A Novel 22 kW Bidirectional All-GaN Integrated Onboard Charger Using a 3L-NPC and Interleaved Dual-Buck With Low Common Mode Voltage

This paper presents a simulation study on a 22 kW bidirectional all-GaN integrated onboard charger (iOBC) that combines a three-level neutral-point-clamped (3L-NPC) AC-DC front end with a two-phase interleaved dual-buck DC-DC back end. Referencing both stages to a split DC link limits device stress to half the bus voltage, enabling the use of 650 V GaN devices and supporting high switching frequency with improved power density and efficiency. The topology inherently lowers common-mode voltage; simulation results show near-complete cancellation at the DC/DC output. The control implemented is a grid-synchronised cascaded dq scheme for the 3L-NPC and phase-shifted interleaving with per-leg current control for the DC-DC stage. PLECS results in G2V and V2G operation confirm near-unity power factor with THD at 2.5 % at 22 kW, drain-source voltage peaks around half of the DC link voltage. By keeping each switch within half-bus voltage while shifting ripple to twice the switching frequency, the proposed architecture enables a compact, efficient, and scalable charger platform.