DC Fault Ride-Through of a Three-Phase Dual-Active Bridge Converter for DC Grids

DC fault ride-through capability is a highly desired feature of three-phase dual-active bridge (DAB3) converters in a dc distribution grid. However, the state-of-the-art modulations schemes for DAB3 converters such as single phase-shift and asymmetrical duty-cycle control have a limited dc fault ride-through capability due to either the resulting high peak currents or a limited power transfer capability and the lack of 0 V ride-through capability. In this paper, a space-vector-based asymmetrical duty-cycle control method is proposed allowing the DAB3 converter to ride through a dc fault down to 0 V with a controllable peak current of the devices and feature a significantly higher power transfer capability at low voltage-ratios. Moreover, soft switching turn-on is still realized for all semiconductor devices during the dc fault ride-through operation. The proposed method can be combined with the asymmetrical duty-cycle control and single phase-shift modulation to achieve a fast-dynamic control of the DAB3 converter even during dc faults. Validity of the proposed method is verified by simulation of a 300 kW DAB3 converter.