Drivetrain-Integrated DC-DC Converter for 48 V Network Vehicles

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Increasing power demand due to further electrification of internal combustion engine (ICE) vehicles has taken the 12 V power supply to its limits. Therefore, major automobile manufacturers have agreed to implement a new twin-voltage network. A 48 V battery is used to power the starter-generator and other high power components, while low power components are fed from a 12 V battery. A bidirectional dc-dc converter is placed between these networks so that the 48 V generator can charge the 12 V system and a 12 V jump starter can start the car.The objective of this research project is to investigate and demonstrate a novel drive topology and a control algorithm that eliminate the dc-dc converter between the 12 V network and the 48 V network. The proposed topology is similar to a conventional six-bridge inverter topology. Additionally, the star point of the machine is connected to the 12 V battery via an asymmetrical half bridge. The zero sequence current through the machine transfers power between the two networks. Preliminary analysis shows that the conventional field-oriented machine controller can be extended such that it can control the power flow between the two batteries. The power transfer between the batteries is independent of the machine speed, therefore the integrated dc-dc converter can also operate when the machine is running and producing torque.Within the scope of the project, a detailed simulation model of the system will be built to prove the feasibility and to compare the performance of this topology with the performance of a conventional dc-dc converter. A fully functional prototype will be built and tested to confirm the simulation results through experiments.