Scalable Auxiliary Power Supply System for SiC-based Modular Medium Voltage Converters

The design of the auxiliary power supply system is critical in modular medium voltage SiC-based conversion systems. Usually, high insulation capability, low common-mode coupling capacitance, high reliability, and a simple structure with a small converter size are preferred. To satisfy all requirements, this paper presents an auxiliary power supply system that is constructed by five individual converters including a high step-down converter, current-transformer-based auxiliary power supply, pre-charge circuit, discharge circuit, and mini-UPS. The operating sequence of the auxiliary power supply system as well as the standalone introduction of each converter are presented. Then, the hardware prototypes are developed and verified by the tests.