Three phase llc resonant converter in railway applications: an advance solution for battery charging

Abstract

The increasing demand for efficient battery charging in railway vehicles is driving the development of compact, high-performance power converters. Small form-factor onboard chargers require high-frequency operation, necessitating the use of small filtering components and high efficiency to ensure thermal stability and reliability. In railway systems, optimizing power losses is crucial to minimizing the converter’s weight and size while maintaining effective passive cooling. This article presents a three-phase LLC resonant converter topology utilizing a wye-wye transformer, identified as a promising solution for achieving high efficiency, compactness, and effective power density while minimizing losses. The design considerations and operational characteristics of the LLC resonant converter are discussed, highlighting its suitability for railway applications. The findings show that this topology meets the stringent requirements for railway vehicle battery charging and enhances overall system performance. The prototype converter utilizes SiC (Silicon Carbide) technology to reduce switching losses and improve thermal performance. It has an output power rating of approximately 10.5 kW, with a regulated output voltage of 400 V, controlled by varying the switching frequency, and demonstrates an efficiency of 97.7 %.