Design consideration of an MMC-HVDC system based on 4500V/4000A emitter turn-off (ETO) thyristor

Excessive power loss is a major concern in high voltage and high power applications and is considered one of the main drawbacks of VSC-HVDC system when compared with traditional HVDC system based on thyristor technology. This is primarily caused by high switching loss associated with switching devices used in the VSC-HVDC. This issue can be largely addressed by using the emerging MMC-HVDC topology, which requires much lower switching frequency than traditional VSC-HVDC. Emitter turn-off thyristor (ETO) is one of the best high power switching devices packed with many advanced features. ETO thyristor based MMC-HVDC system is therefore an extremely attractive choice for ultra-high voltage and high power HVDCs. This paper discusses the operation principle of ETO based MMC-HVDC as well as its design and loss comparison with other solutions.