Loss Characteristics of Input-Series Output-Parallel SiC DC-DC Converter Used in Auxiliary Power Systems

Abstract

With regard to the auxiliary power systems used in public transport such as hybrid bus, trolleybus, light rail trams, and subways, riding the weight and volume of the power equipment need to be reduced in order to accommodate more passengers or provide a more comfortable space. A converter with a higher capacity density, smaller volume, and lower weight was developed to improve the vehicle layout design and transport capability. With advantages such as faster switching frequency, lower power losses, and higher working temperature, silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET) devices can be used to promote the operation of auxiliary power converters. In most of the metro trains in China, such as Beijing, Shanghai, and Guangzhou, the power supply line is at a level of DC 1500V. However, 3300V SiC devices are rarely available in the market, series SiC MOSFETs are mostly available at levels of 600V to 1200V. In this research, a cascaded full-bridge topology with input-series output-parallel (ISOP) connected converter adapting 1700V/300A SiC MOSFET is proposed. An improved input voltage sharing control method is applied to improve the system rapidity and stability of the ISOP converter. The working characteristics, device losses, and system efficiency of a phase-shifted full-bridge (PSFB) converter with ISOP topology based on 1700V/300A SiC MOSFET are studied. Aiming at the application to auxiliary power systems, the other two types of converter topologies are also analyzed. The 1700V/300A (silicon-based insulated gate bipolar transistor) Si IGBT PSFB converter with ISOP topology and the 3300V/400A Si IGBT single unit PSFB converter are investigated of the control, weight, losses, efficiency, cost, and structure complexity. Simulation and experiment show the application of SiC devices exerting a positive effect on the volume reducing, weight decreasing and efficiency increasing.