Circulating Power and Winding Current Minimization in a Triple Active Bridge DC-DC Converter with Optimized Leakage Inductance Design

The 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 reduces system efficiency. This paper proposes a closed-form analytical model of estimating the circulating power based on time-domain analysis, along with the accurate determination of the RMS winding currents. The model is useful for the 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 leakage inductance among the ports is modeled and analyzed. The analytical model is verified with a PLECS simulation. Experimental results from a hardware setup of the TAB show the efficacy of the analytical model.