he isolated multiport Triple Active Bridge (TAB) DC-DC converter is an attractive topology for high power density, bidirectional power flow control with multiple ports, and galvanic isolation. However, the presence of circulating power in the TAB does not contribute to real power flow and instead circulates within the system reducing efficiency. This paper proposes a closed-form analytical model of circulating power based on time-domain analysis, along with accurate determination of the RMS winding current. The model is useful for design and optimization of the circuit parameters that minimize the circulating power and winding current. For a given power flow with a fixed equivalent inductance of the three-winding transformer, the impact of redistributing the external leakage inductance among the ports is modeled and analyzed, and an estimation method with optimization is presented. The analytical model is verified with a PLECS simulation. Experimental result from a hardware setup of the TAB is also presented.
