Comparison of 2L and 3L-NPC Power Converter-Based a Level-2 Isolated Off-Board Charger

This paper presents an off-board charger system for any electric vehicle based on a single-stage power converter operation that performs as a three-phase pulse width modulation rectifier. To enhance the safety issue by itself, a step-down transformer with galvanic isolation is added. Additionally, the off-board charger system allows bidirectional power flow in both grid-to-vehicle (G2V) and vehicle-to-grid operations. To analyze this system, only G2V operation is shown by comparing a two-level power converter charger with a three-level neutral point clamped power converter charger. In light of its controller, the off-board charger is designed to charge a battery in constant current and constant voltage mode in compliance with Level 2 of charging power. Based on this controller, it can support grid power quality under a unity power factor. Simulation-based verification is conducted on a maximum power rating of 22 kW to claim the performance of steady-state operation and dynamic operation.