Common mode current minimization of Capacitor-Coupled Dual-Active-Bridge for SIPO MVDC-LVDC Distribution Converter

Abstract

Recently, series-input-parallel-output (SIPO) capacitor-coupled dual-active-bridge (CCDAB) is getting attention for the high voltage conversion ratio converter. In this paper, SIPO CCDAB for MVDC-LVDC distribution converter is analyzed. The DC-DC converter for grid application, the ground connection is needed for safety; it changes the characteristics of CCDAB. The ground connection separates CCDAB into two series-resonant dual-active-half-bridge (SR-DAHB) and offers a common mode (CM) path of current. The minimum current trajectory of the SR-DAHB is reviewed, and the magnitude of the harmonic current along with the minimum current trajectory is calculated. Because CM current causes voltage fluctuation and additional ESR loss, CM current should be minimized. To minimize CM current, a control strategy to minimize CM current is proposed. The harmonic analysis results confirm the advantages and the simulation and experimental results verify the effectiveness of the proposed control strategy.