Bidirectional dual active bridge converter using a tap changer for extended voltage ranges
Aachen (2017, 2018) [Book, Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (viii, 94 Seiten) : Illustrationen, Diagramme
In electric vehicles today, typical power train architecture calls for a traction machine and battery pack, with an inverter between them. The inverter adjusts the state-of-charge-dependent voltage of the batteries to the speed-dependent voltage of the electric machine. To decouple the inverter and battery voltages, a DC-DC converter between the inverter and the battery pack is added, which, particularly at low speed, can enhance the overall efficiency and reduce its size. The nominal voltages of the batteries currently used in electric vehicles are in the order of hundreds of volts. The use of a DC-DC converter can be used to lower the voltage of the battery packs below the 60 V safety threshold. In this thesis, DC-DC converters with a low voltage port for the battery storage systems and a high voltage port for the electric machines are designed and implemented. These DC-DC converters base on the dual active bridge DC-DC converter, which has inherent galvanic isolation combined with the capability of high voltage transformation and bidirectional power flow. To obtain a wide voltage operation range at the high voltage port, the use of a transformer with a tap changer is investigated. In the final setup, a dual active bridge converter with tap changer for a rated power of 10 kW is constructed. The low-voltage port reaches from 30 V to 60 V, and the high-voltage port spans a range from 100 V to 400 V. The converter exhibits efficiency above 90% over the whole voltage and power range. The maximum efficiency is up to 98%. The thesis concludes with an overview and design considerations of a three-phase dual active bridge with tap changer.
de Doncker, Rik W.