Generalised Harmonic Model for a Triple Active Bridge DC-DC Converter

Triple Active Bridge (TAB) converter is a popular topology used for interfacing multiple sources and loads. In this paper, we show that the large-signal and small-signal model of the TAB converter based on Fundamental Harmonic Analysis (FHA) presented in literature can be erroneous for a range of operating conditions. It could result in an error in the power flow calculation in addition to performance degradation of the closed-loop control systems. Further, we present a Generalised Harmonic Model (GHM) for the Triple Active Bridge (TAB) converter that offers superior accuracy. The small-signal transfer functions for the TAB converter are derived based on the proposed model and are verified using switching circuit simulations. A TAB converter hardware prototype has been developed and experimental results are provided to validate the proposed GHM.