Peak Current Optimized Hybrid Modulation for NPC DAB Converter with a Wide Voltage Range

Energy storage devices can smooth out fluctuations in renewable energy generation and are widely present in DC microgrids. However, the isolated bidirectional DC-DC converters interfacing these devices face the challenge of a wide voltage range. The neutral point clamped (NPC) dual active bridge (DAB) converter is a promising topology in this scenario. The high degrees of freedom in the NPC DAB provide an opportunity to optimize the peak current. However, the methods proposed in existing studies are either complex or in lack of physical basis. Therefore, this paper first presents a hybrid modulation scheme of the NPC DAB based on the voltage-second matching principle. Next, a simple peak current optimization control method with clear physical meaning and a smooth phase-shift modulation strategy are proposed. The soft-switching characteristics are analyzed, and a loss model suitable for a high-frequency NPC DAB is developed. Additionally, a method to correct switching loss parameters based on the gate charge curve of SiC MOSFETs is introduced. Finally, the effectiveness of the proposed method is verified for a NPC DAB with a wide voltage range.