Modulation Strategy Assessment for 3-Level Unidirectional Rectifiers in Electric Vehicle Ultra-Fast Charging Applications

Abstract

This paper proposes a complete analysis and comparison of the most significant pulse-width modulation (PWM) strategies for unidirectional 3-level rectifiers. The basic operation of the converter is described and the stresses on the major passive components (i.e. DC-link capacitors, differential-mode inductors, common-mode chokes) are calculated, highlighting the general performance trade-off of each modulation strategy. This analysis is applied to a rectifier for electric vehicle (EV) ultra-fast charging connected to the European low-voltage grid (i.e. 50 Hz, 400 V line-to-line), adopting a 650 V DC-link. The best candidates concerning different performance metrics are identified and the most suitable strategy for EV battery charging is selected.