Abstract：The back-to-back active neutral-point-clamped（ANPC）converter，as the core component of the

unified power flow controller of the distribution network，is widely used for the flexible closed-loop operation.

However，the ANPC converter has more switching devices and commutation paths，which significantly increases

the complexity of modeling.To solve the above problems，an average modeling method of the ANPC converter was

proposed. The controlled source equivalent substitution method was used to replace the switching devices. The

resistance-capacitance-inductance devices of other parts of the circuit were retained while averaging each branch，

which greatly simplified the circuit model of the ANPC converter. On this basis，combined with the flexible control

principle based on back-to-back ANPC converters，the average model of a back-to-back ANPC flexible control

system was further built. By comparing the simulation results of the switch model and the average model，it was

shown that the average model was consistent with the switch model in the internal branch and external

characteristics，which verified the correctness and accuracy of the proposed average model and its feasibility in the

application of flexible closed-loop system.

      Key words：back-to-back active neutral-point-clamped（ANPC）converter; flexible closed-loop; controlledsource equivalent substitution method; average model