Time-Domain-Based Superposition Analysis for Triple Active Bridge and Its Application for ZVS and Current Stress Optimization

With the advantages of simple topology, voltage matching, electrical isolation, and bidirectional energy control, the triple active bridge (TAB) has become an active exploration and attempt for the flexible interconnection of dc ports. The high-frequency chain current (HFCC) calculation is the crucial step in determining zero-voltage-switching (ZVS) regions and current stresses, providing the basis for the subsequent performance optimization of TAB. Due to the number of switches increasing, TAB's degrees of freedom (the phase-shift angles and duty cycles) have multiplied compared with its two-port topology. The existing current calculation methods of TAB are challenging to balance accuracy and simplicity. Currently, the simple and accurate HFCC model, considering all the TAB variables, can hardly be found in the literature. This article proposes a unified and novel solution for TAB HFCC calculation based on the superposition theorem, Thevenin's theorem, and the time-domain method. It can get the uniform formula of the HFCC when all the control variables change. Based on the formula derived, this article further presents the corresponding ZVS and current stress analysis of TAB. A multiobjective optimal control method demonstrating efficiency improvement is proposed. Moreover, the tradeoffs between the control simplicity and optimization effect are analyzed based on the proposed HFCC model. The modulation pattern with the least algorithmic complexity for efficiency maximization is found. The validity and accuracy of the proposed method have been verified experimentally.