Implementation of a drivetrain integrated Dc-Dc converter for 48 V vehicles

The increasingly ambitious CO2 emission regulations for internal combustion engine (ICE) vehicles prove unachievable without at least some degree of electrification of the drivetrain. Therefore, a 48 V battery solution has been adopted by the automotive industry as a transitional step towards full electrification. The low power components are still fed from the 12 V network. A bidirectional dc-dc converter is placed between these networks. A novel topology and a control algorithm have been recently proposed by the authors to eliminate this dc-dc converter, thereby saving cost, weight and volume. Power transfer between these two networks is achieved by controlling the zero sequence current of the starter-generator, independent of the machine speed and torque. Therefore, dc-dc conversion can also be achieved when the machine is running. A prototype has been produced to explore the functionality and feasibility of this drivetrain. Control challenges, experimental results and performance of this prototype are discussed in this paper.