Three-Phase Bidirectional Buck-Boost Current DC-Link EV Battery Charger Featuring a Wide Output Voltage Range of 200 to 1000V

Abstract

High power EV chargers connected to an AC power distribution bus are employing a three-phase AC/DC Power Factor Correction (PFC) front-end and a series-connected isolated DC/DC converter to efficiently regulate the traction battery voltage and supply the required charging current. In this paper, the component stresses and the design optimization of a novel two-stage three-phase bidirectional buck-boost current DC-link PFC rectifier system, realized solely with SiC power MOSFETs and conveniently requiring only a single magnetic component, are introduced. This topology offers a high efficiency in a wide operating range thanks to the synergetic operation of its two stages, the three-phase buck-type current source rectifier stage and the subsequent three-level boost-type DC/DC-stage, which makes it suitable for on-board as well as off-board charger applications. The calculated voltage and current component stresses of the proposed converter system, considering an output voltage range of 200 to 1000 V and up to 10 kW of output power, help to identify its operating boundaries, maximizing the utilization of the power semiconductors and of the DC-link inductor. The optimum values of the circuit parameters are selected after evaluating the converter average efficiency η¯ and volumetric power density ρ in the Pareto performance space and analyzing its design space diversity, focusing on the semiconductor losses and on the characteristics of the inductor. Considering typical EV battery charging profiles, i.e. taking both full-load and part-load operation into account, a power converter realization featuring η¯ = 98.5% and ρ = 13.9 kW/dm3 is achieved. © 2020 IEEE.