Large- and Small-Signal Modeling Derived Loss Optimal Power Loop Decoupling Mechanism of TAB Converter

This article presents a precisely synthesized full order as well as reduced order continuous time large signal and small signal model of a hybrid phase-duty controlled triple-active bridge (TAB) converter based on higher order harmonic frequency inclusive averaging model. Such model helps to accurately predict the steady state circuit parameters such as inductor current, average output voltage, output voltage ripple etc. that in turn can be used to formulate the loss minimized optimal phase-duty modulation strategy for a TAB. Further, the derived full order small signal model can specifically model the high frequency dynamics of the converter which are neglected in the reduced order modeling. Moreover, in order to facilitate decoupled power flow in a TAB, a decoupler network is formulated based on meticulously modeled converter plant considering higher order harmonics of the bridge voltages into calculation. Finally, a controller-based decoupled power management strategy is proposed in this study that decouples the TAB control loops and facilitates faster transient performance with two independent PI controllers. An 800 W TAB converter proof-of-concept is designed, fabricated, and tested to verify the established modeling techniques and the proposed controller decoupling action. With the implementation of the decoupled control under an 80% load transient at the 2nd output port, the experimental results show 30% improvement in overshoot compared to the fundamental harmonic based decoupling method.