given the calculation method of switching current due to its complexity. In this thesis, a new switching current calculation method for LCC-S compensation is proposed and compared with the existing calculation method. A tuning method for ZVS implementation based on this calculation method is also proposed. Results from simulation and experiments under various operating conditions are provided to verify the accuracy of the newly proposed switching current calculation method. In the experiments, the LCC-S compensation and S-S compensation are compared under different power and input voltages. Experimental results show that the efficiency of LCC-S compensation is higher at low power, because of the lower conduction loss on MOSFETs. However, the efficiency of S-S compensation is higher at high power due to less losses on compensation components.