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Quasi Two-Level Operation and Neutral-Point Voltage Balance Method for a Four-Level ANPC based Dual Active Bridge DC-DC Converter

The multi-level dual active bridge (DAB) DC-DC converter can operate in medium voltage applications with low blocking voltage SiC MOSFETs, featured with high power density and efficiency. A four-level active neutral-point (NP) clamped based DAB (4L-ANPC-DAB) converter is discussed in this paper, which has simple commutation path and low parasitic parameter for SiC MOSFET applications. To achieve efficient power transferring, the quasi-two-level (Q2L) operation of 4L-ANPC-DAB is proposed in this paper. The soft-switching performance of 4L-ANPC-DAB in Q2L operation is also analyzed in detail. Based on Q2L operation, a NP voltage balance method by adjusting the dwell time of Q2L is proposed. The prototype hardware of 4L-ANPC-DAB is built and simulation and experimental results are both presented to verify the proposed Q2L operation and NP voltage balance method for 4L-ANPC-DAB.