Soft-Start Procedure for DC Microgrid Fed by PWM-Controlled DAB Converter

In dc microgrids or nanogrids, the presence of large dc-link capacitors poses significant challenges during system initialization, particularly in managing inrush currents that can lead to overcurrent conditions. At the same time, dual active bridge (DAB) converters, commonly used as dc gridforming or interlinking converters in these systems, suffer from circulating current issues when operating across wide voltage ranges. This circulating current, besides inrush conditions, can cause high stress on the converter components, especially if the dc-link capacitor is not properly pre-charged. To address these challenges, this paper proposes a pulse-width modulation (PWM) strategy designed to eliminate circulating and inrush currents in DAB converters during the initialization phase of dc microgrids/nanogrids. The proposed approach ensures controlled pre-charging of the dc-link capacitor while maintaining stable converter operation, thereby enhancing system reliability and reducing the risk of faults during initialization.