Power Dense Converters for Future Transport Systems

Abstract

Over the last decades, diverse debates based on scientific judgments have concluded that the consumption of fossil fuel does not provide, either economically or environmentally, a sustainable development to the countries of the world. Moreover, due to the heavy dependence of industrial economies on fossil fuels, the rapid depletion of the earth’s petroleum resources has become a serious problem, particularly because most of the current transportation systems still rely on fossil-fuel-based technologies. In this regard, nowadays there are many efforts on reducing the consumption of fossil fuel in the transportation sectors around the world. At present, these efforts are beginning to create a competition between renewable energy technologies versus well-established fossil-fuel-based technologies. In the same direction, the continuous development of power electronics technology and the arrival of wide band-gap devices has created new possibilities for improving fuel economy (& lower CO2 emissions) of transportation systems in general. One priority is obtaining weight reduction of on-board electrical power trains of electrified vehicles by using highly efficient power-dense powertrain components, such as DC-DC converters or inverters. Furthermore, nowadays, the excessive currents needed by very fast battery charging methods preferred by EV customers, have become one of the main motivations that is pushing to the EV industry to raise the electric power train DC bus voltage from 400 V to 800 V. In order to have information to make conclusions on relevant aspects such as reliability, affordability, efficiency, power density and so on, this work has studied analytically and by simulations, three DC-DC multilevel converters under demanding specifications as expected by DC-DC converters that are connected to a high-voltage DC bus. To perform the aforementioned, it has been necessary to derive a new set of mathematical expressions for one of these converters, and for the others mathematical expressions from the available literature have been utilized. This investigation has also determined the potential that these DC-DC multilevel converters have to maintain the highest levels of efficiency when using actual SiC MOSFETs (Wolfspeed), under a wide variation of the voltage ratio, as desired in on-board battery chargers.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Geoffrey Baines (Supervisor) & Judith Apsley (Supervisor)