Three-Port Series-Resonant Converter DC Transformer with Integrated Magnetics for High Efficiency Operation

The series-resonant converter has become a very attractive topology for solid-state transformers due to its fixed voltage gain and soft-switching conditions when operating at the resonance frequency. This paper presents an open-loop three-port series-resonant converter (TP-SRC) capable of interconnecting three dc microgrids. High efficiency power electronics is a key enabler for the future dc distribution systems. In this paper, efficiency optimization and rms current reduction of the TP-SRC is achieved by a detailed analysis of the resonance frequency and dead-time selection. The analysis is supported by a losses modelling of the main components of the converter. In addition, Gallium Nitride (GaN) MOSFETs are used to reduce semiconductors' losses. Furthermore, the resonance inductance of the distributed resonant tank has been integrated into the leakage inductance of the transformer and the PCB parasitic inductances. In order to ensure a fixed resonance frequency, an experimental resonance frequency matching methodology for the resonant tank has been presented. Experimental results were obtained for a 1.4kW featuring a peak efficiency of 98.8%.