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First and foremost, I'd like to thank God for guiding me through this difficult period of my life and for sending me the right people at the right time. This study would not have been possible if it were not for the guidance and support of people from both Robert Bosch Southeast Asia Private Limited and Nanyang Technological University. On Bosch's side, I'd like to thank the power electronics team and my other colleagues at Robert Bosch, in particular, Dr Pham, who has provided the necessary guidance to hone my programming skills and improve my publication quality. Special thanks also goes out to the other members of Bosch's power electronics team -Jan Riedal, Jitendra Solanki, Nima Saadat, He Maojun and Zaki Mohzani for providing me technical guidance and moral support throughout this study. I'd also like to thank Konstantin Spanos from Robert Bosch's Stuttgart-based power electronics department for introducing me to the basics of device characterisation and for advising on the printed circuit board layouts of both my prototype converters and my switch characterisation equipment. On the University's side, I'd like to thank Professor Tseng King Jet, who has provided insight and advice on device physics as well as which direction to steer my research. I wish him well in his new endeavour at the Singapore Institute of Technology. I'd like to also thank Jennifer from the Electric Power Research Lab for supporting me on administrative issues. Finally, I'd like to thank Professor Ali Maswood, who agreed to take me on after Professor Tseng left to see my study to completion. ContentsAcknowledgements.

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The control of the active front-end rectifier of the three-stage solid-state transformer (SST) system is addressed in this paper. A comprehensive precharging sequence is introduced for the active front-end rectifier of the SST to limit the inrush current during the start-up process to its nominal current. The proposed precharging algorithm consists of two phases, passive and active precharging. The precharging resistor limits the current during the passive precharging, while a ramp increase of the voltage reference is used in the controller during the active precharging to prevent large inrush currents. Additionally, a feedforward voltage compensator is added to the voltage reference of the controller to improve the dynamic response at the beginning of the active precharging. The proposed algorithm is detailed and simulation results on a 4-kW active frontend converter are presented to validate its performance. The simulation results under various operation conditions show the ability of the proposed algorithm to limit the converter current to its nominal value during the precharging as well as to control the dc-link voltage under different load changes.

Practical guidelines for device characterization and power converter design involving SiC MOSFETs