Abstract: A DC power flow controller is an effective technical means to solve the problem of incomplete controllability of power flow in a ring DC distribution network. However, existing methods fail to exploit its potential in fault current limiting fully. This paper establishes a fault modulus analysis model for a triple active bridge power flow controller (TAB-PFC). It proposes an active current limiting strategy for bipolar DC distribution networks based on TAB-PFC. Firstly, the current limiting principle of TAB-PFC is explained, and an active current limiting control strategy based on TAB-PFC is proposed. Then, this paper models the different fault stages of TAB-PFC and constructs an equivalent fault modulus model for bipolar DC distribution networks with TAB-PFC considering mutual inductance. On this basis, analyze the impact of different parameters on the current limiting ability of TAB-PFC, and provide a basis for its parameter selection. A simulation model of a bipolar DC distribution network with TAB-PFC was established in MATLAB/Simulink to verify the effectiveness of the proposed active current limiting strategy and the correctness of the fault equivalent circuit model and parameter analysis.