A transformerless modular step-up dc-dc converter for high power applications

This study presents a new step-up dc-dc converter topology suitable for medium voltage, megawatt scale applications. The proposed converter interconnects unipolar or bipolar dc networks using a single inductor and a modular active switching network. The active switching network contains multiple series-connected identical converter modules. Each module consists of four switches and one capacitor. The modular nature of the switching network allows scalable implementation of the converter, and utilisation of low-voltage switches and capacitors. The proposed converter avoids the use of medium-frequency isolation transformers. Soft switching is utilised to reduce the converter's switching losses. An analytical model of the converter is developed to facilitate converter design. Theoretical predictions are supported by a 7.6 kW scaled laboratory prototype achieving an efficiency of as high as 93.2%.