Four-Port Dual-Active-Bridge 컨버터의 계통연계와 단독운전 시 전력 비동조화 기법

Abstract

This study proposed a power decoupling method for a four-port dual-active-bridge (DAB) converter for grid-connected and islanding operation modes. Four-port converters based on the DAB converter have recently attracted attention due to its capability to transfer power in a bidirectional manner and its high power density in DC microgrid systems. The four-port converter can also be connected to various distributed resources. However, this converter causes a power coupling problem where the unintended power induces poor dynamic performance and prevents the converter from effectively regulating the output voltage. Conventional four-port converters use three inductors to prevent a power coupling problem among output ports. However, this conventional method cannot transfer power when the operating mode transitions from the grid-connected mode to the islanding mode. The proposed power decoupling method for the four-port DAB converter employs a relay circuit for the coupling inductors. Using this method, the power decoupling phenomenon was mitigated in both the grid-connected and islanding modes. A 3 kW prototype four-port DAB converter was implemented to verify the validity and performance of the proposed power decoupling method.