Common-mode Current Analysis and Cancellation Technique for Dual Active Bridge Converter based DC System

Isolated bi-directional DC-DC converter is required in many applications, such as solid-state transformer, DC distribution system for future grids, naval power systems, and electrical mobility. Dual Active Bridge (DAB) is a preferred candidate in these applications because of the soft-switching operation and bidirectional power flow capability. The conducted Electromagnetic Interference (EMI), due to high dv/dt and parasitic capacitance, of the DAB based isolated DC-DC system is analyzed. Isolated DC-DC systems based on single-phase and three-phase DAB are analyzed for different modulation schemes. Stray capacitance of the semiconductor device package and medium-frequency transformer is considered. Based on the analysis of the existing systems, an improved DC-DC converter architecture is proposed that can significantly reduce the conducted EMI. The proposed approach ensures synchronization and matching of the rising edge of the node voltage of one converter leg with the falling edge of node voltage of another converter leg to cancel the common-mode current.