Thyristor dodged VSC: An Enhanced Efficiency Conception for HVDC Applications

The ever-increasing energy demand requires efficient transmission of power from the point of generation to the point of utilization. Several converters are used in the modern-day HVDC transmission path; one such converter is a modular multilevel converter (MMC). It offers several advantages, the primary being reduced switching losses. But it uses fully controlled devices like IGBT, increasing the conduction loss. Various MMC-derived topologies have been published since the idea of MMC emerged to reduce conduction losses, yet none could achieve the efficiency of a line-commutated converter. Integration of thyristors in voltage source converter (VSC) to produce a hybrid topology offering better performance is the idea of this article. Including a thyristor provides superior characteristics such as higher voltage blocking capability, reliability, high surge current rating, efficient power handling capability and low on-state losses. The article presents the emergence, assessment and topology preference of hybrid converters incorporating IGBTs and thyristors. A comparative study of all the recent topologies is carried out to identify their advantages and limitations.