Analysis on load-factor dependence of triple active bridge converter's transmission efficiency for autonomous power networks

Abstract

A hybrid AC/DC microgrid systems that uses a triple active bridge (TAB) converter as a power routing unit has been proposed. Since the demand and supply balance of power fluctuates in the microgrid system, the power handled by the TAB converter also varies with time. Therefore, a TAB converter with a small load-factor dependence of transmission efficiency is necessary to reduce the unit's overall loss and design highly efficient microgrid systems. We previously fabricated a prototype TAB converter rated at 400 V, 20 kHz, and 10 kW using SiC-MOSFETs and demonstrated that it can control transmission power. In this study, the load-factor dependence of the TAB converter's transmission efficiency was investigated based on experimental results. The results show that the transmission efficiency of the TAB converter decreased under low-load conditions such as a load factor of less than 20%. In addition, the loss components involved in this dependence was analyzed. The analysis results indicate that switching loss is the main component of transmission-efficiency degradation under low-load conditions.