Multiport dc-dc converters have been intensively concerned and studied in power electronics-based systems. However, the instability issue and its suppression method are rarely discussed. This article investigates the stability of the triple active bridge (TAB) converter with two constant power loads by impedance-based method, where the output impedance of the TAB converter is derived by the extra element theorem. Then, a virtual impedance-based active damping (AD) control is proposed, where the virtual impedance has four different positions at the output capacitor of the dc port. The effect of the proposed AD control on output impedance and system dynamic response is analyzed. Meanwhile, the range of the virtual impedance is specified. Simulation is performed in PLECS and experimental tests are conducted on a scale-down TAB prototype to verify the effectiveness of the proposed AD control.

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This article investigates the stability of triple active bridge (TAB) converter with different types of loads. In this paper, port2 of TAB converter adopts voltage control to supply a constant power load (CPL), and port3 uses voltage control to supply a resistor or uses current control to supply a battery. Then, an extra element theorem-based (EET) modelling method based on the small signal model of the TAB converter is developed to derive the output impedance of different cases. The AC sweeping is implemented to validate the effectiveness of derivation. Furthermore, the impedance-based analysis method is applied to analyze the system stability. The analysis result shows that the instability issue caused by CPL at port2 can be suppressed by reducing the resistance load value at port3 or output current of port3. Simulation and experimental results are given to validate the stability analysis.@en