The continual development of high-power-density power electronic converters is driven particularly by modern transportation applications like electrical vehicles and more electric aircraft where the space and carrier capability is limited. However, there are several challenges related to transportation applications such as fault tolerance for safety concern, high temperature operation in extreme environments and more strict electromagnetic compatibility requirement. These challenges will increase difficulties for more electrical system adoption in the transportation applications. In this dissertation, comprehensive methodologies including more efficient energy storage solution, better power electronics devices capability, better packaging performance and more compact EMI filter design are analyzed and proposed for the goal of high power density converter design in transportation applications. / Ph. D.