Circuit Configuration and Operation Principle of Electrical Insulation Circuit for AC Fed Transformer-less Electric Vehicles Using High Withstand Voltage Property of SiC Power Module

Abstract

This study aims to develop a power supply system without a traction transformer for weight reduction and downsizing. Transformer-less power supply is expected to realize step-down, rectification, isolation, and motor drive using a high voltage silicon carbide (SiC) power device. The primary challenge of this work is developing a novel circuit that isolates the motor drive circuit from the AC line without using the traction transformer. Accordingly, we devised a flying capacitor circuit to solve the existing problems and aims for capacitive isolation. Subsequently, we devise a nesting capacitor as a short-circuit prevention measure. We report the isolated circuit configuration and operating principle.