A Novel Five-Level Hybrid Dual Active Bridge Converter with Optimized Switching Principle

The dual-active-bridge (DAB) topology has been widely accepted for high power density and highly efficient dcdc conversion systems. With the recently increased demand for the high frequency and medium voltage interface for the state-of-the-art applications, the multilevel DAB configurations are also being researched. This paper proposes such a five-level hybrid NPC-based DAB converter comprising Silicon (Si) and Silicon-carbide (SiC) switches. Further, a novel control scheme to enhance the operating range of the proposed converter is proposed. The proposed control scheme utilizes the low switching loss property of the SiC switches to enhance the ZVS operating range for the Si switches and thus, achieves effective utilization of Si and SiC switches. In this way, high power density is achieved at high efficiency over wide operating range. This paper presents operating principle of the proposed converter with the proposed control scheme. Further analytical investigation is presented to obtain ZVS range for the proposed converter, which is then compared with an existing Si switch-based NPC-DAB converter topology. The simulation results demonstrate the operation of the proposed converter. These results are then validated with the presented experimental results using the reduced scale converter prototype.