Design of Triple-Active Bridge Converter with Inherently Decoupled Power Flows

For the realization of DC grid, the high-power multi-port isolated DC/DC converter is necessary to integrate various DC sources and loads. Triple-Active Bridge (TAB) converter is one of the most popular topologies which has three-port high frequency transformer and three active bridges. It can realize the bi-directional power flow among different sources and loads. However, the intrinsic power coupling in each port of three-port transformer leads to the unwanted voltage fluctuation of DC side. The power coupling among three ports can be minimized by a low leakage inductance at one port. However, it can decrease the power efficiency in some power flow conditions of TAB converter. This paper has analyzed the reason for the degradation of power efficiency in various power flow condition. To estimate the power loss components in TAB converter, the power loss breakdown method is used. With the two experimental configuration of TAB converter: the conventional leakage inductance and a low leakage inductance, the power loss is estimated. From the experimental results, it can be concluded that the designing method of leakage inductance with a low leakage inductance at one port is appropriate for the TAB converter which has fixed power flow condition.