Wide input voltage range compensation in DC/DC resonant architectures for on-board traction power supplies

Several methods to reduce the effect of wide input voltage variation in soft-switched DC/DC converters for high-power and high-voltage traction applications are presented in this paper. To enhance high conversion efficiency together with high reliability and cost reduction, the document addresses the use of a power architecture whose front-end is a three-level half-bridge converter non standard NPC configuration. Thanks to a structured control methodology based on the possibility to use either a two-level or a three-level modulation strategy according to the input voltage level, it is possible to optimize the converter performance over the whole input voltage range. First, the soft-switching implementation of the converter which allows ZVS operation in the entire load range by using the magnetizing inductance of the transformer is discussed. Then, the operation of the converter at both two-level and three-level operation is addressed. Concluding, experimental results obtained in the specified input voltage range are presented to confirm the validity of the theoretical analysis.