To decrease direct serial number and switching frequency of electronic devices,and simplify the main circuit topology,a module-cascade based BTB HVDC-flexible system is proposed.

• 从降低电力电子器件直接串联数目、器件开关频率和简化主电路拓扑结构3个方面出发,提出一种基于模块级联的背靠背柔性直流输电结构。