Abstract：Cascaded DC-DC converter structure is a common form of DC distributed power systems. A converter designed individually can operate independently and stably. However, it may cause the instability of the whole system due to the interaction between the source and load converter after cascading. In this paper, a cascaded buck converter is taken as an example. The large-signal model is established by state space average method to analyze the open-loop stability of the cascaded system, and the parallel resistance range that can be stable in the full load range is derived. Then the influence of the resistance on the close-loop output impedance of the source converter is analyzed. Accordingly, an active damping control strategy based on paralleling virtual resistor is proposed to improve the stability of the cascaded system. This strategy can meet the stability requirement of matching the input impedance of the load converter without affecting the closed-loop dynamic of the source converter. The Lyapunov indirect method is used to analyze the stability conditions of the control strategy. The reasonable selection of the paralleling virtual resistor can satisfy the stability of the whole system. Finally, the effectiveness of the proposed control strategy is verified by simulation and experiment.
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2020, Vol. 35 
